Title of Invention	METHOD AND APPARATUS FOR SENSORLESS POSITION CONTROL OF A PERMANENT MAGNET SYNCHRONOUS MOTOR (PMSM) DRIVE SYSTEM
Abstract	Methods and apparatus are provided for generating zero- sequence voltages based on voltage commands and a motor output signal. At least one of the methods includes, but is not limited to, receiving a torque command and generating three-phase voltage commands based on the torque command. The method also includes, but is not limited to, generating a motor output responsive to the three-phase voltage commands and generating three- phase zero-sequence voltage samples based on the three-phase voltage commands and the motor output.

Title of Invention

METHOD AND APPARATUS FOR SENSORLESS POSITION CONTROL OF A PERMANENT MAGNET SYNCHRONOUS MOTOR (PMSM) DRIVE SYSTEM

Abstract

Methods and apparatus are provided for generating zero- sequence voltages based on voltage commands and a motor output signal. At least one of the methods includes, but is not limited to, receiving a torque command and generating three-phase voltage commands based on the torque command. The method also includes, but is not limited to, generating a motor output responsive to the three-phase voltage commands and generating three- phase zero-sequence voltage samples based on the three-phase voltage commands and the motor output.

Full Text	METHOD AND APPARATUS FOR SENSORLESS POSITION CONTROL OF A PERMANENT MAGNET SYNCHRONOUS MOTOR (PMSM) DRIVE SYSTEM TECHNICAL FIELD [0001] The present invention generally relates to control systems and power inverter modules, and, more particularly, to control systems, methods and apparatus for control of a PMSM drive system. BACKGROUND OF THE INVENTION [0002] An electric traction drive system typically includes a power inverter module (PIM) and an AC motor. [0003] Many common sensorless position control methods of a traction drive systems either rely on spatial variation of rotor saliency of a rotor of the drive system or Back EMF of the inherent saliency machine of the drive system. These methods are more suitable with Interior Permanent Magnet Synchronous Motor (IPMSM), Synchronous Reluctance Motor and Switched Reluctance Motor machine types which inherently have magnetically salient rotors. [0004] Other methods of detecting rotor angular position include high frequency signal injection and modified PWM test pulse excitation. [0005] In the high frequency signal injection method, a balanced high frequency test signal, such as a voltage or current signal, can be injected on a stator winding of an inherently salient machine and the resultant effect of the balanced high frequency test signal on stator current can be measured. The effect of the balanced high frequency test signal injection can be observed in a measured stator current which takes the form of amplitude modulation at two times the fundamental frequency rate. This effect is due to the spatial modulation of the magnetic saliency as the rotor rotates. This method works quite well when the machine under test has inherent saliency, such as an Interior Permanent Magnet type machine. However, Surface Mount Permanent Magnet (SMPM) machines have no saliency and therefore require a very high magnitude injection signal in order to retrieve the position information. Thus, due to additional losses and noise generated by such a high magnitude injection signal, this method is not suitable for SMPM type application. [0006] In the modified PWM test pulse excitation method, modified PWM test pulses can be used to excite the high frequency impedance of the machine. When PWM test pulses are injected, the current control is ignored for the test period. This can be a good method for an industrial drive. However, a traction machine has low inductance and not controlling current during test period may result in an uncontrolled condition. This technique retrieves the position information from sensed stator current which must be sampled immediately after injecting the test pulses. This increases number of times the stator current is being sampled. [0007] According to another method of rotor position estimation discussed in European patent # EP 0962045 Bl, the resultant effect of modified PWM test pulses on leakage inductances can be measured via a measured phase to neutral voltage of an induction machine. This technique utilizes the property of a squirrel cage type rotor construction in an induction machine. By injecting the PWM test pulses, the "mechanical" saliency induced due to the rotor bars of the induction machine can be utilized. A saliency image rotates as the rotor rotates and this information can be used to deduce rotor position information. [0008] However, magnetic saliency is not a feature of a Surface Mount Permanent Magnet Motor (SMPMM). Thus, position sensorless control for a SMPMM can be challenging. [0009] A high performance permanent magnet ("PM") machine drive system requires an absolute position sensor which is an expensive component. Moreover, the circuitry required to process its signals can also be expensive. It would be desirable to eliminate this position sensor. It would also be desirable to eliminate mechanical interface hardware, reduce cost and weight, reduce cost and weight and improve the reliability of an electric traction drive system. Other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background. DESCRIPTION OF THE DRAWINGS [0010] The present invention will be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and [0011] FIG. 1 is a diagram of a simple 2-pole SMPMM showing a configuration of stator windings a, b, c and a PM; [0012\| FIG. 2 is a diagram which illustrates switching vectors and switching status of switches of a 2-level 3-phase inverter having eight available switching vectors; [0013] FIG. 3 is a circuit diagram which represents a three phase stator winding configuration of stator windings with respect to the switching vector V1 shown in FIG. 2; [0014] FIG. 4 is a circuit diagram which represents a three phase stator winding configuration of stator windings with respect to the switching vector V2 shown in FIG. 2; [0015] FIG. 5 is a circuit diagram which represents a three phase stator winding configuration of stator windings with respect to the switching vector V3 shown in FIG. 2; [0016] FIG. 6 is a circuit diagram which represents a three phase stator winding configuration of stator windings with respect to the switching vector V4 shown in FIG. 2; [0017] FIG. 7 is a circuit diagram which represents a three phase stator winding configuration of stator windings with respect to the switching vector V5 shown in FIG. 2; [0018] FIG. 8 is a circuit diagram which represents a three phase stator winding configuration of stator windings with respect to the switching vector V6 shown in FIG. 2; and q-axis stationary reference frame with an Alpha component and a Beta component of the zero sequence voltages plotted in x-y coordinates; [0021] FIG. 11 is a graph showing the phase of the vector (Vsn) represented by 0EstRaw (Flux angle) in FIG. 10; [0022] FIG. 12 is a block diagram of a control system which implements a sensorless algorithm using control hardware and 50 kW axial flux SMPMM; [0023] FIG. 13 is a graph showing injecting vectors (Sia, Sib and Sic) for zero sequence voltage measurement; [0024] FIG. 14 is a graph showing a normal Space Vector PWM (SVPWM) waveform for current control with switching states (Sa, Sb and Sc) for phases A, B and C, respectively; [0025] FIG. 15 is a graph showing a synthesized PWM waveform with modified switching vectors (Sa, Sb and Sc) used to switch IGBT switches in PWM inverter to generate three phase sinusoidal voltage commands; [0026] FIG. 16 is a graph showing three phase saturation induced (zero sequence voltage) signals at no load condition when no load torque is applied; [0027] FIG. 17 is a graph showing three phase saturation induced (zero sequence voltage) signals at a 40% load condition when no load torque is applied; [0028] FIG. 18 is a graph showing measured and estimated rotor position angles with two phase saturation induced signals at no load condition when no load torque is applied; and [0029] FIG. 19 is a graph showing measured and estimated rotor position angles with two phase saturation induced signals at full load condition when 100% load torque is applied. DESCRIPTION OF AN EXEMPLARY EMBODIMENT [0030] The following detailed description is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding technical field, background, brief summary or the following detailed description. The word "exemplary" is used herein to mean "serving as an example, instance, or illustration." Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments. All of the embodiments described in this Detailed Description are exemplary embodiments provided to enable persons skilled in the art to make or use the invention and not to limit the scope of the invention which is defined by the claims. Overview [0031] Embodiments of the present invention provide methods and apparatus that allow for generating of zero-sequence voltages based on voltage commands and a motor output signal. [0032] It has been observed that the PM (permanent magnet) in rotor and the stator electric circuit can cause a saturation effect of a stator core due to the magnetic flux. The saturation affects the inductance of three phase windings. For example, in an iron-based stator core, the more saturated winding has a lower inductance. Therefore if the inductance variation of the three phase winding is measured, stator flux information can be determined. The stator flux of the permanent magnet synchronous motor is represented in a stationary reference frame by equation (1), where are d-axis and q- axis stator flux linkage, respectively, pM is the stator flux linkage of the permanent magnet, are the d-axis and q-axis stator current, and is the rotor angle. [0033] If the stator current and inductances are known, the rotor-oriented component of the stator flux can be derived among the total stator flux, and then the rotor flux angle can be calculated. [0034] FIG. 1 is a diagram of a simple 2-pole SMPMM in a showing a configuration of stator windings a, b, c and a PM. FIG. 1 describes the relation between the stator inductance variation and the zero sequence voltage which is the sum of the phase to neutral voltages of phase A, B and C of the motor. For simplicity the 2 pole machine is used for the analysis, however, it should be appreciated that a similar analysis would apply to higher pole machines. [0035] The variation of the stator inductance in the motor depends on the flux distribution of the PM and the electromagnetic design magnetic design. [0036] In equations (3)-(5), is the average stator inductance, a is the coefficient of stator inductance variance, and is a periodic function with period of 7t. The stator inductances of a SMPMM for example can be assumed as: [0037] To obtain stator inductance variance information, this embodiment utilizes the zero sequence voltage components. When the three inductances of phase A, B and C are equivalent, the zero sequence voltage component is zero. However, if the inductances are not equivalent, it has a value according to the configuration of the inverter switches. This condition may occur due to the main flux saturation. The main flux is composed of the stator and the rotor PM flux. Thus by observing the zero sequence voltage, the rotor position information can be deduced. Inverter Switching Configuration [0038] FIG. 2 is a diagram which illustrates switching vectors and switching status of switches of a 2-level 3-phase inverter having eight available switching vectors (Vo ...V7). The zero sequence voltage is dependent on both the inductance variance and the inverter configuration due to switching status. Therefore by investigating the zero sequence voltage profile at each switching status, the appropriate combination can be derived to produce unbalanced three phase inductances at every switching instance. [0039] FIGS. 3-8 are circuit diagrams which represent possible three phase stator w inding configurations of stator windings with respect to the switching vectors shown in FIG. 2. [0040] FIG. 3 is a circuit diagram m which represents a three phase stator winding configuration of stator windings with respect to the switching vector Vi shown in FIG. 2. In FIG. 3, a voltage (Vdc) exists between node a and node be, an inductance (la) is coupled between node a and node n, an inductance (lb) is coupled between node n and node b, and , an inductance (lc) is coupled between node n and node c. [0041] FIG. 4 is a circuit diagram which represents a three phase stator winding configuration of stator windings with respect to the switching vector V2 shown in FIG. 2. In FIG. 4, a voltage (Vdc) exists between node ab and node c, an inductance (la) is coupled between node a and node n, an inductance (lb) is coupled between node n and node b, and an inductance (lc) is coupled between node n and node c. [0042] FIG. 5 is a circuit diagram which represents a three phase stator winding configuration of stator windings with respect to the switching vector V3 shown in FIG. 2. In FIG. 5, a voltage (Vdc) exists between node b and node ac, an inductance (lb) is coupled between node b and node n, an inductance (la) is coupled between node n and node a, and an inductance (lc) is coupled between node n and node c. [0043] FIG. 6 is a circuit diagram which represents a three phase stator winding configuration of stator windings with respect to the switching vector V4 shown in FIG. 2. In FIG. 6, a voltage (Vdc) exists between node be and node a, an inductance (la) is coupled between node n and node a, an inductance (lb) is coupled between node n and node b, and an inductance (lc) is coupled between node n and node c. [0044] FIG. 7 is a circuit diagram which represents a three phase stator winding configuration of stator windings with respect to the switching vector V5 shown in FIG. 2. In FIG. 7, a voltage (Vdc) exists between node