Title of Invention

METHOD AND APPARATUS FOR MONITORING AN ELECTRICAL CURRENT SENSING SYSTEM

Abstract A method and article of manufacture are provided to monitor a sensing system operative to monitor electrical current in a transmission line between an electrical storage device and an electrical machine. The sensing system comprises first and second sensors, operative to monitor first and second ranges of electrical current. The method comprises determining outputs of the first and second sensors are valid, and comparing outputs of the first and second sensors when current is substantially zero. The method comprises comparing magnitudes of the outputs of the first and second sensors when the monitored electrical current, and monitoring polarity of each of the outputs of the first and second sensors.
Full Text METHOD AND APPARATUS FOR MONITORING AN ELECTRICAL
CURRENT SENSING SYSTEM
TECHNICAL FIELD
[0001] This disclosure is related to electrical current sensing systems.
BACKGROUND
[0001] Electric and hybrid powertrain architectures utilize electric machines
to generate motive torque transmitted to a vehicle driveline. The electrical
machines are operatively connected to an electrical energy storage device for
interchanging electrical power therebetween. The electrical machines are
further operable to transform vehicle kinetic energy, transmitted through the
vehicle driveline, to electrical energy potential that is storable in the electrical
energy storage device. A control system monitors various inputs from the
vehicle and the operator and provides operational control of the powertrain
system including controlling the torque-generative devices and regulating the
electrical power interchange between the electrical energy storage device and
the electrical machines.
[0002] Vehicles employing such powertrain architectures benefit from a
robust method to determine a state-of-charge of the electrical energy storage
device, in that operation and management of the powertrain system can be
optimized based thereon. Determining a parametric value for state-of-charge
requires an accurate determination of electrical current flow in and out of the

electrical energy storage device. However, current flow can range from under
1.0 ampere to as high as 300 amperes in an integrated electrical energy storage
device operative to supply electrical power to electrical torque-generative
machines and meet other electrical needs in the vehicle. Therefore, it is
beneficial to have an electrical current monitoring device that is accurate over
the range of operation.
[0002] A fault occurring in the electrical current monitoring device leads
to the system not operating as intended, resulting in customer dissatisfaction.
Furthermore, state and federal regulations impose requirements to monitor
operation of devices such as the electrical current monitoring device, including
diagnosing presence of a fault and informing a vehicle operator of the
presence of the fault, under regulated conditions. Monitoring conditions can
include presence of open or short circuits, out-of-range/rationality checking,
and proper functional response to inputs.
SUMMARY
[0003] A method and article of manufacture monitor electrical current in a
transmission line between an electrical storage device and an electrical
machine. The sensing system includes a first sensor operative to monitor a
first range of electrical current and a second sensor operative to monitor a
second range of electrical current. The method includes determining outputs
of the first and second sensors are valid, and comparing outputs of the first and
second sensors when current in the transmission line is substantially zero. The
method also includes comparing magnitudes of the outputs of the first and

second sensors when the monitored electrical current is within a monitoring
range common to the first and the second sensors, and monitoring polarity of
each of the outputs of the first and second sensors.
BRIEF DESCRIPTION OF THE DRAWINGS
[0004] One or more embodiments will now be described, by way of
example, with reference to the accompanying drawings, in which:
[0005] Fig. 1 is a schematic diagram of an exemplary architecture for a
control system for a powertrain, in accordance with the present disclosure;
and,
[0006] Fig. 2 is a logic flowchart, in accordance with the present
disclosure.
DETAILED DESCRIPTION
[0007] Referring now to the drawings, wherein the showings are for the
purpose of illustrating certain exemplary embodiments only and not for the
purpose of limiting the same, Fig. 1 depicts a schematic drawing of a system
comprising an engine 14 connected via shaft 12 to electrically variable
transmission 10, which is connected via shaft 64 to a driveline, and distributed
control module system, which has been constructed in accordance with an
embodiment of the present disclosure. The engine 14 preferably comprises a
conventional internal combustion engine with engine control module ('ECM')
23 operably connected. The ECM 23 functions to acquire data from a variety

