Motor control device, motor device, and direction control system

Abstract

A motor control device, a motor device, and a direction steering system according to the present invention are provided with: a third inverter connected to a first branch point between a first polyphase winding group and a first inverter, and connected to a second branch point between a second polyphase winding group and a second inverter, aC power can be supplied to the first multi-phase winding group or the second multi-phase winding group; a switching relay including a first switching relay disposed between the first branch point and the third inverter, and a second switching relay disposed between the second branch point and the third inverter; and a cut-off relay disposed between the first branch point and the ground and between the second branch point and the ground, the first switching relay and the second switching relay having diodes for conducting a current in a direction from the motor to the third inverter, and the cut-off relay having a diode for conducting a current in a direction from the ground to the motor.

Description

Technical Field

[0001] The invention relates to a motor control device, a motor device and a steering control system. Background Art

[0002] The motor control device of patent document 1 comprises: a main motor drive circuit for driving and controlling a multi-phase motor; a backup motor drive circuit for driving and controlling the multi-phase motor when an abnormality occurs in the main motor drive circuit; and an abnormality diagnosis unit for performing abnormality diagnosis on the main motor drive circuit and the backup motor drive circuit, and comprises: a normal drive state in which the multi-phase motor is driven only in the main motor drive circuit; and a backup drive state in which, when a diagnosis result of the main motor drive circuit based on the abnormality diagnosis unit is abnormal, the motor current of the phase output unit that will become abnormal is cut off, and the cut-off phase output unit is switched to a phase output unit of the backup motor drive circuit of the same phase to drive the multi-phase motor.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: International Publication No. 2015 / 129271 Summary of the invention

[0006] Problems to be solved by the invention

[0007] However, in the case where the motor has a first multi-phase winding set and a second multi-phase winding group, it is considered to have a third inverter as a backup for the first inverter and the second inverter in addition to a first inverter that supplies AC power to the first multi-phase winding group and a second inverter that supplies AC power to the second multi-phase winding group, and to enable the third inverter to continue to control the motor when a failure occurs in the first inverter or the second inverter.

[0008] Furthermore, conventionally, the switching of the driving path of the motor is performed by switching the conduction and interruption of the driving path using a semiconductor switching element such as a FET (Field Effect Transistor) disposed in the driving path.

[0009] However, even when a semiconductor switching element such as a FET is in an OFF control state, current flows through a parasitic diode (or body diode) existing inside the semiconductor switching element.

[0010] Therefore, in the case of a structure in which the drive path is switched by semiconductor switching elements such as FETs, the output current of the inverter flows into the normal system via a parasitic diode, or a short-circuit fault occurs in the switching element of the lower arm of the inverter, forming a ground-fault circuit, and there is a concern that the power-on control of the first multi-phase winding group or the second multi-phase winding group may no longer be performed normally.

[0011] The present invention has been completed in view of previous actual situations, and its purpose is to provide a motor control device, a motor device and a steering control system that can normally control the power supply of the first multi-phase winding group and the second multi-phase winding group even when any one of the first inverter, the second inverter and the third inverter fails.

[0012] Means for solving problems

[0013] According to the present invention, in one embodiment thereof, it comprises: a first inverter for supplying AC power to a first multi-phase winding group of a motor; a second inverter for supplying AC power to a second multi-phase winding group of the motor; a third inverter, which is connected to a first branch point between the first multi-phase winding group and the first inverter, and is connected to a second branch point between the second multi-phase winding group and the second inverter, and is capable of supplying AC power to the first multi-phase winding group or the second multi-phase winding group; a switching relay, the switching relay comprising a first switching relay arranged between the first branch point and the third inverter, and a second switching relay arranged between the second branch point and the third inverter, the first switching relay and the second switching relay having a diode that conducts current in a direction from the motor toward the third inverter; and a cut-off relay, the cut-off relay being arranged between the first branch point and ground, and between the second branch point and ground, and having a diode that conducts current in a direction from the ground toward the motor.

[0014] Effects of the Invention

[0015] According to the present invention, even when any one of the first inverter, the second inverter, and the third inverter fails, the energization control of the first multi-phase winding group and the second multi-phase winding group can be performed normally. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a structural diagram of the direction control system.

[0017] Figure 2 : is a block diagram showing the structure of the motor control device.

[0018] Figure 3This is a block diagram showing a detailed configuration of a motor control device according to a first embodiment.

[0019] Figure 4 It is a circuit diagram showing details of the inverter and the relay according to the first embodiment.

[0020] Figure 5 This is a circuit diagram showing a control state when a failure occurs in the first inverter in the first embodiment.

[0021] Figure 6 This is a circuit diagram showing a control state when a failure occurs in the first inverter in the first embodiment.

[0022] Figure 7 It is a block diagram showing a detailed structure of a motor control device according to a second embodiment.

[0023] Figure 8 It is a circuit diagram showing details of an inverter and a relay according to the second embodiment.

[0024] Fig. 9 This is a circuit diagram showing a control state when a failure occurs in the first inverter in the second embodiment.

[0025] Fig.10 This is a circuit diagram showing a control state when a failure occurs in the first inverter in the second embodiment.

[0026] Fig.11 This is a circuit diagram showing a control state when a failure occurs in the third inverter in the second embodiment.

[0027] Fig.12 This is a circuit diagram showing a control state when a failure occurs in the first inverter and the second inverter in the second embodiment.

[0028] Fig.13 This is a circuit diagram showing a control state when a failure occurs in the first inverter and the fifth relay in the second embodiment.

[0029] Fig.14 This is a circuit diagram showing a control state when a failure occurs in the third inverter and the fourth relay in the second embodiment.

[0030] Fig.15 This is a circuit diagram showing a control state when a failure occurs in the third relay and the fourth relay in the second embodiment.

[0031] Fig.16 It is a block diagram showing a detailed structure of a motor control device according to a third embodiment.

[0032] Fig.17It is a circuit diagram showing details of an inverter and a relay according to a third embodiment.

[0033] Fig.18 This is a circuit diagram showing a control state when a failure occurs in the first inverter in the third embodiment.

[0034] Fig.19 This is a circuit diagram showing a control state when a failure occurs in the third inverter in the third embodiment.

[0035] Fig. 20 It is a block diagram showing a detailed structure of a motor control device according to a fourth embodiment.

[0036] Fig.21 This is a circuit diagram showing a control state when a failure occurs in the third inverter in the fourth embodiment.

[0037] Fig. 22 : is a flowchart showing the control process by the first control device and the second control device.

[0038] Fig.23 : is a flowchart showing the control process by the first control device and the second control device.

[0039] Fig.24 1 is a flowchart showing a drive switching determination process based on the accumulated drive time, which is performed by the first control device and the second control device.

[0040] Fig.25 1 is a flowchart showing a drive switching determination process based on the FET estimated temperature, which is performed by the first control device and the second control device.

[0041] Fig.26 : is a flowchart showing the control process by the third control device.

[0042] Fig. 27 : is a flowchart showing the control process by the third control device.

[0043] Fig.28 1 is a flowchart showing a drive switching determination process based on the accumulated drive time, which is performed by the third control device.

[0044] Fig.29 1 is a flowchart showing a drive switching determination process based on the FET estimated temperature, which is performed by the third control device. DETAILED DESCRIPTION

[0045] Hereinafter, embodiments of a motor control device, a motor device, and a steering system according to the present invention will be described with reference to the drawings.

[0046] Figure 1 1 is a structural diagram showing one embodiment of a steering system 1000 provided in a vehicle 1 such as an automobile.

[0047] The steering system 1000 includes a steering device 2000 and a reaction force generating device 3000 .

[0048] The steering device 2000 is a device that can steer the front wheels 2L and 2R as steering wheels by operating the motor 100 as an actuator for steering.

[0049] The reaction force generating device 3000 is a device capable of applying reaction force torque to the steering wheel 500 by operating the motor 600 as an actuator for reaction force.

[0050] Here, the direction control device 2000 and the reaction force generating device 3000 are mechanically separated.

[0051] That is, the steering system 1000 is a steer-by-wire type steering system in which the steering wheel 500 and the front wheels 2L and 2R serving as steering wheels are mechanically separated.

[0052] In addition, the steering system 1000 may include a mechanism for mechanically connecting the steering device 2000 and the reaction force generating device 3000 (in other words, the front wheels 2L, 2R and the steering wheel 500) when an abnormality occurs in the system.

[0053] The steering device 2000 comprises: a motor 100 for generating a turning force applied to the front wheels 2L and 2R; a motor control device 200 for controlling the motor 100; a steering mechanism 300; and a steering angle detection device 400 for detecting the steering angle of the front wheels 2L and 2R, in other words, the position of the steering mechanism 300.

[0054] The motor 100 is a brushless motor and includes a motor rotation angle sensor 101 that detects a rotor position, in other words, a rotation angle of an output shaft.

[0055] The direction steering mechanism 300 is a mechanism for converting the rotational motion of the output shaft of the motor 100 into the linear motion of the steering rod 310 , and in this embodiment, a rack and a pinion are used.

[0056] The rotational driving force of the motor 100 is transmitted to the gear shaft 330 via the speed reducer 320 .

[0057] Meanwhile, the steering rod 310 includes a rack 311 meshing with a gear 331 provided on the gear shaft 330 . When the gear 331 rotates, the steering rod 310 moves horizontally in the left-right direction of the vehicle 1 , thereby changing the steering angle of the front wheels 2L, 2R.

