Method for monitoring a rotary encoder in a torque machine

Abstract

Method for monitoring an electrically operated torque machine (35) configured to generate torque in a hybrid powertrain system (20), the method comprising: Signal outputs are monitored by a rotary encoder (37) which is designed to monitor a rotary position of the torque machine (35); when a fault warning condition (203) is detected, which is associated with the signal outputs of the rotary indicator (37), a motor torque capacity (212) of the torque machine (35) is reduced; When the fault warning condition (203) is cleared, a condition (250) with a ramped increase in torque is executed to increase the motor torque capacity (212) of the torque machine (35); and a notification of a fault event (245, 245', 245"), which is associated with the signal outputs of the rotary encoder (37), is only provided if the motor torque capacity (212) fails to reach a motor torque capacity threshold (270) within a recovery time interval threshold while the condition (250) is operating with ramped torque; wherein, after the fault warning state (203) is cleared, a recovery state (240) is executed before the state (250) with ramped torque increase is executed, and where the execution of the recovery state (240) includes setting the motor torque capacity (212) to 0% for a period of time before the ramp-up torque state (250) is executed.

Description

TECHNICAL AREA

[0001] This invention relates to drive train systems that use electrically operated torque machines to generate torque, and in particular to a method for monitoring an electrically operated torque machine. BACKGROUND

[0002] The statements in this section provide only background information relating to the present invention and may not represent the prior art.

[0003] Powertrain systems use electrically driven torque machines to generate drive torque for propulsion. Common torque machines include multiphase electric motors / generators electrically coupled to energy storage devices via high-voltage electrical buses and rectifier / inverter modules. Torque machines can use rotary encoders to monitor rotational position and speed, and use this information to control and operate them. Rotary encoder failures can result in suboptimal torque machine behavior, with poor torque control or a complete inability to control the motor. Rotary encoder failures can lead to other motor failure modes, such as overcurrent conditions. Rotary encoder failures can include intermittent faults that are difficult to diagnose and detect.

[0004] Known rotary encoder errors include a signal loss error (LOS error), a signal degradation error (DOS error), and a track loss error (LOT error). Known schemes for monitoring and diagnosing rotary encoders include monitoring the duration and number of displayed rotary encoder errors and monitoring any motor torque output associated with a rotary encoder error. A rotary encoder error can be detected if the duration and number of displayed errors exceed a predetermined threshold or if the motor torque output is outside a predetermined window. Known schemes for rotary encoder error detection include counting the number of displayed errors during a key-on cycle.

[0005] Document CN 102 756 667 A discloses a torque control method for electric vehicles that precisely controls the output torque of an electric motor according to the driver's intentions. If a motor torque sensor fault occurs, a motor control unit outputs a fault limit torque.

[0006] German patent application DE 10 2008 022 979 A1 discloses methods for diagnosing faults in a motor-rotary encoder system comprising two motor-rotary encoder units, each coupled to a decoder of a motor controller such that a first rotary encoder can be coupled to a first or second decoder of the motor controller. By switching the couplings, faults in the rotary encoders and the decoders can be detected.

[0007] In addition, reference should be made here to DE 10 2010 034 106 A1, which, however, was not yet known on the priority date relevant here. SUMMARY

[0008] According to the invention, a method for monitoring an electrically operated torque machine is presented, characterized by the features of claim 1.

