JP2005254888A - Device and method for failure diagnosis of power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To effectively utilize a memory in a failure diagnosis device of an electric power steering device, and to easily change the design thereof. <P>SOLUTION: A failure diagnosis unit 140 monitors the torque signal, the power supply voltage, or the like, starts the clocking when an abnormality is detected, and determines whether or not the predetermined failure detection time and failure determination time are elapsed. If the failure detection time and failure determination time are elapsed, each time stamp is recorded in a storage unit 160. The failure diagnosis unit 140 diagnoses a failure of an EPS based on these time stamps. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a failure diagnosis device, a method, and a program for a power steering device that diagnoses a failure by storing an event of the power steering device using a time stamp.

  As an auxiliary steering device for automobiles, an electric power steering device (EPS) using the torque of an electric motor is used. This electric power steering apparatus includes a torque sensor that detects a steering operation and a vehicle movement by a driver, an electric power steering control unit (ECU) that calculates an auxiliary steering force based on a detection signal from the torque sensor, and an ECU An electric motor that generates rotational torque based on the output signal, a reduction gear that transmits the rotational torque to the steering mechanism, and the like are provided.

In such an electric power steering apparatus, an abnormality in the torque sensor, the power source, etc. directly poses a danger to life and the like, and thus a failure diagnosis apparatus is incorporated in the ECU. This failure diagnosis apparatus performs a predetermined operation or warning by detecting a voltage abnormality such as a torque sensor or a power supply. Since noise may be mixed in the voltage of the torque sensor, it is determined as a failure when the voltage abnormality continues for a predetermined time. That is, as shown in FIG. 6 , the failure is detected after the output voltage of the torque sensor is lowered, and the failure is deterministically determined when a predetermined time has passed.

  The operation of the conventional failure diagnosis apparatus has been executed as shown in the flowchart of FIG. 12, for example. This flowchart represents a failure diagnosis program module, and is executed every predetermined time (for example, 5 msec) as a part of the main routine. First, the voltage detected from the torque sensor is A / D converted (step S1001), and it is determined whether or not the detected voltage is an abnormal value (for example, ground potential) (step S1002). If it is determined that the voltage is normal (NO in step S1002), the counter is cleared (step S1007), and the process returns to the main routine. On the other hand, if it is determined that the detected voltage is an abnormal value (YES in step S1002), the counter is incremented and the detection result is stored in the memory (step S1003). Further, in step S1005, it is determined whether or not a failure has definitely occurred, that is, whether or not the abnormal voltage has continued for a predetermined time. When a voltage abnormality is first detected, it is not determined that a failure has occurred deterministically, and the process returns to the main routine.

  It is determined whether or not the abnormal voltage is continuously detected for a predetermined time (for example, 500 msec) (step S1004), and when the abnormal voltage is continuously detected for a predetermined time, a predetermined fail-safe process is executed. (Step S1005).

  First, when a voltage abnormality is detected, fail-safe processing is not executed in steps S1004 to S005, and the processing returns to the main routine. Thereafter, the failure diagnosis processing program module is executed every predetermined time, and when the abnormal voltage is continuously detected, the detection results are sequentially recorded in the memory (step S1004). Further, when the abnormal voltage is detected exceeding a predetermined time, it is definitely determined that there is a failure, and a predetermined fail-safe process is executed (step S1005). Further, when the power steering device returns from the failure state, the diagnostic device executes failure return processing (step S1006).

  As described above, in the conventional diagnostic apparatus, after a voltage abnormality is detected, an event every predetermined time must be continuously recorded in the memory. For this reason, there has been a problem that the required capacity of the memory is increased and the utilization efficiency of the memory is degraded.

  In addition, since the time was measured based on the counter value when diagnosing and determining failure, the counter value had to be changed if the detection period was changed due to a design change, and the design flexibility was lacking. It was. That is, since the time for failure confirmation or the like is determined by the counter value incremented by the detection cycle, for example, if the detection cycle is changed from 10 msec to 20 msec, the cycle of the counter value must be changed. As a result, the time for failure detection is affected by the failure detection cycle, and thus a great amount of labor is required for the design change. Furthermore, according to the conventional method, when the detection process cannot be executed due to an overload of the process, there is a problem that the counter value is shifted and accurate time measurement cannot be performed.

