|Title of Invention||
PROCESS AND DEVICE FOR AXIS STABILIZATION OF AT LEAST ONE PAIR OF MOVING/MOTION AXES OF A MACHINE
|Abstract||Process for axis stabilization/position regulation of at least one pair (xl, x2; yK 2) of moving/ axis of a machine which run parallel to one another, is characterized through a splitting of the axis stabilization/position regulation in a rough positioning of the first moving-axis (xl; yl) and a fine positioning of the second moving-axis (x2; y2), whereby the first moving-axis has a greater vibration tendency than the second moving-axis, and through a compensation of a contour-error of the first movement-axis (xl; yl) through a positioning of the second moving-axis (x2; y2) capable of compensating the contour-error, whereby the compensation of the contour-error is carried out on the basis of a predictive contour-error model under use of a Desired-Position of the first Movement-Axis|
Process and Device for axis stabilization of at least one pair of moving/motion axes of a machine
The above invention relates to a process and to a device for axis stabilization in accordance with the generic description of the Patent Claim K and the generic description of the Patent Claim 5 respectively.
Background to the Invention
A machine or an individual axle/axis of a machine tends to vibrate, on account of its structural dynamic, and thus represents a limitation with regard to the maximum possible controller-dynamic and thereby the machine productivity. Whenever one reaches the limits of such structural dynamic - that is, the positioning-dynamic and the mechanical properties are limited - it is desirable that one is in a position to come out with a simple retrofit-solution with which the total performance of the machine can be augmented.
During the position process, machines or axles are run in the operating-mode 'axis stabilization'. The objective here is to follow a Position-Desired Value Pattern as accuratelv as possible - that is with minimum contouring error.
For controlling the positioning (axis stabilization) of the individual axles of a machine (motor and in-built mechanism) the so-called Cascade Regulation is known. This cascade regulation consists of a position regulation circuit with down-stream r. p m. control circuit, to which in turn a current regulator is cascaded.
The current control circuit of a cascade control consists generally of a PI Controller, a power electronic control/correction element and the electrical part of the motor. Typically a Pl-Controller is used as RPM-Regulator, and a P-controller as position-controller.
To move to a predetermined destination/end position, a sequence of position-desired-values is prescribed for the drive. The control then tries to regulate or control the motor such that the drive and/or the motor follow the position-desired-values as far as possible without any drag (free of any delay or drag occurrences). Such cascade controls lead to enormous deviations between the Desired and Actual positions. These deviations (drags) cannot be accepted in a large number of applications.
For several applications it is all the more desirable that the Position Actual Value essentially follows the Position Desired Value without any drag (that means with minimum drag occurrences). For realizing this goal, high-dynamic drives are applied, which in the context of the already mentioned cascade control are extended by a speed and acceleration pilot control.
Through such a pilot-control, on the one hand the drag is minimized and on the other, however, the structural dynamic of a machine and/or an axle is excited, in case of very high-dynamic position- desired -values, that is for example in case of jumpy and wild fluctuations of the desired-acceleration and desired-speed. The result of this could be undesirable fluctuations, which in the restricted structural dynamic are attributable to the mechanical properties of the machine.
If now the mechanical properties of the machine are not alterable, but nevertheless it must be positioned predominantly without any drag, then one has to go in search of new concepts for arriving at a solution.
Under the framework of a known concept, as part of an active vibration-mitigation exercise, the vibration of a machine and/or an axle is compiled and is attenuated through additional control algorithms. This methodology calls for an additional measuring-sensor (for example an Acceleration Sensor) and a technology-function - that is an additional algorithm in the drive. This concept is not ideal considering the fact that the vibrations continue to be there and are merely controlled /regulated with a delay.
What is attempted with the invention is to present an improved machine-kinematic, in which the contouring errors can be minimized.
This objective is achieved through a process with the characteristics of the Patent Claim . as well as a Device with the characteristics of the Patent Claim 5.
