JP5754088B2 - Electric power steering device - Google Patents

Description

  The present invention relates to an electric power steering apparatus.

  2. Description of the Related Art Conventionally, there is an electric power steering device (EPS) using a motor as a drive source as a power steering device for a vehicle. Such EPS has a feature that a layout has a high degree of freedom and energy consumption is small. ing. Therefore, in recent years, the adoption has been promoted in a wide range of vehicle types from small vehicles to large vehicles.

  Conventionally, in EPS, many abnormality determination processes (diagnostic processes) are performed in an information processing apparatus (electronic control apparatus such as a microcomputer) that executes the power assist control. For example, a microcomputer is composed of a CPU, a memory (RAM and ROM), and various electronic circuits (A / D conversion, etc.). When the microcomputer is started up (when the ignition is ON), an execution program and its work data An initial check is performed to confirm that the memory serving as the storage area is normal (see, for example, Patent Document 1). Even after startup, it is monitored whether the microcomputer and various electronic circuits under its control are functioning normally. And in the abnormality determination process, when some abnormality is detected, it is configured to ensure high reliability and safety by promptly fail-safe.

JP 2006-331086 A

  However, in recent years, in EPS, various compensation controls are executed in order to achieve a better steering feeling, and the time required for the initial check is increased due to the increase in the memory capacity associated therewith. Is getting longer. In addition, the function check after activation is performed, for example, by providing a monitoring microcomputer independent of the microcomputer (main microcomputer) that executes power assist control. In this case, the main microcomputer is sent from the monitoring microcomputer. Test calculations must be performed in real time. Further, by providing a new monitoring circuit (abnormality determination circuit) including such a monitoring microcomputer, the main microcomputer needs to monitor whether or not the monitoring circuit functions normally. For example, the processing capability required to execute the abnormality determination has been steadily increasing, and this has also contributed to increase the manufacturing cost.

  In addition, by providing a large number of monitoring circuits, the increase in the failure occurrence rate due to the increase in the number of constituent elements becomes remarkable, and as a result, there is no influence on the operation of EPS due to the execution of various abnormality determinations. There is a possibility that even a trivial event without a mark will be judged as abnormal. And since this is counted as a failure, there is a problem that the failure occurrence rate is further raised. In this respect, there is still room for improvement.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an electric power steering apparatus that can perform abnormality determination with a simple configuration and high reliability.

In order to solve the above problems, the invention according to claim 1 is directed to a steering force assisting device that applies an assist force to a steering system using a motor as a drive source, and a control unit that controls the operation of the steering force assisting device. The control means includes a control signal output means for outputting a motor control signal to generate a motor torque corresponding to the assist force, and a drive circuit for supplying drive power based on the motor control signal to the motor. And the control signal output means generates a motor control signal by calculating a current command value corresponding to the target assist force based on the detected steering torque and executing a current feedback calculation. In the apparatus, the motor includes a U-phase coil, a V-phase coil, and a W-phase coil as three-phase motor coils. , The V-phase coil, and the W-phase coil are non-connected brushless motors that are not connected to each other, and the control means corresponds to the U-phase coil, the V-phase coil, and the W-phase coil. Three independent drive circuits and two independent control signal output means for executing the same current feedback calculation, and the drive circuits are turned on / off based on the motor control signal. Are formed by connecting two switching arms connected in series, and each switching arm is controlled by the motor control output by the corresponding control signal output means. together operate independently on the basis of the signal, the calculation result of the current feedback calculation in each of the control signal output means Operate synchronously when an, the respective control signal output means, a current deviation the underlying of the current feedback computation, in case of discrepancies in the calculation result of the current feedback calculation in each of the control signal output unit has occurred There performing the abnormality determination by monitoring the excessive deviation generated by rising, and the gist.

  That is, the current feedback calculation executed by each control signal output means is the same, and the detection object of the basic state quantity is also common, so that the calculation result is also the same unless there is an abnormality in the two control systems. It is. Therefore, also with the above configuration, each switching arm can be operated in synchronism as in the case where each control signal output means performs control independently.

  On the other hand, when any abnormality occurs in these two control systems, a difference occurs in the result of the current feedback calculation executed by each control signal output means. As a result, the operation of each drive circuit follows the motor control signal on the side showing a small energization amount regardless of the correctness, and as a result, on the side outputting the motor control signal showing a larger energization amount, The current deviation, which is the basis of the current feedback calculation, increases. Therefore, by monitoring the occurrence of the excessive current deviation, it is possible to make a reliable abnormality determination with a simple configuration.

