JP5092538B2 - Motor control device and electric power steering control device using the same - Google Patents

Description

  The present invention relates to a motor control device and an electric power steering control device configured to continue control of an electric motor as far as possible even when an abnormality occurs in a phase current.

  In this type of electric power steering control device, when the system detects an abnormality in the current detection value such as an overcurrent, the current detection circuit has no redundancy or a level at which a failure can be determined. Since there is only redundancy, steering is possible even while the vehicle is running to avoid unintended vehicle behavior even if no overcurrent actually flows due to a failure in the detection circuit. Need to stop assist.

  As described above, stopping the steering assist is a technique for minimizing the influence on the driver. However, as the output of the system increases, stopping the steering assist means that the driver does not This means that a great deal of force is required to perform the operation. Therefore, it is desirable to continue the steering assist unless it is a fatal failure to the system, such as an inverter short circuit.

  For this reason, it has been proposed that when a failure occurs in the system, the failure level is diagnosed, and when the failure is minor, control is resumed (see, for example, Patent Document 1). However, in this case, since the control state is judged on the assumption that the information obtained from each sensor is correct, for example, even if the control circuit is normal, the control is continued if a failure occurs in the sensor. There is a problem that can not be.

In order to avoid this, for example, a current detection circuit is provided for each phase of the electric motor, and the abnormality detection of the current detection circuit is performed when the electric motor is not driven, and any abnormality of the current detection circuit is detected. In some cases, the detection value of another normal current detection circuit is used to detect a phase current to be detected by the current detection circuit in which an abnormality is detected, and this is used to continue control. (For example, refer to Patent Document 2).
JP 2004-205118 A JP 2005-184966 A

  However, in the method in which the abnormality detection of the current detection circuit is performed when the electric motor is not driven as described above, the output of the current detection circuit is fixed to a constant value within the normal output range, for example. Therefore, it is impossible to detect an abnormality in the current detection circuit. For this reason, if control is continued using the current detection circuit in which an abnormality actually occurs, the current of the fixed phase is always increased or decreased when performing torque control of the motor (the direction varies depending on the control state). Thus, current feedback control is performed. For this reason, a current value different from the normal value actually flows in the non-fixed phase, which also affects the current detection value of the non-fixed phase. The greater the torque to be output to the motor, the greater the effect. In some cases, an overcurrent is generated in a normal phase where the current detection value of the current detection circuit is not fixed. As a result, the abnormality is detected in the current normal phase current detection circuit, and if the current detection value of the current detection circuit excluding this current detection circuit is used for control, there is a possibility that unintended behavior may occur. is there.

  Also, if the output of the current detection circuit is abnormal, it is not an abnormality of the current detection circuit itself, such as when a short-circuit failure occurs in the field effect transistor that constitutes the motor drive circuit that drives the electric motor. And a case where an abnormality has occurred in the current detection circuit itself. For this reason, when abnormality determination is performed based on the output of the current detection circuit, there is a possibility that the control is actually stopped although the abnormality is in the current detection circuit itself and not in the control device itself. There is a problem that an unnecessary burden is placed on the driver.

  Therefore, the present invention has been made paying attention to the above-mentioned conventional unsolved problems, and when a current abnormality is detected, this abnormality is caused by an abnormality of the current detection circuit itself or an abnormality of the other part. It is an object of the present invention to provide a motor control device capable of determining whether the current detection circuit itself is in an abnormal state and continuing motor drive control when an abnormality occurs in the current detection circuit itself, and an electric power steering control device using the motor control device.

To achieve the above object, a motor control device according to claim 1 of the present invention, a multi-phase electric motor, the phase current detection means for detecting the phase current of each phase of the electric motor individually, the phase And a motor control unit that performs drive control of the electric motor using a plurality of phase current detection values detected by the current detection unit, and a plurality of phase currents detected by the phase current detection unit Current value abnormality detection means for detecting current value abnormality using the detected value, and when the current value abnormality is detected by the current value abnormality detection means, the current value abnormality is an abnormality of the phase current detection means itself. An abnormal part determination unit that determines whether or not the phase current detection unit itself is abnormal by the abnormal part determination unit, and ranking is performed in which the phases are ranked in a preset order. Means and the ranking The phase current of the phase with the highest rank is estimated using the phase current detection value of the other phase, and thereafter, every time an abnormality of the phase current detection means is detected, the phase ranking is in descending order. Phase current estimation means for switching the estimation target phases one by one and estimating the phase current of the estimation target phase, and the motor control means determines that the phase current detection means itself is abnormal In this case, the drive control is performed using the phase current estimation value instead of the phase current detection value corresponding to the phase to be estimated by the phase current estimation means.

When the motor control device according to claim 2 detects an abnormality in the phase current detection unit after switching to all phases as the estimation target phase in the phase current estimation unit, the motor control unit The drive control is stopped.
According to a third aspect of the present invention, in the motor control device according to the third aspect , the motor control unit continues the drive control using the phase current estimated value, and the phase current detection value or the phase current command value corresponding to the phase current estimated value. When the phase current detection value or the phase current command value is determined as a normal value, the phase current estimation value is switched to the phase current detection value and the drive control is continued.

In the motor control device according to claim 4, when the motor control unit continues the drive control using the phase current detection value excluding one phase current detection value among the plurality of phase current detection values, The control amount of the electric motor is reduced.
In the motor control device according to claim 5, when the motor control means continues the drive control using the phase current estimation value, the control amount of the electric motor is reduced and the phase current estimation value is also reduced. The phase current detection value or the phase current command value corresponding to is monitored, and when the phase current detection value or the phase current command value is determined to be a normal value, the phase current estimated value is switched to the phase current detection value. The reduction of the control amount of the electric motor is canceled and the drive control is continued.