[0058] In addition, the direction turning mechanism 300 is not limited to the rack and pinion, and may be a mechanism using a ball screw, for example.

[0059] The reaction force generating device 3000 includes a steering wheel 500 operated by a driver of the vehicle 1, a steering shaft 510 connected to the steering wheel 500 and rotating along with the rotation of the steering wheel 500, a motor 600 generating a steering reaction force, a motor control device 700 controlling the motor 600, and a steering angle detection device 800 detecting a steering angle as an operating angle of the steering wheel 500.

[0060] Moreover, the motor control device 200 of the steering device 2000 (in other words, the steering control device) compares the information of the target steering angle corresponding to the steering angle of the steering wheel 500 detected by the steering angle detection device 800 with the information of the actual steering angle detected by the steering angle detection device 400, and controls the motor 100 serving as a steering actuator.

[0061] Furthermore, the motor control device 700 of the reaction force generating device 3000 (in other words, the reaction force control device) obtains a target reaction force torque based on information on the steering angle of the steering wheel 500 , information on the speed of the vehicle 1 , and the like.

[0062] Then, the motor control device 700 controls the motor 600 as the reaction force actuator based on the target reaction force torque so as to generate the steering reaction force.

[0063] The motor 600 is a brushless motor and includes a motor rotation angle sensor 601 that detects a rotor position, in other words, a rotation angle of an output shaft.

[0064] Furthermore, the motor control device 200 of the steering device 2000 and the motor control device 700 of the reaction force generating device 3000 are configured to be able to communicate with each other.

[0065] Figure 2 It is a block diagram schematically showing the configuration of the motor control device 200 of the steering device 2000 and the motor control device 700 of the reaction force generating device 3000 .

[0066] The steering device 2000 is a device capable of steering the front wheels 2L and 2R based on the output of the motor 100 as an actuator for steering.

[0067] Here, the motor 100 is a three-phase brushless motor having two multi-phase winding groups (three-phase winding groups) including a first winding group 100a and a second winding group 100b each including a U-phase coil, a V-phase coil, and a W-phase coil.

[0068] In other words, the motor 100 includes a first motor 100A having a first winding group 100a as a stator of three-phase windings, and a second motor 100B having a second winding group 100b as a stator of three-phase windings.

[0069] Furthermore, in the steering device 2000 , the first motor 100A and the second motor 100B act in parallel to steer the front wheels 2L and 2R.

[0070] The motor control device 200 has a first control device 200A connected to the first winding group 100a and capable of controlling the power supply to the first winding group 100a, a second control device 200B connected to the second winding group 100b and capable of controlling the power supply to the second winding group 100b, and a spare third control device 200C that can switch the connection with the first winding group 100a and disconnect it and can switch the connection with the second winding group 100b and disconnect it as a control unit.

[0071] Furthermore, the motor control device 200 and the motor 100 constitute a motor device.

[0072] The first control device 200A is an ECU (Electronic Control Unit) including a first MCU (Micro Controller Unit) 200A1 , a first drive circuit 200A2 , and a first relay 200A3 .

[0073] The second control device 200B is an ECU including a second MCU 200B1 , a second drive circuit 200B2 , and a second relay 200B3 .

[0074] The third control device 200C is an ECU including a third MCU 200C1 , a third drive circuit 200C2 , a third relay 200C3 , and a fourth relay 200C4 .

[0075] Here, among the MCUs 200A1 , 200B1 , and 200C1 , for example, the MCUs 200A1 and 200B1 can be multi-core (multi-core) including a plurality of processor cores.

[0076] For example, when dual-core is used as multi-core, when an abnormality occurs in the first processor core constituting the dual-core, the motor control can be continued by the second processor core. In addition, the pre-driver, inverter, power supply, etc. can be continued to be monitored by the second processor core.

[0077] In addition, MCU can be rewritten as a microcomputer, a processor, a processing device, a computing device, etc.

[0078] The MCUs 200A1 , 200B1 , and 200C1 output control signals for controlling the AC power supplied to the first motor 100A or the second motor 100B to the drive circuits 200A2 , 200B2 , and 200C2 .

[0079] The drive circuits 200A2, 200B2, and 200C2 include a pre-driver, an inverter, and the like, and supply AC power to the first winding group 100a or the second winding group 100b.

[0080] The first relay 200A3 is controlled to be turned on (ON) and off (OFF) by the first MCU 200A1 of the first control device 200A, and switches the connection and disconnection between the first drive circuit 200A2 and the first winding group 100a.

[0081] The second relay 200B3 is controlled to be turned on and off by the second MCU 200B1 of the second control device 200B, and switches the connection and disconnection between the second drive circuit 200B2 and the second winding group 100b.

[0082] The first relay 200A3 and the second relay 200B3 are composed of semiconductor switching elements arranged on the three-phase drive lines between the drive circuit and the winding group in the first control device 200A and the second control device 200B, respectively, and are phase relays that switch the connection and disconnection between the drive circuit and the winding group.

[0083] The third relay 200C3 is controlled to be turned on and off by the third MCU 200C1 of the third control device 200C, and switches the connection and disconnection between the third drive circuit 200C2 and the first winding group 100a.

[0084] The fourth relay 200C4 is controlled to be turned on and off by the third MCU 200C1 of the third control device 200C, and switches the connection and disconnection between the third drive circuit 200C2 and the second winding group 100b.

[0085] The third relay 200C3 is a first switching relay for switching the circuit driving the first winding group 100a from the first drive circuit 200A2 to the third drive circuit 200C2, and the fourth relay 200C4 is a second switching relay for switching the circuit driving the second winding group 100b from the second drive circuit 200B2 to the third drive circuit 200C2.

[0086] In addition, the first relay 200A3 can be configured to be controllable to be opened (disconnected state) by the third MCU 200C1 of the third control device 200C.

[0087] Furthermore, the switch can be configured to be turned off when at least one of the first MCU 200A1 of the first control device 200A and the third MCU 200C1 of the third control device 200C outputs an off command.

[0088] Similarly, the second relay 200B3 can be configured to be controllable to be opened by the second MCU 200B1 of the second control device 200B.

[0089] Furthermore, it can be configured so as to be turned off when at least one of the second MCU 200B1 of the second control device 200B and the third MCU 200C1 of the third control device 200C outputs an off command.

[0090] The first control device 200A monitors whether or not there is a failure in the first drive circuit 200A2 and the like.

[0091] Furthermore, the second control device 200B monitors the presence or absence of a failure in the second drive circuit 200B2 and the like.

[0092] Furthermore, the third control device 200C monitors whether or not there is a failure in the third drive circuit 200C2 and the like.

[0093] When a fault occurs in the first drive circuit 200A2 of the first control device 200A, the first relay 200A3 is turned off to disconnect the first drive circuit 200A2 from the first winding group 100a, and the third relay 200C3 is turned on to connect the third drive circuit 200C2 to the first winding group 100a.

[0094] That is, if a failure occurs in the first control device 200A that controls the first winding group 100a, the third control device 200C can control energization of the first winding group 100a instead of the first control device 200A.

[0095] If a fault occurs in the second drive circuit 200B2 of the second control device 200B, the second relay 200B3 is turned off to disconnect the second drive circuit 200B2 from the second winding group 100b, and the fourth relay 200C4 is turned on to connect the third drive circuit 200C2 to the second winding group 100b.

[0096] That is, if the second control device 200B that drives and controls the second winding group 100b fails, the third control device 200C can control the energization of the second winding group 100b instead of the second control device 200B.

[0097] If a failure occurs in the third drive circuit 200C2 of the third control device 200C, the first drive circuit 200A2 is connected to the first winding group 100a, and the second drive circuit 200B2 is connected to the second winding group 100b, that is, the normal state is maintained.

[0098] Therefore, even if a fault occurs in any one of the first control unit 200A, the second control unit 200B, and the third control unit 200C, the steering device 2000 can continue to control the first motor 100A and the second motor 100B, thereby continuing the steering of the front wheels 2L and 2R based on the steering device 2000 without reducing performance.

[0099] Even if a failure occurs in the first control device 200A and the second control device 200B, the third control device 200C can control the first motor 100A and the second motor 100B, and the steering device 2000 can continue to steer the front wheels 2L and 2R.

[0100] On the other hand, the reaction force generating device 3000 is a device that can apply reaction force torque to the steering wheel 500 by the output of the motor 600 serving as an actuator for reaction force.

[0101] Here, the motor 600 is a three-phase brushless motor, and includes two multi-phase winding groups, namely, a first winding group 600a and a second winding group 600b, each of which is composed of a U-phase coil, a V-phase coil, and a W-phase coil.

[0102] In other words, the motor 600 includes a first motor 600A having a first winding group 600a as a stator of three-phase windings, and a second motor 600B having a second winding group 600b as a stator of three-phase windings.

[0103] In the reaction force generating device 3000 , the first motor 600A and the second motor 600B act in parallel to apply reaction force torque to the steering wheel 500 .

[0104] The motor control device 700 includes a first control device 700A connected to the first winding group 600a and capable of controlling energization of the first winding group 600a, and a second control device 700B connected to the second winding group 600b and capable of controlling energization of the second winding group 600b.