Advantages of the Invention
Under the invention-based solution, an axis stabilization and/or positioning is to be split in a rough-positioning of a first displacement/movement axis, and a fine positioning of a second displacement/movement axis, whereby the first displacement axis (dynamic axis) has a larger vibration than the second movement axis (un-dynamic axis), and the application of a predictive contour-error model facilitates to minimize the contour error that might occur in a relatively simple and inexpensive manner.
With the application of a predictive contour-error model it can be especially prevented that for carrying out the regulation first a comparison between Position-Actual Value and Position-Desired Value must be done through measurement, whereby a measured deviation of a control-device is added, which in its turn computes a position correction
for the first or second axis. Such a methodology is considered as relatively calculation-intensive and therefore slower.
Advantageous design forms of the invention are objects of the Sub-Claims.
It is preferred that the predictive contour-error model is still corrected with the use of an Actual-Position of the first movement/displacement axis. Such a correction allows more effectively and without disproportionate computing expenditure, a further precision of the invention-based process for axis stabilization.
Ideally, the Actual-Position of the first movement axis is provided to the Drive of the second movement axis through a cyclical communication interface. Such a direct communication between the respective drives of the first and second movement axes enables an especially efficient regulation/stabilization.
Purposefully, a superior/up-stream control is used for transmitting Position-Desired Values to the respective drives of the movement-axes.
Such a control can be designed pui-posefully with a SERCOS-lnterface. whereby an especially effective communication between the drives and the superior control is possible.
The invention-based process can be especially advantageously deployed in a Stamping/Punching-Laser Machine; however, it can also be made use of in other machines, in which a quick and dynamic positioning of displacement/movement axes in one. two or three dimensions is necessary.
Description of the Figures
The invention is further explained below on the basis of the attached Drawing. The figures show:
Figure 1 a perspective view of a Stamping-Laser Machine, in which the
invention-based process can be advantageously applied.
Figure 2 a demonstration for further elucidating the positions and/or
trajectories as well as drag-intervals of the movement/displacement axes of the Laser Stamping/Punching Machine, as per figure 1.
Figure 3 a Block Diagram for elucidating a preferred design form of the
invention-based process, with which especially the machine as per Figure 1 can be controlled and/or regulated/stabilized.
Figure 4 a Block Diagram of a preferred design form of the closed-loop
position control used according to the invention
Figure 5 a Block Diagram for further explaining the invention-based
A Stamping/Punching Laser Machine is identified in Figure 1 as a whole with 100. The machine has a table 102, which in x-direction can be moved along a table-axis xl and in y-direction along an axis yl. With the use of these table axes xl, x2 a sheet 150 placed on the table 102 can be positioned.
The machine further has a laser device 110, which is equipped/designed with a laser-head 112. The laser-head 112 can be positioned m x-direction along a axis x2, and in y-direction along an axis y2.
If the sheet 150 is to be processed by the laser-head - that means for example, should contours be laser-cut, then the sheet 150 must be positioned without any drag (deceleration/retardation) with respect to the laser-head 112.
In case of a multi-dimensional positioning one would speak of 'Desired-Trajectories\ which the table 102 (and thereby the sheet 150 placed on the table 102) must caiTy out. The time-based sequence of desired-trajectories forms a desired-path and the splitting in individual coordinate systems, the position-desired values for the respective axes.
The machine 100 has a numerical control (schematically illustrated) 120. which puts these position-desired-values at the disposal of the drives (not individually illustrated) of the respective axes xl. yK x2, y2.
The table axes xL yl and/or sheet axes usually receive their Position-desired values with reference to the Machine Center/Zero Point MNP, which is identical with the Zero/Center Point of the Laser Head (Tool Center Point). The Position-Actual Value emerges from the distance of sheet and TCP.
If. as in the above case, additional axes (laser axes x2. y2) come to be applied, then the Position-Desired values of the sheet are purposefully referenced to the MNP, and the Position-Actual values to the TCP, where (as will be explained below) the TCP can be now positioned over the laser axis in a restricted range of movement.