According to a sixth aspect of the present invention, in the motor control device according to the sixth aspect, the motor control unit stops the drive control of the electric motor when the abnormal part determination unit determines that the phase current detection unit is not abnormal. It is a feature.
The motor control device according to claim 7, wherein the abnormal portion determination means temporarily stops the drive control by the motor control means when the current value abnormality detection means detects the abnormality of the phase current. The determination is performed based on the terminal voltage of each phase of the electric motor in a state where the supply of the drive current to the electric motor is cut off.
A motor control device according to claim 8 of the present application is a motor control device that controls the driving of the electric motor using the phase current of each phase of a multiphase electric motor. A current value abnormality detection means for detecting a current value abnormality using a plurality of phase current detection values detected by the phase current detection means to detect, and when the current value abnormality is detected by the current value abnormality detection means, the current When it is determined that the value abnormality is an abnormality of the phase current detection unit itself and an abnormal part determination unit that determines whether or not the phase current detection unit itself is abnormal, A ranking means for ranking each phase in a preset order, and estimating the phase current of the phase with the highest ranking ranking using the phase current detection value of the other phase, and thereafter the phase current Each time an abnormality of the detection means is detected, Phase estimation means for switching the phases to be estimated one by one in descending order and estimating the phase current of the phase to be estimated, and the motor control means includes the phase current detection means itself. When the phase current estimation unit determines that the phase current estimation value is abnormal, the drive control is performed using the phase current estimation value instead of the phase current detection value corresponding to the phase to be estimated. Yes.
Furthermore, in the electric power steering control device according to claim 9 of the present application, the motor control device according to any one of claims 1 to 8 is applied to a motor control device for generating steering assist force. It is a feature.

According to the motor control device of the present invention , when the current value abnormality is an abnormality of the phase current detection means itself, the phases are ranked in a preset order for the phases, and the phase currents of the phases with higher rankings are assigned. Is detected using the phase current detection value of the other phase, the drive control of the electric motor is continued using the estimated phase current estimation value and the phase current detection value of the other phase, and if an abnormality is detected again, an abnormality is detected. Each time detection is performed, the phase current estimation target phase is switched in the order of ranking and the electric motor drive control is continued. Therefore, the phase current detection circuit in which an abnormality has occurred by sequentially switching the estimation target phase is searched. As a result, the drive control of the electric motor can be continued using the estimated phase current value without using the detected phase current value of the phase current detection circuit in which an abnormality has occurred. Longer motor drive control It can be continued between.

Further, according to the motor control device of the second aspect , when the abnormality of the phase current detection means is detected again after switching all the phases to the estimation target phase, the drive control of the electric motor is stopped. Even if any phase current detection value is used, it is possible to stop the drive control immediately at a time when it is considered that control cannot be continued, and it is possible to avoid the drive control being continued in an unstable state. .

According to the motor control device of the third aspect , the phase current detection value or the phase current command value corresponding to the phase current estimated value is determined to be a normal value while the drive control is continued using the phase current estimated value. That is, when the phase current detection circuit is predicted to be normal, drive control is performed by switching from the phase current estimated value to the phase current detected value, so the phase current estimated value is used even though the phase current detected value is normal. Thus, it is possible to avoid continuing drive control, and normal drive control can be resumed promptly.

According to the motor control device of the fourth aspect , when the drive control is performed using the phase current detection value excluding one phase current detection value among the plurality of phase current detection values, all the phase current detection values are used. Although the control accuracy may be lower than when performing drive control, the control amount of the electric motor is reduced, so the effect of unstable control due to the decrease in control accuracy is reduced. can do.

According to the motor control device of the fifth aspect , when the drive control is continued using the phase current estimated value, the control accuracy is lowered as compared with the case where the drive control is performed using the phase current detection value. Although there is a possibility, since the control amount of the electric motor is reduced, it is possible to reduce the influence caused by the control becoming unstable as the control accuracy decreases. In addition, when the phase current detection value or the phase current command value corresponding to the phase current estimation value is determined to be a normal value, the phase current detection value is used instead of the phase current estimation value, and the control amount of the electric motor is further reduced. Since it is canceled, it can be returned to the same state as before the abnormality of the phase current detection means occurs.

According to the motor control device of the sixth aspect, when it is determined that the current value abnormality is not due to the abnormality of the phase current detection means but due to other factors, the drive control of the electric motor is stopped. Therefore, it is possible to avoid the drive control being continued in a situation where the control may become unstable.
According to the motor control device of the seventh aspect , since the determination is made based on the terminal voltage of each phase of the electric motor in the state where the supply of the drive current to the electric motor is interrupted, the abnormality of the phase current detection means itself It can be easily and reliably detected.

Furthermore, according to the electric power steering control device according to claim 9 of the present application, the motor control device according to any one of claims 1 to 8 is applied to a motor control device for generating steering assist force. Therefore, the steering assist can be continued for a longer period, and the load on the driver can be reduced.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is an overall configuration diagram showing an embodiment of an electric power steering apparatus to which the present invention is applied. In the figure, 1 is a steering wheel, and a steering force applied to the steering wheel 1 from a driver. Is transmitted to the steering shaft 2 having the input shaft 2a and the output shaft 2b. The steering shaft 2 has one end of the input shaft 2a connected to the steering wheel 1 and the other end connected to one end of the output shaft 2b via a torque sensor 3 as steering torque detecting means.

  The steering force transmitted to the output shaft 2 b is transmitted to the lower shaft 5 via the universal joint 4 and further transmitted to the pinion shaft 7 via the universal joint 6. The steering force transmitted to the pinion shaft 7 is transmitted to the tie rod 9 via the steering gear 8 and steers steered wheels (not shown). Here, the steering gear 8 is configured in a rack and pinion type having a pinion 8a connected to the pinion shaft 7 and a rack 8b meshing with the pinion 8a, and the rotational motion transmitted to the pinion 8a goes straight in the rack 8b. It has been converted to movement.

A steering assist mechanism 10 for transmitting a steering assist force to the output shaft 2b is connected to the output shaft 2b of the steering shaft 2. The steering assist mechanism 10 includes a reduction gear 11 connected to the output shaft 2b and an electric motor 12 made of, for example, a three-phase brushless motor that generates a steering assist force connected to the reduction gear 11.
The torque sensor 3 detects the steering torque applied to the steering wheel 1 and transmitted to the input shaft 2a. For example, the torsion bar (not shown) in which the steering torque is interposed between the input shaft 2a and the output shaft 2b is used. It converts into angular displacement, and it is comprised so that this torsional angular displacement may be converted into resistance change or magnetic change and detected.