As a timer processing method in general embedded software, a method described in Japanese Patent Laid-Open No. 2001-337840 has been devised. This method merely uses a timer with a minimum counter value among a plurality of timers requested to be activated, and does not measure an EPS failure event by a time stamp as in the present invention.
Japanese Patent Application Laid-Open No. 61-5294 discloses a dispatching method in multiprogramming, but does not suggest an invention related to a time stamp.
JP 2001-337840 A JP-A 61-52494

  The present invention has been made in view of the above-mentioned problems, and the problem to be solved by the present invention is that the failure detection of the EPS is performed using the time stamp, thereby making it possible to effectively use the memory and facilitate the design. It aims to realize the purpose.

  In order to solve the above-described problem, the present invention provides a detection unit that detects an abnormality of a power steering device at a predetermined period, a time stamp generation unit that generates a time stamp, a time point when the abnormality is detected, and the abnormality Comprises a storage means for storing a time stamp at the time when the power steering apparatus has continued for a predetermined time, and a determination means for determining a failure of the power steering device based on the time stamp.

Further, the present invention tentatively determines a failure of the power steering device when the abnormality has elapsed for a first time, and deterministically determines a failure of the power steering device when the second time has elapsed. It is characterized by.
Further, the time stamp generating means is composed of a free-run timer.
The storage means stores a failure detection flag that is set when the first time has elapsed and a failure confirmation flag that is set when the second time has elapsed, and the determination means When the failure detection flag and the failure confirmation flag are set, the failure is definitely determined.

The best mode for carrying out the present invention will be described below with reference to the drawings.
FIG. 1 is a schematic view of an electric power steering apparatus according to the present invention. In this figure, the end of the shaft 9a of the handle 9 is connected to the rack and pinion 6 via universal joints 6a and 6b. The rack and pinion 6 is provided with a wheel tie rod 6c so that the rotational movement of the handle 9 is converted into the axial movement of the tie rod 6c.

  A torque sensor 4 is provided on the shaft 9a of the handle 9, and this torque sensor 4 outputs the steering torque of the handle 9 as an electric signal. Further, a reduction gear 8 and a motor 3 are attached to the shaft 9a, and the rotational torque of the motor 3 is transmitted to the shaft 9a via the reduction gear 8.

  The ECU 1 calculates the auxiliary steering torque based on the detection signal from the torque sensor 4 and the vehicle speed signal from the vehicle speed sensor 2 as described above, and sends a drive signal based on the calculation result to the motor 3. A power supply 5 is connected to the ECU 1 via an ignition key 5a, and a current is supplied to the ECU 1 by turning on the ignition key 5a.

  FIG. 2 is a block diagram showing the hardware configuration of the ECU 1. The ECU 1 includes an A / D converter 110, an I / O interface 111, a timer 112, a CPU 113, a ROM 114, a RAM 115, a flash ROM 116, a PWM 117, an A / D converter 118, a motor drive circuit 118, a motor current detection circuit 120, and a bus 121. Has been.

  The A / D converter 110 converts the detection signal output from the torque sensor 4 and the voltage of the power source 5 into a digital signal. The I / O interface 111 counts the vehicle speed pulse from the vehicle speed sensor 2 and converts it into a digital signal. To convert.

  The timer 112 is for measuring the time used as a time stamp, and when an EPS failure event is detected, the occurrence time of the event is sent to the CPU 113. As shown in FIG. 7, the timer 112 is composed of a free-run counter that repeatedly counts up from 0000h to FFFFh. The count-up cycle can be arbitrarily determined. For example, when it is set to 1 msec, a time stamp having a cycle of 65536 msec (about 1 minute) can be generated. When the count-up cycle is 2 msec, a time stamp having a cycle of about 2 minutes can be generated. The time stamp generated in this way is recorded as a counter value.

  The ROM 114 is used as a memory for storing a control program for the motor 3 and a fail safe function program, and the RAM 115 is used as a work memory for operating the program. The flash ROM 116 is a memory that can retain the stored contents even after the power is shut off, and a failure diagnosis result or the like is written therein.