[0105] The first control device 700A includes a first MCU 700A1 , a first drive circuit 700A2 , and a first relay 700A3 .

[0106] The second control device 700B includes a second MCU 700B1 , a second drive circuit 700B2 , and a second relay 700B3 .

[0107] The MCUs 700A1 and 700B1 output control signals for controlling the AC power supplied to the first motor 600A or the second motor 600B to the drive circuits 700A2 and 700B2.

[0108] The drive circuits 700A2 and 700B2 include a pre-driver, an inverter, and the like, and supply AC power to the first motor 600A or the second motor 600B.

[0109] The first relay 700A3 is controlled to be turned on and off by the first MCU 700A1, and switches the connection and disconnection between the first drive circuit 700A2 and the first winding group 600a.

[0110] The second relay 700B3 is controlled to be turned on and off by the second MCU 700B1 to switch the connection and disconnection between the second drive circuit 700B2 and the second winding group 600b.

[0111] In addition, similar to the motor control device 200 , the motor control device 700 may include a third control device in addition to the first control device 700A and the second control device 700B.

[0112] Furthermore, the motor control device 700 including the third control device is configured so that when the first control device 700A fails, the third control device controls energization of the first winding group 600a, and when the second control device 700B fails, the third control device controls energization of the second winding group 600b.

[0113] "First Implementation Method"

[0114] Figure 3 This is a block diagram showing a detailed structure of the motor control device 200 according to the first embodiment.

[0115] In addition, Figure 3 In, with Figure 2 The same elements are provided with the same reference numerals.

[0116] The first drive circuit 200A2 of the first control device 200A includes a first pre-driver 200A21 and a first inverter 200A22 .

[0117] The second drive circuit 200B2 of the second control device 200B includes a second pre-driver 200B21 and a second inverter 200B22 .

[0118] The third drive circuit 200C2 of the third control device 200C includes a third pre-driver 200C21 and a third inverter 200C22 .

[0119] The motor 100 includes a first motor rotation angle sensor 101A and a second motor rotation angle sensor 101B as the motor rotation angle sensor 101 that detects the rotation angle of the output shaft of the motor 100 .

[0120] The first motor rotation angle sensor 101A and the second motor rotation angle sensor 101B are, for example, magnetic angle sensors that convert changes in a magnetic field caused by a magnet 102 provided on an output shaft of the motor 100 into resistance.

[0121] The first MCU 200A1 and the third MCU 200C1 obtain the output signal of the first motor rotation angle sensor 101A, and the second MCU 200B1 and the third MCU 200C1 obtain the output signal of the second motor rotation angle sensor 101B.

[0122] The vehicle 1 includes a first battery 11 as a first power source and a second battery 12 as a second power source.

[0123] Furthermore, the first inverter 200A22 receives power supply from the first battery 11 via the power supply relay 13 .

[0124] The second inverter 200B22 receives power supply from the second battery 12 via the power supply relay 14 .

[0125] The third inverter 200C22 receives power supply from the first battery 11 via the power supply relay 15 , and also receives power supply from the second battery 12 via the power supply relay 16 .

[0126] The MCUs 200A1 , 200B1 , and 200C1 are connected to a communication line 20 and are configured to be able to communicate with each other.

[0127] Furthermore, the first control device 200A includes a diagnosis circuit 201 that monitors the operation of the first MCU 200A1 , and the second control device 200B includes a diagnosis circuit 202 that monitors the operation of the second MCU 200B1 .

[0128] On the other hand, the wake-up circuit 203 included in the third control device 200C obtains a signal indicating the diagnosis result of the first MCU 200A1 outputted from the diagnosis circuit 201 and a signal indicating the diagnosis result of the second MCU 200B1 outputted from the diagnosis circuit 202 .

[0129] Then, when the wake-up circuit 203 detects an abnormality in the first MCU 200A1 or the second MCU 200B1 , it outputs a wake-up signal to the third MCU 200C1 to start the third MCU 200C1 .

[0130] Furthermore, the first control device 200A includes a main voltage regulator (regulator) 210 and a sensor voltage regulator 211 .

[0131] The main voltage regulator 210 converts the voltage of the first battery 11 into an operating voltage of the first MCU 200A1 and the like, and supplies the converted voltage to the first MCU 200A1 , the first pre-driver 200A21 , the diagnosis circuit 201 and the like.

[0132] The sensor voltage regulator 211 converts the output voltage of the main voltage regulator 210 into an operating voltage of the first direction steering angle sensor 400A constituting the direction steering angle detection device 400, and supplies the converted voltage to the first direction steering angle sensor 400A.

[0133] In addition, the steering angle detection device 400 includes a first steering angle sensor 400A and a second steering angle sensor 400B to be redundant.

[0134] The second control device 200B includes a main voltage regulator 220 and a sensor voltage regulator 221 .

[0135] The main voltage regulator 220 converts the voltage of the second battery 12 into an operating voltage of the second MCU 200B1 and the like, and supplies the converted voltage to the second MCU 200B1 , the second pre-driver 200B21 , the diagnosis circuit 202 and the like.

[0136] The sensor voltage regulator 221 converts the output voltage of the main voltage regulator 220 into an operating voltage of the second direction steering angle sensor 400B constituting the direction steering angle detection device 400, and outputs the converted voltage to the second direction steering angle sensor 400B.

[0137] The third control device 200C includes a main voltage regulator 230 and a sensor voltage regulator 231 .

[0138] The main voltage regulator 230 converts the voltage of the first battery 11 or the second battery 12 into an operating voltage of the third MCU 200C1 and the like, and supplies the converted voltage to the third MCU 200C1 , the third pre-driver 200C21 and the like.

[0139] The sensor voltage regulator 231 converts the output voltage of the main voltage regulator 230 into an operating voltage of the first direction steering angle sensor 400A and the second direction steering angle sensor 400B constituting the direction steering angle detection device 400, and supplies the converted voltage to the first direction steering angle sensor 400A or the second direction steering angle sensor 400B.

[0140] That is, the first direction steering angle sensor 400A operates using the output voltage of the sensor voltage regulator 211 or the sensor voltage regulator 231 as a power supply voltage.

[0141] Furthermore, the second direction steering angle sensor 400B operates using the output voltage of the sensor voltage regulator 221 or the sensor voltage regulator 231 as a power supply voltage.

[0142] On the other hand, the first motor rotation angle sensor 101A operates using the output voltage of the main voltage regulator 210 or the main voltage regulator 230 as a power supply voltage.

[0143] Furthermore, the second motor rotation angle sensor 101B operates using the output voltage of the main voltage regulator 220 or the main voltage regulator 230 as a power supply voltage.

[0144] The first MCU 200A1 obtains the output signal of the first direction steering angle sensor 400A via the sensor interface 261 .

[0145] The second MCU 200B1 obtains the output signal of the second direction steering angle sensor 400B via the sensor interface 262 .

[0146] The third MCU 200C1 obtains the output signal of the first direction steering angle sensor 400A and the output signal of the second direction steering angle sensor 400B via the sensor interface 263 .

[0147] Furthermore, the first MCU 200A1 is connected to a CAN bus 251 constituting an in-vehicle network via a CAN interface 241 .

[0148] The second MCU 200B1 is connected to the CAN bus 251 via the CAN interface 242 .

[0149] The third MCU 200C1 is connected to the CAN bus 251 via the CAN interface 243 .

[0150] Furthermore, the first MCU 200A1 , the second MCU 200B1 , and the third MCU 200C1 communicate with each other among other MCUs connected to the CAN bus 251 .

[0151] Furthermore, the main voltage regulator 210 , the main voltage regulator 220 , and the main voltage regulator 230 operate based on a signal from an ignition switch 260 .

[0152] Figure 4 It is shown Figure 3 Detailed circuit diagram of the inverters 200A22, 200B22, 200C22 and the relays 200A3, 200B3, 200C3, 200C4 shown.

[0153] The first inverter 200A22 is a three-phase bridge circuit including three sets of semiconductor switching elements.

[0154] The semiconductor switching elements 1UH, 1UL, 1VH, 1VL, 1WH, and 1WL constituting the first inverter 200A22 are each composed of an N-channel MOS-FET (Metal Oxide Semiconductor Field Effect Transistor) having parasitic diodes D11, D12, D13, D14, D15, and D16 formed between the source terminal and the drain terminal.

[0155] In other words, the first inverter 200A22 is composed of semiconductor switching elements 1UH, 1VH, 1WH for each phase constituting an upper arm and semiconductor switching elements 1UL, 1VL, 1WL for each phase constituting a lower arm.

[0156] In addition, the drain terminal side of the parasitic diode of the N-channel MOS-FET serves as a cathode, and the source terminal side serves as an anode.

[0157] Similarly, the second inverter 200B22 is a three-phase bridge circuit including three sets of semiconductor switching elements.

[0158] Furthermore, each semiconductor switch element 2UH, 2UL, 2VH, 2VL, 2WH, 2WL constituting the second inverter 200B22 is constituted by an N-channel MOS-FET having a parasitic diode D21, D22, D23, D24, D25, D26 formed between the source terminal and the drain terminal.

[0159] Similarly, the third inverter 200C22 is a three-phase bridge circuit including three sets of semiconductor switching elements.