  In particular, when an abnormality occurring in each control signal output means affects the execution of the power assist control, the influence always appears in at least one of the current deviations. Therefore, if the execution of the power assist control is stopped after detecting the abnormality, an information processing device (electronic control device such as a microcomputer) that constitutes each control signal output means such as the initial check of the memory at the time of startup as described above. It is possible to eliminate the other abnormality determination control (monitoring circuit) related to ()) and replace it with an abnormality determination based on this current deviation. As a result, not only the start-up time can be shortened, but also the cost can be reduced by reducing the processing capability required for the information processing apparatus, and the failure rate can be reduced by reducing the circuit scale.

  In addition, as described above, even when an abnormality occurs, the operation of each drive circuit follows the motor control signal that indicates a smaller energization amount, thereby preventing the occurrence of excessive assist at the time of the abnormality. Can do. In particular, when one motor control signal indicates that the assist force should be applied in the opposite direction, the switching element on the power supply side and the switching element on the ground side in each switching arm are turned on simultaneously. / Off, that is, so-called “upper all on” and “lower all on”. Therefore, according to the said structure, generation | occurrence | production of reverse assist can be prevented and higher reliability and safety | security can be ensured now.

The gist of the invention described in claim 2 is that it comprises two systems of current sensors provided independently corresponding to each of the control signal output means.
According to the above configuration, an abnormality that occurs in the current detection process also appears as the current deviation. Therefore, the abnormality determination in the current detection process can be replaced with the abnormality determination based on the current deviation. As a result, the configuration can be further simplified and the reliability can be improved.

  According to a third aspect of the present invention, two independent sensor signals capable of detecting a steering torque transmitted to the steering system are input to the control means, and each of the control signal output means includes Based on the steering torque detected by the sensor signal corresponding to, each of them independently calculates a current command value.

  According to the above configuration, an abnormality that occurs in the steering torque detection process also appears as the current deviation. Therefore, the abnormality determination in the steering torque detection process can be replaced with the abnormality determination based on the current deviation, and as a result, further simplification of the configuration and improvement of reliability can be achieved.

The gist of the invention described in claim 4 is that it comprises two motor rotation angle sensors provided independently for each of the control signal output means.
According to the above configuration, an abnormality that has occurred in the motor rotation angle detection process also appears as the current deviation. Therefore, the abnormality determination in the motor rotation angle detection process can be replaced with the abnormality determination based on the current deviation. As a result, the configuration can be further simplified and the reliability can be improved.

  The gist of the invention described in claim 5 is that the control means stops power assist control for applying assist force to the steering system when it is determined to be abnormal by the abnormality determination.

  According to the said structure, a motor can be stopped rapidly and a fail safe can be aimed at.

  According to the present invention, it is an object to provide an electric power steering apparatus capable of performing abnormality determination with a simple configuration and high reliability.

The schematic block diagram of an electric power steering device (EPS). The block diagram which shows the electric constitution of EPS. The control block diagram which shows the aspect of motor control by each microcomputer, and abnormality determination. The flowchart which shows the process sequence of abnormality determination. The flowchart which shows the process sequence of the abnormality determination of another example.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the invention will be described with reference to the drawings.
As shown in FIG. 1, in the electric power steering apparatus (EPS) 1 of this embodiment, a steering shaft 3 to which a steering 2 is fixed is connected to a rack shaft 5 via a rack and pinion mechanism 4. The rotation of the steering shaft 3 accompanying the steering operation is converted into a reciprocating linear motion of the rack shaft 5 by the rack and pinion mechanism 4. The steering shaft 3 of this embodiment is formed by connecting a column shaft 3a, an intermediate shaft 3b, and a pinion shaft 3c. Then, the reciprocating linear motion of the rack shaft 5 accompanying the rotation of the steering shaft 3 is transmitted to a knuckle (not shown) via tie rods 6 connected to both ends of the rack shaft 5, whereby the steering angle of the steered wheels 7. That is, the traveling direction of the vehicle is changed.

  Further, the EPS 1 includes an EPS actuator 10 as a steering force assisting device that applies an assist force for assisting a steering operation to the steering system, and an ECU 11 as a control unit that controls the operation of the EPS actuator 10. .

  The EPS actuator 10 of the present embodiment is configured as a so-called column-type EPS actuator in which a motor 12 that is a drive source is drivingly connected to a column shaft 3 a via a speed reduction mechanism 13. In the present embodiment, a known worm and wheel is adopted as the speed reduction mechanism 13. The EPS actuator 10 is configured to apply the motor torque as an assist force to the steering system by decelerating the rotation of the motor 12 and transmitting it to the column shaft 3a.

  On the other hand, a torque sensor 14 and a vehicle speed sensor 15 are connected to the ECU 11. In this embodiment, the torque sensor 14 can detect the steering torque τ transmitted through the steering shaft 3 based on the torsion bar 16 provided in the middle of the column shaft 3 a and the torsion of the torsion bar 16. Two independent sensor units 14a and 14b for outputting sensor signals (Sa, Sb) are provided.