  In addition, as shown in FIG. 2, the electric motor 12 includes, for example, one end of a U-phase coil, a V-phase coil, and a W-phase coil connected to each other to form a star connection, and the other end of each coil is a steering assist control device. The phase current supplied to each phase of the electric motor 12 and the rotor position detection circuit 13 composed of a Hall element, a resolver, etc., which detect the rotational position of the rotor, are supplied to the individual phase currents. Phase current detection circuits 22u, 22v, and 22w for detection, and motor terminal voltage detection circuits 28u, 28v, and 28w for detecting motor terminal voltages of the respective phases of the electric motor 12 are provided.

  The torque detection value T output from the torque sensor 3, the rotor rotation angle θ detected by the rotor position detection circuit 13, and the vehicle speed detection value V detected by the vehicle speed sensor 21 are input to the steering assist control device 20. The steering current is detected by the phase currents Iu, Iv and Iw of the electric motor 12 detected by the phase current detection circuits 22u to 22w and the motor terminal voltages Vv, Vu and Vw detected by the motor terminal voltage detection circuits 28u, 28v and 28w. Input to the control device 20.

  The steering assist control device 20 calculates a steering assist current target value based on the torque detection value T, the vehicle speed detection value V, the phase current detection values Iu to Iw, and the rotor rotation angle θ, and uses this as a current command value. A control arithmetic unit 23 that outputs a PWM (pulse width modulation) signal having a duty ratio determined based on the current command value; a motor drive circuit 24 configured by a field effect transistor (FET) that drives the electric motor 12; An FET gate drive circuit 26 that controls the gate current of the field effect transistor of the motor drive circuit 24 based on the PWM signal from the control arithmetic unit 23, and a cutoff circuit 27 connected between the motor drive circuit 24 and the electric motor 12. And.

As shown in FIG. 2, the motor drive circuit 24 includes a series circuit in which two field effect transistors Qua and Qub are connected in series, and two field effect transistors Qva and Qva connected in parallel with the series circuit. The inverter circuit includes a series circuit of Qvb and a series circuit of field effect transistors Qwa and Qwb. The connection point of the field effect transistors Qua and Qub, the connection point of the field effect transistors Qva and Qvb, and the connection point of the field effect transistors Qwa and Qwb of this inverter circuit are connected to each of the star-connected excitation coils of the electric motor 12. Phase current detection circuits 22u to 22w are interposed between the field effect transistors Qub, Qvb, and Qwb and the ground, respectively.
Further, the FET gate drive circuit 26 turns on / off each field effect transistor of the motor drive circuit 24 by a PWM (pulse width modulation) signal output from the control arithmetic unit 23 described later, and thereby the actual electric motor. The magnitude of the current flowing through 12 is controlled.

  The interrupting circuit 27 is individually inserted between each phase coil of the electric motor 12 and the connection point of the field effect transistors Qua and Qub, Qva and Qvb, Qwa and Qwb of the motor driving circuit 24. It is composed of normally open relay circuits RLY1, RLY2, and RLY3. The relay circuits RLY1 to RLY3 are for electrically disconnecting the connection between the electric motor 12 and the motor drive circuit 24, and are electrically operated when the steering assist control process by the electric power steering control device is not operated. By disconnecting between the motor 12 and the motor drive circuit 24, when the steering wheel 1 is rotated in a state where the electric motor 12 and the motor drive circuit 24 are conducted, the electric motor 12 and the motor drive circuit 24 The phenomenon that the steering wheel locks due to the current flowing between them is avoided. In addition, when the electric power steering control device is in operation, the electric motor 12 and the motor drive circuit 24 are controlled to be in a conductive state so that electric power can be supplied to the electric motor 12. While the electric power steering control device is in operation, an abnormality in each field effect transistor constituting the motor drive circuit 24 or an abnormality in the current value supplied to the electric motor 12 based on the detection results of the phase current detection circuits 22u to 22w. When the control using the phase current detection value from the normal phase current detection circuit is determined not to be continued, the electric motor 12 is disconnected from the motor drive circuit 24. Avoid malfunctions.

The control arithmetic unit 23 executes a known steering assist control process based on the torque detection value T and the vehicle speed detection value V detected by the torque sensor 3, the phase current detection values Iu to Iw, and the rotor rotation angle θ. Then, a pulse width variation (PWM) signal for generating the steering assist force according to the torque detection value T and the vehicle speed detection value V by the electric motor 12 is formed, and these are output to the FET gate drive circuit 26. For example, the steering assist command value I _M ^* for generating the steering assist force according to the torque detection value T and the vehicle speed detection value V by the electric motor 12 is calculated by a known procedure, and the steering assist command value I _M ^* and the rotor are calculated. Based on the rotation angle θ, three-phase phase separation processing is performed to convert the U-phase, V-phase, and W-phase target phase current values Iud ^* , Ivd ^*, and Iwd ^* of the electric motor 12, and phase current detection circuits 22u to 22w. Based on the detected phase current values Iu to Iw and the target phase currents Iud ^* , Ivd ^*, and Iwd ^* , the PID process is performed on the deviation between them, and the current feedback process is performed to calculate the current command values Iut, Ivt, and Iwt. The pulse width variable (PWM) signal corresponding to the calculated current command values Iut, Ivt and Iwt of each phase is formed.

In addition, when operating the electric motor 12 in accordance with the steering assist control process, the control arithmetic unit 23 controls the relay circuits RLY1 to RLY3 of the cutoff circuit 27 so that they are in a conductive state. In addition to outputting a signal, it is checked whether or not each of the relay circuits RLY1 to RLY3 is actually in a conduction state. When a conduction abnormality is detected, for example, an alarm device 30 provided near the driver's seat is activated to generate a voice or Notifies conduction abnormality by turning on the lamp.
Further, after the steering assist control process is completed, a relay control signal for controlling the relay circuits RLY1 to RLY3 of the cutoff circuit 27 to be in an open state is output.

  Further, the control arithmetic device 23 executes a current value abnormality detection process during the steering assist control process, and monitors the phase current detection value based on the phase current detection values Iu to Iw of the phase current detection circuits 22u to 22w. . In this current value abnormality detection process, for example, it is determined whether or not the sum of the phase current detection values Iu to Iw becomes zero, or the phase current detection values Iu to Iw are within a value allowable range that can be originally taken. It is determined whether or not a current value abnormality such as an overcurrent has occurred by determining whether or not there is, and when these states continue for a specified time or more, it is determined that the current value is abnormal. When the current value abnormality is detected, the phase current detection circuits 22u to 22w are in an abnormal state or the phase current detection circuits 22u to 22w such as a ground fault or a power fault in the motor drive circuit 24 composed of an inverter, for example. It is determined whether or not the current value is abnormal due to an abnormality in a portion excluding the phase current. The steering assist is prohibited after that. On the other hand, when it is determined that the current value abnormality is due to the abnormality in the phase current detection circuits 22u to 22w, the phase current detection value from the phase current detection circuit that is likely to be abnormal is replaced with another phase current detection value. The steering assist control is continuously performed using the phase current estimated value estimated based on the value.