[0160] Furthermore, each semiconductor switch element 3UH, 3UL, 3VH, 3VL, 3WH, 3WL constituting the third inverter 200C22 is constituted by an N-channel MOS-FET forming a parasitic diode D31, D32, D33, D34, D35, D36 between the source terminal and the drain terminal.

[0161] Furthermore, the first relay 200A3 is formed of semiconductor switching elements 1RU, 1RV, 1RW respectively arranged on the first drive lines 1DU, 1DV, 1DW of each phase connecting the first inverter 200A22 and the first winding group 100a.

[0162] Here, the semiconductor switch elements 1RU, 1RV, 1RW are N-channel MOS-FETs, and are connected to the first drive lines 1DU, 1DV, 1DW respectively so that their drain terminals are on the first winding group 100a side and their source terminals are on the first inverter 200A22 side.

[0163] Furthermore, regarding the orientation of the parasitic diodes DR11 , DR12 , and DR13 of the semiconductor switch elements 1RU, 1RV, and 1RW, the cathode is on the first winding group 100 a side, and the anode is on the first inverter 200A22 side.

[0164] That is, the semiconductor switch elements 1RU, 1RV, 1RW constituting the first relay 200A3 include parasitic diodes DR11, DR12, DR13 for conducting (passing) a current in a direction from the first inverter 200A22 toward the first winding group 100a.

[0165] Similarly, the second relay 200B3 is composed of semiconductor switching elements 2RU, 2RV, and 2RW respectively arranged on the second drive lines 2DU, 2DV, and 2DW of each phase connecting the second inverter 200B22 and the second winding group 100b.

[0166] Here, the semiconductor switch elements 2RU, 2RV, and 2RW are N-channel MOS-FETs, and are connected so that their drain terminals are on the second winding group 100b side and their source terminals are on the second inverter 200B22 side.

[0167] Furthermore, regarding the orientation of the parasitic diodes DR21, DR22, and DR23 of the semiconductor switch elements 2RU, 2RV, and 2RW, the cathode is on the second winding group 100b side, and the anode is on the second inverter 200B22 side.

[0168] That is, the semiconductor switch elements 2RU, 2RV, 2RW constituting the second relay 200B3 include parasitic diodes DR21, DR22, DR23 that conduct a current in a direction from the second inverter 200B22 toward the second winding group 100b.

[0169] First branch points 1BU, 1BV, 1BW are provided in the first drive lines 1DU, 1DV, 1DW between the first relay 200A3 and the first winding group 100a.

[0170] Furthermore, second branch points 2BU, 2BV, 2BW are provided in the second driving lines 2DU, 2DV, 2DW between the second relay 200B3 and the second winding group 100 b.

[0171] Furthermore, third branch points 3BU, 3BV, 3BW are provided on the third drive lines 3DU, 3DV, 3DW connecting the third inverter 200C22 and the first branch points 1BU, 1BV, 1BW.

[0172] Furthermore, a third relay 200C3 is arranged on the third drive line 3DU, 3DV, 3DW between the first branch point 1BU, 1BV, 1BW and the third branch point 3BU, 3BV, 3BW.

[0173] Furthermore, a fourth relay 200C4 is disposed on the fourth drive line 4DU, 4DV, 4DW of each phase connecting the third branch point 3BU, 3BV, 3BW and the second branch point 2BU, 2BV, 2BW.

[0174] The third relay 200C3 is configured by arranging a set of two semiconductor switch elements connected in series so that the parasitic diodes thereof are oriented in opposite directions to each other on the third drive lines 3DU, 3DV, and 3DW, respectively.

[0175] Specifically, a semiconductor switch element 3RU1 and a semiconductor switch element 3RU2 are connected in series to the third drive line 3DU between the first branch point 1BU and the third branch point 3BU.

[0176] Here, the semiconductor switch element 3RU1 is arranged so that the drain terminal is on the third inverter 200C22 side (the third branch point 3BU side) and the source terminal is on the first winding group 100a side (the first branch point 1BU side).

[0177] Thus, the anode of the parasitic diode DR311 of the semiconductor switch element 3RU1 is on the first winding group 100a side (on the first branch point 1BU side), and the cathode is on the third inverter 200C22 side (on the third branch point 3BU side).

[0178] That is, the semiconductor switch element 3RU1 includes a parasitic diode DR311 that conducts a current in a direction from the first winding group 100a (first branch point 1BU) toward the third inverter 200C22 (third branch point 3BU).

[0179] On the other hand, the semiconductor switch element 3RU2 that forms a pair with the semiconductor switch element 3RU1 is arranged so that its source terminal is on the third inverter 200C22 side (third branch point 3BU side) and its drain terminal is on the first winding group 100a side (first branch point 1BU side).

[0180] Thus, the cathode of the parasitic diode DR312 of the semiconductor switch element 3RU2 is on the first winding group 100a side (on the first branch point 1BU side), and the anode is on the third inverter 200C22 side (on the third branch point 3BU side).

[0181] That is, the semiconductor switch element 3RU2 includes a parasitic diode DR312 that conducts a current in a direction from the third inverter 200C22 (third branch point 3BU) to the first winding group 100a (first branch point 1BU).

[0182] In this way, the semiconductor switch element 3RU1 and the semiconductor switch element 3RU2 are connected in series so that the directions of the parasitic diodes DR311 and DR312 are opposite to each other.

[0183] Similarly, in the third drive line 3DV between the first branch point 1BV and the third branch point 3BV, the semiconductor switch element 3RV1 and the semiconductor switch element 3RV2 are connected in series so that the parasitic diodes DR321 and DR322 are oriented in opposite directions to each other.

[0184] Furthermore, in the third drive line 3DW between the first branch point 1BW and the third branch point 3BW, the semiconductor switch element 3RW1 and the semiconductor switch element 3RW2 are connected in series so that the parasitic diodes DR331 and DR332 are oriented in opposite directions to each other.

[0185] The fourth relay 200C4 is similar to the third relay 200C3 , and is configured by arranging a set of two semiconductor switch elements connected in series so that the parasitic diodes thereof are oriented in opposite directions to each other on the fourth drive lines 4DU, 4DV, 4DW, respectively.

[0186] Specifically, in the fourth drive line 4DU between the second branch point 2BU and the third branch point 3BU, the semiconductor switch element 4RU1 and the semiconductor switch element 4RU2 are connected in series so that the parasitic diodes DR411 and DR412 are oriented in opposite directions to each other.

[0187] Furthermore, in the fourth drive line 4DV between the second branch point 2BV and the third branch point 3BV, the semiconductor switch element 4RV1 and the semiconductor switch element 4RV2 are connected in series so that the parasitic diodes DR421 and DR422 are oriented in opposite directions to each other.

[0188] Furthermore, in the fourth drive line 4DW between the second branch point 2BW and the third branch point 3BW, the semiconductor switch element 4RW1 and the semiconductor switch element 4RW2 are connected in series so that the parasitic diodes DR431 and DR432 are oriented in opposite directions to each other.

[0189] Here, the first relay 200A3 is a relay disposed between the first branch points 1BU, 1BV, 1BW and the ground GND of the first inverter 200A22 and having a parasitic diode that conducts current in a direction from the ground GND of the first inverter 200A22 toward the first winding group 100a (first motor 100A).

[0190] The second relay 200B3 is disposed between the second branch points 2BU, 2BV, 2BW and the ground GND of the second inverter 200B22 and has a parasitic diode that conducts current in a direction from the ground GND of the second inverter 200B22 toward the second winding group 100b (second motor 100B).

[0191] Furthermore, the semiconductor switch elements 3RU2, 3RV2, 3RW2 constituting the third relay 200C3 are arranged between the first branch points 1BU, 1BV, 1BW and the ground GND of the first inverter 200A22.

[0192] The semiconductor switch elements 3RU2, 3RV2, 3RW2 constituting the third relay 200C3 have parasitic diodes that conduct a current in a direction from the ground GND of the third inverter 200C22 toward the first winding group 100a (first branch points 1BU, 1BV, 1BW).

[0193] Furthermore, the semiconductor switch elements 4RU2, 4RV2, 4RW2 constituting the fourth relay 200C4 are arranged between the second branch points 2BU, 2BV, 2BW and the ground GND of the third inverter 200C22.

[0194] The semiconductor switch elements 4RU2, 4RV2, 4RW2 constituting the fourth relay 200C4 are relays having parasitic diodes that conduct current from the ground GND of the third inverter 200C22 toward the second winding group 100b (second branch points 2BU, 2BV, 2BW).

[0195] Figure 4 The control states of the semiconductor switching elements constituting the inverters 200A22, 200B22, 200C22 and the relays 200A3, 200B3, 200C3, 200C4 are shown as the case where the first inverter 200A22 (first drive circuit A2) and the second inverter 200B22 (second drive circuit B2) are normal.

[0196] Therefore, in Figure 4 In the control state shown, AC power is supplied from the first inverter 200A22 to the first winding group 100a, and AC power is supplied from the second inverter 200B22 to the second winding group 100b.

[0197] At this time, the on (ON) and off (OFF) of each semiconductor switching element 1UH, 1UL, 1VH, 1VL, 1WH, 1WL of the first inverter 200A22 and each semiconductor switching element 2UH, 2UL, 2VH, 2VL, 2WH, 2WL of the second inverter 200B22 are controlled by PWM (Pulse Width Modulation) based on a steering angle command or a steering force command.