  Such a torque sensor includes, for example, a plurality of Hall ICs as sensor units 14a and 14b serving as detection elements on the radially outer side of a sensor core (not shown) that generates a magnetic flux change due to torsion of the torsion bar 16. Can be formed (see, for example, JP-A-2003-149062). Then, the ECU 11 of the present embodiment uses the motor 12 that is a drive source of the EPS actuator 10 based on the steering torque τ (τa, τb) detected by the torque sensor 14 and the vehicle speed V detected by the vehicle speed sensor 15. The power assist control is executed by controlling the assist torque generated.

Next, the electrical configuration of the EPS of this embodiment will be described.
As shown in FIG. 2, in this embodiment, the motor 12 that is the drive source of the EPS actuator 10 is not connected to the three-phase (U, V, W) motor coils 12u, 12v, 12w. A connected brushless motor is used. The ECU 11 is configured to supply three-phase drive power to the motor 12 by energizing the motor coils 12u, 12v, and 12w of each phase independently with a sine wave.

  Specifically, the ECU 11 of the present embodiment is provided independently corresponding to the two microcomputers 21 (21a, 21b) provided independently as the control signal output means and the motor coils 12u, 12v, 12w of each phase. The three driving circuits 22u, 22v, and 22w are provided.

  In the present embodiment, each of the drive circuits 22u, 22v, and 22w employs a known PWM inverter in which four switching elements SW1 to SW4 are connected in an H bridge shape. These drive circuits 22u, 22v, and 22w drive the DC power of the vehicle-mounted power supply (battery) in three phases based on the motor control signals Smcu, Smcv, and Smcw output from the microcomputers 21 (21a and 21b). The electric power is converted into electric power and output to the motor 12.

  Specifically, each of the drive circuits 22u, 22v, and 22w has a pair of switching elements SW1, SW3, SW2, and SW4 connected in series as a basic unit (switching arm), and the two switching arms SA1 and SA2 are connected in parallel. It is formed by connecting to. In the present embodiment, power MOSFETs are used for the switching elements SW1 to SW4. Each switching arm SA1, SA2 uses the connection point of the two switching elements constituting each switching arm SA1, SA2, that is, the connection point P1 of the switching elements SW1, SW3 and the connection point P2 of SW2, SW4 as an output part. The motor coils 12u, 12v, 12w of the corresponding phases are connected.

  That is, the motor control signals Smcu, Smcv, Smcw output from the microcomputers 21 (21a, 21b) are turned on / off (switching arms) of the switching elements SW1 to SW4 constituting the drive circuits 22u, 22v, 22w. (Duty of SA1 and SA2). The switching elements SW1 to SW4 are turned on / off in response to the motor control signals Smcu, Smcv, and Smcw, so that the phase is shifted by 2 / 3π with respect to the motor coils 12u, 12v, and 12w of each phase. Three-phase (U, V, W) sine wave energization is performed.

  More specifically, in this embodiment, each microcomputer 21 (21a, 21b) is based on sensor signals Sa, Sb output from the two sensor units 14a, 14b constituting the torque sensor 14 (see FIG. 1). Independently, the steering torque τ transmitted through the steering system (the steering shaft 3) is detected. Specifically, the microcomputer 21a detects the steering torque τa based on the sensor signal Sa of the sensor unit 14a, and the microcomputer 21b detects the steering torque τb based on the sensor signal Sb of the sensor unit 14b.

  In the present embodiment, two independent currents corresponding to the microcomputers 21a and 21b are provided in the power supply path between the motor coils 12u, 12v, and 12w of each phase and the drive circuits 22u, 22v, and 22w. A sensor is provided. And each microcomputer 21a, 21b detects each phase current value Iu, Iv, Iw each independently using the corresponding current sensor.

  Specifically, the microcomputer 21a detects the phase current values Iu_a, Iv_a, and Iw_a based on the output signals of the current sensors 23ua, 23va, and 23wa. The microcomputer 21b detects the phase current values Iu_b, Iv_b, and Iw_b based on the output signals of the current sensors 23ub, 23vb, and 23wb.

  Furthermore, the motor 12 of this embodiment is provided with two independent motor rotation angle sensors (motor resolvers 24a and 24b) corresponding to the microcomputers 21a and 21b. Each microcomputer 21a, 21b detects the motor rotation angle θm (θm_a, θm_b) independently using the corresponding motor resolver 24a, 24b.

  Specifically, the microcomputer 21a detects the motor rotation angle θm_a based on the output signal of the motor resolver 24a. Then, the microcomputer 21b detects the motor rotation angle θm_b based on the output signal of the motor resolver 24b.