Next, the above embodiment will be described with reference to the flowchart of FIG. 3, which shows an example of the processing procedure of the current value abnormality detection executed by the control arithmetic device 23 when the current value abnormality is detected. To do.
In the control arithmetic unit 23, the steering assist control process is executed, the current value abnormality detection process is performed on the phase current detection values Iu to Iw detected by the phase current detection circuits 22u to 22w, and the abnormality is detected by the current value abnormality detection process. When not detected, the steering assist control process is executed in a predetermined cycle to generate a steering assist force as necessary to perform the steering assist. In the current value abnormality detection process, any one of the phase current detection values Iu to Iw is detected. When an abnormality is detected and this state continues for a predetermined time or more, it is determined that the current value is abnormal, and the process at the time of detecting the current value abnormality is executed according to the flowchart of FIG.

Now, for example, if it is assumed that an overcurrent appears to be applied to the u-phase phase current detection circuit 22u, the occurrence of this overcurrent is detected by the current value abnormality detection process, and this state is predetermined. When the time continues, it is determined that the current value is abnormal.
The control arithmetic device 23 starts the process when the current value abnormality is detected in FIG. 3, and first determines whether or not the number of tries is less than a specified value (step S1). The prescribed value of the number of tries is set to the number of phases of the electric motor 12, and in this case, since it is the three-phase electric motor 12, it is set to "3". Also, the number of tries is set to zero at startup.

  Since the number of tries is set to the initial value of zero, the process proceeds from step S1 to step S2, and subsequently, the phase in which the abnormality detected in the current value abnormality detection process has occurred is determined from the system logic described later. It is determined whether the phase corresponds to the phase current detection circuit 22 that has been disconnected. At this time, since none of the phase current detection circuits 22 has been disconnected yet, the process proceeds from step S2 to step S3, and each phase current detection value Iu to Iw at this time is read and this is detected as the initial phase current detection. The value I (Iu0, Iv0, Iw0) is stored in a predetermined storage area. For example, the initial phase current detection value (Iu0, Iv0, Iw0) is detected as (100, 5, -12).

Subsequently, the gate signal to each field effect transistor (FET) of the motor drive circuit 24 is turned OFF, the field effect transistor is switched to a cut-off state so that no current flows through the electric motor 12, and the steering assist control process is stopped. (Step S4). As a result, the rotation of the electric motor 12 decreases and eventually shifts to a stopped state.
Then, for example, the motor rotation speed R of the electric motor 12 is calculated from the rotor rotation angle θ detected by the rotor position detection circuit 13 (step S5), and the absolute value of the motor rotation speed R is equal to or larger than a preset specified value. Sometimes, the process returns from step S6 to step S5, waits for the rotational speed of the electric motor 12 to decrease, and when the absolute value of the motor rotational speed R falls below the specified value, the process proceeds from step S6 to step S7. The specified value used to determine the motor speed R can detect the motor terminal voltage that should be present and the ideal current value of each phase from the motor speed R with sufficient accuracy for the system. It is set to an equivalent speed.

  The motor terminal voltages Vu, Vv, and Vw detected by the motor terminal voltage detection circuits 28u to 28w and the phase current detection circuits 22u to 22w are detected when the absolute value of the motor rotation speed R falls below a specified value. The phase current detection values Iu, Iv, and Iw are read, the motor terminal voltages Vu, Vv, and Vw are stored in a predetermined storage area, and the phase current detection values Iu, Iv, and Iw are stored in the phase current detection values I1 (Iu1,. Iv1, Iw1) are stored in a predetermined storage area. For example, the phase current detection values (Iu1, Iv1, Iw1) are detected as (100, 0, 0).

  Subsequently, it is determined whether any of the motor terminal voltages Vu, Vv, Vw is equal to the battery voltage Vbat or the GND voltage supplied to the motor drive circuit 24 (step S8), and the motor terminal voltages Vu, When either Vv or Vw is equal to the battery voltage Vbat or the GND voltage, a power fault or ground fault has occurred in any part, or a field effect transistor (FET) short circuit has occurred in the motor drive circuit 24 Therefore, the process proceeds from step S8 to step S9, it is difficult to continue the steering assist, the steering assist control process is stopped, and the steering assist is prohibited thereafter.

On the other hand, when none of the motor terminal voltages Vu, Vv, Vw is equal to the battery voltage Vbat and the GND voltage, that is, when the motor terminal voltage is in the normal range, the phase current detection circuit 22 (22u, 22v, 22w). ) And the process proceeds to step S11.
Here, if the upper stage FET of the inverter constituting the motor drive circuit 24 has a short circuit fault, the motor terminal voltage becomes a value near the all-phase battery voltage Vbat, and conversely if the lower stage FET has a short circuit fault. Is a value in the vicinity of the GND voltage, but when the electric motor 12 is rotating, the motor terminal voltage fluctuates with reference to the value in the vicinity of the battery voltage Vbat or the GND voltage for the phase in which the short circuit failure has not occurred. there's a possibility that. In this case, the determination may be made using the average value of the motor terminal voltage. If the determination is made in a state where the electric motor 12 is not rotating, it can be determined with higher accuracy whether a power fault, a ground fault, an FET short-circuit, or the like has occurred.

  Subsequently, in step S11, it is determined whether or not the number of tries is zero. In this case, since the number of tries is zero, the process proceeds from step S11 to step S12, and the phase current detection value Iu1 read in step S7. , Iv1 and Iw1 are all substantially zero, that is, it is determined whether or not each of the phase current detection circuits 22u to 22w is responding to the current state where the current supply to the electric motor 12 is interrupted.

