JP2013172543A - Motor control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a motor control device capable of appropriately controlling a motor even when an output value from variable value detection means returns from "abnormal" to "normal".SOLUTION: A motor control device 100 for electric power steering comprises: a torque sensor 1 which detects a steering torque; an abnormality/failure determination unit 2 which determines whether an output value from the torque sensor 1 is abnormal or normal; a low-pass filter 3 which sets an alternative value of the output value from the torque sensor 1; and a delay circuit 4. If the output value from the torque sensor 1 becomes "abnormal" when the motor control device is controlling a motor 11 on the basis of the output value from the torque sensor 1, the motor control device switches a change-over switch SW from "normal" to "abnormal" and controls the motor 11 on the basis of the alternative value instead of the output value from the torque sensor 1. In addition, if the output value from the torque sensor 1 returns from "abnormal" to "normal", the motor control device switches the change-over switch SW from "abnormal" to "normal" and controls the motor 11 on the basis of the output value from the torque sensor 1 instead of the alternative value.

Description

  The present invention relates to an electric motor control device that controls an electric motor based on an output value of a fluctuation value detecting means and controls the electric motor based on an alternative value when the output value of the fluctuation value detecting means is abnormal.

  As an electric motor control device, for example, there is an electronic control device for electric power steering as disclosed in Patent Documents 1 to 3. In this electronic control device, the steering torque of the steering is detected by a torque sensor (fluctuation value detecting means) in order to control a motor (electric motor) that applies steering assist force of the steering.

  The electronic control device of Patent Document 1 detects whether the output value of the torque sensor is abnormal or normal, and determines that the torque sensor is faulty if the output value of the torque sensor continues for a certain period of time. In addition, an alternative value of the torque sensor output value is calculated, and when the torque sensor output value is abnormal, it is based on the alternative value instead of the torque sensor output value even before determining that the torque sensor is faulty. Control the motor.

  In the electronic control device of Patent Document 2, when the output value of the torque sensor is normal, the target current value is set based on the output value of the torque sensor, the motor is controlled, and the target current value is stored in the RAM. Remember. When the output value of the torque sensor is abnormal, the past target current value is read from the RAM and the motor is controlled.

  In the electronic control device of Patent Document 3, a high-frequency component of the output value of the torque sensor is removed by a low-pass filter, and the motor is controlled based on the output value of the low-pass filter. Further, when an abnormality in the output value of the torque sensor is detected, the time constant of the low-pass filter is increased. Thereafter, when no abnormality is detected in the output value of the torque sensor, the time constant of the low-pass filter is restored.

  In Patent Documents 1 and 2, when the output value of the torque sensor becomes abnormal, the motor is appropriately controlled by controlling the motor based on an alternative value instead of the output value. In addition, a certain amount of time from when the output value of the torque sensor becomes abnormal until when the torque sensor failure is determined is secured to prevent erroneous determination. However, after the output value of the torque sensor once becomes abnormal, it may return to normal. In such a case, if the motor is continuously controlled based on the substitute value, the motor cannot be appropriately controlled.

JP-A-2005-75026 JP 2003-63433 A JP 2009-132344 A

  The subject of this invention is providing the electric motor control apparatus which can control an electric motor appropriately, even when the output value of a fluctuation value detection means returns to normal from abnormality.

  In the motor control device according to the present invention, the fluctuation value detecting means for detecting the fluctuation value necessary for controlling the electric motor, and the output value determining section for judging whether the output value of the fluctuation value detecting means is abnormal or normal And alternative value setting means for setting an alternative value for the output value of the fluctuation value detecting means. Then, when the motor is controlled based on the output value of the fluctuation value detecting means, if the output value of the fluctuation value detecting means becomes abnormal, it is based on the alternative value instead of the output value of the fluctuation value detecting means. When the output value of the fluctuation value detecting means becomes normal after becoming abnormal once, the electric motor is controlled based on the output value of the fluctuation value detecting means instead of the substitute value.

  According to the above, when the output value of the fluctuation value detecting means becomes abnormal, the motor is controlled based on the alternative value instead of the output value, and the output value of the fluctuation value detecting means becomes normal from the abnormality In addition, the electric motor is controlled based on the output value of the fluctuation value detecting means instead of the substitute value. For this reason, the electric motor can be appropriately controlled not only when the output value of the fluctuation value detecting means becomes abnormal, but also when the output value returns to normal from the abnormality.