  The PWM controller 117 is for converting a signal representing the torque of the motor 3 into a pulse width modulated signal. The motor drive circuit 119 is composed of an inverter circuit, and is for generating drive power based on a signal output from the PWM controller 117. The motor current detection circuit 120 is for detecting a counter electromotive voltage generated in the motor 3, and the counter electromotive voltage is converted into a digital signal by the A / D converter 118 and then sent to the CPU 113. Yes.

  FIG. 3 shows a functional block diagram of the ECU 1. The functions of the auxiliary torque calculation unit 130, the state transition control unit 170, the failure diagnosis processing unit 140, the timing unit 150, and the storage unit 160 shown in this figure are realized by the CPU 113. The auxiliary torque calculation unit 130 has a function of calculating auxiliary torque based on the torque signal from the torque sensor 4 and the vehicle speed signal from the vehicle speed sensor 2.

  The failure diagnosis processing unit 140 is for monitoring a torque signal, a power supply voltage, and the like, and executing failure diagnosis processing, failure recovery processing, and the like when an abnormality is detected. Examples of the voltage abnormality include voltage drop (8 V or less), voltage increase (16 V or more), instantaneous interruption (about 5 msec), and the like. By setting a predetermined threshold value in advance, it is possible to determine voltage abnormality.

  The timer unit 150 has a function of generating a time stamp by a counter and giving it to the failure diagnosis processing unit 140. The storage unit 160 displays the event when an abnormality such as a torque signal is detected in the failure diagnosis processing unit 140. A memory for storing together with a time stamp. The state transition control unit 170 is for controlling the auxiliary torque based on the diagnosis result by the failure diagnosis processing unit 140. That is, when the EPS failure is diagnosed, the state transition control unit 170 gives an instruction such as a gradual reduction process of the auxiliary torque to the auxiliary torque calculation unit 130, and again permits the generation of the auxiliary torque when the failure is recovered. And the like are given to the auxiliary torque calculator 130. In this way, the fail safe at the time of EPS failure is executed.

  FIG. 4 is a functional block diagram of the auxiliary torque calculator 130 of the ECU 1. The auxiliary speed calculation unit 130 represents a transfer function based on so-called PID control. The steering torque T detected by the torque sensor 4 is input to the phase compensator 131. The phase compensator 131 is also for performing control stably by compensating for the phase shift of the steering torque T. The steering assist command value calculator 132 determines a steering assist command value I that is a control target value of a current to be supplied to the motor 3 based on the phase compensated steering torque TA and the vehicle speed V from the vehicle speed sensor 2.

  The steering assist command value I is input to the subtractor 108 and to the differential compensator 133. The differential compensator 133 is provided to improve the response speed of the control. The deviation (Ii) of the subtractor 138 is input to the proportional calculator 104, and a product of the deviation (Ii) and a predetermined proportional coefficient is output from the proportional calculator 134. Further, the deviation (I-i) is input to the integration calculator 105, and an integral value is calculated on the time axis of the deviation (I-i).

  The adder 139 outputs the current control value E by adding the calculated values from the differential compensator 133, the proportional calculator 134, and the integral calculator 135. The motor drive circuit 136 applies a drive current based on the current control value E to the motor 7 so that the motor 3 generates a predetermined torque. The motor current detection circuit 137 detects the motor current value i and feeds it back to the subtracter 138. In this way, control is performed such that the motor current value i matches the current control value E.

  In addition to the transfer function described above, the ECU 1 has handle return compensation, motor maximum current control, a self-diagnosis function, a communication function, and the like. For example, the steering wheel return compensation performs control for restoring the steering wheel 9 to the neutral position. In general, in the electric power steering apparatus, the self-aligning torque is likely to be weak due to the influence of the reduction gear 8 and the like, and thus the handle is difficult to return to the neutral position. Therefore, the motor angular velocity is detected by detecting the voltage between the motor terminals and the motor current when the motor 3 is rotated by the action of the self-aligning torque, and the compensation current value for restoring the handle to the neutral position is calculated. doing.