of sensors and control a variety of actuators, respectively, of the engine 14
over a plurality of discrete lines collectively shown as aggregate line 35.
[0008] The exemplary transmission preferably comprises a two-mode,
compound-split, electro-mechanical hybrid transmission including a
compound planetary gear arrangement and four torque-transmitting clutches
controlled by an electro-hydraulic control system. The transmission control
module ('TCM') 17 is operably connected to the transmission 10 and
functions to acquire data from a variety of sensors and provide command
signals to the electro-hydraulic control system of the transmission. The
transmission incorporates a pair of electrical machines 56, 72 which comprise
motor/generator devices, and are referred to as MG-A 56 and MG-B 72. The
transmission 10 receives input motive torque from the torque-generative
devices, including the engine 14 and the MG-A 56 and MG-B 72, as a result
of energy conversion from fuel, or from electrical potential stored in an
electrical energy storage device ('ESD') 74. The ESD 74 typically comprises
one or more batteries capable of storing and transmitting high electrical power
levels. Other electrical energy and electrochemical energy storage devices that
have the ability to store electric power and dispense electric power may be
used in place of the batteries without altering the concepts of the present
disclosure. The ESD 74 is preferably sized based upon factors including
regenerative requirements, application issues related to typical road grade and
temperature, and propulsion requirements such as emissions, power assist and
electric range. The ESD 74 is high voltage DC-coupled to transmission power
inverter module ('TPIM') 19 via electrical transmission line 27.

[0009] The TPIM 19 is operable to generate torque commands for MG-A
56 and MG-B 72 based upon input from a hybrid control module ('HCP') 5,
which is driven by operator input through User Interface ('UP) 13 and other
system operating parameters. The motor torque commands for MG-A and
MG-B are implemented by the control system, including the TPIM 19, to
control MG-A and MG-B. The electrical energy storage device 74 is high-
voltage DC-coupled to the TPIM 19 via electrical transmission line 27
Electrical current is transferable to or from the TPIM 19 in accordance with
whether the ESD 74 is being charged or discharged. The TPIM 19
communicates with the first electrical machine 56 by transfer conductors 29,
and the TPIM 19 similarly communicates with the second electrical machine
MG-B 72 by transfer conductors 31.
[0010] TPIM 19 includes the pair of power inverters and respective motor
control modules configured to receive motor control commands and control
inverter states therefrom for providing motor drive or regeneration
functionality. In motoring control, the respective inverter receives DC
electrical current from ESD 74 via the transfer line 27 and provides AC
current to the respective electrical machine, i.e. MG-A and MG-B, over
transfer conductors 29 and 31. In regeneration control, the respective inverter
receives AC electrical current from the electrical machine over transfer
conductors 29 and 31 and supplies DC electrical current to the ESD 74 via
electrical transmission line 27. A current monitoring system 30 is mechanized
to monitor current flow through transmission line 27. The net DC current
provided to or from the inverters determines the charge or discharge operating

mode of the electrical energy storage device 74. Preferably, MG-A 56 and
MG-B 72 are three-phase AC machines and the inverters comprise
complementary three-phase power electronics.
[0011] Other elements of the control system depicted with reference to
Fig. 1 comprise distributed control module architecture comprise a subset of
an overall vehicle control architecture operable to provide coordinated system
control of the vehicle powertrain system. The control system is operable to
synthesize pertinent information and inputs, and execute algorithms to control
various actuators to achieve control targets, including such parameters as fuel
economy, emissions, performance, driveability, and protection of hardware,
including batteries of ESD 74 and MG-A and MG-B 56, 72. The distributed
control module architecture includes the engine control module ('ECM') 23,
the transmission control module ('TCM') 17, battery pack control module
('BPCM') 21, and the Transmission Power Inverter Module ('TPIM') 19. The
hybrid control module ('HCP') 5 provides overarching control and
coordination of the aforementioned control modules. The UI 13 operably
connected to a plurality of devices through which a vehicle operator typically
controls or directs operation of the powertrain through a request for torque,
including the transmission 10. Exemplary vehicle operator inputs to the UI 13
include an accelerator pedal, a brake pedal, transmission gear selector, and,
vehicle speed cruise control. Each of the aforementioned control modules
communicates with other control modules, sensors, and actuators via a local
area network ('LAN') bus 6. The LAN bus 6 allows for structured
communication of control parameters and commands between the various