  Further, in the present invention, in the above motor control device, when the output value of the fluctuation value detecting means becomes normal after becoming abnormal once, and the normal state continues for a predetermined time, the fluctuation value is replaced with a substitute value. You may make it control an electric motor based on the output value of a detection means.

  In the present invention, in the motor control device, the time required for switching from the output value of the fluctuation value detecting means to the alternative value is shorter than the time required for switching from the alternative value to the output value of the fluctuation value detecting means. Also good.

  In the present invention, the motor control device may further include a failure determination unit that determines that the variation value detection unit is faulty when an abnormal state of the output value of the variation value detection unit continues for a predetermined time. . In this case, the time required for the failure determination means to determine the failure of the fluctuation value detection means may be longer than the time required to switch from the substitute value to the output value of the fluctuation value detection means.

  Further, according to the present invention, in the above motor control device, the motor is composed of a motor that applies a steering assist force of the steering, for example, and the fluctuation value detecting means is composed of a torque sensor that detects the steering torque of the steering, for example. The electric motor control device in this case is an electronic control device for electric power steering, and controls the motor with a target value set based on the output value or alternative value of the torque sensor.

  ADVANTAGE OF THE INVENTION According to this invention, even when the output value of a fluctuation value detection means returns to normal from abnormality, it becomes possible to provide the electric motor control apparatus which can control an electric motor appropriately.

It is the block diagram which showed an example of the electric motor control apparatus of this invention. It is the flowchart which showed operation | movement of the electric motor control apparatus by 1st Embodiment. It is the time chart which showed an example of the change of each output value of the electric motor control apparatus by 1st Embodiment. It is the time chart which showed an example of the change of each output value of the electric motor control apparatus by 1st Embodiment. It is the time chart which showed the other example of the change of each output value of the electric motor control apparatus by 1st Embodiment. It is the flowchart which showed operation | movement of the electric motor control apparatus by 2nd Embodiment. It is the time chart which showed an example of the change of each output value of the motor control apparatus by 2nd Embodiment. It is the time chart which showed the other example of the change of each output value of the electric motor control apparatus by 2nd Embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals.

  FIG. 1 is a block diagram showing an example of an electric motor control device 100 of the present invention. The electric motor control device 100 is an electronic control device (EPS-ECU) for electric power steering of a vehicle.

  The motor 11 provides a steering assist force for steering. The electric motor control device 100 controls the motor 11 to assist steering and reduce the steering force applied by the driver to the steering. The angle sensor 12 detects the rotation angle of the motor 11. The motor 11 is an example of the “electric motor” in the present invention.

  The torque sensor 1 detects a steering torque applied to the steering. This steering torque is one of the fluctuation values necessary for controlling the motor 11. The torque sensor 1 is an example of the “variation value detecting means” in the present invention.

  The abnormality / fault determination unit 2 determines whether the output value is abnormal or normal by comparing the output value of the torque sensor 1 (a sampling value of the torque sensor signal) with a predetermined threshold value. Then, the abnormality / failure determination unit 2 switches the abnormality determination flag to ON or OFF based on the determination result, and switches the switch SW (switch) to “abnormal” or “normal”.

  Further, the abnormality / failure determination unit 2 determines that the torque sensor 1 is in failure when the abnormal state of the output value of the torque sensor 1 continues for a predetermined time. The abnormality / failure determination unit 2 is an example of the “output value determination unit” and “failure determination unit” in the present invention.

  The low pass filter 3 removes a high frequency component of the torque signal output from the switching SW. The delay circuit 4 holds the filtered torque signal output from the low-pass filter 3 for one sample. As the torque signal passes through the low-pass filter 3 and the delay circuit 4, an alternative value for the output value of the torque sensor 1 is set. The low-pass filter 3 and the delay circuit 4 are an example of “alternative value setting means” in the present invention.

When the switch SW is switched to “normal”, the torque sensor signal output from the torque sensor 1 becomes a torque signal (torque sensor signal = torque signal).
When the switching SW is switched to “abnormal”, the output signal (alternative value) from the delay circuit 4 becomes a torque signal (alternative value = torque signal).

  The torque command calculation unit 5 calculates a torque command value (current value) with reference to the table 5a based on the torque signal output from the switching SW and the vehicle speed signal output from the vehicle speed detection unit 13. The table 5a shows the relationship between the steering torque and the torque command value for each representative vehicle speed (for example, Va = 0 km / h, Vb = 50 km / h, Vc = 100 km / h).