c and node ab, an inductance (lc) is coupled between node c and node n, an inductance (la) is coupled between node n and node a, and an inductance (lb) is coupled between node n and node b. [0045] FIG. 8 is a circuit diagram which represents a three phase stator winding configuration of stator windings with respect to the switching vector V6 shown in FIG. 2. In FIG. 3, a voltage (Vdc) exists between node ac and node b. an inductance (la) is coupled between node a and node n, an inductance (lb) is coupled between node n and node b, and an inductance (lc) is coupled between node n and node c. [0048] When the stator phase inductances ( l°l, ,l c) are equivalent, the sum of equation (11) is zero. However, when the stator inductances are different due to the saturation effect, the sum of equation (11) will not be zero and will have the information regarding the inductance variation. Similarly, the zero sequence voltage due to each voltage vector V2 ...Vs can be calculated as shown in equations (12) -(16). three phase-to-neutral voltages is shown as a function ot rotor angle, lhese voltage waveforms are generated from equations (6) through (8) with 10% variation of the average inductances (i.e. ° =0.1* s0) and 300V DC link voltage. The voltage Vs" is the sum of the three phase-to-neutral voltages resulting due to the voltage vector Vi. The voltages and " are the sums of three phase-to-neutral voltages resulting from the voltage vectors V3 and V5, respectively. FIG. 9 shows that the small change (i.e. 10%) in the stator inductance produces a strong voltage signal (±30V). The zero sequence voltage is directly related to the inductance variance, which is caused by the V V V stator saturation. The zero sequence voltages ( A-s", B-s" and c-s") are spatially separated by 120° and are of twice the rotor fundamental frequency. [0051] FIG. 10 is a graph showing a trace of vector (Vsn) which represents zero sequence voltages (VA sn,VBm andFc m) transformed to d- and q-axis stationary reference frame with an Alpha component and a Beta component of the zero sequence voltages plotted in x-y coordinates. In FIG. 10, these three signals are transformed to d-axis and q-axis stationary reference frame using the transformation as shown in equation (17). The Alpha and Beta component of the zero sequence voltages are plotted in x-y coordinate in figure 10. The traces periodically rotate along the circle with small distortion. [0052] FIG. 11 is a graph showing the phase of the vector (Vsn) represented by flux angle (9EstRaw) in FIG. 10. The flux angle (0EstRaw) is shown as a function of rotor angle. The flux angle (0EstRaw) is shown in equation (18). [0053] As shown in FIG. 11, the frequency is twice that of the rotor angle and the phase is synchronized with the rotor angle. The rotor angle can be derived using digital signal processing of the phase information. The result shows that the rotor angle can be estimated by measuring the three zero Implementation of Invention [0054] FIG. 12 is a block diagram of a control system which implements a sensorless algorithm using control hardware and an axial flux SMPMM. However, the same method is also valid for the general 3-phase synchronous motor, such as Brushless DC Motor (BLDC), Interior Permanent Magnet Synchronous Motor (IPMSM) and Reluctance Motors. [0055] The control system comprises a stator current converter 100, a motor 200, a voltage generator module 220, and an output module 240. [0056] In this implementation, the stator current converter 100 can receive a torque command (Te) and generate three-phase sinusoidal voltage commands (Vap...Vcp). The motor 200 can receive the three-phase sinusoidal voltage commands (Vap...Vcp) and generate the motor output (Vn). [0057] The voltage generator module 220 can receive the three-phase sinusoidal voltage commands (Vap...Vcp) and the motor output (Vn) and generate sampled three-phase zero-sequence voltages (VAsn ...VC_sn). [0058] The output module 240 can receive sampled three-phase zero- sequence voltages (VA_sn ...VCsn) and generate the final estimated rotor position angle (6r_est). [0059] According to one possible non-limiting implementation, components or modules which may be used to implement such a control system comprise a current mapping module (1), summer junctions (2) and (3), a current controller module (4), a synchronous-to-stationary conversion module (5), a Space Vector PWM module (6), a multiplexer module (7), a PWM inverter (8), a stationary-to-synchronous conversion module (9), an injection vector generator module (10), a 3-phase permanent magnet synchronous motor (11), a phase-neutral voltage calculator module (12), a summing junction (13), a zero sequence voltage sampling module (14), a three phase-to-two phase conversion module (15), an angle calculator module (16), a divider module (17), and an angle calibrator module (18). [0060] In one implementation, the stator current converter 100 comprises a torque-to-current mapping module (1), a current-controller module (4), a synchronous-to-stationary conversion module (5), a space-vector PWM module (6), an injection vector generator, a multiplexer (7), a PWM inverter (8), a stationary-to-synchronous conversion module (9), and a (10). [0061] The torque-to-current mapping module (1) can receive the torque command (Te) and generate the d-axis current command (Idse) and the q- axis current command (Iqse). The current-controller module (4) can receive the d-axis current error and the q-axis current error and generate the d-axis voltage command (Vdse) and the q-axis voltage command (Vqse), wherein the d-axis current error and the q-axis current error comprises a combination of the d-axis current command (Idse) and the q-axis current command (Iqse) and the synchronous reference frame currents (Iqse, Idse). [0062] The synchronous-to-stationary conversion module (5) can receive the d-axis voltage command (Vdse) and the q-axis voltage command (Vqse) and the final estimated rotor position angle (Grest) and generate the three- phase sinusoidal voltage commands (Va...Vc). The space-vector PWM module (6) can receive the three-phase sinusoidal voltage commands (Va...Vc) and generate switching vectors (Sa...Sc). [0063] The injection vector generator (10) can generate injection vectors (Sia...Sic). The multiplexer (7) can receive switching vectors (Sa...Sc) and injection vectors (Sia...Sic) and generate modified switching vectors (Sa'...Sc'). The PWM inverter (8) can receive modified switching vectors (Sa'...Sc') and generate the three-phase sinusoidal voltage commands (Vap...Vcp) which can be converted to resultant stator currents (Ias...Ics). [0064] The stationary-to-synchronous conversion module (9) can receive resultant stator currents (Ias...Ics) and (0r_Est) and generate the synchronous reference frame currents (Iqse, Idse). [0065] In one implementation, the motor 200 comprises a three-phase permanent-magnet synchronous motor (PMSM) (11) configured to receive the three-phase sinusoidal voltage commands (Vap...Vcp) and generate a motor output (Vn). [0066] In one implementation, the voltage generator module 220 comprises a phase-to-neutral voltage generator (12), a summing junction (13), and a sampler module (14). The phase-to-neutral voltage generator (12) can receive the three-phase sinusoidal voltage commands (Vap...Vcp) and the motor output (Vn) and can generate the machine phase voltages (Van...Vcn). The summing junction (13) can receive the machine phase voltages (Van...Vcn) and generate the zero-sequence voltage (Vsn). The sampler module (14) can receive the zero-sequence voltage (Vsn) and generate sampled three-phase zero-sequence voltages (VAsn ...VCsn). [0067] In one implementation, the output module 240 comprises a three- to-to converter module (15), an angle calculator module (16), an angle converter module (17), and an angle calibrator module (18). The three-to-to converter module (15) can receive the sampled three-phase zero-sequence voltages (VAsn ...VC_sn) and generate two-phase zero-sequence voltages (VAlphasn). The angle calculator module (16) can receive two-phase zero- sequence voltages (VAlpha_sn) and generate angle of the saturation induced saliency. The angle converter module (17) can receive angle of the saturation induced saliency and generate rotor position angle (OEstRaw). [0068] The angle calibrator module (18) can receive rotor position angle (GEstRaw) and generate the final estimated rotor position angle (0r_est). Operation of Control System [0069] The current mapping module (1) is coupled to summer junctions (2) and (3), which are coupled to a current controller module (4) and receive the output of the stationary-to-synchronous conversion module (9). Torque command (Te) is passed to torque to current mapping module (1) which generates the d and q axes current commands Idse and Iqse* respectively. These current commands are added to the feedback measured current Idse and Iqse via the summer junctions (2) and (3) respectively. The d and q-axes current error is fed to current controller module (4) which generates the d and q-axes voltage commands Vdse* and Vqse* respectively. [0070] The output voltage commands are processed through synchronous to stationary conversion module (5) to generate three phase sinusoidal voltage commands Va, Vb and Vc. The synchronous-to-stationary conversion module (5) receives inputs from the current controller module (4) and the angle calibrator module (18), and generates outputs sent to the Space Vector PWM module (6). The Space Vector PWM module (6) uses the output of the synchronous-to-stationary conversion module (5) to generate inputs for the multiplexer module (7) which also receives inputs from the injection vector generator module (10). [0071] FIGS. 13-15 are a series of graphs showing synthesis of normal Space Vector PWM (SVPWM) waveform and injecting vectors. It should be appreciated that there are several different choices in the sequence of the injecting vectors and the position of injecting vectors. In this example, the injecting vectors (Sia, Sib and Sic) are positioned at the center of the zero vector (V7( 1,1,1)) in the SVPWM waveforms. The two complementary vectors (VI-V4, V3-V5 and V5-V2) are injected sequentially to minimize the deviation of motor currents. [0072] FIG. 13 is a graph showing injecting vectors (Sia, Sib and Sic) for zero sequence voltage measurement. These voltage commands are then converted to switching states (Sa, Sb and Sc) for phases A, B and C respectively via Space Vector PWM module (6). FIG. 14 is a graph showing a normal Space Vector PWM (SVPWM) waveform for current control with switching states (Sa, Sb and Sc) for phases A, B and C, respectively. [0073] Referring again to FIG. 12, the multiplexer module (7) generates inputs for the PWM inverter (8). The multiplexer module (7) modifies these switching vectors with injection vectors Sia, Sib and. Sic generated by module (10). The modified switching vectors Sa', Sb' and Sc' are then used to switch the IGBT switches in PWM inverter (8) to generate three phase sinusoidal voltage commands. FIG. 15 is a graph showing a synthesized PWM waveform with modified switching vectors (Sa', Sb' and Sc') used to switch IGBT switches in PWM inverter to generate three phase sinusoidal voltage commands. [0074] Referring again to FIG. 12, the output generated by the PWM inverter (8) is supplied to the 3-phase permanent magnet synchronous motor (11) to generate the commanded torque Te and to the phase-neutral voltage calculator module (12). The resultant stator currents (las, lbs and Ics) are sensed, sampled and passed to the stationary-to-synchronous conversion module (9). The output of the stationary-to-synchronous conversion module (9) is synchronous reference frame currents (Iqse and Ids6) which are supplied to the summing junctions (2) and (3) to generate the current errors (Iqse* and Ids6*). [0075] Machine terminal phase voltages (Van, Vbn and Vcn) are measured with respect to the neutral point and supplied to the phase-neutral voltage calculator module (12). The phase-neutral voltage calculator module (12) receives the output of both the PWM inverter (8) and the 3-phase permanent magnet synchronous motor (11), and uses these to generate phase to neutral voltages (Van, Vbn, Vcn) which are provided to the summing junction (13). [0076] The summing junction (13) combines the input signals (Van, Vbn, Vcn) to generate a zero sequence voltage (Vsn). The zero sequence voltage (Vsn) is supplied to zero sequence voltage sampling module (14). The zero sequence voltage sampling module (14) samples the zero sequence voltages for each of the three phases to align the sample with the injected vector. The zero sequence voltage sampling module (14) samples the zero sequence voltage (Vsn) according to injecting sequence, and generates three-phase zero sequence voltages (VAsn, VB_Sn, Vc_sn), which are supplied to a three phase- to-two phase conversion module (15) for three phase to two phase conversion. [0077] The three phase-to-two phase conversion module (15) converts the three-phase zero sequence voltages (VA_Sn, Vssn, Vc_sn) to two-phase voltages (VAipha.sn, Vseta.sn), which are then passed through to the angle calculator module (16). The output of module (16) is the angle of the saturation induced saliency which is of the twice the fundamental frequency. The divider module (17) converts this signal to the rotor position angle by dividing with 2. The estimated raw rotor position is passed to an angle calibrator module (18) to calculate the final estimated rotor position angle 0r_Est. Experimental Results: [0078] The proposed sensorless algorithm of FIG. 12 was implemented and tested using a General Motors prototype traction control hardware which includes the motor controller and 50 kW axial flux wheel hub motor or SMPMM. The experimental results are shown in FIGS. 16-19. [0079] FIG. 16 is a graph showing three phase saturation induced (zero sequence voltage) signals at no load condition when no load torque