[0198] Furthermore, the semiconductor switch elements 1RU, 1RV, 1RW of the first relay 200A3 and the semiconductor switch elements 2RU, 2RV, 2RW of the second relay 200B3 are maintained in an ON-state.

[0199] On the other hand, the semiconductor switching elements 3UH, 3UL, 3VH, 3VL, 3WH, and 3WL of the third inverter 200C22 are maintained in an OFF state.

[0200] Furthermore, the semiconductor switch elements 3RU1 , 3RU2 , 3RV1 , 3RV2 , 3RW1 , and 3RW2 of the third relay 200C3 are maintained in the OFF state.

[0201] Furthermore, the semiconductor switch elements 4RU1 , 4RU2 , 4RV1 , 4RV2 , 4RW1 , and 4RW2 of the fourth relay 200C4 are maintained in the OFF state.

[0202] Here, the third relay 200C3 and the fourth relay 200C4 are configured by connecting two semiconductor switch elements in series, the parasitic diodes of which are oriented in opposite directions to each other. Therefore, when each semiconductor switch element is in the off state, current is prevented from flowing through the parasitic diode.

[0203] That is, when the third relay 200C3 and the fourth relay 200C4 are in the off state, the output current of the first inverter 200A22 and the output current of the second inverter 200B22 do not flow into the third inverter 200C22 through the third relay 200C3 or the fourth relay 200C4.

[0204] Specifically, the semiconductor switch elements 3RU2, 3RV2, and 3RW2 constituting the third relay 200C3 function as a cutoff relay that blocks the output current of the first inverter 200A22 from flowing to the third inverter 200C22.

[0205] Furthermore, the semiconductor switch elements 4RU2, 4RV2, and 4RW2 constituting the fourth relay 200C4 function as a cutoff relay that blocks the output current of the second inverter 200B22 from flowing to the third inverter 200C22.

[0206] Therefore, even if a short-circuit failure occurs in the semiconductor switching elements 3UL, 3VL, 3WL of the lower arm of the third inverter 200C22, the current is interrupted by the third relay 200C3 and the fourth relay 200C4.

[0207] Therefore, the formation of a short-circuit circuit to the ground via the semiconductor switch elements 1UL, 3VL, 3WL in which the short-circuit failure has occurred is prevented, and the energization control of the first winding group 100a and the second winding group 100b can be normally performed.

[0208] Furthermore, the output current of the first inverter 200A22 is prevented from flowing into the second winding group 100b via the third relay 200C3 and the fourth relay 200C4, or the output current of the second inverter 200B22 is prevented from flowing into the first winding group 100a via the fourth relay 200C4 and the third relay 200C3.

[0209] Therefore, the energization control of the first winding group 100a and the second winding group 100b is normally performed.

[0210] Figure 5 The control state when a short-circuit failure occurs in the semiconductor switching element 1UL of the lower arm among the semiconductor switching elements 1UH, 1UL, 1VH, 1VL, 1WH, and 1WL constituting the first inverter 200A22 is shown.

[0211] Here, since the first inverter 200A22 fails, the AC power is supplied to the first winding group 100a from the backup third inverter 200C22 instead of the first inverter 200A22.

[0212] At this time, the semiconductor switch elements 1UH, 1UL, 1VH, 1VL, 1WH, 1WL of the first inverter 200A22 are switched from the PWM control state to the OFF state, and the semiconductor switch elements 1RU, 1RV, 1RW of the first relay 200A3 are switched from the ON state to the OFF state.

[0213] Moreover, in order to supply AC power from the third inverter 200C22 to the first winding group 100a, PWM control of the semiconductor switch elements 3UH, 3UL, 3VH, 3VL, 3WH, and 3WL of the third inverter 200C22 is started. In addition, the semiconductor switch elements 3RU1, 3RU2, 3RV1, 3RV2, 3RW1, and 3RW2 of the third relay 200C3 are switched from the off state to the on state.

[0214] Thus, AC power is supplied from the third inverter 200C22 to the first winding group 100a, and even if a failure occurs in the first inverter 200A22, the supply of AC power to the first winding group 100a can continue.

[0215] Here, the first relay 200A3 prevents the AC power supplied from the third inverter 200C22 to the first winding group 100a from being short-circuited to the ground via the semiconductor switching element 1UL in which the short-circuit failure has occurred.

[0216] The first relay 200A3 is a relay disposed between the first branch points 1BU, 1BV, 1BW and the ground GND of the first inverter 200A22, and has a parasitic diode that conducts current in the direction from the ground GND of the first inverter 200A22 toward the first winding group 100a (the first branch points 1BU, 1BV, 1BW).

[0217] Therefore, when a failure occurs in the first inverter 200A22, the first relay 200A3 switches to the open state, thereby functioning as a cutoff relay that cuts off the flow of AC power supplied from the third inverter 200C22 to the first winding group 100a into the first inverter 200A22.

[0218] On the other hand, since the second inverter 200B22 is normal, the PWM control of the semiconductor switch elements 2UH, 2UL, 2VH, 2VL, 2WH, 2WL of the second inverter 200B22 is continued, and the conductive state of the semiconductor switch elements 2RU, 2RV, 2RW of the second relay 200B3 is also continued.

[0219] Furthermore, the semiconductor switch elements 4RU1 , 4RU2 , 4RV1 , 4RV2 , 4RW1 , and 4RW2 of the fourth relay 200C4 are kept in the off state.

[0220] Thus, even if the first inverter 200A22 fails, the second inverter 200B22 supplies AC power to the second winding group 100b.

[0221] The semiconductor switch elements 4RU1 , 4RU2 , 4RV1 , 4RV2 , 4RW1 , and 4RW2 of the fourth relay 200C4 are held in the OFF state, and the fourth relay 200C4 is configured by combining two semiconductor switch elements such that the parasitic diodes thereof are oriented in opposite directions to each other.

[0222] Therefore, the output current of the third inverter 200C22 is prevented from flowing into the second driving lines 2DU, 2DV, 2DW of the second winding group 100b via the parasitic diodes of the semiconductor switching elements 4RU1, 4RU2, 4RV1, 4RV2, 4RW1, 4RW2.

[0223] Furthermore, the semiconductor switch elements 4RU2, 4RV2, and 4RW2 constituting the fourth relay 200C4 function as a cutoff relay that blocks the output current of the second inverter 200B22 from flowing to the third inverter 200C22.

[0224] Therefore, even if a failure occurs in the first inverter 200A22, the first winding group 100a and the second winding group 100b can be controlled normally.

[0225] Figure 6 Shown with Figure 5 Similarly, another mode of the control state when a short-circuit fault occurs in the semiconductor switching element 1UL among the semiconductor switching elements 1UH, 1UL, 1VH, 1VL, 1WH, and 1WL constituting the first inverter 200A22 is described.

[0226] exist Figure 6 In the control method shown, the AC power is supplied from the second inverter 200B22 to the first winding group 100a instead of the first inverter 200A22 in which a failure has occurred.

[0227] That is, when the first inverter 200A22 fails, the backup third inverter 200C22 is not operated, and the AC power is supplied to the first winding group 100a and the second winding group 100b from the normal second inverter 200B22.

[0228] At this time, the semiconductor switch elements 1UH, 1UL, 1VH, 1VL, 1WH, 1WL of the first inverter 200A22 are switched from the PWM control state to the OFF state, and the semiconductor switch elements 1RU, 1RV, 1RW of the first relay 200A3 are switched from the ON state to the OFF state.

[0229] Furthermore, the semiconductor switching elements 3UH, 3UL, 3VH, 3VL, 3WH, and 3WL of the third inverter 200C22 are not shifted to the PWM control state but are maintained in the off state.

[0230] On the other hand, the semiconductor switch elements 3RU1, 3RU2, 3RV1, 3RV2, 3RW1, 3RW2 of the third relay 200C3 and the semiconductor switch elements 4RU1, 4RU2, 4RV1, 4RV2, 4RW1, 4RW2 of the fourth relay 200C4 are switched from the OFF state to the ON state.

[0231] Thus, the output current of the second inverter 200B22 is supplied to the first winding group 100a via the second branch points 2BU, 2BV, 2BW, the fourth relay 200C4, the third branch points 3BU, 3BV, 3BW, the third relay 200C3, and the first branch points 1BU, 1BV, 1BW.

[0232] Here, the semiconductor switch elements 1RU, 1RV, 1RW of the first relay 200A3 are in the off state, and the parasitic diodes DR11, DR12, DR13 conduct the current from the first inverter 200A22 toward the first winding group 100a, but do not allow the current to flow from the first winding group 100a toward the first inverter 200A22.

[0233] Therefore, the AC power output by the second inverter 200B22 flowing to the first drive lines 1DU, 1DV, 1DW via the first branch points 1BU, 1BV, 1BW does not flow to the first inverter 200A22 side but is supplied to the first winding group 100a.

[0234] That is, the first relay 200A3 functions as a cutoff relay that blocks the current output from the second inverter 200B22 from flowing into the first inverter 200A22 side.

[0235] "Second Implementation Method"

[0236] Figure 7 It is a block diagram showing a detailed structure of the motor control device 200 according to the second embodiment.

[0237] exist Figure 7 In, with Figure 3The same elements are denoted by the same reference numerals, and detailed descriptions thereof are omitted.