  The differential control unit 6 calculates a differential value of the torque signal, and calculates a differential command value based on the differential value and the vehicle speed signal output from the vehicle speed detection unit 13. The motor rotation number calculation unit 8 calculates the rotation number of the motor 11 based on the angle signal output from the angle sensor 12 and outputs the rotation number to the convergence control unit 7. The convergence control unit 7 calculates a convergence command value based on the vehicle speed signal output from the vehicle speed detection unit 13 and the rotation number signal output from the motor rotation number calculation unit 8.

  The computing unit 14 adds the torque command value output from the torque command calculation unit 5 and the differential command value output from the differentiation control unit 6, subtracts the convergence command value from the convergence control unit 7, and gain Output to the variable unit 9. Based on the determination result of the abnormality / failure determination unit 2, the gain variable unit 9 varies the gain multiplied by the output value of the computing unit 14 and calculates a current command value. The motor drive unit 10 drives the motor 11 based on the current command value output from the gain variable unit 9.

  The torque sensor 1, the motor 11, and the angle sensor 12 are separate from the motor control device 100 and are provided near the steering shaft. The vehicle speed detection unit 13 is provided separately from the motor control device 100 and is provided in the automobile. The other units 2 to 10, 5 a and 14, and the switching SW are provided in the motor control device 100.

  FIG. 2 is a flowchart showing the operation of the motor control device 100 according to the first embodiment. A series of operations in FIG. 2 is repeatedly executed while the motor control device 100 is activated. FIG. 3 is a time chart showing an example of a change in each output value of the motor control device 100. FIG. 4 is a time chart showing an example of changes in output values of the motor control device 100 according to the first embodiment. FIG. 5 is a time chart illustrating another example of changes in output values of the motor control device 100 according to the first embodiment.

  In FIG. 2, first, the steering torque is detected by the torque sensor 1 (step S1). Then, the abnormality / failure determination unit 2 determines whether or not the output value Tq of the torque sensor 1 is smaller than a threshold value (step S2).

  At this time, if the level of the torque sensor signal output from the torque sensor 1 is higher than the threshold value, as shown on the left side of the time point J1 in FIGS. Is determined to be normal when the output value Tq is equal to or greater than the threshold (step S2 in FIG. 2: NO). Then, the abnormality / failure determination unit 2 turns off the abnormality determination flag and switches the switching SW to “normal” (step S8).

  Thus, the torque sensor signal is input as a torque signal to the low-pass filter 3, the torque command calculation unit 5, and the differentiation control unit 6 (see FIG. 1). Based on the command values from the torque command calculation unit 5, the differentiation control unit 6, and the convergence control unit 7, the current variable value is calculated by the gain variable unit 9. Further, the motor 11 is driven by the motor drive unit 10 based on the current command value. That is, when the output value Tq of the torque sensor 1 is normal, the motor 11 is controlled based on the output value Tq of the torque sensor 1.

  At that time, as shown before the time point J1 in FIGS. 3 to 5, the torque signal becomes higher than the threshold value, the filtered torque signal output from the low-pass filter 3, and the torque command output from the torque command calculation unit 5. Value is a high level. The current command value output from the gain variable unit 9 is also at a high level.

  On the other hand, as shown at time J1 in FIGS. 3 to 5, when a torque under-abnormality in which the level of the torque sensor signal is reduced occurs, the abnormality / failure determination unit 2 determines that the output value Tq of the torque sensor 1 is smaller than the threshold value. (Step S2 in FIG. 2: YES). Then, the abnormality / failure determination unit 2 turns on the abnormality determination flag and switches the switch SW to “abnormal” (step S3).

  As a result, the substitute value set based on the past torque signal by the low-pass filter 3 and the delay circuit 4 is input to the low-pass filter 3, the torque command calculation unit 5, and the differentiation control unit 6 as the current torque signal. The past torque signal is a normal torque sensor signal before becoming abnormal. Therefore, the alternative value is set based on the past output value Tq of the normal torque sensor 1.

  Then, the torque command calculation unit 5 and the differential control unit 6 calculate the torque command value and the differential command value based on the alternative values, respectively. The gain variable unit 9 calculates a current command value based on the command values from the torque command calculation unit 5, the differential control unit 6, and the convergence control unit 7. Further, the motor 11 is driven by the motor drive unit 10 based on the current command value. That is, when the output value Tq of the torque sensor 1 is abnormal, the motor 11 is controlled based on the alternative value of the output value Tq of the torque sensor 1.