is applied. In this example, Vdc=300V, 60 rpm, Width=9us, SampDelay=9uS, Te = 0, [50V/div]. The experimental results shown in FIG. 16 illustrate strong zero sequence signals which can be used to deduce the rotor position. Thus, robust rotor position estimation is possible. [0080] FIG. 17 is a graph showing three phase saturation induced (zero sequence voltage) signals at a 40% load condition when no load torque is applied. In this example, Vdc=300V, 60 rpm, Width=9us, SampDelay=9uS, Te = 200 Nm. Chi: Measured rotor cosition f2.5rad/sec/divl Ch2.3.4: illustrate that even under loaded condition the zero sequence signal strength is maintained. The test results under loaded condition exhibit additional harmonic contents which can be eliminated to estimate the second order harmonic (i.e., saturation induced saliency component) to estimate the rotor position. [0081] FIG. 18 is a graph showing measured and estimated rotor position angles with two phase saturation induced signals at no load condition when no load torque is applied. In this example, Vdc=300V, 60 rpm, Width=9us, SampDelay=9uS, Te = 0 Nm, Chi,2: Measured and estimated rotor position showing measured and estimated rotor position angles with two phase saturation induced signals at full load condition when 100% load torque is applied. In this example, Vdc=300V, 60 rpm, Width=9us, SampDelay=9uS, Te = 500 Nm, Chi,2: Measured and estimated rotor position [2.5rad/sec/div], Ch3,4: VMpha_, and Bttajm [50V/div]. The experimental results shown in FIGS. 18 and 19, show that under no load and full load conditions the estimated rotor position signal exhibits excellent performance. [0082] The sequence of the text in any of the claims does not imply that process steps must be performed in a temporal or logical order according to such sequence unless it is specifically defined by the language of the claim. The process steps may be interchanged in any order without departing from the scope of the invention as long as such an interchange does not contradict the claim language and is not logically nonsensical. Furthermore, numerical ordinals such as "first," "second," "third," etc. simply denote different singles of a plurality and do not imply any order or sequence unless specifically defined by the claim language. [0083] Furthermore, words such as "connect" or "coupled to" used in describing a relationship between different elements do not imply that a direct physical connection must be made between these elements. For example, two elements may be connected to each other physically, electronically, logically, or in any other manner, through one or more additional elements, without departing from the scope of the invention. [0084] Those of skill in the art would understand that information and signals may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the above description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof. [0085] Those of skill would further appreciate that the various illustrative logical blocks, modules, circuits, and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention. [0086] The various illustrative logical blocks, modules, and circuits described in connection with the embodiments disclosed herein may be implemented or performed with a general purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general-purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration. The word "exemplary" is used exclusively herein to mean "serving as an example, instance, or illustration." Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments. [0087] The steps of a method or algorithm described in connection with the embodiments disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. An exemplary storage medium is coupled to the processor such the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium may be integral to the processor. The processor and the storage medium may reside in an ASIC. The ASIC may reside in a user terminal. In the alternative, the processor and the storage medium may reside as discrete components in a user terminal. [0088] While at least one exemplary embodiment has been presented in the foregoing detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing the exemplary embodiment or exemplary embodiments. It should be understood that various changes can be made in the function and arrangement of elements without departing from the scope of the invention as set forth in the appended claims and the legal equivalents thereof. CLAIMS What is claimed is: 1. A method, comprising: receiving a torque command; generating three-phase voltage commands based on the torque command; generating a motor output responsive to the three-phase voltage commands; and generating three-phase zero-sequence voltage samples based on the three-phase voltage commands and the motor output. 2. A method according to claim 1, further comprising: generating a final estimated rotor position angle output based on sampled three-phase zero-sequence voltages. 3. A method according to claim 1, wherein generating three-phase zero-sequence voltage samples further comprises: generating machine phase voltages based on the three-phase voltage commands and the motor output; summing the machine phase voltages to generate a zero-sequence voltage; and sampling the zero-sequence voltages to generate the three-phase zero-sequence voltage samples. 4. A method according to claim 2, wherein generating a final estimated rotor position angle output comprises: converting the sampled three-phase zero-sequence voltages into two-phase zero-sequence voltages; calculating the angle of the saturation induced saliency based on the two-phase zero-sequence voltages; converting the angle of the saturation induced saliency into a rotor position angle; and generating a final estimated rotor position angle output based on the rotor position angle. 5. A method according to claim 1, wherein generating three-phase voltage commands based on the torque command comprises: generating a d-axis current command and a q-axis current command based on the torque command; generating a d-axis voltage command and a q-axis voltage command based on a d-axis current error comprising a combination of the d- axis current command and the synchronous reference frame currents and a q- axis current error comprising a combination of the q-axis current command and the synchronous reference frame currents; generating three-phase sinusoidal voltage commands based on the d-axis voltage command, the q-axis voltage command and the final estimated rotor position angle; generating switching vectors based on the three-phase sinusoidal voltage commands; generating modified switching vectors by multiplexing the switching vectors and the injection vectors; and generating three-phase voltage commands and resultant stator currents based on the modified switching vectors. 6. A computer program product for executing the method of claim 5. 7. A system, comprising a voltage generator configured to receive voltage commands and a motor output, and configured to generate sampled zero-sequence voltages in response to the voltage commands and the motor output. 8. A system according to claim 7, further comprising a motor configured to receive the voltage commands and generate the motor output. 9. A system according to claim 8, further comprising an output element configured to receive the sampled zero-sequence voltages and configured to generate a final estimated rotor position angle. 10. A system according to claim 9, wherein: the voltage generator is configured to receive the voltage commands and the motor output, and to generate the machine phase voltages; the voltage generator comprises a summing junction configured to receive the machine phase voltages and generate the zero-sequence voltage; and the voltage generator comprises a sampler configured to receive the zero-sequence voltage and generate sampled zero-sequence voltages. 11. A system according to claim 10, wherein the output element comprises: a converter configured to receive sampled zero-sequence voltages and generate two-phase zero-sequence voltages; a processor configured to: receive two-phase zero-sequence voltages and generate angle of the saturation induced saliency; receive angle of the saturation induced saliency and generate rotor position angle; and receive rotor position angle and generate the final estimated rotor position angle. 12. A system according to claim 11, further comprising a current converter configured to receive a torque command and generate the voltage commands. 13. A system according to claim 11, wherein the current converter comprises: a mapper configured to receive the torque command and generate the d-axis current command and the q-axis current command; 5 a current-controller configured to receive the d-axis current error and the q-axis current error and generate the d-axis voltage command and the q-axis voltage command, wherein the d-axis current error and the q-axis current error comprises a combination of the d-axis current command and the q-axis current command and the synchronous reference frame currents; a first converter configured to receive the d-axis voltage command and the q-axis voltage command and the final estimated rotor position angle and generate the sinusoidal voltage commands; a vector generator configured to receive the sinusoidal voltage commands and generate switching vectors and to generate injection vectors; a combiner configured to receive the switching vectors and the injection vectors and generate modified switching vectors; an inverter configured to receive modified switching vectors and generate the voltage commands which are also converted to resultant stator currents; and a second converter configured to receive resultant stator currents and generate the synchronous reference frame currents. 14. A system according to claim 8, wherein the motor comprises a permanent-magnet synchronous motor (PMSM) configured to receive the voltage commands and generate a motor output. 15. A system, comprising a voltage generator module configured to receive three-phase voltage commands and a motor output, and configured to generate sampled three-phase zero-sequence voltages in response to the three- 5 phase voltage commands and the motor output. 16. A system according to claim 15, further comprising a motor configured to receive the three-phase voltage commands and generate the motor output. 17. A system according to claim 16, further comprising an output module configured to receive the sampled three-phase zero-sequence voltages and generate a final estimated rotor position angle. 18. A system according to claim 17, wherein the voltage generator module comprises: a phase-to-neutral voltage generator configured to receive the three-phase voltage commands and the motor output and to generate the machine phase voltages; a summing junction configured to receive the machine phase voltages and generate the zero-sequence voltage; and a sampler module configured to receive the zero-sequence voltage and generate sampled three-phase zero-sequence voltages. 19. A system according to claim 18, wherein the output module comprises: a three-to-to converter module configured to receive sampled three- phase zero-sequence voltages and generate two-phase zero-sequence voltages; an angle calculator module configured to receive two-phase zero- sequence voltages and generate angle of the saturation induced saliency; an angle converter module configured to receive angle of the saturation induced saliency and generate rotor position angle; and an angle calibrator module configured to receive rotor position angle and generate the final estimated rotor position angle. 20. A system according to claim 19, further comprising a stator current converter configured to receive a torque command and generate the three-phase voltage commands. 21. A system according to claim 15, wherein the stator current converter comprises: a torque-to-current mapping module configured to receive the torque command and generate the d-axis current command and the q-axis current command; a current-controller module configured to receive the d-axis current error and the q-axis current error and generate the d-axis voltage command and the q-axis voltage command, wherein the d-axis current error and the q- axis current error comprises a combination of the d-axis current command and the q-axis current command and the synchronous reference frame currents; a synchronous-to-stationary conversion module configured to receive the d-axis voltage command and the q-axis voltage command and the final estimated rotor position angle and generate the three-phase sinusoidal voltage commands; a space-vector PWM module configured to receive the three-phase sinusoidal voltage commands and generate switching vectors; an injection vector generator configured to generate injection vectors; a multiplexer configured to receive switching vectors and injection vectors and generate modified switching vectors; a PWM inverter configured to receive modified switching vectors and generate the three-phase voltage commands which is converted to resultant stator currents; and a stationary-to-synchronous conversion module configured to receive resultant stator currents and generate the synchronous reference frame currents. 22. A system according to claim 16, wherein the motor comprises a three-phase permanent-magnet synchronous motor (PMSM) configured to receive the three-phase voltage commands and generate a motor output. Methods and apparatus are provided for generating zero- sequence voltages based on voltage commands and a motor output signal. At least one of the methods includes, but is not limited to, receiving a torque command and generating three-phase voltage commands based on the torque command. The method also includes, but is not limited to, generating a motor output responsive to the three-phase voltage commands and generating three- phase zero-sequence voltage samples based on the three-phase voltage commands and the motor output.