control modules. The specific communication protocol utilized is application-
specific. The LAN bus and appropriate protocols provide for robust
messaging and multi-control module interfacing between the aforementioned
control modules, and other control modules providing functionality such as
antilock brakes, traction control, and vehicle stability.
[0012] The HCP 5 provides overarching control of the hybrid powertrain
system, serving to coordinate operation of the ECM 23, TCM 17, TPIM 19,
and BPCM 21. Based upon various input signals from the UI 13 and the
powertrain, including the battery pack, the HCP 5 generates various
commands, including: operator torque, engine torque, clutch torque for the
clutches of the transmission 10; and motor torque commands for MG-A and
MG-B. The BPCM 21 is signally connected one or more sensors operable to
monitor electrical current or voltage parameters of the ESD 74 to provide
information about the state of the batteries to the HCP 5.
[0013] Each of the aforementioned control modules is preferably a
general-purpose digital computer generally comprising a microprocessor or
central processing unit, storage mediums comprising read only memory
(ROM), random access memory (RAM), electrically programmable read only
memory (EPROM), high speed clock, analog to digital (A/D) and digital to
analog (D/A) circuitry, and input/output circuitry and devices (I/O) and
appropriate signal conditioning and buffer circuitry. Each control module has
a set of control algorithms, comprising resident program instructions and
calibrations stored in ROM and executed to provide the respective functions of

each computer. Information transfer between the various computers is
preferably accomplished using the aforementioned LAN 6.
[0014] Algorithms for control and state estimation in each of the control
modules are typically executed during preset loop cycles such that each
algorithm is executed at least once each loop cycle. Algorithms stored in the
non-volatile memory devices are executed by one of the central processing
units and are operable to monitor inputs from the sensing devices and execute
control and diagnostic routines to control operation of the respective device,
using preset calibrations. Loop cycles are typically executed at regular
intervals, for example each 3.125, 6.25, 12.5, 25 and 100 milliseconds during
ongoing engine and vehicle operation. Alternatively, algorithms may be
executed in response to occurrence of an event.
[0015] The electrical transmission line 27 between the ESD 74 and TPIM
27 is mechanized with the current monitoring system 30, comprising first and
second current sensors. Each sensor is operative to monitor magnitude and
direction of current flow to the ESD. Signal outputs from the current sensors
of current monitoring system 30 are input to the TPIM, and are used to
facilitate operations for monitoring the ESD 74, e.g. state-of-charge
estimations. The first and second current sensors each preferably comprise
known open-loop Hall-effect sensors operative to generate an electrical
voltage output that is substantially proportional to the magnitude of current.
The first sensor is preferably an open-loop Hall-effect sensor adapted to
provide a linear output over a low current range of+/- 30 amperes with an
accuracy of about 1%, or 0.3 amperes. The second sensor is preferably an

open-loop Hall-effect sensor adapted to provide a linear output over a high
current range of+/-300 amperes with an accuracy of about 1%, or 3.0
amperes. In the control system mechanized with first and second current
monitoring sensors, the control system preferably uses signal information from
the first current sensor when the current level is between -30 amperes and
approximately +30 amperes, and transitions to use signal information from the
second current sensor when the current level is between approximately 30
amperes and 300 amperes. Sources of error in reading from the sensors
include magnetic hysteresis at zero amperes and temperature drift. It is
understood that the specifically described Hall-effect sensors are meant to be
exemplary and not limiting. The substance of the disclosure is applicable to
various types of current sensors.
[0016] Referring now to Fig. 2, a flowchart is provided comprising a
description of actions executed in the control system to monitor operation of
the electrical current sensing system 30. The actions described herein are
preferably executed as one or more algorithms resident in one of the
distributed control modules, using predetermined calibrations. The disclosure
is with reference to the aforementioned powertrain and control system,
although it is understood that the disclosure is applicable to numerous systems
which have a need to monitor operation of an electrical current monitoring
device.
[0017] Initially, output signals from the first and second current sensors of
the sensing system 30 are read, preferably through an I/O device of one of the
control modules, e.g. the TPIM (Block 102). The output signals are analyzed