  At that time, as shown from time point J1 to time point J2 in FIGS. 3 and 5, even if the torque sensor signal is abnormally decreased, the torque signal does not decrease and maintains a level higher than the threshold value. Further, the post-filter torque signal, the torque command value, and the current command value also maintain high levels. That is, even if the output value Tq of the torque sensor 1 becomes abnormal, an appropriate torque signal is secured and the motor 11 is appropriately controlled.

  After step S3 in FIG. 2, the process waits for a predetermined time M1 to elapse in an abnormal state where the output value Tq of the torque sensor 1 is smaller than the threshold (waiting for abnormality detection in steps S4 and S5). Then, in an abnormal state where the output value Tq of the torque sensor 1 is smaller than the threshold value (step S4: YES), when the predetermined time M1 has elapsed (step S5: YES), the abnormality / failure determination unit 2 detects the abnormality of the torque sensor 1. The gain is notified to the gain variable section 9 (time point J2 in FIGS. 3 and 5).

  When receiving the notification of abnormality detection of the torque sensor 1, the gain variable unit 9 calculates the current command value by gradually decreasing the gain level multiplied by the output value of the calculator 14. As a result, the current command value is gradually reduced as shown after time J2 in FIGS.

  After step S5 in FIG. 2, the process waits for a predetermined time M2 to elapse in an abnormal state where the output value Tq of the torque sensor 1 is smaller than the threshold value (waiting for the abnormality confirmation in steps S6 and S7). The predetermined time M2 waiting for abnormality confirmation is set longer than the predetermined time M1 waiting for abnormality detection (M1 <M2).

  Then, in an abnormal state where the output value Tq of the torque sensor 1 is smaller than the threshold value (step S6: YES), when the predetermined time M2 has elapsed (step S7: YES), the abnormality / failure determination unit 2 causes the torque sensor 1 to malfunction. It is determined that there is. Further, the abnormality / failure determination unit 2 notifies the gain variable unit 9 that the abnormality of the torque sensor 1 has been determined (time point J3 in FIG. 3).

  When the variable gain unit 9 receives notification of the abnormality confirmation of the torque sensor 1, the gain variable unit 9 continues to gradually decrease the gain level multiplied by the output value of the computing unit 14 to “0”. As a result, the current command value output from the gain variable section 9 gradually decreases as shown after time J3 in FIG. 3 (right side) and finally becomes “0”, and the motor 11 stops.

  On the other hand, when waiting for abnormality detection in steps S4 and S5 in FIG. 2 and waiting for abnormality determination in steps S6 and S7, the level of the torque sensor signal is a threshold value as shown at time point J4 in FIG. 4 and time point J8 in FIG. May be higher. In this case, the abnormality / failure determination unit 2 determines that the output value Tq of the torque sensor 1 is equal to or higher than the threshold value (step S4: NO, step S6: NO in FIG. 2). Then, the abnormality / failure determination unit 2 turns off the abnormality determination flag and switches the switching SW to “normal” (step S8).

  Thus, the torque sensor signal is input as a torque signal to the low-pass filter 3, the torque command calculation unit 5, and the differentiation control unit 6 (see FIG. 1). Based on the command values from the torque command calculation unit 5, the differentiation control unit 6, and the convergence control unit 7, the current variable value is calculated by the gain variable unit 9. Further, the motor 11 is driven by the motor drive unit 10 based on the current command value. That is, the motor 11 is controlled based on the output value Tq of the torque sensor 1.

  At this time, the torque signal becomes equal to the torque sensor signal at the time point J4 in FIG. 4 or the time point J8 in FIG. Then, since the torque sensor signal slightly increases and decreases from time J4 in FIG. 4 and time J8 in FIG. 5, the torque signal also decreases after slightly increasing. The torque command value and the current command value are affected by the torque signal, and after decreasing at time J4 in FIG. 4 or time J8 in FIG. Since the high-frequency component of the torque signal is removed, the post-filter torque signal slightly decreases from time J4 in FIG. 4 and time J8 in FIG.

  When the level of the torque sensor signal again falls below the threshold at time J5 in FIG. 4 or time J9 in FIG. 6, the abnormality / failure determination unit 2 performs the torque sensor after step S1 in FIG. It is determined that the output value Tq of 1 is an abnormality smaller than the threshold (step S2: YES). Then, the abnormality / failure determination unit 2 turns on the abnormality determination flag and switches the switch SW to “abnormal” (step S3).