[0238] Figure 7 The motor control device 200 of the present invention is provided with a fifth relay 200C5 between the third inverter 200C22 and the ground GND, which is controlled to be turned on and off by the third MCU 200C1 of the third control device 200C. Figure 3 The motor control device 200 is different.

[0239] also, Figure 7 The motor control device 200 and Figure 3 The motor control device 200 similarly includes the third relay 200C3 and the fourth relay 200C4, but is different in that the semiconductor switch elements 3RU2, 3RV2, 3RW2, 4RU2, 4RV2, and 4RW2 are omitted as described in detail later.

[0240] Figure 8 It is shown Figure 7 Detailed circuit diagram of the inverters 200A22, 200B22, 200C22 and relays 200A3, 200B3, 200C3, 200C4, 200C5 shown.

[0241] In addition, Figure 8 In, with Figure 4 The same elements are denoted by the same reference numerals, and detailed descriptions thereof are omitted.

[0242] The fifth relay 200C5 is composed of a semiconductor switch element 5R disposed between the third inverter 200C22 and the ground GND.

[0243] Here, the semiconductor switch element 5R constituting the fifth relay 200C5 is an N-channel MOS-FET, and is connected so that the drain terminal is on the third inverter 200C22 side and the source terminal is on the ground GND side.

[0244] Furthermore, regarding the orientation of the parasitic diode DR5 of the semiconductor switch element 5R, the cathode is on the third inverter 200C22 side, and the anode is on the ground GND side.

[0245] That is, the semiconductor switch element 5R constituting the fifth relay 200C5 includes a parasitic diode DR5 that conducts a current in a direction from the ground GND toward the third inverter 200C22.

[0246] In other words, the fifth relay 200C5 is arranged between the first branch points 1BU, 1BV, 1BW and the ground GND of the third inverter 200C22, and is arranged between the second branch points 2BU, 2BV, 2BW and the ground GND of the third inverter 200C22.

[0247] The fifth relay 200C5 has a parasitic diode that conducts a current in a direction from the ground GND of the third inverter 200C22 toward the motor 100, and functions as a cutoff relay that cuts off a short-circuit path from the third inverter 200C22 to the ground GND.

[0248] also, Figure 8 The third relay 200C3 of the second embodiment shown in FIG. Figure 4 The third relay 200C3 of the first embodiment shown in the figure omits the semiconductor switch elements 3RU2 , 3RV2 , and 3RW2 , and is composed of the semiconductor switch elements 3RU1 , 3RV1 , and 3RW1 .

[0249] Here, the anodes of the parasitic diodes DR311, DR321, and DR331 of the semiconductor switch elements 3RU1, 3RV1, and 3RW1 are on the first winding group 100a side (the first branch points 1BU, 1BV, and 1BW side), and the cathodes are on the third inverter 200C22 side (the third branch points 3BU, 3BV, and 3BW side).

[0250] Right now, Figure 8 The semiconductor switching elements 3RU1, 3RV1, 3RW1 constituting the third relay 200C3 of the second embodiment shown have parasitic diodes DR311, DR321, DR331 that conduct current in the direction from the first winding group 100a (first branch point 1BU, 1BV, 1BW) toward the third inverter 200C22 (third branch point 3BU, 3BV, 3BW).

[0251] also, Figure 8 The fourth relay 200C4 of the second embodiment shown in FIG. Figure 4 The fourth relay 200C4 of the first embodiment shown in the figure omits the semiconductor switch elements 4RU2 , 4RV2 , and 4RW2 , and is composed of the semiconductor switch elements 4RU1 , 4RV1 , and 4RW1 .

[0252] Here, the anodes of the parasitic diodes DR411, DR421, and DR431 of the semiconductor switch elements 4RU1, 4RV1, and 4RW1 are on the second winding group 100b side (on the second branch points 2BU, 2BV, and 2BW side), and the cathodes are on the third inverter 200C22 side (on the third branch points 3BU, 3BV, and 3BW side).

[0253] Right now, Figure 8 The semiconductor switching elements 4RU1, 4RV1, 4RW1 constituting the fourth relay 200C4 of the second embodiment shown have parasitic diodes DR411, DR421, DR431 that conduct current in the direction from the second winding group 100b (second branch points 2BU, 2BV, 2BW) toward the third inverter 200C22 (third branch points 3BU, 3BV, 3BW).

[0254] In the second embodiment, although the semiconductor switch element 5R constituting the fifth relay 200C5 is added, the number of semiconductor switch elements constituting the third relay 200C3 and the fourth relay 200C4 is reduced to half compared with the first embodiment.

[0255] Thus, the motor control device 200 according to the second embodiment can reduce the number of semiconductor switching elements by five as compared with the motor control device 200 according to the first embodiment.

[0256] Figure 8 The control states of the semiconductor switching elements constituting the inverters 200A22, 200B22, 200C22 and relays 200A3, 200B3, 200C3, 200C4, 200C5 shown in the figure indicate that the first inverter 200A22 and the second inverter 200B22 are in a normal state, that is, AC power is supplied from the first inverter 200A22 to the first winding group 100a, and AC power is supplied from the second inverter 200B22 to the second winding group 100b.

[0257] At this time, the on and off of each semiconductor switching element 1UH, 1UL, 1VH, 1VL, 1WH, 1WL of the first inverter 200A22 and each semiconductor switching element 2UH, 2UL, 2VH, 2VL, 2WH, 2WL of the second inverter 200B22 are controlled by PWM (Pulse Width Modulation) based on a steering angle command or a steering force command.

[0258] Furthermore, the semiconductor switch elements 1RU, 1RV, 1RW of the first relay 200A3 and the semiconductor switch elements 2RU, 2RV, 2RW of the second relay 200B3 are maintained in the on state.

[0259] On the other hand, the semiconductor switching elements 3UH, 3UL, 3VH, 3VL, 3WH, and 3WL of the third inverter 200C22 are maintained in the OFF state.

[0260] Furthermore, the semiconductor switch elements 3RU1 , 3RV1 , and 3RW1 of the third relay 200C3 are maintained in the OFF state.

[0261] Furthermore, the semiconductor switch elements 4RU1 , 4RV1 , and 4RW1 of the fourth relay 200C4 are maintained in the OFF state.

[0262] Furthermore, the semiconductor switch element 5R of the fifth relay 200C5 is maintained in the OFF state.

[0263] Here, the parasitic diodes DR311, DR321, DR331, DR411, DR421, and DR431 of the semiconductor switch elements 3RU1, 3RV1, 3RW1, 4RU1, 4RV1, and 4RW1 constituting the third relay 200C3 and the fourth relay 200C4 conduct the current in the direction from the first winding group 100a or the second winding group 100b toward the third inverter 200C22.

[0264] However, the semiconductor switch elements 3UL, 3VL, 3WL constituting the lower arm of the third inverter 200C22 are turned off, and the parasitic diodes D32, D34, D36 of the semiconductor switch elements 3UL, 3VL, 3WL do not allow current to flow from the third relay 200C3 and the fourth relay 200C4 side toward the ground GND side.

[0265] Furthermore, the semiconductor switch element 5R of the fifth relay 200C5 is also turned off, and the parasitic diode DR5 of the semiconductor switch element 5R does not allow the current to flow from the third relay 200C3 and the fourth relay 200C4 side to the ground GND side.

[0266] Therefore, a short-circuit circuit to the ground is not formed via the semiconductor switching elements 3UL, 3VL, and 3WL constituting the lower arm of the third inverter 200C22 and the semiconductor switching element 5R of the fifth relay 200C5.

[0267] Therefore, the energization control of the first winding group 100a and the second winding group 100b is normally performed.

[0268] Fig. 9 The diagram shows the control states of the semiconductor switch elements constituting the inverters 200A22, 200B22, 200C22 and the relays 200A3, 200B3, 200C3, 200C4, 200C5 when a short circuit fault occurs in the semiconductor switch element 1UL of the lower arm among the semiconductor switch elements 1UH, 1UL, 1VH, 1VL, 1WH, 1WL constituting the first inverter 200A22 in the second embodiment.

[0269] Here, it is assumed that the AC power is supplied from the second inverter 200B22 to the first winding group 100a instead of the failed first inverter 200A22, and the second inverter 200B22 supplies the AC power to the second winding group 100b and the first winding group 100a.

[0270] Since the first inverter 200A22 fails, the PWM control of the first inverter 200A22 is stopped.

[0271] Furthermore, the semiconductor switch elements 1RU, 1RV, and 1RW constituting the first relay 200A3 are switched from the on state to the off state.

[0272] On the other hand, the semiconductor switching elements 3UH, 3UL, 3VH, 3VL, 3WH, and 3WL of the third inverter 200C22 are maintained in the OFF state.

[0273] Furthermore, the semiconductor switch element 5R of the fifth relay 200C5 is also maintained in the OFF state.

[0274] Furthermore, the semiconductor switch elements 3RU1, 3RV1, 3RW1 constituting the third relay 200C3 and the semiconductor switch elements 4RU1, 4RV1, 4RW1 constituting the fourth relay 200C4 are switched from the OFF state to the ON state.

[0275] In this case, the output current of the second inverter 200B22 reaches the third branch points 3BU, 3BV, 3BW from the second branch points 2BU, 2BV, 2BW through the semiconductor switch elements 4RU1, 4RV1, 4RW1 constituting the fourth relay 200C4.