  Further, in the present embodiment, each microcomputer 21 (21a, 21b) independently generates its target assist force based on the steering torque τ (τa, τb) detected independently as described above and the vehicle speed V. The current command value corresponding to is calculated. In the present embodiment, for the vehicle speed V, a common value is input to each microcomputer 21 (21a, 21b) via an in-vehicle network (not shown). Further, each microcomputer 21 (21a, 21b) has its independently calculated current command value and each independently detected phase current value Iu (Iu_a, Iu_b), Iv (Iv_a, Iv_b), Iw (Iw_a, Iw_b). ) And the motor rotation angle θm (θm_a, θm_b), current feedback calculation is executed. Then, motor control signals Smcu (Smcu_a, Smcu_b), Smcv (Smcv_a, Smcv_b), Smcw (Smcw_a, Smcw_b) generated by executing the current feedback calculation are output to the drive circuits 22u, 22v, 22w.

  Specifically, as shown in FIG. 3, each microcomputer 21 calculates the current command value Iq * corresponding to the target assist force based on the steering torque τ and the vehicle speed V in the current command value calculation unit 31. Next, the two-phase / three-phase conversion unit 32 generates U, V, W phase current command values Iu *, Iv *, Iw * based on the current command value Iq *. Then, in the three subtracters 33u, 33v, 33w provided corresponding to the respective phases, the actual phase current values Iu, Iv, Iw * from the corresponding phase current command values Iu *, Iv *, Iw *, respectively. By subtracting Iw, current deviations ΔIu, ΔIv, ΔIw of each phase are calculated.

  In the present embodiment, the current command value Iq * is calculated as a q-axis current command value in the d / q coordinate system (d-axis current command value is zero). The current command value calculation unit 31 of the present embodiment calculates a current command value Iq * that generates a larger assist force as the steering torque τ is larger and the vehicle speed V is smaller.

  Next, the current deviations ΔIu, ΔIv, ΔIw of the phases calculated in the subtracters 33u, 33v, 33w are respectively F / B control units (feedback control units) 34u, 34v, 34w of the corresponding phases. Is input. Each F / B control unit 34u, 34v, 34w executes a feedback calculation based on the input current deviations ΔIu, ΔIv, ΔIw and a predetermined feedback gain (proportional: P, integral: I), The phase voltage command values Vu *, Vv *, Vw * for each phase are calculated.

  Specifically, each of the F / B control units 34u, 34v, 34w, respectively, has a proportional component obtained by multiplying the input current deviations ΔIu, ΔIv, ΔIw by a proportional gain, and the current deviations ΔIu, ΔIv. , ΔIw is multiplied by an integral gain to calculate an integral component obtained by multiplying the integral value by ΔIw. Then, the phase voltage command values Vu *, Vv *, and Vw * are calculated by adding these proportional components and integral components.

  Next, these phase voltage command values Vu *, Vv *, Vw * are input to motor control signal output units (35u, 35v, 35w) provided corresponding to the respective phases. Specifically, the U-phase phase voltage command value Vu * is input to the U-phase motor control signal output unit 35u, the V-phase phase voltage command value Vv * is input to the V-phase motor control signal output unit 35v, and W The phase voltage command value Vw * of the phase is input to the W-phase motor control signal output unit 35w. Each microcomputer 21 is configured to output motor control signals Smcu, Smcv, and Smcw for each phase generated in each phase motor control signal output unit (35u, 35v, 35w).

  As shown in FIG. 2, the ECU 11 of the present embodiment is provided with three pre-drivers 36 (36u, 36v, 36w) corresponding to the drive circuits 22u, 22v, 22w, and the microcomputers 21 ( The motor control signals Smcu (Smcu_a, Smcu_b), Smcv (Smcv_a, Smcv_b), and Smcw (Smcw_a, Smcw_b) output from the output signals 21a and 21b) are input to the pre-drivers 36, respectively. Each pre-driver 36 (36u, 36v, 36w) has its corresponding motor control signals Smcu (Smcu_a, Smcu_b), Smcv (Smcv_a, Smcv_b), Smcw (Smcw_a, Smcw_b). A gate drive voltage is applied to each of the switching elements SW1 to SW4 constituting the drive circuits 22u, 22v, and 22w.

  Here, in this embodiment, as described above, the two rows of switching arms SA1 and SA2 constituting each of the drive circuits 22u, 22v, and 22w are associated with one of the microcomputers 21a and 21b, respectively. Specifically, the switching arm SA1 is associated with the microcomputer 21a, and the switching arm SA2 is associated with the microcomputer 21b. The pre-drivers 36 (36u, 36v, 36w) are respectively provided with motor control signals Smcu (Smcu_a, Smcu_b), Smcv (Smcv_a) output from the microcomputers 21a, 21b associated with the switching arms SA1, SA2. , Smcv_b) and Smcw (Smcw_a, Smcw_b), the gate drive voltage is output to the switching elements SW1 to SW4 constituting the switching arms SA1 and SA2.