[0009] A hybrid powertrain system includes an electrically driven torque machine designed to generate torque. A method for monitoring the torque machine involves monitoring the signal outputs of a rotary encoder designed to monitor the rotational position of the torque machine. Upon detection of a fault warning condition associated with the rotary encoder's signal outputs, the torque machine's motor torque capacity is reduced.Upon clearing a fault warning condition, a ramp-up torque state is executed to increase the motor torque capacity of the torque machine. Following the clearing of the fault warning condition, a recovery state is executed before the ramp-up torque state is executed. The recovery state includes setting the motor torque capacity to 0% for a specified time period before the ramp-up torque state is executed. A fault notification associated with the rotary encoder signal outputs is provided only if the motor torque capacity fails to reach a threshold value within a specified recovery time period while the ramp-up torque state is executed. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] One or more embodiments will now be described with reference to examples in the accompanying drawings, in which: Fig. 1 a vehicle which includes a hybrid powertrain system coupled to a final drive and controlled by a control system, shown schematically according to the invention; Fig. 2 a data graph showing several simultaneous signals associated with controlling the operation of a torque machine, which include signals associated with monitoring the operation of a rotary encoder according to the invention; Fig.3 is a data graph that shows several simultaneous signals associated with controlling the operation of a torque machine and represents the motor speed control states, which indicate recovery states and subsequent states with ramped increase of torque associated with detected rotation sensor faults according to the invention; and Fig. 4 schematically shows a control scheme in the form of a flowchart for monitoring the operation of the torque machine, which includes the detection of faults associated with the operation of the rotary encoder during continuous drive train operation according to the invention. DETAILED DESCRIPTION

[0011] Referring now to the drawings, in which what is shown is intended only to illustrate certain exemplary embodiments, it shows Fig.Figure 1 schematically represents a vehicle 100 containing a hybrid powertrain system 20 coupled to a final drive 60 and controlled by a control system 10. Reference numerals throughout the description denote identical elements.

[0012] The hybrid powertrain system 20 includes a mechanical power path 84 comprising an internal combustion engine 40 and an electrically driven torque machine 35, which are mechanically coupled to a hybrid transmission 50 having an output element 62 coupled to the final drive 60. The mechanical power path 84 of the hybrid powertrain system 20 can be a series mechanical power path, a parallel mechanical power path, a mechanical power path with a belt-driven generator-starter, or any other suitable mechanical power path for transmitting torque between the engine 40, the torque machine 35, the transmission 50, and the final drive 60.

[0013] The hybrid powertrain system 20 includes a communication path 82, which contains a communication bus 18, to enable communication in the form of sensor signals and actuator command signals between the control system 10 and the elements of the hybrid powertrain system 20. It can be stated that the communication path 82 facilitates the transmission of information to and from the control system 10 using one or more communication systems and one or more communication devices, which include, for example, the communication bus 18, a direct connection, a local network bus, a serial peripheral interface bus (SPI bus), and wireless communication.

[0014] High-voltage electrical power can be provided by a high-voltage battery 25, which is electrically connected to a rectifier / inverter module 32 via a high-voltage DC bus 29. The rectifier / inverter module 32 is electrically connected to the torque machine 35 via a power bus 31. In one embodiment, an electrical DC / DC power converter 34 is electrically connected to a low-voltage bus 28 and a low-voltage battery 27, and it is also electrically connected to the high-voltage bus 29. Such electrical power connections are known and are not described in detail here.

[0015] A hybrid powertrain system 20 comprises the engine 40, a multi-cylinder internal combustion engine that converts fuel into mechanical power through a combustion process. The engine 40 is equipped with multiple actuators and sensing devices for monitoring operation and supplying fuel to form a combustion charge in order to generate torque that responds to a torque request from an operator.

[0016] The electrically driven torque machine 35 is preferably a multiphase electric motor / generator configured to convert stored electrical energy into mechanical power and to convert mechanical power into electrical energy that can be stored in the high-voltage battery 25. The torque machine 35 is mechanically coupled to either the power machine 40 or the transmission 50 at a suitable location to transmit torque between them. In one embodiment, the torque machine 35 is mechanically coupled to a torque transmission element of the transmission 50. In another embodiment, the torque machine 35 is mechanically coupled to a torque transmission element of the power machine 40, e.g., a crankshaft, via a pulley and belt or another suitable connection.