  In this case, the phase current detection values are (Iu1, Iv1, Iw1) = (100, 0, 0), the phase current detection value Iu is abnormal, and the other phase current detection values Iv, Iw are normal. Therefore, the process proceeds from step S12 to step S21. Then, since the phase current detection value Iu1 is not zero although it should originally be zero, it is determined that there is a high possibility that the phase current detection circuit 22u is abnormal, and the process proceeds to step S22. It is determined whether or not the detection values Iv1 and Iw1 are both substantially zero.

  In this case, the phase current detection values Iv1 and Iw1 are both substantially zero, and at this time, the electric motor 12 is approximately equal to the stopped state, and both the phase current detection values Iv1 and Iw1 should be substantially zero. Therefore, it is determined that the possibility that the phase current detection circuits 22v and 22w are abnormal is low, the process proceeds to step S23, and the phase current detection circuits 22u to 22w are sequentially arranged from the one that is predicted to be highly likely to be abnormal. Ranking is performed for. In this case, since the phase current detection circuit 22u is highly likely to be abnormal as judged in step S21, this is ranked first, and the phase current detection circuits 22v and 22w have phase current detection values I0 and I1. Of the difference currents | Iv1-Iv0 | and | Iw1-Iw0 |

In this case, since the difference current between the phase current detection values I0 and I1 is (| Iv1-Iv0 |, | Iw1-Iw0 |) = (| -5 |, | 12 |), the difference current is large. The ranking of the w phase becomes higher, and as a result, the ranking is performed in the order of the u phase, the w phase, and the v phase.
And it transfers to step S14 and the result ranked in step S23 is memorize | stored in a predetermined storage area. Next, the process proceeds to step S15, and after the number of tries is counted up by “1”, the process proceeds to step S16, and the steering assist control process is resumed. At this time, in the steering assist control process, the phase current detection circuit is logically disconnected from the system for the phase ranked first, the phase current estimated value is used for this phase current, and the other phases are The processing is performed using the phase current detection value detected by the phase current detection circuit 22. Further, in the steering assist control process, the maximum current that can be supplied to the electric motor 12 is limited to, for example, about 80%, or the maximum duty ratio is limited. It is possible to prevent the control from becoming unstable due to continuing the auxiliary control process.

  In this case, assuming that there is a high possibility that an abnormality has occurred in the phase having the highest rank, that is, the phase current detection circuit 22u corresponding to the u phase, the phase current detection circuit corresponding to the first u phase. The phase current detection value Iu of 22u is not used, but the phase current of the u phase is estimated using the other phase current detection values Iv and Iw. For example, since the sum of the phase currents of the three phases is zero, the remaining u-phase current is estimated from the sum of the phase current detection values Iv and Iw, and the estimated phase current is estimated for the u-phase ranked first. For the estimated values and other phases, the process of setting the phase current detection values Iv and Iw detected by the phase current detection circuits 22v and 22w as the phase current detection values used in the steering assist control process is started.

Then, the steering assist control process is resumed using the phase current estimated value and the phase current detected value set as the phase current detection value used for the steering assist control process in this way, and at this time, the performance of the steering assist function is resumed. Degenerate and control.
As a result, for the u-phase, the steering assist control process is executed using the phase current estimated value estimated based on the phase current detected value of the other phase, so although the control performance of the electric motor 12 is somewhat reduced, it continues. The electric motor 12 can be driven and controlled, that is, the steering assist can be continued.

  From this state, when the current value abnormality is detected again in the current value abnormality detection processing, the processing at the time of current value abnormality detection in FIG. 3 is executed again. In this case, the number of tries is “1”, which is less than the specified number. Since it is small, the process proceeds from step S1 to step S2. If the phase current detection value in which the current value abnormality has occurred is the u-phase phase current detection value corresponding to the phase current detection circuit that has already been logically disconnected from the system, countermeasures have already been taken. The process is terminated as it is, but when the current value abnormality is detected with the phase current detection value Iv or Iw other than the u phase, the process proceeds from step S2 to step 3, and thereafter the initial phase current detection value I0 is set in the same manner as described above. The motor terminal voltage V and the stopped phase current detection value I1 are acquired in a state where the electric motor 12 is temporarily stopped (step S4 to step S7). If a short circuit, a ground fault or the like has occurred (step S8) ), The steering assist control process is stopped, and the steering assist control process is stopped. Thereafter, the execution of the steering assist control process is prohibited (step S9).

On the other hand, if no short circuit, ground fault or the like has occurred, the process proceeds from step S8 to step S11. In this case, since the number of tries is “1”, the process proceeds from step S11 to step S31, and the number of tries is set to “1”. Then, the process proceeds to step S32. In this step S32, in accordance with the ranking stored in a predetermined storage area, the phase current estimation value is used for the phase whose rank is the number of tries, and the phase detected by the phase current detection circuit 22 is used for the other phases. Processing is performed using the current detection value. That is, as the phase current detection value used in the steering assist control process, the phase current estimation value is calculated and set for the phase of the number of tries, and the phase current detected by the phase current detection circuit 22 is set for the other phases. The process for setting the detection value I is started. Then, the steering assist control process is restarted using the phase current detection value set thereby. At this time, only one phase is logically separated from the system.

  In this case, since the number of trials is “2”, as a result of ranking, the w-phase phase current detection circuit 22w that ranks second is logically disconnected from the system, while the phase current detection circuit 22u is connected to the system. Logically connected to estimate the w-phase phase current from the phase current detection values Iu and Iv, and the steering assist control process using the estimated w-phase phase current estimation value and the phase current detection values Iu and Iv To resume. In this case as well, control is performed by degrading the performance of the steering assist function, such as limiting the maximum energizable current in the steering assist control process.

  When switching the phase current detection circuit 22 that is logically disconnected from the system, the field effect transistor FET of the motor drive circuit 24 is temporarily switched to the OFF state, and the state where the overcurrent flows is stopped. Switching may be performed. By doing in this way, it can avoid that the state in which the overcurrent before switching has occurred is detected as an abnormality after switching.

  Then, the current value abnormality is detected again in a state where the phase current detection circuit 22w of the second rank is logically disconnected from the system, and the u phase and the phase corresponding to the phase current detection circuit that has already been logically disconnected from the system are detected. When the current value abnormality is detected by the phase current detection circuit 22v excluding the w phase, if a short circuit, a ground fault, or the like has occurred, the process proceeds from step S8 to step S9, and the steering assist is prohibited thereafter. If no ground fault or the like has occurred, the process proceeds from step S11 to step S31 to step S32. At this time, the number of tries is “3”. The circuit 22v is logically disconnected from the system and the u-phase phase current detection circuit 22u is logically connected to the system, and the v-phase current is estimated from the phase current detection values Iu and Iw. And the phase current estimated value of the boss was v-phase, and a phase-current detection values Iu and Iw, and the phase current detection value used in the steering assist control process resumes steering assisting control processing using these.