  More specifically, the U-phase pre-driver 36u applies a gate drive voltage to the switching arm SA1 of the corresponding drive circuit 22u (which constitutes each switching element SW1, SW3) based on the motor control signal Smcu_a output from the microcomputer 21a. Output. Based on the motor control signal Smcu_b output from the microcomputer 21b, the gate drive voltage is output to the switching arm SA2 (which constitutes each switching element SW2, SW4) of the drive circuit 22u.

  Similarly, the V-phase pre-driver 36v outputs a gate drive voltage to the switching arm SA1 of the corresponding drive circuit 22v based on the motor control signal Smcv_a output from the microcomputer 21a, and the motor control signal Smcv_b output from the microcomputer 21b. Based on the above, a gate drive voltage is output to the switching arm SA2 of the drive circuit 22v. Based on the motor control signal Smcw_a output from the microcomputer 21a, the W-phase pre-driver 36w outputs a gate drive voltage to the corresponding switching arm SA1 of the drive circuit 22w, and outputs the motor control signal Smcw_b output from the microcomputer 21b. Based on this, a gate drive voltage is output to the switching arm SA2 of the drive circuit 22w.

  In this embodiment, the two rows of switching arms SA1 and SA2 constituting each of the drive circuits 22u, 22v, and 22w thereby cause the motor control signals Smcu_a and Smcv_a output from the corresponding microcomputers 21a and 21b, respectively. , Smcw_a, or motor control signals Smcu_b, Smcv_b, Smcw_b.

  That is, in the EPS 1 of the present embodiment, main state quantities (steering torque τ, phase current values Iu, Iv, Iw, motor rotation angle θm) used for current feedback calculation for executing the power assist control are detected and the same. Each process from the execution of the current feedback calculation to the voltage application to the motor coils 12u, 12v, 12w of each phase is an independent dual system. In addition, although these two control systems are independent of each other, they share the same detection object (torsion bar 16 and motor 12) of the basic state quantity, and execute the same current feedback calculation.

  Therefore, as long as each control system is normal, the control target of each microcomputer 21a, 21b is limited to only one of the two rows of switching arms SA1, SA2 constituting each drive circuit 22u, 22v, 22w. In addition, it is possible to normally control the operation of the drive circuits 22u, 22v, and 22w.

  In other words, the current feedback calculation executed by the two microcomputers 21a and 21b is the same, and the detection object of the state quantity that is the basis thereof is also common. Therefore, as long as there is no abnormality in these two control systems, the calculation result is It will be the same. In this embodiment, the switching arms SA1 and SA2 corresponding to the microcomputers 21a and 21b operate in synchronization with each other based on the input motor control signals (Smcu_a, Smcv_a, Smcw_a or Smcu_b, Smcv_b, Smcw_b). By doing this, the microcomputer 21a, 21b is configured to perform the same power supply as when it is controlled independently.

  On the other hand, when some abnormality occurs in these two control systems and a difference occurs in the result of the current feedback calculation executed by each of the microcomputers 21a and 21b, the operation of each of the drive circuits 22u, 22v, and 22w is asked whether it is correct or incorrect. Instead, it follows the side that outputs a motor control signal that should generate a smaller energization amount.

  That is, the power supply by each drive circuit 22u, 22v, 22w is such that the switching element on the power supply side is turned on in one of the two switching arms SA1, SA2, and the switching element on the ground side (for example, switching element SW1) is turned on the other. This is performed by turning on (see FIG. 2, for example, the switching elements SW1 and SW3 are on). Therefore, the energization time follows the shorter of the two switching arms SA1 and SA2, and as a result, the motor control signal indicating that the switching arms SA1 and SA2 should be turned on for a longer time. On the output side, the current deviation (ΔIu, ΔIv, ΔIw) which is the basis of the current feedback calculation increases.

  In the present embodiment, the microcomputers 21a and 21b monitor the occurrence of excessive current deviations, thereby performing abnormality determination of the system (an EPS system realized by the two control systems).

  More specifically, as shown in FIG. 3, each microcomputer 21 (21 a, 21 b) is provided with an abnormality determination unit 40, and the abnormality determination unit 40 has a basis for current feedback calculation executed by each microcomputer 21. The current deviations ΔIu, ΔIv, ΔIw of the respective phases are input. And the abnormality determination part 40 of this embodiment performs the abnormality determination by monitoring the excessive current deviation (DELTA) Iu, (DELTA) Iv, and (DELTA) Iw of each phase.

  In addition, when the abnormality determination unit 40 detects a system abnormality by the abnormality determination, the microcomputer 21 (for example, the microcomputer 21a) on the side where the abnormality determination unit 40 exists and the microcomputer 21 (for example, the microcomputer) on the other side exist. An abnormality detection signal S_tr indicating the occurrence of the abnormality is output to each phase motor control signal output unit (35u, 35v, 35w) of 21b). In this embodiment, based on the abnormality detection signal S_tr, each phase motor control signal output unit (35u, 35v, 35w) outputs a motor control signal for stopping motor driving, that is, its power assist control. By stopping, it is configured to promptly fail-safe.