  Thereby, the alternative value of the output value Tq of the torque sensor 1 is again output from the switch SW as a torque signal. For this reason, the torque signal, the torque command value, and the current command value rise to a high level as shown at time J5 in FIG. 4 and time J9 in FIG. The post-filter torque signal no longer drops and remains at a high level.

  In the example shown in FIG. 4, the level of the torque sensor signal remains smaller than the threshold after time J5. For this reason, from time J5, the abnormal state of the output value Tq of the torque sensor 1 (step S4: YES in FIG. 2) continues for a predetermined time M1 (step S5: YES), and the abnormality of the torque sensor 1 is detected. (Time point J6 in FIG. 4). Then, the current command value calculated by the gain variable unit 9 is gradually reduced.

  Furthermore, since the abnormal state of the output value Tq of the torque sensor 1 continues from the time point J6 (step S6: YES in FIG. 2) for a predetermined time M2 (step S7: YES), the abnormality of the torque sensor 1 is determined ( Time J7 in FIG. Then, the current command value calculated by the gain variable unit 9 continues to be gradually reduced to finally become “0”, and the motor 11 stops.

  In the example shown in FIG. 5, the torque sensor signal decreases to some extent from time J9 and then rises, reaches a threshold value or more at time J10, and thereafter maintains a level higher than the threshold value. Therefore, after the re-executed steps S1 to S4 in FIG. 2 and before the predetermined time M1 has elapsed from the time point J9 (step S5: NO), the output value Tq of the torque sensor 1 at the time point J8 is normal above the threshold. (Step S4: NO). Then, the abnormality determination flag is turned OFF, and the switch SW is switched to “normal” (step S8).

  As a result, the torque signal becomes equal to the torque sensor signal at the time point J10 in FIG. 5, so that the torque signal once decreases and then increases, and thereafter the level higher than the threshold is maintained. The torque command value is affected by the torque signal, and once decreases at time J10 in FIG. 5, then increases, and maintains a high level. The current command value is affected by the torque signal, and once decreases at a time point J10 in FIG. 5, the current command value increases at a two-step gradient and maintains a high level.

  Since the high-frequency component of the torque signal is removed, the post-filter torque signal maintains a high level after slightly rising from the time point J10 in FIG. That is, when the output value Tq of the torque sensor 1 returns to normal from the abnormality at the time point J10, an appropriate torque signal is secured and the motor 11 is appropriately controlled.

  According to the above embodiment, when the output value Tq of the torque sensor 1 becomes abnormal, the motor 11 is controlled based on an alternative value instead of the output value Tq. Further, when the output value Tq of the torque sensor 1 becomes normal from an abnormality, the motor 11 is controlled based on the output value Tq of the torque sensor 1 instead of the substitute value.

  For this reason, the motor 11 can be appropriately controlled not only when the output value Tq of the torque sensor 1 becomes abnormal, but also when the output value Tq of the torque sensor 1 returns from normal to normal. This also prevents a significant change in steering behavior and prevents the vehicle from becoming unstable.

  FIG. 6 is a flowchart showing the operation of the motor control device 100 according to the second embodiment. A series of operations in FIG. 6 are repeatedly executed while the motor control device 100 is activated. FIG. 7 is a time chart showing an example of changes in output values of the motor control device 100 according to the second embodiment. FIG. 8 is a time chart showing another example of changes in output values of the motor control device 100 according to the second embodiment. In the following second embodiment, FIG. 3 is also referred to in addition to FIGS.

  In FIG. 6, first, the steering torque is detected by the torque sensor 1 (step S1), and it is determined whether or not the output value Tq of the torque sensor 1 is smaller than a threshold value (step S2). At this time, if the level of the torque sensor signal is higher than the threshold value as shown before the time point J1 in FIGS. 3, 7, and 8, the abnormality / failure determination unit 2 determines that the output value Tq of the torque sensor 1 is the threshold value. As described above, it is determined to be normal (step S2 in FIG. 6: NO). Then, the abnormality determination flag is turned OFF, and the switching SW is switched to “normal” (step S8).

  As a result, the torque sensor signal becomes a torque signal, and based on the torque signal, the filtered torque signal, the torque command value, and the current command value are shown before the time point J1 in FIG. 3, FIG. 7, and FIG. Is set to a high level. Based on the current command value, the motor 11 is driven by the motor drive unit 10. That is, the motor 11 is controlled based on the output value Tq of the torque sensor 1.