[0017] The torque machine 35 comprises a rotor and a stator and an associated rotary encoder 37. The rotary encoder 37 is a variable reluctance device comprising a rotary encoder stator and a rotary encoder rotor mounted on the rotor and stator, respectively, of the torque machine 35. The rotary encoder 37 preferably includes a signal decoding chip 39 that monitors signals output by the rotary encoder 37 and calculates an angular position and a rotational speed of the rotary encoder rotor. The angular position and rotational speed of the rotary encoder rotor are used to monitor the angular position and rotational speed of the torque machine 35 in a manner suitable for controlling its operation, which includes controlling the torque output.

[0018] The decoder chip 39 is designed to monitor the rotational position and speed of the rotor of the torque machine 35 in a manner suitable for controlling its operation. The decoder chip 39 is also designed to detect and transmit errors associated with its generated signal, including signal loss errors (LOS errors), signal degradation errors (DOS errors), and track loss errors (LOT errors). A LOS error can be detected when the rotation indicator signal is below a threshold value. A DOS error can be detected when the rotation indicator signal is saturated or exhibits excessive noise. A LOT error can be detected when the quality of the rotation indicator signal prevents the operation of a phase-locked loop or other similar tracking strategy for monitoring the motor position.This can include the torque machine 35 operating at a speed rate exceeding a threshold. Rotational indicator errors are associated with one or more of the LOS, DOS, and LOT errors of the decode chip 39. Rotational indicator errors include a short-duration error (SD error), a medium-duration error (MD error), a long-duration error (LD error), and a repeated medium-duration error (RMD error). The different rotational indicator errors can be distinguished based on their duration relative to a predetermined time interval associated with the motor control.

[0019] The rectifier / inverter 32 can be operated to transform high-voltage DC electrical power into high-voltage AC electrical power, and it can also be operated to transform high-voltage AC electrical power into high-voltage DC electrical power. The rectifier / inverter 32 preferably uses pulse-width modulation control to convert stored DC electrical power from the high-voltage battery 25 into AC electrical power to drive the torque machine 35 to generate drive torque. Similarly, the rectifier / inverter 32 converts mechanical power in the torque machine 35 into DC electrical power, which can be stored in the high-voltage battery 25 as part of a regenerative control strategy.It can be stated that the rectifier / inverter 32 is designed to receive motor control commands and to control the states of the rectifier / inverter in such a way as to provide the drive and regeneration functionality of the motor.

[0020] The transmission 50 preferably includes one or more differential gear sets and actuated clutch components to achieve torque transmission between the power unit 40, the torque unit 35, and the output element 62 over a range of speeds. The transmission 50 includes any suitable configuration, which includes the ability to operate in fixed-gear modes and continuously variable modes to transmit torque.

[0021] The final drive 60 can include a differential gear device 65, which is mechanically coupled to an axle 64 or a half-shaft, which in one embodiment is mechanically coupled to a wheel 66. The final drive 60 transmits drive power between the hybrid transmission 50 and a road surface. It should be noted that the hybrid powertrain system 20 serves for illustrative purposes.

[0022] The control system 10 includes a control module 12, which is connected to an operator interface 14 via signal transmission. The control module 12 is preferably connected to individual elements of the hybrid powertrain system 20 either directly or via the communication bus 18. The control module 12 is connected to the sensing devices of the high-voltage battery 25, the rectifier / inverter module 32, the torque motor 35, the power motor 40, and the hybrid transmission 50 via signal transmission in order to monitor their operation and determine their parameter states.

[0023] The operator interface 14 of the vehicle 100 contains several human / machine interface devices through which the vehicle operator commands the operation of the vehicle 100, which include, for example, an ignition switch to enable an operator to crank and start the engine 40, an accelerator pedal, a brake pedal, a gear range selector lever (PRNDL), a steering wheel and a headlight switch.