This aspect is now illustrated on the basis of Figure 2.
One recognizes that the Point MNP lies in Center-Point of the Coordinate-System XY. Based on the traversing facility of the laser head 112 a traversing range/area for the Point TCP emerges, which is identified as dotted square 210. A Desired-Distance of the Table 102 and thereby the Sheet 150 on a Desired-Trajectory is identified with 220. For example, because of vibrations and not so ideal stiffness of the table 102, there arises a difference between the Desired-Distance 220 and an Actual-Distance 230. This distance
is described as "drag interval/distance' or retardation-distance (identified here with 240). Because of the already explained positionability of the laser head - that is of the Point TCP - this drag distance 240 can be compensated through a corresponding shifting of the TCP. This shifting - that is the Actual-Distance of the TCP from Machine Center Point MNP - is identified with 250. Finally, for the sake of greater clarity, the Actual-Distance between TCP and Table is illustrated and identified with 260.
Therefore, for the reason that the table axes xl, yl as per Figure 1 are positioned affected with drag/retardation distance, a retardation distance 240 emerges for the table 102, which must be compensated through the laser axes x2, y2 in the opposite direction, so that the distance between the sheet and the TCP (Actual Distance 260 between Table and TCP) corresponds both in the amount/extent/value and direction to the Desired-Distance.
The axes xl, yl of the table 102 have, because of their mechanical properties, a relatively greater tendency for vibration, and are therefore usefully designed with relatively 'soft' parameters. These axes xl, yl are therefore un-dynamic axes and/or non-retardation-free movement- and/or positioning-axes.
On the contrary, the axes x2, y2 of the laser head have mostly no vibration tendency. Such "dynamic axes'" are therefore to be designed with very 'hard" parameters. Such a parameterization can be achieved with the use of pilot control.
According to the above invention a partition of the positioning of the table 102 and/or the sheet 150 is done with reference to the laser-head in a rough positioning of the (un-dynamic) axes xl, yl and a fine positioning of the (dynamic) axes x2, y2. Further a contour-error model is used for predictive determination of the contour-error and/or generation of position-desired-value for the retardation-free positioning of the axes x2, y2. and the contour-error compensation of the axes xl, yl.
These inter-relationships are now explained based on Figure 3.
The Control 120. which is designed with a SERCOS-Interface 12K transmits Position-Desired-Values to the Drives of the Table axes xl, yl and the Laser axes x2. y2. The drive for the table axes is illustrated schematically with Block 102a, and the Drive for the Laser axes with Block 112a. The provision/supply of the Position-Desired Values is preferabh' done through a Master-Data-Telegramme MDT. identified here with 180.
A control of the drive 112a of the laser axes x2, y2 determines, based on a contour-error model - which is further explained in detail below - predictive a contour-error of the table axes xl. yl on the basis of the known parameters of the machine 100. The contour error is corrected with the use of an Actual-Positioning of the Table axes xK y 1, which is provided to the Drive 112a directly by the Drive 102a through a cyclical communication inter-face 185. The communication inter-face 185 can be realized both as analog and as CCD (Cross Communication Drive).
Thus the determination of the contour-error of the table axes xl, yl is so calculated that the contour-error is already known substantially, before it at all occurs ('prediction'). Thereby the cumulative- contour- error of the table-axes and laser-axes as against a simple transmission of the really occurring contour-error by the table axes to the laser axes can be minimized.
As can be further seen in Figure 3, the rough positioning of the table axes xl, yl is done through a Position-Actual Position indicator 190, and the fine-positioning of the laser axes through a further Position-Actual/ Position indicator 192. Totally therefore the compensated and/or regulated/stabilized Actual-Position for Sheet 150 lying on the Table 102 is obtained (in Figure 3 identified with 194).
IT may be said that a communication between the drives 102a and 112a and the Control 120 through a Drive-Telegram AT (identified in Figure 3 with 182) is possible. Time-constants of the different components are identified respectively with 'T-plus index".