  FIG. 5 is a diagram for explaining a configuration of a failure flag and failure management data according to the present embodiment. These flags and data are written in the storage unit 160 including the RAM 115 or the flash ROM 116.

  The failure flag includes a determination assistance flag, a failure detection flag, a failure confirmation flag, a failure record flag, a failure mask flag, an initial diagnosis flag, and the like. The determination auxiliary flag represents the previous determination result, and is an auxiliary flag used for determining failure detection and determination. The failure detection flag is a flag indicating that a failure has been detected. The failure detection is judged when a predetermined time has elapsed after the torque signal, the power supply voltage, etc. are out of the threshold range. In this way, it is possible to prevent erroneous detection due to noise by determining that a failure occurs when a voltage abnormality has passed for a predetermined time. The failure confirmation flag is a flag that is set when a predetermined time has elapsed since the failure was detected. When it is determined that the failure has been confirmed, the failure diagnosis processing unit 140 executes fail-safe processing at the time of failure.

  The failure record flag is a flag for recording a confirmed failure. This failure record flag is retained even after the ECU 1 is powered off, and it is necessary to manually execute the all clear function in order to erase the failure record flag. The failure mask flag is a flag for invalidating the failure. That is, when there is no need to execute processing such as detection, determination, and recording of a failure for some reason, this failure mask flag may be set. The initial diagnosis flag is a flag indicating that the initial diagnosis is completed. The initial diagnosis items are set in the initial process, and the initial diagnosis flag is reset when each initial diagnosis is completed.

The measurement start time represents a time stamp when an abnormal voltage is detected. Based on the time stamp of the measurement start time, determination of failure detection and failure determination is made. The address to the time stamp indicates an area on the RAM 115 in which the time at the start of measurement is stored. The CPU 113 can acquire the measurement start time by referring to this address. The failure detection time represents the time (msec) until a failure is detected. For example, when the failure detection time is set to 50 msec, it is determined that a failure has been detected after 50 msec has elapsed since the abnormality of the torque sensor signal was detected. The failure confirmation time represents the time from when a failure is detected until the failure is determined. For example, when the failure confirmation time is set to 500 msec, the failure is definitely determined based on the passage of 500 msec after the failure is detected. The failure recovery time represents the time from when the EPS resumes normal operation until it is determined that the failure is recovered. The failure flag index is a name for indicating the various flags described above, and the failure flag position represents the bit position of the various flags. The CPU 113 can determine the state of the EPS by referring to the failure flag index and the failure flag position.
Subsequently, the operation of the failure diagnosis apparatus according to the present embodiment will be described with reference to the flowcharts of FIGS.

<Overall processing>
FIG. 8 is a flowchart showing the overall processing of the failure diagnosis apparatus. First, the CPU 113 sets flags and variables on the RAM 115 to initial values (step S601), and acquires a torque signal and a signal obtained by A / D converting the power supply voltage (step S602). Further, the CPU 113 inputs a signal from the vehicle speed sensor 2 and outputs predetermined power to the motor 3 (step S603). The CPU 113 executes an auxiliary torque calculation process based on the input torque signal or the like (step S605). After the diagnosis cycle has elapsed (YES in step S605), the CPU 113 executes failure diagnosis processing (S606). That is, the CPU 113 executes a failure diagnosis process for each predetermined diagnosis cycle while repeating the processes of steps S601 to S606 described above.

  FIG. 9 is a flowchart showing an overview of the failure diagnosis process shown in step S606 described above. First, when an execution diagnosis condition such as a diagnosis time is satisfied (YES in step S701), the CPU 113 determines whether the detected voltage exceeds 4.5V, that is, whether the torque sensor 4 is short-circuited to the power supply potential. Judging. If the determination result is YES, the CPU 13 executes a fault step-up process (step S703), otherwise executes a fault step-down process (step S704). Details of the fault step-up and fault step-down processes will be described later. These processes are for executing detailed processes such as failure diagnosis, failure determination, and failure recovery as described later. Similarly, the CPU 113 determines whether or not the detected voltage has become lower than 0.5 V in step S705, that is, whether or not the torque sensor 4 is short-circuited to the ground potential. If the determination result is YES, the CPU 113 executes a fault step-up process (step S706), otherwise executes a fault step-down process (S707). Next, details of the failure diagnosis process of FIG. 9 will be described in time series.