[0024] Control module, module, controller, control unit, processor and similar terms refer to any suitable or various combinations of one or more application-specific integrated circuits (ASICs), electronic circuits, central processing units (preferably microprocessors) and associated working and mass storage (read-only memory, programmable read-only memory, random access memory, hard disk drive, etc.) that execute one or more software or firmware programs, combinational logic circuits, input / output circuits and devices, suitable signal conditioning and buffering circuits and other suitable components to provide the described functionality.The control module includes a set of control algorithms, comprising resident software program instructions and calibrations, which are stored in memory and executed to provide the desired functions. The algorithms are preferably executed during preset loop cycles. These algorithms are executed, for example, by a central processing unit and can be used to monitor inputs from sensing devices and other network control modules, and to execute control and diagnostic routines to manage the operation of actuators. Loop cycles can be executed at regular intervals, for example, every 3, 125, 6, 25, 12.5, 25, and 100 milliseconds during continuous operation of the power unit and vehicle. Alternatively, algorithms can be executed in response to the occurrence of an event.

[0025] Fig.Figure 2 is a data graph that graphically displays several simultaneous signals associated with controlling the operation of the torque machine 35, including signals associated with monitoring the operation of the rotary encoder 37, preferably using signals output by the decoder chip 39. The signals comprise a rotary encoder state 202, an error counter 204, a motor control state 206, a rotor position determination function 208, a motor command state 210, a motor control state 211, a motor torque capacity 212, and a validity state 214 of an angular position. Elapsed time is indicated on the time axis 200.

[0026] At the beginning, i.e., before time T0 220, the rotary encoder state 202 is a fault-free state 201, indicating normal operation and the absence of a fault. Consequently, the fault counter 204 is zero, the motor control state 206 indicates that the rotary encoder 37 is operating as intended, i.e., is in a good state 255, the rotor position determination function 208 is in a first state 207 where the rotor position is determined using data from the rotary encoder 37, the motor command state 210 indicates that the torque machine 35 can be controlled to generate torque, the motor control state 211 is a pulse-width modulated control signal corresponding to the commanded motor torque, and the motor torque capacity 212 is not limited.is at 100%, and the validity state 214 of the angular position is valid 215, which indicates that the angular position output by the rotary encoder 37 is valid and thus the angular position of the torque machine 35 is valid and can be used for control purposes.

[0027] An error output by the rotary encoder 37 at time T0 220 causes the rotary encoder error state 202 to be moved from the error-free state 201 to an error warning state 203. Thus, the error counter 204 begins to increment, and the motor control state 206 indicates a corresponding caution state 235. During operation in caution state 235, the rotor position determination function 208 is in a second state 209, in which the rotor position can initially be determined by extrapolating the rotor position using previously acquired data from the rotary encoder 37. The motor command state 210 continues to indicate that the torque machine 35 can be controlled to generate torque. The motor control state 211 proceeds with the pulse-width modulated control signal corresponding to the commanded motor torque and with the unrestricted motor torque capacity 212, i.e., at 100%.The validity state 214 of the angular position is valid 215, indicating that the angular position output by the rotary encoder 37 is still considered valid. This initial time interval following the display of the rotary encoder state 202 in the fault warning state 203 is referred to as an initial run-out time interval and lasts until the fault counter 204 reaches a predetermined increment 205, which indicates a continuous time interval during which the rotary encoder state 202 is shifted into the fault warning state 203. The initial run-out time interval is associated with the ability to accurately extrapolate the angular position of the torque machine 35 for control purposes and can be on the order of 20 ms in one embodiment.

[0028] If the rotary encoder state 202 has been shifted into the fault warning state 203 for a period of time exceeding a threshold, as indicated by the rotary encoder state 202 in fault warning state 203 from time T0 220 to time T1 222, the torque machine 35 is switched off and the flow of electrical power to it is discontinued. The fault counter 204 may or may not continue incrementing. The motor control state 206 indicates a warning state 265. The rotor position determination function 208 is in a second section of the second state 209', in which the rotor position can no longer be determined by extrapolating the rotor position, and consequently, the rotor position is no longer available or is invalid. The motor command state 210 continues to indicate that the torque machine 35 can be controlled. The motor control state 211 interrupts the pulse-width modulated control signal, i.e.,It is at a PWM signal of 0%. The motor torque capacity 212 is set to 0%, indicating that the power output of the torque machine 35 is now reduced. The validity state 214 of the angular position is invalid 216, indicating that the angular position output by the rotary encoder 37 is invalid, and thus the angular position of the torque machine 35 is invalid and unusable for control purposes.