to determine whether either output signal has been shorted to ground, or has an
open electrical circuit due, e.g. to a break in an electrical wire (Block 104).
This is preferably accomplished by the comparing the signal outputs to a
system ground voltage and a system operating voltage. When it is determined
that there is no open circuit or short circuit in the electrical system for the
current sensors, the output signals are deemed valid (Block 106) and
monitored during ongoing operation. Under a circumstance wherein it is
determined that the output signals are not valid, e.g. presence of a short circuit
or open circuit is found, then a fault is identified, a sensoroutputinvalid flag
is set (Block 122), and monitoring of the current sensing system is
discontinued (Block 124).
[0018] Monitoring the output signals includes monitoring sensor output at
zero current (Block 108). This can include measuring an initial value for zero
current through the first and second sensors at initial key-on and startup of
vehicle operation, prior to any command for electrical current. Furthermore, a
zero-current output can be measured at other opportune times during operation
when it is known that there is zero current flowing, such as when a circuit
contactor is commanded opened. Each time a zero-current output is measured,
the signals for zero-current output from the first and second sensors are
compared (Block 110). When the output from one of the sensors is
substantially different from the output from the other sensor, e.g. greater than
a value of sensor error or measurement accuracy (1% of full-scale in this
embodiment), a fault in sensor rationality is identified and captured (Block
126), and monitoring is discontinued (Block 128).

[0019] During ongoing operation of the vehicle, outputs from the first and
second current sensors are regularly monitored and captured, in this
embodiment at a sample rate of about 20 milliseconds (Block 112). When the
magnitude of the current is within the linear monitoring ranges common to
both the first sensor and the second sensor, i.e. between zero and thirty
amperes in this embodiment, the magnitudes of the outputs of the first and
second current sensors are compared (Block 114). A difference is determined
between the outputs of the first and second sensors, and evaluated compared to
measurement accuracies of the first and second sensors, which are
predetermined and pre-calibrated in the control module. In this example, the
measurement accuracy of the first sensor is 0.3 amperes and the measurement
accuracy of the second sensor is 3.0 amperes. Therefore, a difference between
of the outputs of the first and second current sensors that is less than 3.3
amperes is deemed acceptable in the exemplary system described herein. A
difference greater than 3.3 amperes is deemed unacceptable, leading to
identification of a fault, and, discontinuing further monitoring.
[0020] The polarities of the outputs from the first and second current
sensors are determined and correlated (Block 116) Determining polarities of
current outputs from the first and second current sensors preferably comprises
monitoring current sensor output signals and voltage of the ESD 74 over an
elapsed period of time. A direction of change in ESD voltage correlates to a
knowable direction of change in sensed current. When the direction of change
in sensed current from the first or second current sensor correlates to the
change in ESD voltage, it can be determined that the current sensor has passed

the polarity check (Block 118). When the direction of change in sensed
current from the first or second current sensor does not correlate to the direct
of change in ESD voltage, it can be determined that the current sensor has not
passed the polarity check (Block 116), and there is a fault in the system. The
fault in sensor rationality is identified and captured (Block 126), and
monitoring is discontinued (Block 128).
[0021] When a fault is identified in the system, the control system is
operable to act, such action including illuminating a malfunction indicator
lamp in a vehicle instrument panel, disabling other related diagnostic
algorithms, and implementing appropriate corrective actions in the control
system, including such actions as necessary to prevent harm to other
components.
[0022] The disclosure has described certain preferred embodiments and
modifications thereto. Further modifications and alterations may occur to
others upon reading and understanding the specification. Therefore, it is
intended that the disclosure not be limited to the particular embodiment(s)
disclosed as the best mode contemplated for carrying out this disclosure, but
that the disclosure will include all embodiments falling within the scope of the
appended claims.

CLAIMS
1. Method to monitor a sensing system operative to monitor electrical
current in a transmission line between an electrical storage device and an
electrical machine comprising a first sensor operative to monitor a first
range of electrical current and a second sensor operative to monitor a
second range of electrical current, the method comprising:
determining outputs of the first and second sensors are valid;
comparing outputs of the first and second sensors when current in the
transmission line is substantially zero;
comparing magnitudes of the outputs of the first and second sensors
when the monitored electrical current is within a monitoring range
common to the first and the second sensors; and
monitoring polarity of each of the outputs of the first and second sensors.
2. The method of claim 1, wherein determining outputs of the first and
second sensors are valid comprises monitoring the outputs of the first
and second sensors, and, identifying an absence of either of a short
circuit and an open circuit in the outputs of the first and second sensors.
3. The method of claim 2, further comprising: identifying a fault when the
output of either of the first and second sensors is invalid, and,
discontinuing further monitoring.