Furthermore, when the phase current detection circuit 22v with the third ranking is logically disconnected from the system and an abnormality is detected again in any of the phase current detection values, the number of tries is “3”. Since the value does not fall below the specified value, the process proceeds from step S1 to step S9. At this point, the steering assist control process is stopped, and thereafter steering assist is prohibited.
As a result, even when a current value abnormality occurs, the u-phase, v-phase, and w-phase phase current detection circuits 22u to 22w are sequentially switched according to the ranking and steered in a state of being logically disconnected from the system. Even if the auxiliary control process is continued and the current value abnormality is still detected even when all the phase current detection circuits are disconnected, it is determined that further steering assist cannot be continued at this time, and the steering auxiliary control process is performed. Will be stopped.

  On the other hand, an abnormality is detected in any of the phase current detection circuits 22u to 22w in the current value abnormality detection process, and no power fault or ground fault has occurred (step S8), and the phase current detection values Iu1, Iv1, and Iw are When all are substantially zero (step S12), it is determined in any of the phase current detection circuits 22u to 22w that a gain abnormality has occurred in the operational amplifier included therein, and the process proceeds to step S13.

In this step S13, it is estimated that a gain abnormality has occurred in any of the phase current detection circuits 22u to 22w. However, the phase current detection values Iu1, Iv1, and Iw1 are all substantially zero, and the phase current detection is performed. From the values Iu1, Iv1, and Iw1, it is difficult to predict which phase current detection circuits 22u to 22w are abnormal. For this reason, the initial phase current detection values Iu0, Iv0, Iw0 detected in step S3 when the current value abnormality is detected, and the phase current detection values Iu1, Iv1, Iw1 when the electric motor 12 is substantially stopped. And the absolute values of these differences | Iu1-Iu0 |, | Iv1-Iv0 |, and | Iw1-Iw0 | are ranked in descending order. Then, this order is stored in a predetermined storage area (step S14). That is, here, assuming a failure mode in which the gain is excessive, ranking is performed assuming that the higher the absolute value of the difference current is, the higher the possibility of a failure in which the gain is excessive.
Then, after proceeding to step S15 and incrementing the number of tries by “1”, the steering assist control process is restarted at step S16, and the phase current estimated value is used for the phase ranked first, and the other phases are The processing is performed using the phase current detection value detected by the phase current detection circuit 22.

  Further, although any one of the phase current detection circuits 22u to 22w is detected in the current value abnormality detection processing, all of the phase current detection values Iu1, Iv1, and Iw1 are not substantially zero (step S12). When the phase current detection value Iu1 of the phase is not Iu1 ≠ 0, that is, when Iu1 = 0 (step S21), the phase current detection circuit 22u is unlikely to be abnormal, and the process proceeds to step S25. It is determined whether the phase current detection value Iv1 is Iv1 ≠ 0. When Iv1 ≠ 0, the possibility that the phase current detection circuit 22v is abnormal is high, and the process proceeds to step S26 to determine whether or not the phase current detection value Iw1 is substantially zero. Since it is unlikely that the circuit 22w is abnormal, the process proceeds to step S27, and ranking is performed in descending order of possibility of abnormality. In this case, since the phase current detection circuit 22v is highly likely to be abnormal as determined in step S25, this is ranked first, and the phase current detection circuit 22u and the phase that are determined to be unlikely to be abnormal Regarding the current detection circuit 22w, of the difference currents | Iu1-Iu0 | and | Iw1-Iw0 | between the phase current detection values I0 and I1, the one with the larger difference current is ranked higher. Then, the process proceeds to step S14.

  Further, although any one of the phase current detection circuits 22u to 22w is detected in the current value abnormality detection processing, all of the phase current detection values Iu1, Iv1, and Iw1 are not substantially zero (step S12). When the phase current detection value Iu1 of the phase is not Iu1 ≠ 0, that is, Iu1 = 0 (step S21), and when the phase current detection value Iv1 is not Iv1 ≠ 0 (step S25), Iv1 = 0 Therefore, the phase current detection circuit 22v shifts to step S28 because the possibility of abnormality is low. In this case, the phase current detection values Iu1, Iv1, and Iw1 are not all zero (step S12), but the phase current detection value Iu1 is Iu1 = 0 (step S21), and the phase current detection value Iv1 is Iv1. Since = 0, the phase current detection value Iw1 is predicted as Iw1 ≠ 0. Therefore, assuming that there is a high possibility that the phase current detection circuit 22w is abnormal, the ranking is performed in descending order of the possibility of being abnormal. In this case, since the phase current detection circuits 22u and 22v are determined to have a low possibility of abnormality in steps S21 and S25, the phase current detection value Iw1 may be abnormal because Iw1 ≠ 0. For the phase current detection circuit 22u and the phase current detection circuit 22v that are determined to have the high phase current detection circuit 22w as the first place and that the possibility of abnormality is low, the difference current | Iv1− between the phase current detection values I0 and I1 Of Iv0 | and | Iw1-Iw0 |, the one with the larger difference current is ranked higher. The process proceeds to step S14.

In addition, abnormality is detected in any of the phase current detection circuits 22u to 22w in the current value abnormality detection processing, but the phase current detection values Iu1, Iv1, and Iw1 are not substantially zero (step S12), and the u phase The phase current detection value Iu1 of Iu1 is not equal to 0 (step S21), but the phase current detection values Iv1 and Iw1 are not substantially zero (step S22), and it is highly possible that both are abnormal, The current detection values Iu1, Iv1, and Iw1 are not all zero (step S12), the u-phase phase current detection value Iu1 is not Iu1 ≠ 0 but Iu1 = 0 (step S21), and the phase current detection value Iv1 is Iv1 Although not 0 (step S25), the phase current detection value Iw1 is not substantially zero (step S26), and the possibility that the u phase is abnormal is low, but the possibility that the v phase and the w phase are abnormal is high. In case , The process proceeds to step S30, and it is determined that the possibility of abnormality is not possible. Of the difference currents | Iu1-Iu0 |, | Iv1-Iv0 |, | Iw1-Iw0 | The ranking is performed in descending order of the difference current.
The phase current detection circuit 22 is logically disconnected from the system in order from the top of the ranking, and the steering assist control process is continued while no current value abnormality is detected.