Full Text

METHOD AND APPARATUS FOR SENSORLESS POSITION CONTROL
OF A PERMANENT MAGNET SYNCHRONOUS MOTOR (PMSM)
DRIVE SYSTEM
TECHNICAL FIELD
[0001] The present invention generally relates to control systems and
power inverter modules, and, more particularly, to control systems, methods
and apparatus for control of a PMSM drive system.
BACKGROUND OF THE INVENTION
[0002] An electric traction drive system typically includes a power
inverter module (PIM) and an AC motor.
[0003] Many common sensorless position control methods of a traction
drive systems either rely on spatial variation of rotor saliency of a rotor of the
drive system or Back EMF of the inherent saliency machine of the drive
system. These methods are more suitable with Interior Permanent Magnet
Synchronous Motor (IPMSM), Synchronous Reluctance Motor and Switched
Reluctance Motor machine types which inherently have magnetically salient
rotors.
[0004] Other methods of detecting rotor angular position include high
frequency signal injection and modified PWM test pulse excitation.
[0005] In the high frequency signal injection method, a balanced high
frequency test signal, such as a voltage or current signal, can be injected on a
stator winding of an inherently salient machine and the resultant effect of the
balanced high frequency test signal on stator current can be measured. The
effect of the balanced high frequency test signal injection can be observed in a
measured stator current which takes the form of amplitude modulation at two
times the fundamental frequency rate. This effect is due to the spatial
modulation of the magnetic saliency as the rotor rotates. This method works
quite well when the machine under test has inherent saliency, such as an

Interior Permanent Magnet type machine. However, Surface Mount
Permanent Magnet (SMPM) machines have no saliency and therefore require
a very high magnitude injection signal in order to retrieve the position
information. Thus, due to additional losses and noise generated by such a high
magnitude injection signal, this method is not suitable for SMPM type
application.
[0006] In the modified PWM test pulse excitation method, modified PWM
test pulses can be used to excite the high frequency impedance of the machine.
When PWM test pulses are injected, the current control is ignored for the test
period. This can be a good method for an industrial drive. However, a
traction machine has low inductance and not controlling current during test
period may result in an uncontrolled condition. This technique retrieves the
position information from sensed stator current which must be sampled
immediately after injecting the test pulses. This increases number of times the
stator current is being sampled.
[0007] According to another method of rotor position estimation discussed
in European patent # EP 0962045 Bl, the resultant effect of modified PWM
test pulses on leakage inductances can be measured via a measured phase to
neutral voltage of an induction machine. This technique utilizes the property
of a squirrel cage type rotor construction in an induction machine. By
injecting the PWM test pulses, the "mechanical" saliency induced due to the
rotor bars of the induction machine can be utilized. A saliency image rotates as
the rotor rotates and this information can be used to deduce rotor position
information.
[0008] However, magnetic saliency is not a feature of a Surface Mount
Permanent Magnet Motor (SMPMM). Thus, position sensorless control for a
SMPMM can be challenging.
[0009] A high performance permanent magnet ("PM") machine drive
system requires an absolute position sensor which is an expensive component.
Moreover, the circuitry required to process its signals can also be expensive.
It would be desirable to eliminate this position sensor. It would also be
desirable to eliminate mechanical interface hardware, reduce cost and weight,