4. The method of claim 1, wherein comparing outputs of the first and
second sensors when current in the transmission line is substantially zero
comprises monitoring outputs of the first and second sensors when an
open circuit is present in the transmission line.
5. The method of claim 4, further comprising: identifying a fault when the
output of either of the first and second sensors is not substantially zero,
and, discontinuing further monitoring.
6. The method of claim 1, wherein comparing magnitudes of the outputs of
the first and second sensors when the monitored electrical current is
within a monitoring range common to both the first and the second
sensors further comprises determining a difference between the outputs
of the first and second sensors does not exceed measurement accuracies
of the first and second sensors.
7. The method of claim 6, further comprising: identifying a fault when the
difference between the outputs of the first and second sensors exceeds
the measurement accuracies for the first and second sensors, and,
discontinuing further monitoring.

8. The method of claim 1, wherein monitoring the polarity of each of the
outputs of the first and second sensors further comprises monitoring
voltage in the electrical storage device during an elapsed time period,
and, comparing a direction of change in the monitored voltage of the
electrical storage device to a direction of change in the outputs of the
first and second sensors.
9. The method of claim 8, further comprising: identifying a fault when the
direction of change in the output of either of the first and second sensors
does not correlate to the direction of change of the monitored voltage of
the electrical storage device, and, discontinuing further monitoring.
10. The method of claim 1, wherein the first sensor operative to monitor a
first range of electrical current comprises the first sensor operative to
monitor a range of current restricted between approximately +/- 30
amperes and having a measurement accuracy of 0.3 amperes.
11. The method of claim 1, wherein the second sensor operative to monitor a
second range of electrical current comprises the second sensor operative
to monitor a range of current restricted between approximately +/- 300
amperes and having a measurement accuracy of 3.0 amperes.

12. Article of manufacture, comprising a storage medium having a computer
program encoded therein for effecting a method to monitor operation of
an sensing system operative to monitor electrical current in a
transmission line between an electrical storage device and an electrical
machine comprising a first sensor operative to monitor a first range of
electrical current and a second sensor operative to monitor a second
range of electrical current, the program comprising:
code for determining outputs of the first and second sensors are valid;
code for comparing outputs of the first and second sensors when current
in the transmission line is substantially zero;
code for comparing magnitudes of the outputs of the first and second
sensors when the monitored electrical current is within a monitoring
range common to the first and the second sensors; and
code for monitoring polarity of each of the outputs of the first and
second sensors.
13. The article of manufacture of claim 12, wherein the code for comparing
outputs of the first and second sensors when current in the transmission
line is substantially zero comprises:
code for monitoring outputs of the first and second sensors when an open
circuit is present in the transmission line.

14. The article of manufacture of claim 12, wherein the code for comparing
magnitudes of the outputs of the first and second sensors when the
monitored electrical current is within a monitoring range common to
both the first and the second sensors further comprises:
code for determining a difference between the outputs of the first and
second sensors does not exceed measurement accuracies of the first
and second sensors.
15. The article of manufacture of claim 12, wherein code for monitoring the
polarity of each of the outputs of the first and second sensors further
comprises code for monitoring voltage in the electrical storage device
during an elapsed time period, and, code for comparing a direction of
change in the monitored voltage of the electrical storage device to a
direction of change in the outputs of the first and second sensors.