  Specifically, as shown in the flowchart of FIG. 4, each microcomputer 21 (21a, 21b) compares the current deviation ΔIu, ΔIv, ΔIw of each phase, which is the basis of the current feedback calculation, with a predetermined threshold value I1. Thus, the occurrence of the excessive deviation is monitored (step 101 to step 103). Further, when it is determined that an excessive deviation has not occurred in each of these steps (steps 101 to 103: all NO), it is subsequently determined whether or not an abnormality detection signal S_tr is input from another microcomputer 21. Is determined (step 104). If no abnormality detection signal S_tr is input (step 104: NO), it is determined that the system is normal, and the motor drive is continued (step 105).

  On the other hand, when the occurrence of an excessive deviation is detected in any one of steps 101 to 103 (ΔIu> I1, step 101: YES, or ΔIv> I1, step 102: YES, or ΔIw> I1, step 103: YES ), It is determined that an abnormality has occurred in the system. Then, an abnormality detection signal S_tr indicating the occurrence of the abnormality is output to the other microcomputer 21 (step 106), and the motor drive is stopped, that is, the execution of the power assist control is stopped (step 107). Similarly, when an abnormality detection signal S_tr is input from another microcomputer 21 at step 104 (step 104: YES), the motor drive is stopped (step 107).

As described above, according to the present embodiment, the following operations and effects can be obtained.
(1) The ECU 11 includes two independent microcomputers 21a and 21b that execute the same current feedback calculation as motor control signal output means. The two rows of switching arms SA1 and SA2 constituting each drive circuit 22u, 22v, and 22w are associated with either of the microcomputers 21a and 21b, respectively, and output from the associated microcomputers 21a and 21b. It operates independently only based on motor control signals Smcu (Smcu_a, Smcu_b), Smcv (Smcv_a, Smcv_b), and Smcw (Smcw_a, Smcw_b). The microcomputers 21a and 21b perform system abnormality determination by monitoring the occurrence of an excessive current deviation in the current feedback calculation.

  That is, the current feedback calculation executed by each of the microcomputers 21a and 21b is the same, and since the detection object of the state quantity that is the basis thereof is also common, the calculation result is also the same unless there is an abnormality in the two control systems. It is. Accordingly, even with the above-described configuration, the switching arms SA1 and SA2 can be operated in synchronization as in the case where the microcomputers 21a and 21b perform control independently.

  On the other hand, when any abnormality occurs in these two control systems, a difference occurs in the result of the current feedback calculation executed by each of the microcomputers 21a and 21b. As a result, the operation of each of the drive circuits 22u, 22v, and 22w follows the motor control signal on the side showing a small energization amount regardless of the correctness, and as a result, the motor control signal indicating a larger energization amount is output. On the other hand, the current deviation that is the basis of the current feedback calculation increases. Therefore, by monitoring the occurrence of the excessive current deviation, it is possible to make a reliable abnormality determination with a simple configuration.

  In particular, when an abnormality occurring in each of the microcomputers 21a and 21b affects the execution of the power assist control, the influence always appears in at least one of the current deviations. Therefore, if the execution of the power assist control is stopped after the abnormality is detected, other abnormality determination control (monitoring circuit) relating to each of the microcomputers 21a and 21b, such as the initial check of the memory at the time of startup as described above, is eliminated. Therefore, it is possible to replace the abnormality determination based on the current deviation. As a result, not only the start-up time can be shortened, but also the cost reduction due to a decrease in processing capability required for each of the microcomputers 21a and 21b, and the failure rate can be reduced by reducing the circuit scale. .

  In addition, as described above, even when an abnormality occurs, the operation of each of the drive circuits 22u, 22v, and 22w follows the motor control signal that indicates a smaller energization amount. Occurrence can be prevented. In particular, when one of the motor control signals indicates that the assist force should be applied in the opposite direction, the switching elements SW1 and SW2 on the power supply side and the switching on the ground side of each switching arm SA1 and SA2. The elements SW1 and SW2 are simultaneously turned on / off, that is, so-called “upper all on” and “lower all on”. Therefore, according to the said structure, generation | occurrence | production of reverse assist can be prevented and higher reliability and safety | security can be ensured now.

  (2) Two independent current sensors corresponding to the microcomputers 21a and 21b are provided in the power supply path between the motor coils 12u, 12v and 12w of each phase and the drive circuits 22u, 22v and 22w. . And each microcomputer 21a, 21b detects each phase current value Iu, Iv, Iw each independently using the corresponding current sensor.

  According to the above configuration, an abnormality that occurs in the current detection process also appears as the current deviation. Therefore, the abnormality determination in the current detection process can be replaced with the abnormality determination based on the current deviation. As a result, the configuration can be further simplified and the reliability can be improved.