reduce cost and weight and improve the reliability of an electric traction drive
system. Other desirable features and characteristics of the present invention
will become apparent from the subsequent detailed description and the
appended claims, taken in conjunction with the accompanying drawings and
the foregoing technical field and background.
DESCRIPTION OF THE DRAWINGS
[0010] The present invention will be described in conjunction with the
following drawing figures, wherein like numerals denote like elements, and
[0011] FIG. 1 is a diagram of a simple 2-pole SMPMM showing a
configuration of stator windings a, b, c and a PM;
[0012| FIG. 2 is a diagram which illustrates switching vectors and
switching status of switches of a 2-level 3-phase inverter having eight
available switching vectors;
[0013] FIG. 3 is a circuit diagram which represents a three phase stator
winding configuration of stator windings with respect to the switching vector
V1 shown in FIG. 2;
[0014] FIG. 4 is a circuit diagram which represents a three phase stator
winding configuration of stator windings with respect to the switching vector
V2 shown in FIG. 2;
[0015] FIG. 5 is a circuit diagram which represents a three phase stator
winding configuration of stator windings with respect to the switching vector
V3 shown in FIG. 2;
[0016] FIG. 6 is a circuit diagram which represents a three phase stator
winding configuration of stator windings with respect to the switching vector
V4 shown in FIG. 2;
[0017] FIG. 7 is a circuit diagram which represents a three phase stator
winding configuration of stator windings with respect to the switching vector
V5 shown in FIG. 2;
[0018] FIG. 8 is a circuit diagram which represents a three phase stator
winding configuration of stator windings with respect to the switching vector
V6 shown in FIG. 2;

and q-axis stationary reference frame with an Alpha component and a Beta
component of the zero sequence voltages plotted in x-y coordinates;
[0021] FIG. 11 is a graph showing the phase of the vector (Vsn)
represented by 0EstRaw (Flux angle) in FIG. 10;
[0022] FIG. 12 is a block diagram of a control system which implements a
sensorless algorithm using control hardware and 50 kW axial flux SMPMM;
[0023] FIG. 13 is a graph showing injecting vectors (Sia, Sib and Sic) for
zero sequence voltage measurement;
[0024] FIG. 14 is a graph showing a normal Space Vector PWM
(SVPWM) waveform for current control with switching states (Sa, Sb and Sc)
for phases A, B and C, respectively;
[0025] FIG. 15 is a graph showing a synthesized PWM waveform with
modified switching vectors (Sa*, Sb* and Sc*) used to switch IGBT switches
in PWM inverter to generate three phase sinusoidal voltage commands;
[0026] FIG. 16 is a graph showing three phase saturation induced (zero
sequence voltage) signals at no load condition when no load torque is applied;
[0027] FIG. 17 is a graph showing three phase saturation induced (zero
sequence voltage) signals at a 40% load condition when no load torque is
applied;
[0028] FIG. 18 is a graph showing measured and estimated rotor position
angles with two phase saturation induced signals at no load condition when no
load torque is applied; and
[0029] FIG. 19 is a graph showing measured and estimated rotor position
angles with two phase saturation induced signals at full load condition when
100% load torque is applied.

DESCRIPTION OF AN EXEMPLARY EMBODIMENT
[0030] The following detailed description is merely exemplary in nature
and is not intended to limit the invention or the application and uses of the
invention. Furthermore, there is no intention to be bound by any expressed or
implied theory presented in the preceding technical field, background, brief
summary or the following detailed description. The word "exemplary" is
used herein to mean "serving as an example, instance, or illustration." Any
embodiment described herein as "exemplary" is not necessarily to be
construed as preferred or advantageous over other embodiments. All of the
embodiments described in this Detailed Description are exemplary
embodiments provided to enable persons skilled in the art to make or use the
invention and not to limit the scope of the invention which is defined by the
claims.
Overview
[0031] Embodiments of the present invention provide methods and
apparatus that allow for generating of zero-sequence voltages based on voltage
commands and a motor output signal.
[0032] It has been observed that the PM (permanent magnet) in rotor and
the stator electric circuit can cause a saturation effect of a stator core due to
the magnetic flux. The saturation affects the inductance of three phase
windings. For example, in an iron-based stator core, the more saturated
winding has a lower inductance. Therefore if the inductance variation of the
three phase winding is measured, stator flux information can be determined.
The stator flux of the permanent magnet synchronous motor is represented in a
stationary reference frame by equation (1), where are d-axis and q-
axis stator flux linkage, respectively, pM is the stator flux linkage of the
permanent magnet, are the d-axis and q-axis stator current, and is
the rotor angle.

[0033] If the stator current and inductances are known, the rotor-oriented
component of the stator flux can be derived among the total stator flux, and
then the rotor flux angle can be calculated.
[0034] FIG. 1 is a diagram of a simple 2-pole SMPMM in a showing a
configuration of stator windings a, b, c and a PM. FIG. 1 describes the
relation between the stator inductance variation and the zero sequence voltage
which is the sum of the phase to neutral voltages of phase A, B and C of the
motor. For simplicity the 2 pole machine is used for the analysis, however, it
should be appreciated that a similar analysis would apply to higher pole
machines.
[0035] The variation of the stator inductance in the motor depends on the
flux distribution of the PM and the electromagnetic design magnetic design.

[0036] In equations (3)-(5), is the average stator inductance,
a is the coefficient of stator inductance variance, and is a periodic
function with period of 7t. The stator inductances of a SMPMM for example
can be assumed as:

[0037] To obtain stator inductance variance information, this embodiment
utilizes the zero sequence voltage components. When the three inductances of
phase A, B and C are equivalent, the zero sequence voltage component is zero.
However, if the inductances are not equivalent, it has a value according to the
configuration of the inverter switches. This condition may occur due to the
main flux saturation. The main flux is composed of the stator and the rotor
PM flux. Thus by observing the zero sequence voltage, the rotor position
information can be deduced.
Inverter Switching Configuration
[0038] FIG. 2 is a diagram which illustrates switching vectors and
switching status of switches of a 2-level 3-phase inverter having eight
available switching vectors (Vo ...V7). The zero sequence voltage is
dependent on both the inductance variance and the inverter configuration due
to switching status. Therefore by investigating the zero sequence voltage
profile at each switching status, the appropriate combination can be derived to
produce unbalanced three phase inductances at every switching instance.
[0039] FIGS. 3-8 are circuit diagrams which represent possible three phase
stator w inding configurations of stator windings with respect to the switching
vectors shown in FIG. 2.
[0040] FIG. 3 is a circuit diagram m which represents a three phase stator
winding configuration of stator windings with respect to the switching vector
Vi shown in FIG. 2. In FIG. 3, a voltage (Vdc) exists between node a and
node be, an inductance (la) is coupled between node a and node n, an

inductance (lb) is coupled between node n and node b, and , an inductance (lc)
is coupled between node n and node c.
[0041] FIG. 4 is a circuit diagram which represents a three phase stator
winding configuration of stator windings with respect to the switching vector
V2 shown in FIG. 2. In FIG. 4, a voltage (Vdc) exists between node ab and
node c, an inductance (la) is coupled between node a and node n, an inductance
(lb) is coupled between node n and node b, and an inductance (lc) is coupled
between node n and node c.
[0042] FIG. 5 is a circuit diagram which represents a three phase stator
winding configuration of stator windings with respect to the switching vector
V3 shown in FIG. 2. In FIG. 5, a voltage (Vdc) exists between node b and
node ac, an inductance (lb) is coupled between node b and node n, an
inductance (la) is coupled between node n and node a, and an inductance (lc) is
coupled between node n and node c.
[0043] FIG. 6 is a circuit diagram which represents a three phase stator
winding configuration of stator windings with respect to the switching vector
V4 shown in FIG. 2. In FIG. 6, a voltage (Vdc) exists between node be and
node a, an inductance (la) is coupled between node n and node a, an inductance
(lb) is coupled between node n and node b, and an inductance (lc) is coupled
between node n and node c.
[0044] FIG. 7 is a circuit diagram which represents a three phase stator
winding configuration of stator windings with respect to the switching vector
V5 shown in FIG. 2. In FIG. 7, a voltage (Vdc) exists between node c and
node ab, an inductance (lc) is coupled between node c and node n, an
inductance (la) is coupled between node n and node a, and an inductance (lb) is
coupled between node n and node b.
[0045] FIG. 8 is a circuit diagram which represents a three phase stator
winding configuration of stator windings with respect to the switching vector
V6 shown in FIG. 2. In FIG. 3, a voltage (Vdc) exists between node ac and
node b. an inductance (la) is coupled between node a and node n, an
inductance (lb) is coupled between node n and node b, and an inductance (lc) is
coupled between node n and node c.