<Normal operation (t <T0)>
In the flowchart of FIG. 9, when the detected torque signal, power supply voltage, and the like are within the threshold range (current time t <T0 in FIG. 6), the determination results in steps S702 and S705 are NO, The fault step down process of step S704 and step S707 is executed. That is, the CPU 113 executes a fault step-down process using data such as various flags, current time, and time stamp as arguments. Details of this fault step-down process are shown in FIG. The CPU 113 acquires various flags, time, and time stamp (step S91), and determines whether or not the auxiliary determination flag is set (ON) (step S902). In the initial state, the determination assisting flag is reset (OFF), so that the processes in steps S905 and after are executed without executing the processes in steps S903 to S904. Since both the failure confirmation flag and the failure detection flag have been reset (NO in step S905, NO in step S906), the process returns to the flowchart of FIG. 9 without executing the processing from step S907.

<When a failure occurs (t = T0)>
When the torque signal becomes an abnormal voltage due to a failure of the torque sensor or the like (YES in step S702 or S705), the CPU 113 executes a fault step-up process using the power fault parameter or the ground fault parameter as an argument. First, the CPU 113 acquires information such as various flags, the current time, and a time stamp (step S801), and determines whether or not the auxiliary determination flag is reset (OFF) (step S802). When an abnormal voltage is detected for the first time, the determination auxiliary flag remains reset, so the determination result is NO and the CPU 113 sets (ON) the determination auxiliary flag (step S803) and acquires a timer value. (Step S804).

  Further, at this time, since the failure confirmation flag is reset (OFF), the determination result of step S805 is NO, and the processing after step S806 is executed. In step S806, since the failure detection flag is reset as well, the result of the determination is NO, and the CPU 113 performs the determination in step S807. That is, it is determined whether or not the current time t has exceeded the failure detection time T1, and if the determination result is YES, a failure detection flag is set. On the other hand, if the current time t is less than the failure detection time T1 (NO in step S807), the processing after step S809 is executed without setting the failure detection flag. In step S809, the CPU 113 determines whether or not the current time t has exceeded the failure confirmation time T2. At this time, since the current time t has not reached the failure confirmation time T2, the process returns to the flowchart of FIG. 9 without executing the processing of steps S810 to S811.

<From failure occurrence to failure detection (T0 <t <T1)>
If the timer value t is between the failure occurrence time T0 and the failure detection time T1, the determination auxiliary flag has already been set (YES in step S702), so the CPU 113 sets the timer value t to the failure detection time in step S705. It is determined whether or not T1 has been reached. If the timer value t has not yet reached the failure detection time (YES in step S705), the process returns to the main routine without being determined as having detected the failure.

<From failure detection to failure confirmation (T1 <t <T2)>
When the timer value t exceeds the failure detection time T1 for the first time, the failure detection flag remains reset (OFF) (NO in step S806), so the processing from step S807 is executed. In step S807, since the current time exceeds the failure detection time T1, the determination result is YES and the CPU 113 sets a failure detection flag (step S808). At this time, since the current matter has not reached the failure confirmation time T2 (NO in step S809), the CPU 113 returns to the flowchart of FIG. 9 without executing the processing in step S810 and subsequent steps.

<When failure is confirmed (t>T2)>
When the failure determination time T2 is reached by counting up the timer value t, the failure is definitely determined. That is, the determination result in step S809 is YES, and the CPU 113 sets a failure confirmation flag and a failure detection flag (steps S810 to S811) and records the current time as a time stamp. Further, the CPU 113 executes predetermined fail-safe processing such as gradual reduction processing of auxiliary torque.

<Failure recovery>
When the EPS returns from the failure state after it is determined that the failure has been confirmed, the voltage such as the torque signal becomes a normal value (NO in steps S702 and S705), and the fault step down process is executed (step S704). S707). When the fault step-down process is executed for the first time after it is determined that the failure has been determined, the determination auxiliary flag is set (YES in step S902), so the CPU 113 resets the determination auxiliary flag (step S903), A timer value is acquired (step S904). If the predetermined failure recovery time is exceeded (YES in step S907), the CPU 113 resets the failure detection flag (step S908) and returns to the flowchart of FIG.