[0029] Starting at T1 222, which coincides with the fault counter 204 reaching a state indicating that the rotary encoder state 202 has been shifted into the fault warning state 203 for a certain period of time, exceeding a threshold, the operating system performs a retry run. During this run, the rotary encoder state 202 is continuously monitored to detect whether a fault has been cleared. There is a minimum time interval, displayed between T1 222 and T2 224, during which the electric motor is reduced to a motor torque capacity 212 of 0%, and motor control actions are suspended before a retry run is performed.

[0030] The detected fault can then be rectified, as shown at time 225. The rotary encoder state 202 changes from the fault warning state 203 to the fault-free state 201. The fault counter 204 begins to decrement, starting at a predetermined down counter value 205'. In one embodiment, the up counter value 205 is greater than the down counter value 205'. This operation is shown to be interrupted by the occurrence of another rotary encoder fault, which is indicated at time 225' by the rotary encoder fault 202 being moved to the fault warning state 203.

[0031] The detected fault is cleared at time 226. A recovery state 240 is displayed when the rotary encoder state 202 is moved from the fault warning state 203 to the fault-free state 201. The fault counter 204 begins to decrement, restarting at the predetermined down counter count 205'. The motor control state 206 indicates a shift to recovery state 240, but the operation of the torque machine 35 does not change during recovery state 240. Recovery state 240 is identified as the time interval associated with the decrementing of the fault counter 204 from the predetermined down counter count 205' to zero. An example of a complete recovery state 240 is displayed between time 226 and time 228.

[0032] Recovery state 240 ends at time T3 228 when fault counter 204 is decremented to zero. A ramp-up torque state 250 begins when fault counter 204 is decremented to zero. The display of ramp-up torque state 250 is a signal to the control system that the torque machine 35 can potentially be controlled to generate torque, even though the torque capacity of the torque machine 35 remains reduced. The torque capacity of the torque machine 35 is controlled, with the torque capacity being reduced and monotonically increased over time in the form of a ramp-up. This involves limiting the motor torque capacity 212 by limiting or restricting the torque output from the torque machine 35 to a rate of torque increase from 0% to 100% over a given time interval.Consequently, the power output of the torque machine 35 during state 250 with ramped torque increase is further reduced to produce a smooth torque transition without a sudden shock or abrupt change in engine torque.

[0033] At time T3 228, the error counter 204 is zero, the motor control state 206 indicates the beginning of state 250 with a ramped increase in torque, the rotor position determination function 208 is in the first state 207, in which the rotor position is determined using data from the rotary encoder 37, the motor command state 210 indicates that the torque machine 35 can be controlled to generate torque, although it is limited by the reduced motor torque capacity 212, and the motor control state 211 is a pulse-width modulated control signal corresponding to a commanded motor torque, which is limited by the reduced motor torque capacity 212. The validity state 214 of the angular position is valid 215, indicating that the angular position output by the rotary encoder 37 is valid, and consequently, the angular position of the torque machine 35 is valid and can be used for control purposes.