[0048] When the stator phase inductances ( l°l, *,l c) are equivalent, the
sum of equation (11) is zero. However, when the stator inductances are
different due to the saturation effect, the sum of equation (11) will not be zero
and will have the information regarding the inductance variation. Similarly,
the zero sequence voltage due to each voltage vector V2 ...Vs can be
calculated as shown in equations (12) -(16).

three phase-to-neutral voltages is shown as a function ot rotor angle, lhese
voltage waveforms are generated from equations (6) through (8) with 10%
variation of the average inductances (i.e. ° =0.1* s0) and 300V DC link
voltage. The voltage Vs" is the sum of the three phase-to-neutral voltages
resulting due to the voltage vector Vi. The voltages and " are the
sums of three phase-to-neutral voltages resulting from the voltage vectors V3
and V5, respectively. FIG. 9 shows that the small change (i.e. 10%) in the
stator inductance produces a strong voltage signal (±30V). The zero sequence
voltage is directly related to the inductance variance, which is caused by the
V V V
stator saturation. The zero sequence voltages ( A-s", B-s" and c-s") are
spatially separated by 120° and are of twice the rotor fundamental frequency.
[0051] FIG. 10 is a graph showing a trace of vector (Vsn) which
represents zero sequence voltages (VA sn,VBm andFc m) transformed to d-
and q-axis stationary reference frame with an Alpha component and a Beta
component of the zero sequence voltages plotted in x-y coordinates. In FIG.
10, these three signals are transformed to d-axis and q-axis stationary
reference frame using the transformation as shown in equation (17). The

Alpha and Beta component of the zero sequence voltages are plotted in x-y
coordinate in figure 10. The traces periodically rotate along the circle with
small distortion.

[0052] FIG. 11 is a graph showing the phase of the vector (Vsn)
represented by flux angle (9EstRaw) in FIG. 10. The flux angle (0EstRaw) is
shown as a function of rotor angle. The flux angle (0EstRaw) is shown in
equation (18).

[0053] As shown in FIG. 11, the frequency is twice that of the rotor angle
and the phase is synchronized with the rotor angle. The rotor angle can be
derived using digital signal processing of the phase information. The result
shows that the rotor angle can be estimated by measuring the three zero

Implementation of Invention
[0054] FIG. 12 is a block diagram of a control system which implements a
sensorless algorithm using control hardware and an axial flux SMPMM.
However, the same method is also valid for the general 3-phase synchronous
motor, such as Brushless DC Motor (BLDC), Interior Permanent Magnet
Synchronous Motor (IPMSM) and Reluctance Motors.
[0055] The control system comprises a stator current converter 100, a
motor 200, a voltage generator module 220, and an output module 240.

[0056] In this implementation, the stator current converter 100 can receive
a torque command (T*e) and generate three-phase sinusoidal voltage
commands (Vap...Vcp). The motor 200 can receive the three-phase sinusoidal
voltage commands (Vap...Vcp) and generate the motor output (Vn).
[0057] The voltage generator module 220 can receive the three-phase
sinusoidal voltage commands (Vap...Vcp) and the motor output (Vn) and
generate sampled three-phase zero-sequence voltages (VAsn ...VC_sn).
[0058] The output module 240 can receive sampled three-phase zero-
sequence voltages (VA_sn ...VCsn) and generate the final estimated rotor
position angle (6r_est).
[0059] According to one possible non-limiting implementation,
components or modules which may be used to implement such a control
system comprise a current mapping module (1), summer junctions (2) and (3),
a current controller module (4), a synchronous-to-stationary conversion
module (5), a Space Vector PWM module (6), a multiplexer module (7), a
PWM inverter (8), a stationary-to-synchronous conversion module (9), an
injection vector generator module (10), a 3-phase permanent magnet
synchronous motor (11), a phase-neutral voltage calculator module (12), a
summing junction (13), a zero sequence voltage sampling module (14), a three
phase-to-two phase conversion module (15), an angle calculator module (16),
a divider module (17), and an angle calibrator module (18).
[0060] In one implementation, the stator current converter 100 comprises a
torque-to-current mapping module (1), a current-controller module (4), a
synchronous-to-stationary conversion module (5), a space-vector PWM
module (6), an injection vector generator, a multiplexer (7), a PWM inverter
(8), a stationary-to-synchronous conversion module (9), and a (10).
[0061] The torque-to-current mapping module (1) can receive the torque
command (T*e) and generate the d-axis current command (Idse*) and the q-
axis current command (Iqse*). The current-controller module (4) can receive
the d-axis current error and the q-axis current error and generate the d-axis
voltage command (Vdse*) and the q-axis voltage command (Vqse*), wherein

the d-axis current error and the q-axis current error comprises a combination
of the d-axis current command (Idse*) and the q-axis current command (Iqse*)
and the synchronous reference frame currents (Iqse, Idse).
[0062] The synchronous-to-stationary conversion module (5) can receive
the d-axis voltage command (Vdse*) and the q-axis voltage command (Vqse*)
and the final estimated rotor position angle (Grest) and generate the three-
phase sinusoidal voltage commands (Va*...Vc*). The space-vector PWM
module (6) can receive the three-phase sinusoidal voltage commands
(Va*...Vc*) and generate switching vectors (Sa...Sc).
[0063] The injection vector generator (10) can generate injection vectors
(Sia...Sic). The multiplexer (7) can receive switching vectors (Sa...Sc) and
injection vectors (Sia...Sic) and generate modified switching vectors
(Sa'...Sc'). The PWM inverter (8) can receive modified switching vectors
(Sa'...Sc') and generate the three-phase sinusoidal voltage commands
(Vap...Vcp) which can be converted to resultant stator currents (Ias...Ics).
[0064] The stationary-to-synchronous conversion module (9) can receive
resultant stator currents (Ias...Ics) and (0r_Est) and generate the synchronous
reference frame currents (Iqse, Idse).
[0065] In one implementation, the motor 200 comprises a three-phase
permanent-magnet synchronous motor (PMSM) (11) configured to receive the
three-phase sinusoidal voltage commands (Vap...Vcp) and generate a motor
output (Vn).
[0066] In one implementation, the voltage generator module 220
comprises a phase-to-neutral voltage generator (12), a summing junction (13),
and a sampler module (14). The phase-to-neutral voltage generator (12) can
receive the three-phase sinusoidal voltage commands (Vap...Vcp) and the
motor output (Vn) and can generate the machine phase voltages (Van...Vcn).
The summing junction (13) can receive the machine phase voltages
(Van...Vcn) and generate the zero-sequence voltage (Vsn). The sampler
module (14) can receive the zero-sequence voltage (Vsn) and generate
sampled three-phase zero-sequence voltages (VAsn ...VCsn).

[0067] In one implementation, the output module 240 comprises a three-
to-to converter module (15), an angle calculator module (16), an angle
converter module (17), and an angle calibrator module (18). The three-to-to
converter module (15) can receive the sampled three-phase zero-sequence
voltages (VAsn ...VC_sn) and generate two-phase zero-sequence voltages
(VAlphasn). The angle calculator module (16) can receive two-phase zero-
sequence voltages (VAlpha_sn) and generate angle of the saturation induced
saliency. The angle converter module (17) can receive angle of the saturation
induced saliency and generate rotor position angle (OEstRaw).
[0068] The angle calibrator module (18) can receive rotor position angle
(GEstRaw) and generate the final estimated rotor position angle (0r_est).
Operation of Control System
[0069] The current mapping module (1) is coupled to summer junctions
(2) and (3), which are coupled to a current controller module (4) and receive
the output of the stationary-to-synchronous conversion module (9). Torque
command (T*e) is passed to torque to current mapping module (1) which
generates the d and q axes current commands Idse* and Iqse* respectively.
These current commands are added to the feedback measured current Idse and
Iqse via the summer junctions (2) and (3) respectively. The d and q-axes
current error is fed to current controller module (4) which generates the d and
q-axes voltage commands Vdse* and Vqse* respectively.
[0070] The output voltage commands are processed through synchronous
to stationary conversion module (5) to generate three phase sinusoidal voltage
commands Va*, Vb* and Vc*. The synchronous-to-stationary conversion
module (5) receives inputs from the current controller module (4) and the
angle calibrator module (18), and generates outputs sent to the Space Vector
PWM module (6). The Space Vector PWM module (6) uses the output of the
synchronous-to-stationary conversion module (5) to generate inputs for the
multiplexer module (7) which also receives inputs from the injection vector
generator module (10).

[0071] FIGS. 13-15 are a series of graphs showing synthesis of normal
Space Vector PWM (SVPWM) waveform and injecting vectors. It should be
appreciated that there are several different choices in the sequence of the
injecting vectors and the position of injecting vectors. In this example, the
injecting vectors (Sia, Sib and Sic) are positioned at the center of the zero
vector (V7( 1,1,1)) in the SVPWM waveforms. The two complementary
vectors (VI-V4, V3-V5 and V5-V2) are injected sequentially to minimize the
deviation of motor currents.
[0072] FIG. 13 is a graph showing injecting vectors (Sia, Sib and Sic) for
zero sequence voltage measurement. These voltage commands are then
converted to switching states (Sa, Sb and Sc) for phases A, B and C
respectively via Space Vector PWM module (6). FIG. 14 is a graph showing a
normal Space Vector PWM (SVPWM) waveform for current control with
switching states (Sa, Sb and Sc) for phases A, B and C, respectively.
[0073] Referring again to FIG. 12, the multiplexer module (7) generates
inputs for the PWM inverter (8). The multiplexer module (7) modifies these
switching vectors with injection vectors Sia, Sib and. Sic generated by module
(10). The modified switching vectors Sa', Sb' and Sc' are then used to switch
the IGBT switches in PWM inverter (8) to generate three phase sinusoidal
voltage commands. FIG. 15 is a graph showing a synthesized PWM waveform
with modified switching vectors (Sa', Sb' and Sc') used to switch IGBT
switches in PWM inverter to generate three phase sinusoidal voltage
commands.
[0074] Referring again to FIG. 12, the output generated by the PWM
inverter (8) is supplied to the 3-phase permanent magnet synchronous motor
(11) to generate the commanded torque Te* and to the phase-neutral voltage
calculator module (12). The resultant stator currents (las, lbs and Ics) are
sensed, sampled and passed to the stationary-to-synchronous conversion
module (9). The output of the stationary-to-synchronous conversion module
(9) is synchronous reference frame currents (Iqse and Ids6) which are supplied
to the summing junctions (2) and (3) to generate the current errors (Iqse* and
Ids6*).