  As described above, according to the failure diagnosis apparatus according to the present embodiment, the time stamp at each event such as when an EPS failure is detected or when a failure is confirmed is recorded, so that the memory can be used effectively. Become. That is, unlike the prior art, since it is not necessary to record all events for each detection cycle in the memory, the amount of memory used can be minimized. Moreover, since the failure detection time T1 and the failure confirmation time T2 can be freely set independently of the detection cycle, it is possible to easily change the design as compared with the prior art.

  Although the present embodiment has been described above, the present invention is not limited to the above-described configuration and can be changed without departing from the gist of the present invention. For example, the electric power steering device is a column type or a rack type. Regardless, it is also applicable to a hydraulic power steering device. Further, the form of the program is not limited to the above-described flowchart, and can be changed as long as the same function can be realized.

1 is a schematic view of an electric power steering apparatus according to the present invention. It is a block diagram of EPS concerning this invention. It is a functional block diagram of EPS concerning the present invention. It is a functional block diagram of the auxiliary torque calculating part which concerns on this invention. It is a figure for demonstrating the various flags and variables which concern on this invention. It is a figure for demonstrating the timer of the failure diagnosis apparatus based on this invention. 6 is a timing chart for explaining a failure diagnosis process according to the present invention. It is a main flowchart showing operation | movement of EPS which concerns on this invention. It is a flowchart showing the failure diagnosis process based on this invention. It is a flowchart showing the fault step-up process which concerns on this invention. It is a flowchart showing the fault step-down process which concerns on this invention. It is a flowchart showing operation | movement of the conventional failure diagnosis apparatus.

Explanation of symbols

112 timer (time stamp generation means)
113 CPU (determination means)
115 RAM (storage means)
140 Fault diagnosis storage unit 150 Timing unit 160 Storage unit

Claims (8)

Detecting means for detecting an abnormality of the power steering device at a predetermined period;
A time stamp generating means for generating a time stamp;
Storage means for storing a time stamp when the abnormality is detected and when the abnormality has continued for a predetermined time;
A failure diagnosis apparatus for a power steering apparatus, comprising: a determination unit that determines a failure of the power steering apparatus based on the time stamp.   The determination means tentatively determines a failure of the power steering device when the abnormality has elapsed for a first time, and deterministically determines a failure of the power steering device when the second time has elapsed. The failure diagnosis apparatus for a power steering apparatus according to claim 1, wherein:   2. The failure diagnosis apparatus for a power steering apparatus according to claim 1, wherein the time stamp generating means comprises a free-run timer.   The storage means stores a failure detection flag that is set when the first time has elapsed, and a failure confirmation flag that is set when the second time has elapsed, and the determination means detects failure The failure diagnosis device for a power steering device according to claim 2, wherein the failure is determined deterministically when the flag and the failure confirmation flag are set. A detection step of detecting an abnormality of the power steering device at a predetermined period;
A generation step for generating a time stamp;
A storage step of storing a time stamp when the abnormality is detected and a time stamp when the abnormality continues for a predetermined time;
A power steering apparatus failure diagnosis method comprising: a determination step of determining a failure of the power steering apparatus based on the time stamp.   In the determining step, a failure of the power steering device is detected when the abnormality has passed for a first time, and a failure of the power steering device is definitely determined when the second time has passed. The power steering apparatus failure diagnosis method according to claim 1.   The storing step stores a failure detection flag that is set when the first time has elapsed and a failure confirmation flag that is set when the second time has elapsed, and the determination step is a failure detection The failure diagnosis method for a power steering apparatus according to claim 2, wherein the failure is deterministically determined when the flag and the failure confirmation flag are set. Detecting an abnormality of the power steering device at a predetermined cycle;
A generation step for generating a time stamp;
A storage step of storing a time stamp when the abnormality is detected and a time stamp when the abnormality continues for a predetermined time;
A power steering apparatus failure diagnosis program comprising: a determination step of determining a failure of the power steering apparatus based on the time stamp

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