  (3) Each of the microcomputers 21a and 21b detects the steering torques τa and τb independently based on the two independent sensor signals Sa and Sb input from the torque sensor 14. Based on the steering torque τ (τa, τb), a current command value Iq * corresponding to the target assist force is calculated.

  According to the above configuration, an abnormality that occurs in the steering torque detection process also appears as the current deviation. Therefore, the abnormality determination in the steering torque detection process can be replaced with the abnormality determination based on the current deviation, and as a result, further simplification of the configuration and improvement of reliability can be achieved.

  (4) The motor 12 is provided with two independent motor rotation angle sensors (motor resolvers 24a and 24b) corresponding to the microcomputers 21a and 21b. Each microcomputer 21a, 21b detects the motor rotation angle θm (θm_a, θm_b) independently using the corresponding motor resolver 24a, 24b.

  According to the above configuration, an abnormality that has occurred in the motor rotation angle detection process also appears as the current deviation. Therefore, the abnormality determination in the motor rotation angle detection process can be replaced with the abnormality determination based on the current deviation. As a result, the configuration can be further simplified and the reliability can be improved.

In addition, you may change each said embodiment as follows.
In the above embodiment, the present invention is embodied in a so-called column type EPS. However, the present invention is not limited to this, and a so-called pinion type or rack assist type EPS may be used.

  In the above embodiment, the torque sensor 14 including the two independent sensor units 14a and 14b that output the sensor signals Sa and Sb that can detect the steering torque τ is used. However, the present invention is not limited to this, and two independent torque sensors may be provided to input respective signals to the corresponding microcomputers 21a and 21b.

  In the above embodiment, two independent current sensors are provided, and each microcomputer 21a, 21b uses the corresponding current sensor to independently detect each phase current value Iu, Iv, Iw. . However, the present invention is not limited to this, and the microcomputers 21a and 21b may be configured to use common phase current values Iu, Iv, and Iw.

  In the above embodiment, the microcomputers 21a and 21b each independently detect the steering torque τ (τa, τb) based on the two independent sensor signals Sa and Sb input from the torque sensor 14. It was decided. However, the present invention is not limited to this, and the microcomputers 21a and 21b may use a common value as the steering torque τ.

  Furthermore, in the above embodiment, the motor 12 is provided with two independent motor rotation angle sensors (motor resolvers 24a and 24b) corresponding to the microcomputers 21a and 21b, and the microcomputers 21a and 21b correspond to the motors 21a and 21b. Using the motor resolvers 24a and 24b, the motor rotation angles θm (θm_a and θm_b) are detected independently. However, the present invention is not limited to this, and the microcomputers 21a and 21b may use a common value as the motor rotation angle θm.

  However, if the abnormality determination based on the current deviation is determined as the abnormality determination of the system, as shown in the above embodiment, two independent current sensors and two independent motor rotation angle sensors are provided, and the steering torque τ Two independent sensor signals Sa and Sb are detected. Then, the microcomputers 21a and 21b respectively independently output the phase current values Iu, Iv, Iw (Iu_a, Iv_a, Iw_a and Iu_b, Iv_b, Iw_b), the motor rotation angle θm (θm_a, θm_b), and the motor rotation angle θm ( It is desirable to detect θm_a, θm_b) and steering torque τ (τa, τb).

  In other words, in this way, the detection of the main state quantities used for the current feedback calculation for executing the power assist control, the execution thereof, and the respective processes up to the voltage application to the motor 12 are made an independent dual system. Thus, any abnormality that has occurred in the main configuration for executing the assist force application will appear as a current deviation. As a result, it is possible to secure high reliability while simplifying the configuration by eliminating other abnormality determination control (monitoring circuit).

  In the embodiment described above, the motor control signal output unit (35u, 35v, 35w) in each microcomputer 21 (21a, 21b) is provided for each phase (see FIG. 3), but these are combined into one. It may be embodied in a configuration.

  In the above embodiment, the pre-drivers 36 (36u, 36v, 36w) interposed between the microcomputers 21 (21a, 21b) and the drive circuits 22u, 22v, 22w are provided for each phase. (See FIG. 2). However, the present invention is not limited to this, and two pre-drivers may be used corresponding to the microcomputers 21a and 21b and the switching arms SA1 and SA2 associated with the microcomputers 21a and 21b. A configuration using a pre-driver may be used.

  In the above embodiment, each microcomputer 21 converts the current command value Iq * corresponding to the target assist force into the three-phase current command values Iu *, Iv *, and Iw *, so that U, V, W For each phase, an abnormality determination based on the output of the motor control signal by executing the current feedback calculation and the monitoring of the current deviations ΔIu, ΔIv, ΔIw is executed. However, the present invention is not limited to this, and the motor control signal for each phase is generated based on the result of the current feedback calculation in the d / q coordinate system. Then, as shown in FIG. 5, the q-axis current deviation ΔIq which is the basis of the current feedback calculation in the d / q coordinate system is compared with a predetermined threshold value I2 (step 201), and the occurrence of the excessive deviation is monitored. Thus, the system may be configured to perform abnormality determination of the system. Even with such a configuration, it is possible to obtain the same effects as in the above embodiment. In FIG. 4, the processing contents of steps 202 to 205 are the same as the processing contents of steps 104 to 207 in FIG.