[0075] Machine terminal phase voltages (Van, Vbn and Vcn) are
measured with respect to the neutral point and supplied to the phase-neutral
voltage calculator module (12). The phase-neutral voltage calculator module
(12) receives the output of both the PWM inverter (8) and the 3-phase
permanent magnet synchronous motor (11), and uses these to generate phase
to neutral voltages (Van, Vbn, Vcn) which are provided to the summing junction
(13).
[0076] The summing junction (13) combines the input signals (Van, Vbn,
Vcn) to generate a zero sequence voltage (Vsn). The zero sequence voltage
(Vsn) is supplied to zero sequence voltage sampling module (14). The zero
sequence voltage sampling module (14) samples the zero sequence voltages
for each of the three phases to align the sample with the injected vector. The
zero sequence voltage sampling module (14) samples the zero sequence
voltage (Vsn) according to injecting sequence, and generates three-phase zero
sequence voltages (VAsn, VB_Sn, Vc_sn), which are supplied to a three phase-
to-two phase conversion module (15) for three phase to two phase conversion.
[0077] The three phase-to-two phase conversion module (15) converts the
three-phase zero sequence voltages (VA_Sn, Vssn, Vc_sn) to two-phase voltages
(VAipha.sn, Vseta.sn), which are then passed through to the angle calculator
module (16). The output of module (16) is the angle of the saturation induced
saliency which is of the twice the fundamental frequency. The divider module
(17) converts this signal to the rotor position angle by dividing with 2. The
estimated raw rotor position is passed to an angle calibrator module (18) to
calculate the final estimated rotor position angle 0r_Est.
Experimental Results:
[0078] The proposed sensorless algorithm of FIG. 12 was implemented
and tested using a General Motors prototype traction control hardware which
includes the motor controller and 50 kW axial flux wheel hub motor or
SMPMM. The experimental results are shown in FIGS. 16-19.

[0079] FIG. 16 is a graph showing three phase saturation induced (zero
sequence voltage) signals at no load condition when no load torque is applied.
In this example, Vdc=300V, 60 rpm, Width=9us, SampDelay=9uS, Te = 0,

[50V/div]. The experimental results shown in FIG. 16 illustrate strong zero
sequence signals which can be used to deduce the rotor position. Thus, robust
rotor position estimation is possible.
[0080] FIG. 17 is a graph showing three phase saturation induced (zero
sequence voltage) signals at a 40% load condition when no load torque is
applied. In this example, Vdc=300V, 60 rpm, Width=9us, SampDelay=9uS,
Te = 200 Nm. Chi: Measured rotor cosition f2.5rad/sec/divl Ch2.3.4:

illustrate that even under loaded condition the zero sequence signal strength is
maintained. The test results under loaded condition exhibit additional
harmonic contents which can be eliminated to estimate the second order
harmonic (i.e., saturation induced saliency component) to estimate the rotor
position.
[0081] FIG. 18 is a graph showing measured and estimated rotor position
angles with two phase saturation induced signals at no load condition when no
load torque is applied. In this example, Vdc=300V, 60 rpm, Width=9us,
SampDelay=9uS, Te = 0 Nm, Chi,2: Measured and estimated rotor position

showing measured and estimated rotor position angles with two phase
saturation induced signals at full load condition when 100% load torque is
applied. In this example, Vdc=300V, 60 rpm, Width=9us, SampDelay=9uS,
Te = 500 Nm, Chi,2: Measured and estimated rotor position [2.5rad/sec/div],
Ch3,4: VMpha_, and Bttajm [50V/div]. The experimental results shown in
FIGS. 18 and 19, show that under no load and full load conditions the
estimated rotor position signal exhibits excellent performance.

[0082] The sequence of the text in any of the claims does not imply that
process steps must be performed in a temporal or logical order according to
such sequence unless it is specifically defined by the language of the claim.
The process steps may be interchanged in any order without departing from
the scope of the invention as long as such an interchange does not contradict
the claim language and is not logically nonsensical. Furthermore, numerical
ordinals such as "first," "second," "third," etc. simply denote different singles
of a plurality and do not imply any order or sequence unless specifically
defined by the claim language.
[0083] Furthermore, words such as "connect" or "coupled to" used in
describing a relationship between different elements do not imply that a direct
physical connection must be made between these elements. For example, two
elements may be connected to each other physically, electronically, logically,
or in any other manner, through one or more additional elements, without
departing from the scope of the invention.
[0084] Those of skill in the art would understand that information and
signals may be represented using any of a variety of different technologies and
techniques. For example, data, instructions, commands, information, signals,
bits, symbols, and chips that may be referenced throughout the above
description may be represented by voltages, currents, electromagnetic waves,
magnetic fields or particles, optical fields or particles, or any combination
thereof.
[0085] Those of skill would further appreciate that the various illustrative
logical blocks, modules, circuits, and algorithm steps described in connection
with the embodiments disclosed herein may be implemented as electronic
hardware, computer software, or combinations of both. To clearly illustrate
this interchangeability of hardware and software, various illustrative
components, blocks, modules, circuits, and steps have been described above
generally in terms of their functionality. Whether such functionality is
implemented as hardware or software depends upon the particular application
and design constraints imposed on the overall system. Skilled artisans may
implement the described functionality in varying ways for each particular

application, but such implementation decisions should not be interpreted as
causing a departure from the scope of the present invention.
[0086] The various illustrative logical blocks, modules, and circuits
described in connection with the embodiments disclosed herein may be
implemented or performed with a general purpose processor, a digital signal
processor (DSP), an application specific integrated circuit (ASIC), a field
programmable gate array (FPGA) or other programmable logic device,
discrete gate or transistor logic, discrete hardware components, or any
combination thereof designed to perform the functions described herein. A
general-purpose processor may be a microprocessor, but in the alternative, the
processor may be any conventional processor, controller, microcontroller, or
state machine. A processor may also be implemented as a combination of
computing devices, e.g., a combination of a DSP and a microprocessor, a
plurality of microprocessors, one or more microprocessors in conjunction with
a DSP core, or any other such configuration. The word "exemplary" is used
exclusively herein to mean "serving as an example, instance, or illustration."
Any embodiment described herein as "exemplary" is not necessarily to be
construed as preferred or advantageous over other embodiments.
[0087] The steps of a method or algorithm described in connection with
the embodiments disclosed herein may be embodied directly in hardware, in a
software module executed by a processor, or in a combination of the two. A
software module may reside in RAM memory, flash memory, ROM memory,
EPROM memory, EEPROM memory, registers, hard disk, a removable disk, a
CD-ROM, or any other form of storage medium known in the art. An
exemplary storage medium is coupled to the processor such the processor can
read information from, and write information to, the storage medium. In the
alternative, the storage medium may be integral to the processor. The
processor and the storage medium may reside in an ASIC. The ASIC may
reside in a user terminal. In the alternative, the processor and the storage
medium may reside as discrete components in a user terminal.

[0088] While at least one exemplary embodiment has been presented in
the foregoing detailed description, it should be appreciated that a vast number
of variations exist. It should also be appreciated that the exemplary
embodiment or exemplary embodiments are only examples, and are not
intended to limit the scope, applicability, or configuration of the invention in
any way. Rather, the foregoing detailed description will provide those skilled
in the art with a convenient road map for implementing the exemplary
embodiment or exemplary embodiments. It should be understood that various
changes can be made in the function and arrangement of elements without
departing from the scope of the invention as set forth in the appended claims
and the legal equivalents thereof.

CLAIMS
What is claimed is:
1. A method, comprising:
receiving a torque command;
generating three-phase voltage commands based on the torque
command;
generating a motor output responsive to the three-phase voltage
commands; and
generating three-phase zero-sequence voltage samples based on the
three-phase voltage commands and the motor output.
2. A method according to claim 1, further comprising:
generating a final estimated rotor position angle output based on
sampled three-phase zero-sequence voltages.
3. A method according to claim 1, wherein generating three-phase
zero-sequence voltage samples further comprises:
generating machine phase voltages based on the three-phase
voltage commands and the motor output;
summing the machine phase voltages to generate a zero-sequence
voltage; and
sampling the zero-sequence voltages to generate the three-phase
zero-sequence voltage samples.
4. A method according to claim 2, wherein generating a final
estimated rotor position angle output comprises:
converting the sampled three-phase zero-sequence voltages into
two-phase zero-sequence voltages;
calculating the angle of the saturation induced saliency based on
the two-phase zero-sequence voltages;

converting the angle of the saturation induced saliency into a rotor
position angle; and
generating a final estimated rotor position angle output based on
the rotor position angle.
5. A method according to claim 1, wherein generating three-phase
voltage commands based on the torque command comprises:
generating a d-axis current command and a q-axis current
command based on the torque command;
generating a d-axis voltage command and a q-axis voltage
command based on a d-axis current error comprising a combination of the d-
axis current command and the synchronous reference frame currents and a q-
axis current error comprising a combination of the q-axis current command
and the synchronous reference frame currents;
generating three-phase sinusoidal voltage commands based on the
d-axis voltage command, the q-axis voltage command and the final estimated
rotor position angle;
generating switching vectors based on the three-phase sinusoidal
voltage commands;
generating modified switching vectors by multiplexing the
switching vectors and the injection vectors; and
generating three-phase voltage commands and resultant stator
currents based on the modified switching vectors.
6. A computer program product for executing the method of claim 5.
7. A system, comprising a voltage generator configured to receive
voltage commands and a motor output, and configured to generate sampled
zero-sequence voltages in response to the voltage commands and the motor
output.