Taking reference to Figure 4. a preferred regulation/stabilization of a axis of the machine is, illustrated in the following, where the illustration is shown especially for an ideal mechanism.
The illustrated current control circuit consisting of a Pl-controller, power-electronic control element and the electrical portion of the motor is shown in a simplified and/or summarized fashion as a P-Tl-Element/Organ 410 with a Current-Control Circuit Substitute Time Constants Toi. A Tl-Controller 420 is applied as RPM controller, and a P-Controller430 as Position-Controller.
The RPM controller circuit further has an additional P-ControUer and an 1-controller 424. The closed-loop position control has an additional I-controller 426. Ky indicates the Position Controller Proportional Sensitivity, TNU the RPM controller reset-time, Kpn the RPM controller proportional sensitivity and I a moment of inertia (m of I).
In order to move to a pre-determined destination, sequence of position-desired values Xsoll (Xdesired) is prescribed for the drive. The controller tries to control the motor in such a manner that it can follow the position-desired values as far as possible without any retardation (drag-interval free). One would recognize that during the illustrated control/regulation a consideration and/or evaluation of the speed/velocity desired value Vsoll (Vdesired) an accelcration-Actual value aist and a speed/velocity Actual value Xjsi. (Xactual). The position control circuit as per Figure 4 represents a closed loop position control circuit without pilot-controls, and with an ideally stiff/robust mechanic. A time-continuous transfer function of this Position control circuit results in a system (return transfer function) Fgxof the third order:
(please see original - hard copy)
Here Kv represents the position-controller-proportional sensitivity, Toi as already mentioned the current control circuit substitute time-constants and a an auxiliary variable.
The auxiliary variable a is obtained as follows: The contour error can now be calculated from
The transfer function Fgx can be simplified to get a Tl-element with the time-constant !/Kv, for instance, in the form:
As the control in the drive is incorporated in a micro controller, the simplified transfer function is transformed in the time-discreet, and is calculated with the help of a differential equation of the model contour error £*. In sum what we get is:
Here H is a time-discreet transfer function. As the contour error, according to the above invention- is calculated from the Desired Value, in contrast to the real
deceleration/retardation distance, which is calculated from Desired-Value and Actual-Value, it is without any noise component.
Further, for the reason that the model contour error is calculated in the control/regulation cycle, in which also the position-desired-value is already given, this value is available already predictive in advance, as already mentioned, in contrast to the real retardation/deceleration distance which is determined only in the next control cycle as drive-reaction to the position-desired-value.
What is meant under a direct desired-value-coupling/linking, as it is realized according to the invention, is that from a Master axis values such as for example position-actual value, desired-value etc are transmitted to one or more slave-axes, from which then the slave-axis derives, for instance, the desired value. These inter-relationships are explained once again based on Figure 5. Reference numbers, which have been used in respect of the other figures, are not once again mentioned explicitly. Different controllers used, which include here also D-controller. are identified with 500.
In the configuration described here, for example, the un-dynamic table axis xl is the Master, and the dynamic laser axis x2 is the slave. The Master transmits to the slave through the communication interface 185 the deceleration/retardation distance (SA and/or Masier) The contour error model error fehler is calculated in the Slave (sFehler = eMaster - e), and the Slave-Position-Desired Value X soll is brought in as correction. The Position-Desired Value of the Slave is composed of two parts: one, the model contour error 8, which is calculated from the Master-Position-Desired Value (MC-Position Desired Value), and secondly the Contour Error Model Error fehier- It should be pointed out once again that only the model contour error is used for calculating the pilot-control value (Velocity/Speed Pilot Control K VV and Acceleration Pilot Control K VA), as this is predictive and photoelectric-noise-less, and the contour-error-model-error is brought in merely as correction value to the position-desired value for the P-Controller (Kv).