[0034] At time T5 230, the motor torque capacity 212 has increased to 100% and the torque capacity of the torque machine 35 is no longer reduced. The motor control state 206 is the good state 255, the rotor position determination function 208 is achieved using data from the rotation sensor 37, the motor command state 210 indicates that the torque machine 35 can be controlled to generate torque without limitation, and the motor control state 211 is a pulse-width modulated control signal corresponding to a commanded motor torque. The validity state 214 of the angular position is valid 215.Based on a definition, the rotary encoder errors, which include short-duration errors (SD errors), medium-duration errors (MD errors), long-duration errors (LD errors), and repeated medium-duration errors (RMD errors), can be distinguished based on their duration relative to a predetermined time interval associated with the motor control. An example error duration is given with reference to... Fig.Figure 2 shows when the rotary encoder state 202 switches from the fault-free state 201 to the fault warning state 203 and then back to the fault-free state 201, e.g., as shown between time 220 and time 225. An SD fault is identified when the fault duration is shorter than the caution state 235. The rotor speed remains substantially unchanged during an SD fault. In one embodiment, an SD fault and an associated caution state 235 have elapsed time intervals of less than 10 ms. An MD fault is identified when the fault duration is longer than the caution state 235 but shorter than a predetermined allowable repetition time interval, which may be in the range of 10 ms to 200 ms. An RMD fault is identified when there are repeated MD faults. An LD fault is identified when the fault duration is longer than the predetermined allowable repetition time interval.

[0035] Fig.Figure 3 is a data graph 300 that graphically displays several simultaneous signals associated with controlling the operation of the torque machine 35. The data graph 300 represents a series of motor speed states 206, indicating the caution states 235, recovery states 240, and subsequent states 250 with ramped torque increases described above. These states are associated with rotary encoder fault warnings, indicated by the movement of the rotary encoder state 202 between the fault-free state 201 and the fault warning state 203. The corresponding motor torque capacity 212 is shown, ranging from 0% to 100%, and includes a torque threshold 270, which is a calibratable torque value. A torque loss timer 213 is operated to measure the elapsed time associated with the reduction of the motor torque.As shown, the torque loss timer 213 is a time interval that starts when the motor torque capacity 212 is reduced, i.e., commanded to 0%, until the motor torque capacity 212 exceeds a predetermined torque threshold 270. In the context of the with reference to . Fig.In the operation described in section 2, the elapsed time period corresponds to the start of the recovery state 240 when the motor torque capacity 212 is reduced and the end of the reduced motor torque capacity 212 when the torque threshold 270 is exceeded during a subsequent state 250 with a ramped increase in torque. The data graph displays recovery time spans 260, 260', and 260". Recovery time span 260 indicates a period during which the engine torque capacity 212 is reduced. The malfunction indicator lamp (MIL) state is either OFF 217 or ON 219. If the recovery time span 260 is less than a predetermined threshold, no fault is indicated; that is, the MIL state is OFF 217. If the recovery time span 260 exceeds the predetermined time threshold, a fault is indicated; that is, the MIL state is ON 219.

[0036] As shown, an initial fault event 245 follows an initial caution condition 235 and includes a single recovery condition 240 and a subsequent condition 250 with a ramped increase in torque, associated with a rotary indicator fault warning condition 203. As shown, the motor torque capacity 212 exceeds the torque threshold 270 during the recovery period 260. The MIL condition is OFF 217.

[0037] A second fault event 245' comprises a further caution state 235 and a single recovery state 240 and a subsequent single time interval 250 with ramped increase, which are associated with a rotary indicator fault warning state 203. As indicated, the motor torque capacity 212 exceeds the torque threshold 270 after the second recovery time interval 260'. The MIL state is OFF 217.

[0038] A third fault event 245" comprises a caution condition 235 followed by several recovery intervals 240 and corresponding subsequent ramped intervals 250, associated with multiple turn-indicator fault warning conditions 203. As shown, the engine torque capacity 212 does not exceed the torque threshold 270 until after the third recovery interval 260", where the third recovery interval 260" exceeds a recovery interval threshold. The MIL condition switches to ON 219. The recovery interval threshold is a calibratable value determined based on the time and magnitude of reduced engine torque that can be perceived by a vehicle operator.