8. A system according to claim 7, further comprising a motor
configured to receive the voltage commands and generate the motor output.
9. A system according to claim 8, further comprising an output
element configured to receive the sampled zero-sequence voltages and
configured to generate a final estimated rotor position angle.
10. A system according to claim 9, wherein:
the voltage generator is configured to receive the voltage
commands and the motor output, and to generate the machine phase voltages;
the voltage generator comprises a summing junction configured to
receive the machine phase voltages and generate the zero-sequence voltage;
and
the voltage generator comprises a sampler configured to receive the
zero-sequence voltage and generate sampled zero-sequence voltages.
11. A system according to claim 10, wherein the output element
comprises:
a converter configured to receive sampled zero-sequence voltages
and generate two-phase zero-sequence voltages;
a processor configured to:
receive two-phase zero-sequence voltages and generate
angle of the saturation induced saliency;
receive angle of the saturation induced saliency and
generate rotor position angle; and
receive rotor position angle and generate the final estimated
rotor position angle.
12. A system according to claim 11, further comprising a current
converter configured to receive a torque command and generate the voltage
commands.

13. A system according to claim 11, wherein the current converter
comprises:
a mapper configured to receive the torque command and generate
the d-axis current command and the q-axis current command;
5 a current-controller configured to receive the d-axis current error
and the q-axis current error and generate the d-axis voltage command and the
q-axis voltage command, wherein the d-axis current error and the q-axis
current error comprises a combination of the d-axis current command and the
q-axis current command and the synchronous reference frame currents;
a first converter configured to receive the d-axis voltage command
and the q-axis voltage command and the final estimated rotor position angle
and generate the sinusoidal voltage commands;
a vector generator configured to receive the sinusoidal voltage
commands and generate switching vectors and to generate injection vectors;
a combiner configured to receive the switching vectors and the
injection vectors and generate modified switching vectors;
an inverter configured to receive modified switching vectors and
generate the voltage commands which are also converted to resultant stator
currents; and
a second converter configured to receive resultant stator currents
and generate the synchronous reference frame currents.
14. A system according to claim 8, wherein the motor comprises a
permanent-magnet synchronous motor (PMSM) configured to receive the
voltage commands and generate a motor output.
15. A system, comprising a voltage generator module configured to
receive three-phase voltage commands and a motor output, and configured to
generate sampled three-phase zero-sequence voltages in response to the three-
5 phase voltage commands and the motor output.

16. A system according to claim 15, further comprising a motor
configured to receive the three-phase voltage commands and generate the
motor output.
17. A system according to claim 16, further comprising an output
module configured to receive the sampled three-phase zero-sequence voltages
and generate a final estimated rotor position angle.
18. A system according to claim 17, wherein the voltage generator
module comprises:
a phase-to-neutral voltage generator configured to receive the
three-phase voltage commands and the motor output and to generate the
machine phase voltages;
a summing junction configured to receive the machine phase
voltages and generate the zero-sequence voltage; and
a sampler module configured to receive the zero-sequence voltage
and generate sampled three-phase zero-sequence voltages.
19. A system according to claim 18, wherein the output module
comprises:
a three-to-to converter module configured to receive sampled three-
phase zero-sequence voltages and generate two-phase zero-sequence voltages;
an angle calculator module configured to receive two-phase zero-
sequence voltages and generate angle of the saturation induced saliency;
an angle converter module configured to receive angle of the
saturation induced saliency and generate rotor position angle; and
an angle calibrator module configured to receive rotor position
angle and generate the final estimated rotor position angle.
20. A system according to claim 19, further comprising a stator
current converter configured to receive a torque command and generate the
three-phase voltage commands.

21. A system according to claim 15, wherein the stator current
converter comprises:
a torque-to-current mapping module configured to receive the
torque command and generate the d-axis current command and the q-axis
current command;
a current-controller module configured to receive the d-axis current
error and the q-axis current error and generate the d-axis voltage command
and the q-axis voltage command, wherein the d-axis current error and the q-
axis current error comprises a combination of the d-axis current command and
the q-axis current command and the synchronous reference frame currents;
a synchronous-to-stationary conversion module configured to
receive the d-axis voltage command and the q-axis voltage command and the
final estimated rotor position angle and generate the three-phase sinusoidal
voltage commands;
a space-vector PWM module configured to receive the three-phase
sinusoidal voltage commands and generate switching vectors;
an injection vector generator configured to generate injection
vectors;
a multiplexer configured to receive switching vectors and injection
vectors and generate modified switching vectors;
a PWM inverter configured to receive modified switching vectors
and generate the three-phase voltage commands which is converted to
resultant stator currents; and
a stationary-to-synchronous conversion module configured to
receive resultant stator currents and generate the synchronous reference frame
currents.
22. A system according to claim 16, wherein the motor comprises a
three-phase permanent-magnet synchronous motor (PMSM) configured to
receive the three-phase voltage commands and generate a motor output.

Methods and apparatus are provided for generating zero-
sequence voltages based on voltage commands and a motor output signal. At
least one of the methods includes, but is not limited to, receiving a torque
command and generating three-phase voltage commands based on the torque
command. The method also includes, but is not limited to, generating a motor
output responsive to the three-phase voltage commands and generating three-
phase zero-sequence voltage samples based on the three-phase voltage
commands and the motor output.

Documents:

02568-kolnp-2008-abstract.pdf

02568-kolnp-2008-claims.pdf

02568-kolnp-2008-correspondence others.pdf

02568-kolnp-2008-description complete.pdf

02568-kolnp-2008-drawings.pdf

02568-kolnp-2008-form 1.pdf

02568-kolnp-2008-form 2.pdf

02568-kolnp-2008-form 3.pdf

02568-kolnp-2008-form 5.pdf

02568-kolnp-2008-gpa.pdf

02568-kolnp-2008-international publication.pdf

02568-kolnp-2008-international search report.pdf

02568-kolnp-2008-pct request form.pdf

2568-KOLNP-2008-(09-04-2014)-ABSTRACT.pdf

2568-KOLNP-2008-(09-04-2014)-CLAIMS.pdf

2568-KOLNP-2008-(09-04-2014)-CORRESPONDENCE.pdf

2568-KOLNP-2008-(09-04-2014)-DESCRIPTION (COMPLETE).pdf

2568-KOLNP-2008-(09-04-2014)-DRAWINGS.pdf

2568-KOLNP-2008-(09-04-2014)-FORM-1.pdf

2568-KOLNP-2008-(09-04-2014)-FORM-2.pdf

2568-KOLNP-2008-(09-04-2014)-OTHERS.pdf

2568-KOLNP-2008-(11-12-2012)-CORRESPONDENCE.pdf

2568-KOLNP-2008-(14-06-2013)-ABSTRACT.pdf

2568-KOLNP-2008-(14-06-2013)-ANNEXURE TO FORM 3.pdf

2568-KOLNP-2008-(14-06-2013)-CLAIMS.pdf

2568-KOLNP-2008-(14-06-2013)-CORRESPONDENCE.pdf

2568-KOLNP-2008-(14-06-2013)-DESCRIPTION (COMPLETE).pdf

2568-KOLNP-2008-(14-06-2013)-DRAWINGS.pdf

2568-KOLNP-2008-(14-06-2013)-FORM-1.pdf

2568-KOLNP-2008-(14-06-2013)-FORM-2.pdf

2568-KOLNP-2008-(14-06-2013)-FORM-3.pdf

2568-KOLNP-2008-(14-06-2013)-FORM-5.pdf

2568-KOLNP-2008-(14-06-2013)-OTHERS.pdf

2568-KOLNP-2008-(14-06-2013)-PA.pdf

2568-KOLNP-2008-(14-06-2013)-PETITION UNDER RULE 137.pdf

2568-KOLNP-2008-(16-05-2014)-CORRESPONDENCE.pdf

2568-KOLNP-2008-(16-05-2014)-FORM-1.pdf

2568-KOLNP-2008-(16-05-2014)-PETITION UNDER RULE 137.pdf

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Patent Number

265018

Indian Patent Application Number

2568/KOLNP/2008

PG Journal Number

06/2015

Publication Date

06-Feb-2015

Grant Date

31-Jan-2015

Date of Filing

24-Jun-2008

Name of Patentee

GM GLOBAL TECHNOLOGY OPERATIONS, INC.

Applicant Address

300 RENAISSANCE CENTER DETROIT, MICHIGAN

Inventors:

#	Inventor's Name	Inventor's Address
1	PATEL NITINKUMAR	8125 ACACIA CIRCLE, CYPRESS, CA 90630
2	NAGASHIMA, JAMES	16608 MOORBROOK AVENUE CERRITOS, CA 90703
3	BAE, BON-HO	20710 AMIE, TORRANCE CA 90503

PCT International Classification Number

H02P 7/00

PCT International Application Number

PCT/US2006/061965

PCT International Filing date

2006-12-13

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	11/300,525	2005-12-14	U.S.A.