100 Punching/stamping laser machine
102a Drive table-axis
110 Laser device
1 ] 2 LASER HEAD
112a Drive - laser-axis
190 Position-Actual-Position Indicator
192 Position-Actual-Position Indicator
210 Traversing Range TCP
220 Desired-Distance Table
230 Actual Distance Table
240 Deceleration/retardation distance
250 Distance MNP-TCP
260 Actual-Distance TCP-Table
410. 420. 422, 424. 426, 430. 500 Controller
Robert Bosch GmbH - 70442 Stuttgart Claims
1. Process for axis stabilization/position regulation of at least one pair (xl, x2; yK 2) of moving/ axis of a machine which run parallel to one another, is characterized through a splitting of the axis stabilization/position regulation in a rough positioning of the first moving-axis (xl; yl) and a fine positioning of the second moving-axis (x2; y2), whereby the first moving-axis has a greater vibration tendency than the second moving-axis, and through a compensation of a contour-error of the first movement-axis (xl; yl) through a positioning of the second moving-axis (x2; y2) capable of compensating the contour-error, whereby the compensation of the contour-error is carried out on the basis of a predictive contour-error model under use of a Desired-Position of the first Movement-Axis (xhyl).
2. Process according to Claim 1 is thereby characterized that the predictive contour-error model is further corrected with the use of an Actual-Position of the first movement-axis (xl; yl).
3. Process according to Claim 2, is thereby characterized that the Actual-Position of the first moving-axis (xl; yl) is placed at the disposal of the drive of the second moving-axis (x2; y2) through a cyclical communication interface (185).
4. Process according to one of the above Claims is thereby characterized that a superior/upstream control (120) indicates the Positions-Desired-Values to the Moving-Axis (xl, yl; yl,y2).
5. Device with means for axis stabilization/position regulation of at least one pair (xl. x2; y], y2) of moving-axis, which run parallel to one another, is characterized through means (102a, 112a) for splitting the position-regulation in a rough-positioning of the first moving-axis (xl. yl) and a fine-positioning of the second movement-axis (x2. y2), where the first moving-axis has a greater vibration tendency than the second moving-axis, and means (102a, 185, 112a, 190. 192. 194) for compensation of a contour-error of the first moving-axis (xl; through a positioning of the second movement axis (x2; y2) capable of compensating the contour-error, and where the compensation of the contour-error is done on the basis of a predictive contour-error model under use of a Desired-Position of the first movement-axis xl; yl).
6. Device according to Claim 5 is thereby characterized that it is designed as
Punching/Stamping Laser Machine with a Table (102) and a Laser-Head (112).
7. Device according to one of the Claims 5 or 6 is characterized through a SERCOS-
Interface for guaranteeing the communication between a control instrument (120)
for providing Desired-Position Values and Drives (102a. 112a) for splitting the
axis stabilization/position regulation in rough-positioning of the first moving-axis
and fine-positioning of the second moving-axis.
8. Use of a Process according to one of the above Claims 1 to 4 in a
Process and Device for Axis/Stabilization/Position Regulation of at least one pair of movement-axes of a machine.
Process for axis-stabilization of at least one pair of movement-axes of a machine, which run parallel to one another, with a splitting of the position-regulation exercise in a rough-positioning of the first movement-axis and a fine-positioning of the second movement-axis, whereby the first movement-axis has a greater vibration-tendency than the second movement-axis, and with a compensation of a contour-error of the first movement-axis through a positioning of the second movement-axis capable of compensating the contour-error, whereby the compensation of the contour-error is carried out on the basis of a predictive contour-error model under use of a Desired-Position of the first movement-axis.
|Indian Patent Application Number||2777/CHE/2007|
|PG Journal Number||12/2014|
|Date of Filing||27-Nov-2007|
|Name of Patentee||ROBERT BOSCH GMBH|
|Applicant Address||POSTFACH 30 02 20, D-70442 STUTTGART, GERMANY.|
|PCT International Classification Number||H04N 5/232|
|PCT International Application Number||N/A|
|PCT International Filing date|