  Thereafter, as shown at time point J1 in FIGS. 3, 7, and 8, when an abnormality in the torque sensor signal is excessively low, the abnormality / fault determination unit 2 detects that the output value Tq of the torque sensor 1 is smaller than the threshold value and is abnormal. (Step S2 in FIG. 6: YES). Then, the abnormality / failure determination unit 2 turns on the abnormality determination flag and switches the switch SW to “abnormal” (step S3).

  Thereby, the substitute value output from the delay circuit 4 becomes a torque signal, and the filtered torque signal, torque command value, and current command value are set based on the torque signal. The substitute value is set higher than the threshold value based on a normal torque sensor signal before becoming abnormal. Therefore, as shown after time J1 in FIGS. 3, 7, and 8, even if the torque sensor signal decreases, the torque signal does not decrease and maintains a high level. Further, the post-filter torque signal, the torque command value, and the current command value are also maintained at a high level without decreasing.

  The motor drive unit 10 drives the motor 11 with the current command value set based on the alternative value. That is, the motor 11 is controlled based not on the output value Tq of the abnormal torque sensor 1 but on the substitute value.

  After step S3 in FIG. 6, when the output value Tq of the torque sensor 1 is in an abnormal state smaller than the threshold value (step S4: YES) and a predetermined time M1 has elapsed (step S5: YES), the abnormality / failure determination unit 2 performs torque. The abnormality detection of the sensor 1 is notified to the gain variable section 9 (time point J2 in FIGS. 3 and 8). Then, the gain variable unit 9 calculates the current command value by gradually decreasing the gain level. As a result, the current command value is gradually reduced as shown after time J2 in FIGS.

  After step S5 of FIG. 6, when the output value Tq of the torque sensor 1 is in an abnormal state smaller than the threshold value (step S6: YES) and a predetermined time M2 has elapsed (step S7: YES), the abnormality / failure determination unit 2 It is determined that the torque sensor 1 is malfunctioning. Further, the abnormality determination of the torque sensor 1 is notified from the abnormality / failure determination unit 2 to the gain variable unit 9 (time point J3 in FIG. 3). Then, the gain variable unit 9 continues to gradually decrease the gain level to “0” and calculates the current command value. As a result, as shown after time J3 in FIG. 3, the current command value continues to be gradually reduced to finally “0”, and the motor 11 stops.

  On the other hand, at the time J4 in FIG. 7 or the time J8 in FIG. 8, the level of the torque sensor signal exceeds the threshold value when waiting for abnormality detection (steps S4 and S5 in FIG. 6) or waiting for abnormality confirmation (steps S6 and S7). It is high. In this case, the abnormality / failure determination unit 2 determines that the output value Tq of the torque sensor 1 is equal to or greater than the threshold value (step S4: NO, step S6: NO in FIG. 6).

  Then, it waits for a predetermined time M3 to elapse in a normal state where the output value Tq of the torque sensor 1 is equal to or greater than the threshold (steps S4 and S9, steps S6 and S10). The predetermined time M3 waiting for normal detection is set shorter than the predetermined time M1 waiting for abnormality detection and the predetermined time M2 waiting for abnormality confirmation (M3 <M1 <M2).

  In the example shown in FIGS. 7 and 8, at a time J4 in FIG. 7 or a time J8 in FIG. 8, the level of the torque sensor signal becomes higher than the threshold value until a predetermined time M3 elapses (step S9 in FIG. 6). : NO, step S10: NO), the level of the torque sensor signal again becomes smaller than the threshold value at the time point J5 in FIG. 7 or the time point J9 in FIG. In this case, the abnormality / failure determination unit 2 determines that the output value Tq of the torque sensor 1 is smaller than the threshold value and is abnormal (step S4: YES, step S6: YES in FIG. 6), and again waits for abnormality detection ( Steps S4 and S5) or abnormality determination wait (steps S6 and S7).

  As a result, as shown in FIGS. 7 and 8, the torque sensor signal once smaller than the threshold value is temporarily (time shorter than the predetermined time M3) at time points J4 to J5 in FIG. 7 and time points J8 to J9 in FIG. ), The abnormality determination flag remains ON, and the switch SW remains “abnormal”. For this reason, the alternative value of the output value Tq of the torque sensor 1 continues to be a torque signal, and the torque signal does not fluctuate as shown in time points J4 and after in FIG. 7 and time points J8 to J9 in FIG. Maintain a higher level. Further, the post-filter torque signal and the torque command value are also maintained at a high level without fluctuation. The current command value continues to decrease gradually.