[0039] Fig.Figure 4 shows a control scheme in the form of a flowchart for monitoring the operation of the torque machine 35, which includes the detection of faults associated with the operation of the rotary encoder 37 during continuous operation of the drive train. The flowchart is executed periodically in a control module of the drive train system, preferably during one of the loop cycles. The control scheme monitors the occurrence of rotary encoder faults with the aim of identifying repetitive medium-duration faults (RMD faults) in a manner that allows repeated repetition runtimes after the elimination of a rotary encoder fault, which include repeated recovery states 240 and states 250 with a ramped increase in torque.This enables continuous operation of the drivetrain and notification of a rotary encoder fault to an operator, while minimizing the probability of prematurely commanding a shutdown of the torque machine 35. The fault detection takes into account elapsed time (duration) and the magnitude of the reduced torque capacity output by the torque machine 35, with threshold values ​​that may be associated with a change in torque output perceptible to a vehicle operator. The control scheme is described with reference to elements and parameters mentioned above in [reference missing]. Fig. 1, Fig. 2 and Fig. 3 were described.

[0040] Table 1 serves as the key to the flowchart of Fig. 4 provided, with the numerically labeled blocks and their associated functions disclosed as follows: Table 1 BLOCK Fig. 4 BLOCK CONTENTS 410 Operate a torque machine in good condition 420 Monitor rotary encoder fault status 422 Error warning displayed 430 Rate error warning 425 Execute precautionary measures 432 Perform rotary encoder restoration 434 Expiry time is expiring 435 Reduce engine torque capacity 445 Run recovery state 450 Check torque capacity reduction % Check duration of torque capacity reduction 452 Recovery time reached 455 Execute a condition with a ramp-like increase in torque 456 Repeat run total time is running out 458 Duration of torque capacity reduction in % exceeds calibration 460 Long-duration error reached 470 Shut down torque machine; illuminate MIL 480 Medium-duration fault reached; MIL illuminated

[0041] A control scheme operates the torque machine in good condition during continuous drive train operation (410), which includes monitoring the fault status of the rotary encoder (420).

[0042] When a fault warning is displayed in conjunction with the rotary encoder (422), the fault warning is evaluated (430). This involves identifying whether the displayed fault is a short-duration fault (SD fault), a medium-duration fault (MD fault), a long-duration fault (LD fault), or a repeated medium-duration fault (RMD fault). The different rotary encoder faults are distinguishable based on their duration relative to a predetermined time interval associated with the motor control, as discussed above. As can be seen, any of the aforementioned types of rotary encoder faults, i.e., LOS, DOS, and LOT, can result in a fault warning.

[0043] A precautionary state (425) is executed, which allows fault debouncing before any further actions affecting a machine's torque output are performed. As with reference to Fig. As described in section 2, during operation in caution state 235, the rotor position determination function 208 determines the rotor position by extrapolating the rotor position using data previously acquired by the rotary encoder 37, and the motor command state 210 continues to indicate that the torque machine 35 can be controlled to generate torque. If the fault warning associated with the rotary encoder is cleared during the caution state, a rotary encoder recovery is performed (432) and the torque machine returns to good state operation (410). This operation is generally associated with the detection and resolution of a short-duration fault (SD fault).

[0044] When a predetermined run-down time elapses during operation in the caution state (434), the motor torque capacity is reduced (435) and a recovery state is executed (445). The recovery state is the recovery state 240 described above, which is identified as the time interval that begins when a rotary encoder fault is cleared until a fault counter is decremented to zero. It should be noted that the recovery state enables signal and fault debouncing. If the recovery state completes successfully (452), a ramp-up torque state is executed (455). The ramp-up torque state involves increasing the torque capacity of the torque machine as described above, which includes a monotonous ramp-up of the motor torque over time.If the ramp-up torque condition is successfully completed, the torque machine returns to good-condition operation (410). This operation is generally associated with the detection and resolution of a single medium-duration fault (MD fault).