16. Powertrain system, comprising:
an electrical storage device electrically connected to an electrical
machine operative to transmit motive torque to a vehicle driveline;
a sensing system operative to monitor electrical current in a transmission
line between the electrical machine and the electrical storage device;
a control system:
adapted to monitor the electrical storage device and control the electrical
machine; and
including a control module comprising a storage medium having a
computer program encoded therein for effecting a method to monitor
operation of the sensing system comprising a first sensor operative to
monitor a first range of electrical current and a second sensor
operative to monitor a second range of electrical current, the program
comprising:
code for determining outputs of the first and second sensors are
valid;
code for comparing outputs of the first and second sensors when
current in the transmission line is substantially zero;
code for comparing magnitudes of the outputs of the first and second
sensors when the monitored electrical current is within a
monitoring range common to the first and the second sensors;
and
code for monitoring polarity of each of the outputs of the first and
second sensors.

17. The powertrain system of claim 16, wherein the first sensor and the
second sensor each comprise open-loop Hall-effect sensors.
18. The powertrain system of claim 17, wherein the first sensor is operative
to monitor a range of current restricted between approximately +/- 30
amperes.
19. The powertrain system of claim 17, wherein the second sensor is
operative to monitor a range of current restricted between approximately
+/- 300 amperes.

A method and article of manufacture are provided to monitor a
sensing system operative to monitor electrical current in a transmission line
between an electrical storage device and an electrical machine. The sensing
system comprises first and second sensors, operative to monitor first and
second ranges of electrical current. The method comprises determining
outputs of the first and second sensors are valid, and comparing outputs of the
first and second sensors when current is substantially zero. The method
comprises comparing magnitudes of the outputs of the first and second sensors
when the monitored electrical current, and monitoring polarity of each of the
outputs of the first and second sensors.

Documents:

1918-KOL-2008-(16-01-2014)-ABSTRACT.pdf

1918-KOL-2008-(16-01-2014)-ANNEXURE TO FORM 3.pdf

1918-KOL-2008-(16-01-2014)-CLAIMS.pdf

1918-KOL-2008-(16-01-2014)-CORRESPONDENCE.pdf

1918-KOL-2008-(16-01-2014)-DESCRIPTION (COMPLETE).pdf

1918-KOL-2008-(16-01-2014)-DRAWINGS.pdf

1918-KOL-2008-(16-01-2014)-FORM-1.pdf

1918-KOL-2008-(16-01-2014)-FORM-2.pdf

1918-KOL-2008-(16-01-2014)-FORM-5.pdf

1918-KOL-2008-(16-01-2014)-OTHERS.pdf

1918-KOL-2008-(16-01-2014)-PETITION UNDER RULE 137.pdf

1918-KOL-2008-(17-04-2014)-ASSIGNMENT.pdf

1918-KOL-2008-(17-04-2014)-CORRESPONDENCE.pdf

1918-kol-2008-abstract.pdf

1918-KOL-2008-ASSIGNMENT.pdf

1918-kol-2008-claims.pdf

1918-KOL-2008-CORRESPONDENCE 1.1.pdf

1918-KOL-2008-CORRESPONDENCE-1.2.pdf

1918-kol-2008-correspondence.pdf

1918-kol-2008-description (complete).pdf

1918-kol-2008-drawings.pdf

1918-kol-2008-form 1.pdf

1918-kol-2008-form 18.pdf

1918-kol-2008-form 2.pdf

1918-kol-2008-form 3.pdf

1918-kol-2008-form 5.pdf

1918-kol-2008-gpa.pdf

1918-kol-2008-specification.pdf

1918-KOL-2008-TRANSLATED COPY OF PRIORITY DOCUMENT.pdf

abstract-1918-kol-2008.jpg


Patent Number 262562
Indian Patent Application Number 1918/KOL/2008
PG Journal Number 35/2014
Publication Date 29-Aug-2014
Grant Date 27-Aug-2014
Date of Filing 03-Nov-2008
Name of Patentee GM GLOBAL TECHNOLOGY OPERATIONS, INC.
Applicant Address 300 GM RENAISSANCE CENTER, DETROIT, MICHIGAN
Inventors:
# Inventor's Name Inventor's Address
1 JAYANTHI PADMANABHAN 4310 BIRCH RUN TROY, MICHIGAN 48098
2 ANDREW M. ZETTEL 1839 MICHELLE COURT ANN ARBOR, MICHIGAN 48105
3 MICHAEL J. MILLER 56690 FAIRCHILD MACOMB, MI 48042
PCT International Classification Number H02H7/08
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 11/936,291 2007-11-07 U.S.A.