  In the example shown in FIG. 7, the level of the torque sensor signal remains smaller than the threshold after time J5. For this reason, after steps S1 to S3 in FIG. 6 executed again, from time J5, the abnormal state of the output value Tq of the torque sensor 1 (step S4 in FIG. 6: YES) continues for a predetermined time M1 (step 1). S5: YES), an abnormality of the torque sensor 1 is detected (time point J6 in FIG. 7). Then, the current command value calculated by the gain variable unit 9 is gradually reduced.

  Further, since the abnormal state of the output value Tq of the torque sensor 1 continues from the time point J6 (step S6: YES in FIG. 6) for a predetermined time M2 (step S7: YES), the abnormality of the torque sensor 1 is determined ( Time J7 in FIG. Then, the current command value calculated by the gain variable unit 9 continues to be gradually reduced to finally become “0”, and the motor 11 stops.

  In the example shown in FIG. 8, the level of the torque sensor signal decreases to some extent from time J9 and then increases, and becomes equal to or greater than the threshold at time J10. For this reason, after the steps S1 to S4 in FIG. 6 which are executed again, before the predetermined time M1 has elapsed from the time J9 (step S5 in FIG. 6: NO), the abnormality / failure determination unit 2 performs the torque at the time J10. It is determined that the output value Tq of the sensor 1 is normal when the output value Tq is equal to or greater than the threshold (step S4 in FIG. 6: NO). And it waits for predetermined time M3 to pass in the normal state whose output value Tq of torque sensor 1 is more than a threshold (Steps S4 and S9).

  After time J10 in FIG. 8, the torque sensor signal maintains a level equal to or higher than the threshold value. For this reason, the normal state where the output value Tq of the torque sensor 1 is equal to or greater than the threshold value continues from time J10 (step S4 in FIG. 6: NO), and a predetermined time M3 elapses at time J11 (step S9 in FIG. 6: YES). Then, the abnormality / failure determination unit 2 turns off the abnormality determination flag and switches the switching SW to “normal” (step S8).

  As a result, the torque signal becomes equivalent to the torque sensor signal at time J11 in FIG. 8, and thereafter, a constant level higher than the threshold value is maintained. The torque command value and the filtered torque signal also maintain a high constant level. The current command value gradually increases from the time point J11, and then maintains a high constant level. After time J11, the motor 11 is appropriately controlled based on the output value Tq of the normal torque sensor 1.

  According to the above embodiment, when the output value Tq of the torque sensor 1 becomes abnormal, the motor 11 is controlled based on the alternative value, and when the output value Tq of the torque sensor 1 becomes normal from the abnormality, the torque The motor 11 is controlled based on the output value Tq of the sensor 1. For this reason, even when the output value Tq of the torque sensor 1 returns from normal to normal, the motor 11 can be appropriately controlled.

  Moreover, in the said embodiment, when the output value Tq of the torque sensor 1 becomes normal from abnormality and this normal state continues for the predetermined time M3, it replaces with a substitute value and is based on the output value Tq of the torque sensor 1. The motor 11 is controlled. For this reason, even if the output value Tq of the torque sensor 1 is temporarily switched from abnormal to normal, the state in which the motor 11 is controlled based on the alternative value is maintained, and the motor 11 is not affected by fluctuations in the output value Tq. 11 can be stably controlled.

  In the above embodiment, when the output value Tq of the torque sensor 1 is in an abnormal state, the switch SW is immediately switched from “normal” to “abnormal”, whereas the output value Tq of the torque sensor 1 is in a normal state for a predetermined time. When M3 has elapsed, the switch SW is switched from “abnormal” to “normal”. That is, the time required for switching from the output value Tq of the torque sensor 1 to the alternative value is shorter than the time required for switching from the alternative value to the output value Tq of the torque sensor 1.

  For this reason, when the output value Tq of the torque sensor 1 becomes abnormal, the motor 11 can be appropriately controlled immediately based on the normal substitute value. Further, when the output value Tq of the torque sensor 1 becomes normal from an abnormality and the normal state is stabilized, the motor 11 can be appropriately controlled based on the output value Tq of the normal torque sensor 1.