[0276] Here, the semiconductor switch elements 3UH, 3UL, 3VH, 3VL, 3WH, and 3WL of the third inverter 200C22 are in the OFF state, while the semiconductor switch elements 3RU1, 3RV1, and 3RW1 constituting the third relay 200C3 are in the ON state.

[0277] Therefore, the output current of the second inverter 200B22 reaches the first branch points 1BU, 1BV, 1BW through the third branch points 3BU, 3BV, 3BW and the third relay 200C3.

[0278] The semiconductor switch elements 1RU, 1RV, 1RW constituting the first relay 200A3 are turned off, and the parasitic diodes DR11, DR12, DR13 of the semiconductor switch elements 1RU, 1RV, 1RW are oriented so that the cathode is on the first winding group 100a side and the anode is on the first inverter 200A22 side.

[0279] Therefore, the output current of the second inverter 200B22 reaching the first branch points 1BU, 1BV, 1BW does not flow to the first inverter 200A22 side through the semiconductor switching elements 1RU, 1RV, 1RW constituting the first relay 200A3, but is supplied to the first winding group 100a from the first branch points 1BU, 1BV, 1BW.

[0280] That is, when a fault occurs in the first inverter 200A22 (when a short-circuit fault occurs in the semiconductor switching element of the lower arm), the first relay 200A3 functions as a cut-off relay to prevent the formation of a short-circuit circuit to the ground, and the first winding group 100a and the second winding group 100b can be normally controlled by the second inverter 200B22.

[0281] In addition, in the case of the first embodiment, Figure 5 , Figure 6 As shown, when a failure occurs in the first inverter 200A22, the first winding group 100a and the second winding group 100b can be normally controlled.

[0282] However, in the second embodiment, in a circuit in which the number of semiconductor switching elements constituting relays is reduced compared to the first embodiment, when a failure occurs in the first inverter 200A22, the first winding group 100a and the second winding group 100b can be normally controlled.

[0283] Fig.10 In the second embodiment, Fig. 9 Similarly to the failure mode in FIG. 1 , the control state of each semiconductor switching element when a short-circuit failure occurs in the semiconductor switching element 1UL of the first inverter 200A22.

[0284] Here, if the first inverter 200A22 fails, the normal state in which the first inverter 200A22 supplies AC power to the first winding group 100a and the second inverter 200B22 supplies AC power to the second winding group 100b is switched to a state in which the third inverter 200C22 supplies AC power to the first winding group 100a and the second winding group 100b.

[0285] Specifically, when the first inverter 200A22 generates a fault, the PWM control of the first inverter 200A22 and the second inverter 200B22 is stopped.

[0286] Furthermore, the semiconductor switch elements 1RU, 1RV, 1RW constituting the first relay 200A3 are switched from the on state to the off state, and further, the semiconductor switch elements 2RU, 2RV, 2RW of the second relay 200B3 are also switched from the on state to the off state.

[0287] On the other hand, PWM control of the semiconductor switching elements 3UH, 3UL, 3VH, 3VL, 3WH, and 3WL of the third inverter 200C22 is started.

[0288] Furthermore, the semiconductor switch elements 3RU1 , 3RV1 , and 3RW1 constituting the third relay 200C3 and the semiconductor switch elements 4RU1 , 4RV1 , and 4RW1 constituting the fourth relay 200C4 are switched from the OFF state to the ON state.

[0289] Under such a control state, the output current of the third inverter 200C22 is supplied to the first winding group 100a through the third relay 200C3 and the first branch points 1BU, 1BV, and 1BW. In addition, the output current of the third inverter 200C22 is supplied to the second winding group 100b through the fourth relay 200C4 and the second branch points 2BU, 2BV, and 2BW.

[0290] Here, a short-circuit fault occurs in the semiconductor switching element 1UL of the first inverter 200A22.

[0291] However, the semiconductor switch elements 1RU, 1RV, 1RW constituting the first relay 200A3 are turned off, and the parasitic diodes DR11, DR12, DR13 of the semiconductor switch elements 1RU, 1RV, 1RW are oriented so that the cathode is on the first winding group 100a side and the anode is on the first inverter 200A22 side.

[0292] Therefore, the output current of the third inverter 200C22 is blocked from flowing into the first inverter 200A22 by the first relay 200A3 functioning as a cutoff relay, thereby preventing a short circuit to ground from being formed via the semiconductor switching element 1UL in which a short-circuit failure has occurred.

[0293] Therefore, when a failure occurs in the first inverter 200A22, AC power can be normally supplied from the third inverter 200C22 to the first winding group 100a and the second winding group 100b.

[0294] Fig.11 It is shown that in the second embodiment, when the first inverter 200A22 supplies AC power to the first winding group 100a and the second inverter 200B22 supplies AC power to the second winding group 100b, even if a short-circuit fault occurs in the semiconductor switch element 3UL of the lower arm of the third inverter 200C22, a short-circuit circuit to the ground is not formed through the semiconductor switch element 3UL.

[0295] When the first inverter 200A22 supplies AC power to the first winding group 100a and the second inverter 200B22 supplies AC power to the second winding group 100b, the semiconductor switch elements 3RU1, 3RV1, 3RW1 constituting the third relay 200C3 and the semiconductor switch elements 4RU1, 4RV1, 4RW1 constituting the fourth relay 200C4 are maintained in the off state.

[0296] However, the parasitic diodes DR311, DR321, DR331, DR411, DR421, and DR431 included in the semiconductor switch elements 3RU1, 3RV1, 3RW1, 4RU1, 4RV1, and 4RW1 have cathodes on the third inverter 200C22 side and anodes on the motor 100 side.

[0297] Therefore, the current supplied to the first winding group 100a and the second winding group 100b can flow into the third inverter 200C22 through the parasitic diodes DR311, DR321, DR331, DR411, DR421, and DR431.

[0298] However, the semiconductor switch element 5R constituting the fifth relay 200C5 is held in the off state, and the parasitic diode DR5 of the semiconductor switch element 5R has its cathode directed toward the third inverter 200C22 and its anode directed toward the ground GND.

[0299] Therefore, the semiconductor switch element 5R (and the parasitic diode DR5 ) cuts off the short-circuit path to the ground, and a short-circuit circuit to the ground is not formed via the semiconductor switch element 3UL in which the short-circuit failure has occurred.

[0300] That is, the fifth relay 200C5 functions as a cutoff relay that cuts off the short-circuit path to the ground through the semiconductor switch element 3UL in which the short-circuit failure has occurred.

[0301] Therefore, even if the semiconductor switching element 3UL of the lower arm of the third inverter 200C22 short-circuits, the output current of the first inverter 200A22 and the output current of the second inverter 200B22 can be prevented from being short-circuited to the ground, and the first winding group 100a and the second winding group 100b can be controlled normally.

[0302] Fig.12 In the second embodiment, control states of the semiconductor switching elements are shown when a short-circuit fault occurs in the semiconductor switching element 1UL of the lower arm of the first inverter 200A22 and further a short-circuit fault occurs in the semiconductor switching element 2UL of the lower arm of the second inverter 200B22.

[0303] Here, instead of the failed first inverter 200A22, the third inverter 200C22 supplies AC power to the first winding group 100a, and stops supplying AC power to the second winding group 100b.

[0304] Specifically, each semiconductor switching element is controlled as follows.

[0305] When the first inverter 200A22 fails due to the short-circuit failure of the semiconductor switching element 1UL and the second inverter 200B22 fails due to the short-circuit failure of the semiconductor switching element 2UL, PWM control of the first inverter 200A22 and the second inverter 200B22 is stopped.

[0306] Furthermore, the semiconductor switch elements 1RU, 1RV, 1RW constituting the first relay 200A3 are switched from the on state to the off state, and the semiconductor switch elements 2RU, 2RV, 2RW constituting the second relay 200B3 are also switched from the on state to the off state.

[0307] Furthermore, each of the semiconductor switch elements 3RU1, 3RV1, and 3RW1 constituting the third relay 200C3 is switched from the OFF state to the ON state.

[0308] On the other hand, the semiconductor switch elements 4RU1 , 4RV1 , and 4RW1 constituting the fourth relay 200C4 are maintained in the OFF state.

[0309] Furthermore, the semiconductor switch element 5R constituting the fifth relay 200C5 is switched from the OFF state to the ON state.

[0310] Then, PWM control of the semiconductor switching elements 3UH, 3UL, 3VH, 3VL, 3WH, and 3WL of the third inverter 200C22 is started.

[0311] By controlling the semiconductor switching elements in this manner, even if the first inverter 200A22 fails, the AC power output by the third inverter 200C22 is supplied to the first winding group 100a, and the first winding group 100a continues to be energized.

[0312] Furthermore, the semiconductor switch elements 1RU, 1RV, 1RW constituting the first relay 200A3 and the semiconductor switch elements 2RU, 2RV, 2RW constituting the second relay 200B3 are switched to the OFF state.

[0313] Furthermore, the cathodes of the parasitic diodes DR11, DR12, DR13, DR21, DR22, and DR23 are located on the first winding group 100a or the second winding group 100b side, and the anodes are located on the first inverter 200A22 or the second inverter 200B22 side.

[0314] Furthermore, the semiconductor switch elements 4RU1, 4RV1, 4RW1 constituting the fourth relay 200C4 are kept in the off state, and the cathodes of the parasitic diodes DR411, DR421, DR431 are on the third inverter 200C22 side, and the anodes are on the second winding group 100b side.