  As described above, when an overcurrent of any phase current detection value I is detected, a short circuit, a ground fault, an FET short circuit, or the like occurs in the gate drive circuit 24 or the electric motor 12 as the cause of the current value abnormality. Current value abnormality due to failure and current value abnormality due to failure of the phase current detection circuit itself can be considered, but when it is predicted that the phase current detection circuit itself has failed, there is a high possibility that it is abnormal The predicted phase current detection circuit of one phase is logically disconnected from the system, and the phase current corresponding to the disconnected phase current detection circuit is estimated using the phase current detection values of the remaining phase current detection circuits. Therefore, the steering assist control process can be continued by using these. In addition, when an abnormality is detected again in a state where any one phase is disconnected from the system, the phase current detection circuit to be disconnected from the system is switched. Therefore, when it is predicted that there is a high possibility of an abnormality and control is continued with one of the phase current detection circuits disconnected from the system, or when the abnormality is detected again from the system, or the phase current detection circuit from the system If a current value abnormality is detected despite disconnection of the power, the phase current detection circuit to be disconnected from the system is switched to try to continue steering assist, and an abnormality occurs even if all the phase current detection circuits are disconnected. Sometimes it is determined that the steering assist cannot be continued, and the steering assist control process is stopped. Therefore, the steering assist control process can be continued to the maximum extent possible, and the steering assist can be continued for a longer period, thereby reducing the driver's load. In particular, the greater the output of the electric power steering device, such as the weight of the vehicle, the more the driver is loaded, so that the effect can be exerted.

  In addition, the possibility of abnormality is predicted, and the phase current detection circuit is separated from the system in the order of high possibility of abnormality, so that it can be effectively separated and the steering assist control process is made stable. It can be recovered quickly. In addition, even if the prediction of the possibility of abnormality is different from the actual or when the possibility of abnormality cannot be predicted, the phase current detection circuit that is disconnected from the system can be switched sequentially. Eventually, the steering assist control process using the normal phase current detection value is settled, and the steering assist control process can be reliably restarted.

  Also, when continuing the steering assist control process using the phase current estimated value, the control is performed in a state where the steering assist function is degenerated, such as suppressing the maximum energizable current or the maximum duty ratio. By performing control using the estimated phase current value, it is possible to avoid the control from becoming unstable. Also, when the normal phase current detection circuit is disconnected from the system and the steering assist control process continues using the phase current detection value of the abnormal phase current detection circuit and the phase current estimation value estimated using this Even so, it is possible to reduce the influence caused by the unstable control caused by continuing the steering assist control process based on the erroneous phase current detection value and the phase current estimation value.

  In addition, the processes from the time when abnormality is detected in the current value abnormality detection process until the phase assist circuit is logically disconnected from the system and the steering assist control process is restarted are all simple, so disconnect The phase current detection circuit can be determined and restarted in a short time, the required time for restarting is short, and the period during which the steering assist is stopped is short. Therefore, the influence on the vehicle behavior due to the abnormality of the phase current detection circuit can be extremely reduced.

  In the above embodiment, when all of the phase current detection values Iu to Iw are substantially zero in the process of step S12 and it is predicted that a gain abnormality has occurred, a failure mode in which the gain is excessive is selected. Assuming that it is determined that there is a high possibility that an abnormality has occurred in descending order of the absolute value of the difference current, a failure mode is assumed in which the gain is excessive when a gain abnormality occurs. You can also. In this case, the ranking may be performed by determining that there is a high possibility that an abnormality has occurred in descending order of the absolute value of the difference current. From the failure mode where the gain is excessive and the failure mode where the gain is too low, prioritize the one with the highest frequency, and rank in descending order of the absolute value of the difference current. May be.

Similarly, when ranking is performed for the three phases in step S30, or when ranking is performed for the two phases in step S23, step S27, and step S28, the difference current is assumed assuming a failure mode in which the gain is too small. Ranking may be performed in order from the smallest absolute value.
Further, in the above-described embodiment, the case has been described in which ranking is performed according to the level of possibility of abnormality, and phase current detection circuits are sequentially switched according to this ranking to be disconnected from the system. is not. Although it takes some time until the phase current detection circuit in which an abnormality has occurred is disconnected, for example, it may be sequentially disconnected in a preset order, or in short, all phases may be switched sequentially. .

  Further, in the above embodiment, while the steering assist control process is continued with any of the phase current detection circuits disconnected from the system, the disconnected phase current detection is performed intermittently or continuously at a predetermined timing. The phase current detection value of the circuit is read, and the actual phase current detection value is compared with the phase current estimation value estimated from the phase current detection value of the other phase. Phase current detection separated from this system when it is determined that the current has returned to normal when the current value is equal to or greater than a predetermined current value and the deviation is within a preset allowable range and this state continues for a predetermined time or longer. The circuit may be connected to the system again, and the steering assist control process using only the phase current detection value may be resumed without using the phase current estimation value. Further, at this time, a case has been described in which the phase current detection value and the phase current estimated value are compared to determine whether or not the normal state has been restored, but the phase current command value is used instead of the phase current estimated value, and the phase current command value is used. By comparing the detected current value and the phase current command value, it may be determined whether or not normal return has occurred.

At this time, by confirming that the same holds true even when the direction of the current is reversed, when a failure occurs on only one of the positive and negative sides of the phase current detection circuit, the normal and abnormal modes are repeated. You can avoid entering.
In addition, when the steering assist control process using the phase current detection value of the phase current detection circuit that has been disconnected instead of the estimated phase current value is resumed, the steering assist that has been degenerated is determined. The steering assist function of the control process may be returned to normal.

  In the above embodiment, a current detection circuit for detecting a current flowing into the inverter may be further provided to monitor whether the current flowing into the inverter is excessive. When one of the phase current detection circuits is logically disconnected from the system and control is performed using the two-phase phase current detection value, if an excessive current flows in the disconnected phase, this may not necessarily be detected. It may not be possible. However, by monitoring the current flowing through the inverter, it can be reliably detected whether or not an excessive current has flowed in the disconnected phase.