  Further, in the above embodiment, the time (M1 + M2) required for the abnormality / failure determination unit 2 to determine the failure of the torque sensor 1 is the time (M3) required to switch from the alternative value to the output value Tq of the torque sensor 1. It is getting longer. For this reason, it is possible to prevent erroneous determination that the torque sensor 1 is faulty before the output value Tq of the torque sensor 1 once becomes abnormal and then returns to normal.

  The present invention can employ various embodiments other than those described above. For example, in the above-described embodiment, an example in which abnormality and normality are determined based on whether or not the output value Tq of the torque sensor 1 is smaller than the threshold value is shown, but the present invention is not limited to this. In addition to this, for example, an upper limit threshold value and a lower limit threshold value are set, and if the output value Tq of the torque sensor 1 is within the range from the upper limit threshold value to the lower limit threshold value, it is determined as normal, and the upper limit threshold value to the lower limit threshold value is determined. If it is out of range, it may be determined as abnormal. Moreover, based on the fluctuation | variation of the output value Tq of the torque sensor 1, you may make it determine whether it is normal or abnormal.

  In the above embodiment, an example is shown in which the substitute value is set based on the past normal output value Tq of the torque sensor 1 by the low-pass filter 3 and the delay circuit 4, but the present invention is limited to this. It is not a thing. For example, a function is calculated from an output value Tq of the torque sensor 1 immediately before becoming abnormal, an average value of output values Tq of the torque sensors 1 of a plurality of samples before becoming abnormal, or an output value Tq of the plurality of samples. A predicted value obtained and predicted may be used as an alternative value. Further, not only the torque value but also a torque command value or current command value before becoming abnormal may be used as a substitute value, or a calculated value based on the command value may be used as a substitute value. Further, the time constant of the low-pass filter 3 may be changed according to the abnormal state of the output value Tq of the torque sensor 1, and the output value from the low-pass filter 3 may be used as an alternative value.

  Furthermore, in the said embodiment, although the example which applied this invention for the fail safe of the torque sensor 1 in the electric motor control apparatus 100 for electric power steering was given, the sensor in the electric motor control apparatus of an application other than this was given. The present invention can also be applied to the fail safe of the fluctuation value detecting means such as the above.

DESCRIPTION OF SYMBOLS 1 Torque sensor 2 Abnormality / failure determination part 3 Low-pass filter 4 Delay circuit 11 Motor 100 Motor control device M1 Predetermined time waiting for abnormality detection M2 Predetermined time waiting for abnormality determination M3 Predetermined time waiting for normal detection Tq Output value of torque sensor

Claims (5)

A fluctuation value detecting means for detecting a fluctuation value necessary for controlling the electric motor;
An output value determining unit for determining whether the output value of the fluctuation value detecting means is abnormal or normal;
An alternative value setting means for setting an alternative value for the output value of the fluctuation value detecting means,
When controlling the electric motor based on the output value of the fluctuation value detecting means,
When the output value of the fluctuation value detecting means becomes abnormal,
In the electric motor control device that controls the electric motor based on the alternative value instead of the output value of the fluctuation value detecting means,
When the output value of the fluctuation value detecting means becomes normal after becoming abnormal once,
An electric motor control device that controls the electric motor based on an output value of the fluctuation value detecting means instead of the substitute value. In the electric motor control device according to claim 1,
When the output value of the fluctuation value detection means becomes normal after becoming abnormal once, and the normal state continues for a predetermined time,
An electric motor control device that controls the electric motor based on an output value of the fluctuation value detecting means instead of the substitute value. In the electric motor control device according to claim 1 or 2,
The electric motor control apparatus characterized in that a time required for switching from the output value of the fluctuation value detecting means to the alternative value is shorter than a time required for switching from the alternative value to the output value of the fluctuation value detecting means. In the electric motor control device according to any one of claims 1 to 3,
A failure determination means for determining that the fluctuation value detection means is faulty when an abnormal state of the output value of the fluctuation value detection means continues for a predetermined time;
An electric motor control device characterized in that the time required for the failure determination means to determine a failure of the fluctuation value detection means is longer than the time required to switch from the substitute value to the output value of the fluctuation value detection means. . In the motor control device according to any one of claims 1 to 4,
The electric motor is composed of a motor that applies steering assist force of steering,
The fluctuation value detecting means comprises a torque sensor for detecting steering torque of the steering wheel,
The electric motor control device is an electronic control device for electric power steering, and controls the motor based on an output value of the torque sensor or the alternative value.

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