[0045] The process of reducing the motor torque (435) and executing the recovery state (445) and the ramp-up torque state (455) can be an iterative process during which medium-duration faults may occur repeatedly, referred to as recurrent medium-duration faults (RMD faults). This includes monitoring the reduced torque capacity and an associated reduced torque capacity timer when there is an indication that a recovery state has started (450).

[0046] Monitoring the reduced torque capacity and the associated reduced torque capacity timer provides a time measurement of the recovery time period 260, which is related to Fig. 3 is described, i.e. the period during which the motor torque capacity is reduced and the torque machine is operated below a predetermined torque threshold.

[0047] If the reduced torque capacity exceeds the predetermined torque threshold and the timer for the reduced torque capacity is less than a predetermined threshold, this indicates that the fault has been rectified within a suitable time period and the operation of the torque machine continues.

[0048] If the reduced torque capacity has not exceeded the predetermined torque threshold and the reduced torque capacity timer has not exceeded the predetermined torque threshold, monitoring of the rotary encoder continues as described. The motor torque capacity remains reduced, but no command is sent to notify the operator.

[0049] If the reduced torque capacity exceeds the predetermined torque threshold, but only after the torque loss timer has exceeded its predetermined threshold, a command is sent to notify the vehicle operator by illuminating the MIL (480). Powertrain system operation can then continue, including the execution of subsequent rerun events.

[0050] If the reduced torque capacity has not exceeded the predetermined torque threshold and the reduced torque capacity timer has exceeded the threshold, the command to notify the vehicle operator is sent by illuminating the MIL (480). This is how repeated medium-duration faults (RMD faults) are detected.

[0051] If a total retry run time elapses without a recovery state being successfully completed (456), this indicates the presence of a mature long-duration fault (460). The torque motor shuts down and a malfunction indicator lamp (MIL) illuminates to notify the operator of the fault. The powertrain system may continue to operate without input from the torque motor in systems that have this capability.

[0052] The control scheme described here allows a torque sensor fault to mature based on factors including the duration of a torque capacity reduction event. These factors include the magnitude of the torque reduction caused by the torque sensor fault and the duration of the torque reduction event. The choice of these two calibration expressions is based on experience gained while driving the vehicle when a torque sensor exhibits repeated faults of medium duration. It should be noted that this control scheme is implemented in a way that minimizes the shutdown of the torque sensor 35 and instead allows the MIL (Malfunction Indicator Lamp) to be illuminated only after a fault has matured.

Claims

A method for monitoring an electrically operated torque machine (35) configured to generate torque in a hybrid powertrain system (20), comprising: monitoring signal outputs from a rotary encoder (37) configured to monitor a rotational position of the torque machine (35); upon detection of a fault warning condition (203) associated with the signal outputs of the rotary encoder (37), reducing the motor torque capacity (212) of the torque machine (35); upon clearance of the fault warning condition (203), executing a ramp-up torque state (250) to increase the motor torque capacity (212) of the torque machine (35);and a notification of a fault event (245, 245', 245") associated with the signal outputs of the rotary encoder (37) is provided only if the motor torque capacity (212) fails to reach a motor torque capacity threshold (270) within a recovery time period threshold while the ramp-up torque state (250) is executed; wherein, upon clearance of the fault warning state (203), a recovery state (240) is executed before the ramp-up torque state (250) is executed, and wherein the execution of the recovery state (240) includes setting the motor torque capacity (212) to 0% for a period of time before the ramp-up torque state (250) is executed. Method according to claim 1, wherein performing the state (250) with ramped increase of torque to increase the motor torque capacity (212) of the torque machine (35) comprises that the motor torque capacity (212) is monotonically increased from 0% to 100% following the elimination of the fault warning state (203). Method according to claim 1, wherein detecting an error event (245, 245', 245") associated with the signal outputs of the rotary encoder (37) comprises detecting a signal loss error, a signal degradation error or a track loss error. Method according to claim 1, wherein detecting a fault event (245, 245', 245") associated with the signal outputs of the rotary encoder (37) comprises detecting a recurring fault of medium duration.

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