  In the above embodiment, the case where an abnormality has occurred in the phase current detection value of the phase current detection circuit has been described. However, the present invention is not limited to this, and in the case of an N-phase electric motor, N Abnormality detection may be performed depending on whether the sum of the phase current detection values of the phases, that is, the sum of the phase current detection values of the three phases in this case is abnormal. If a current detection circuit is provided at a position where the flowing current can be detected, and the current value flowing into the inverter circuit detected by the current detection circuit cannot be correlated with the phase current detection value, the phase current detection value circuit is predicted to be abnormal. Even if it is done, it can be applied.

In the above embodiment, the case where the three-phase electric motor 12 is used has been described. However, the present invention is not limited to this, and a multi-phase electric motor is used. Even if the system is disconnected from the system, the system can be applied as long as the control can be continued by using the phase current detection value of another phase current detection circuit.
In the above embodiment, the case where the present invention is applied to an electric power steering control device has been described. However, the present invention is not limited to this, and any device that performs control using a multiphase electric motor can be applied. .

In the above embodiment, the phase current detection circuits 22u to 22w correspond to the phase current detection means, the steering assist control device 20 corresponds to the motor control means, and the current value abnormality detection executed by the steering assist control device 20 is performed. The processing corresponds to the current value abnormality detection means, and the processing from step S4 to step S8 in FIG. 3 corresponds to the abnormal part determination means.
Further, the processing from step S12, step S13, step S21 to step S30 in FIG. 3 corresponds to the ranking means. In steps S16 and S32, the phase to be estimated is switched one by one to estimate the phase current of this phase. This processing corresponds to the phase current estimation means.

It is a schematic block diagram which shows an example of the electric power steering control apparatus to which this invention is applied. It is a block diagram which shows the specific structure of the steering auxiliary control apparatus of FIG. It is a flowchart which shows an example of the process sequence of the process at the time of the electric current value abnormality detection performed with a control arithmetic unit.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Steering wheel 2 Steering shaft 3 Torque sensor 8 Steering gear 10 Steering assist mechanism 11 Reduction gear 12 Three-phase brushless motor 13 Rotor position detection circuit 20 Steering assist control device 21 Vehicle speed sensor 22u-22w Phase current detection circuit 23 Control arithmetic device 24 Motor Drive circuit 26 FET gate drive circuits 28u to 28w Motor terminal voltage detection circuit

Claims (9)

A multi-phase electric motor,
Phase current detection means for individually detecting the phase current of each phase of the electric motor;
In a motor control device comprising: motor control means for performing drive control of the electric motor using a plurality of phase current detection values detected by the phase current detection means,
Current value abnormality detection means for detecting a current value abnormality using a plurality of phase current detection values detected by the phase current detection means;
When detecting the current value abnormality by the current value abnormality detection means, an abnormal site determination means for determining whether the current value abnormality is an abnormality of the phase current detection means itself;
When the abnormal part determination means determines that the phase current detection means itself is abnormal, a ranking means that ranks each phase in a preset order;
The phase current of the phase with the highest ranking is estimated using the phase current detection value of the other phase, and thereafter, each time the abnormality of the phase current detection means is detected, Phase current estimation means for switching the phases to be estimated one by one in descending order and estimating the phase current of the phase to be estimated;
When the motor control means determines that the phase current detection means itself is abnormal, the phase current estimation value is replaced with the phase current detection value corresponding to the phase to be estimated by the phase current estimation means. A motor control apparatus that performs the drive control using a motor. The motor control unit stops the drive control when detecting an abnormality in the phase current detection unit after switching to all phases as the phase to be estimated by the phase current estimation unit. Item 2. The motor control device according to Item 1 . The motor control means includes
While continuing the drive control using the phase current estimated value, monitoring the phase current detection value or the phase current command value corresponding to the phase current estimated value,
When the phase current detection value or the phase current command value is determined as a normal value,
The motor control device according to claim 1 or 2, wherein the drive control is continued by switching the phase current estimated value to the phase current detection value. The motor control means reduces the control amount of the electric motor when continuing the drive control using a phase current detection value excluding one phase current detection value among the plurality of phase current detection values. The motor control device according to any one of claims 1 to 3 . When the motor control means continues the drive control using the phase current estimated value, the motor control means reduces the control amount of the electric motor and also detects a phase current detected value or a phase current command value corresponding to the phase current estimated value. Monitor
When the phase current detection value or the phase current command value is determined as a normal value,
3. The motor control according to claim 1, wherein the phase current estimation value is switched to the phase current detection value, and the drive control is continued by canceling the reduction of the control amount of the electric motor. apparatus. Said motor control means, in the abnormal condition part determination unit, when it is determined not to be abnormal in the phase current detection unit, any of claims 1 to 5, characterized in that stopping the driving control of the electric motor The motor control apparatus of Claim 1. The abnormal part determination means temporarily stops the drive control by the motor control means when the abnormality of the phase current is detected by the current value abnormality detection means,
The said determination is performed based on the terminal voltage of each phase of the said electric motor in the state which interrupted supply of the drive current to the said electric motor, The any one of Claim 1-6 characterized by the above-mentioned. Motor control device. The motor control device for controlling the driving of said electric motor with a phase of the phase current of the electric motor of the multi-phase,
Current value abnormality detection means for detecting current value abnormality using a plurality of phase current detection values detected by the phase current detection means for individually detecting the phase current of each phase;
When detecting the current value abnormality by the current value abnormality detection means, an abnormal site determination means for determining whether the current value abnormality is an abnormality of the phase current detection means itself;
When the abnormal part determination means determines that the phase current detection means itself is abnormal, a ranking means that ranks each phase in a preset order;
The phase current of the phase with the highest ranking is estimated using the phase current detection value of the other phase, and thereafter, each time the abnormality of the phase current detection means is detected, Phase current estimation means for switching the phases to be estimated one by one in descending order and estimating the phase current of the phase to be estimated;
When the motor control means determines that the phase current detection means itself is abnormal, the phase current estimation value is replaced with the phase current detection value corresponding to the phase to be estimated by the phase current estimation means. A motor control apparatus that performs the drive control using a motor. An electric power steering control device, wherein the motor control device according to any one of claims 1 to 8 is applied to a motor control device for generating a steering assist force.

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