  In the above embodiment, each microcomputer 21 (21a, 21b) is provided with the abnormality determination unit 40 so that the microcomputer 21 constitutes an abnormality determination unit. However, the present invention is not limited to this, and the abnormality determining means may be provided independently. However, it is needless to say that the configuration shown in the above embodiment is more suitable from the viewpoint of simplification of configuration and enjoyment of benefits associated therewith (reduction of failure rate due to circuit scale reduction, etc.). Absent.

  DESCRIPTION OF SYMBOLS 1 ... Electric power steering apparatus (EPS), 2 ... Steering, 3 ... Steering shaft, 10 ... EPS actuator, 11 ... ECU, 12 ... Motor, 12u, 12v, 12w ... Motor coil, 14 ... Torque sensor, 14a, 14b ... Sensor unit, 21 (21a, 21b) ... microcomputer, 22u, 22v, 22w ... drive circuit, SW1-SW4 ... switching element, SA1, SA2 ... switching arm, 23ua, 23ub, 23va, 23vb, 23wa, 23wb ... current sensor, 24a, 24b ... motor resolver, 31 ... current command value calculation unit, 32 ... two-phase / three-phase conversion unit, 33u, 33v, 33w ... subtractor, 34u, 34v, 34w ... F / B control unit, 35u ... U phase Motor control signal output unit, 35v... V phase motor control signal output unit, 35w W-phase motor control signal output unit 36 ... pre-driver 36u ... U-phase pre-driver 36v ... V-phase pre-driver 36w ... W-phase pre-driver 40 ... abnormality determination unit Sa, Sb ... sensor signal, τ (τa , Τb) Steering torque, θm (θa, θb) Motor rotation angle, Iq * Current command value, Iu *, Iv *, Iw * Phase current command value, Iu (Iu_a, Iu_b), Iv (Iv_a, Iv_b), Iw (Iw_a, Iw_b) ... phase current value, Vu *, Vv *, Vw * ... phase voltage command value, ΔIu, ΔIv, ΔIw, ΔIq ... current deviation, I1, I2 ... threshold, Smcu (Smcu_a, Smcu_b ), Smcv (Smcv_a, Smcv_b), Smcw (Smcw_a, Smcw_b) ... motor control signal, S_tr ... abnormality detection signal.

Claims (5)

A steering force assisting device for applying an assist force to the steering system using a motor as a drive source; and a control means for controlling the operation of the steering force assisting device, wherein the control means generates a motor torque corresponding to the assist force. Control signal output means for outputting a motor control signal to be generated, and a drive circuit for supplying drive power based on the motor control signal to the motor, wherein the control signal output means is adapted to detect detected steering torque. In the electric power steering device that generates the motor control signal by calculating a current command value corresponding to the target assist force based on the current feedback calculation,
The motor has a U-phase coil, a V-phase coil, and a W-phase coil as three-phase motor coils, and the U-phase coil, the V-phase coil, and the W-phase coil are not connected to each other. A non-wired brushless motor,
The control means includes three drive circuits provided independently for the U-phase coil, the V-phase coil, and the W-phase coil, and two independent controls that execute the same current feedback calculation. Signal output means,
The drive circuit is formed by connecting in parallel two switching arms formed by connecting a pair of switching elements that are turned on / off based on the motor control signal in series,
Each of the switching arms operates independently based on the motor control signal output by the corresponding control signal output means, and the current feedback calculation results in the control signal output means are the same. Operates synchronously,
Wherein the control signal output means, an excessive deviation of the current deviation difference in calculation results of the current feedback calculation in each of the control signal output means underlying said current feedback computation when generated occurs by raising An electric power steering apparatus characterized by performing abnormality determination by monitoring. The electric power steering apparatus according to claim 1, wherein
An electric power steering apparatus comprising two current sensors provided independently corresponding to each of the control signal output means. In the electric power steering device according to claim 1 or 2,
Two independent sensor signals that can detect steering torque transmitted to the steering system are input to the control means,
Each of the control signal output means independently calculates a current command value based on the steering torque detected by the corresponding sensor signal;
An electric power steering device. In the electric power steering device according to any one of claims 1 to 3,
An electric power steering apparatus comprising two motor rotation angle sensors provided independently corresponding to each of the control signal output means. In the electric power steering device according to any one of claims 1 to 4,
The control means stops power assist control for applying assist force to the steering system when it is determined abnormal by the abnormality determination;
An electric power steering device.

Images