[0315] Therefore, the formation of a short-circuit circuit to the ground via the semiconductor switch element 1UL having a short-circuit failure and a short-circuit circuit to the ground via the semiconductor switch element 2UL having a short-circuit failure is avoided, and the first winding group 100a can be normally controlled.

[0316] That is, the first relay 200A3 functions as a cutoff relay for cutting off the short-circuit circuit to the ground via the short-circuited semiconductor switch element 1UL, and the second relay 200B3 functions as a cutoff relay for cutting off the short-circuit circuit to the ground via the short-circuited semiconductor switch element 2UL.

[0317] Furthermore, the fourth relay 200C4 blocks the output current of the third inverter 200C22 from flowing to the second winding group 100b side.

[0318] Fig.13 The fifth relay 200C5 as a cutoff relay for cutting off the short-circuit path to the ground GND flowing into the third inverter 200C22 is shown to be composed of a first semiconductor switch element 5R1 (first cutoff relay) and a second semiconductor switch element 5R2 (second cutoff relay) connected in series with the first semiconductor switch element 5R1.

[0319] Here, regarding the orientation of the parasitic diode DR51 of the first semiconductor switch element 5R1 and the orientation of the parasitic diode DR52 of the second semiconductor switch element 5R2, the cathode is set to the third inverter 200C22 side, and the anode is set to the ground GND side.

[0320] That is, the first semiconductor switch element 5R1 constituting the fifth relay 200C5 includes a parasitic diode DR51 that conducts a current in a direction from the ground GND toward the third inverter 200C22.

[0321] Similarly, the second semiconductor switch element 5R2 constituting the fifth relay 200C5 includes a parasitic diode DR52 that conducts a current in a direction from the ground GND toward the third inverter 200C22.

[0322] Furthermore, the first semiconductor switch element 5R1 and the second semiconductor switch element 5R2 are connected in series.

[0323] here, Fig.13 It shows that when AC power is supplied from the first inverter 200A22 to the first winding group 100a and AC power is supplied from the second inverter 200B22 to the second winding group 100b, a short-circuit fault occurs in the semiconductor switch element 3UL of the lower arm of the third inverter 200C22, and further, a short-circuit fault occurs in the first semiconductor switch element 5R1 constituting the fifth relay 200C5.

[0324] At this time, formation of a short-circuit to ground via the semiconductor switch element 3UL and the first semiconductor switch element 5R1 is prevented by the second semiconductor switch element 5R2.

[0325] That is, even if a short-circuit fault occurs in any of the semiconductor switching elements constituting the lower arm of the third inverter 200C22, and further, a short-circuit fault occurs in any of the first semiconductor switching element 5R1 and the second semiconductor switching element 5R2 constituting the fifth relay 200C5, the driving current of the first winding group 100a and the second winding group 100b can be prevented from being short-circuited to the ground.

[0326] Therefore, even if the third inverter 200C22 fails, and further, any one of the two semiconductor switching elements constituting the fifth relay 200C5 fails, the first winding group 100a and the second winding group 100b can be normally controlled, and a high fault safety performance can be achieved compared to the case where the fifth relay 200C5 is composed of one semiconductor switching element.

[0327] Fig.14 The control states of the semiconductor switch elements are shown when the fifth relay 200C5 is composed of the first semiconductor switch element 5R1 and the second semiconductor switch element 5R2, the semiconductor switch element 3UL of the lower arm of the third inverter 200C22 short-circuits and the semiconductor switch element 4RV1 of the fourth relay 200C4 short-circuits.

[0328] Here, the supply of AC power from the first inverter 200A22 to the first winding group 100a continues, while the supply of AC power to the second winding group 100b is stopped.

[0329] Specifically, the PWM control of the second inverter 200B22 is stopped, and the PWM control of the third inverter 200C22 is also kept in the stopped state.

[0330] Furthermore, the second relay 200B3 , the third relay 200C3 , the fourth relay 200C4 , and the fifth relay 200C5 are controlled to be in an open state.

[0331] Then, AC power is supplied from the first inverter 200A22 to the first winding group 100a.

[0332] Here, the fifth relay 200C5 functioning as a cutoff relay prevents the output current of the first inverter 200A22 from being short-circuited to the ground via the semiconductor switching element 3UL in which the short-circuit failure has occurred.

[0333] Furthermore, the second inverter 200B22 and the second relay 200B3 are disconnected and the supply of AC power to the second winding group 100b is stopped, so that the output current of the first inverter 200A22 does not flow to the second winding group 100b via the short-circuited semiconductor switching element 4RV1 or short-circuit to the ground.

[0334] Therefore, even if a short-circuit fault occurs in the lower arm of the third inverter 200C22 and further, a short-circuit fault occurs in the fourth relay 200C4, the first winding group 100a can be normally controlled.

[0335] Fig.15 The control state of each semiconductor switch element when the semiconductor switch element 3RU1 of the third relay 200C3 and the semiconductor switch element 4RV1 of the fourth relay 200C4 have a short-circuit failure is shown.

[0336] In this case, the supply of AC power from the first inverter 200A22 to the first winding group 100a continues, while the supply of AC power to the second winding group 100b is stopped.

[0337] Specifically, the PWM control of the second inverter 200B22 is stopped, and the PWM control of the third inverter 200C22 is kept in the stopped state.

[0338] Furthermore, the second relay 200B3 , the third relay 200C3 , the fourth relay 200C4 , and the fifth relay 200C5 are controlled to be in the OFF state.

[0339] On the other hand, by continuing the PWM control of the first inverter 200A22 and keeping the first relay 200A3 in the on state, the supply of AC power from the first inverter 200A22 to the first winding group 100a continues.

[0340] Here, the second inverter 200B22 and the second relay 200B3 are turned off, and the supply of AC power to the second winding group 100b is stopped.

[0341] Therefore, the output current of the first inverter 200A22 does not flow to the second winding group 100b via the short-circuited semiconductor switch element 3RU1 or the short-circuited semiconductor switch element 4RV1, or is short-circuited to the ground.

[0342] Therefore, even if a short-circuit failure occurs in the third relay 200C3 and the fourth relay 200C4, the first winding group 100a can be normally controlled.

[0343] "Third Implementation Method"

[0344] Fig.16 It is a block diagram showing a detailed structure of a motor control device 200 according to a third embodiment.

[0345] Fig.16 The motor control device 200 includes a sixth relay 200A6 disposed between the first inverter 200A22 and the ground GND.

[0346] The sixth relay 200A6 is controlled to be turned on and off by the first MCU 200A1 of the first control device 200A.

[0347] Furthermore, a seventh relay 200B7 is arranged between the second inverter 200B22 and the ground GND.

[0348] The seventh relay 200B7 is controlled to be turned on and off by the second MCU 200B1 of the second control device 200B.

[0349] in addition, Fig.16 The motor control device 200 shown in the figure is similar to the motor control device 200 shown in the figure except that the sixth relay 200A6 and the seventh relay 200B7 mentioned above are added. Figure 7 The motor control device 200 of the second embodiment shown in FIG.

[0350] Therefore, in Fig.16 In, with Figure 7 The same elements are denoted by the same reference numerals, and detailed descriptions thereof are omitted.

[0351] Fig.17 It is shown Fig.16Detailed circuit diagram of the inverters 200A22, 200B22, 200C22 and relays 200A3, 200B3, 200C3, 200C4, 200C5, 200A6, 200B7 shown.

[0352] In addition, Fig.17 In, with Figure 8 The same elements are denoted by the same reference numerals, and detailed descriptions thereof are omitted.

[0353] The sixth relay 200A6 is composed of a semiconductor switch element 6R disposed between the first inverter 200A22 and the ground GND.

[0354] Here, the semiconductor switch element 6R constituting the sixth relay 200A6 is an N-channel MOS-FET, and is connected so that the drain terminal is on the first inverter 200A22 side and the source terminal is on the ground GND side.

[0355] Furthermore, regarding the orientation of the parasitic diode DR6 of the semiconductor switch element 6R, the cathode is on the first inverter 200A22 side, and the anode is on the ground GND side.

[0356] That is, the semiconductor switch element 6R constituting the sixth relay 200A6 includes a parasitic diode DR6 that conducts a current in a direction from the ground GND toward the first inverter 200A22.

[0357] Furthermore, the seventh relay 200B7 is composed of a semiconductor switch element 7R disposed between the second inverter 200B22 and the ground GND.

[0358] Here, the semiconductor switch element 7R constituting the seventh relay 200B7 is an N-channel MOS-FET, and is connected so that the drain terminal is on the second inverter 200B22 side and the source terminal is on the ground GND side.

[0359] Furthermore, regarding the orientation of the parasitic diode DR7 of the semiconductor switch element 7R, the cathode is on the second inverter 200B22 side, and the anode is on the ground GND side.

[0360] That is, the semiconductor switch element 7R constituting the seventh relay 200B7 includes a parasitic diode DR7 that conducts a current in a direction from the ground GND toward the second inverter 200B22.

[0361] The sixth relay 200A6 is arranged between the first branch points 1BU, 1BV, 1BW and the ground GND of the first inverter 200A22, and has a parasitic diode DR6 that conducts current in the direction from the ground GND of the first inverter 200A22 toward the first winding group 100a, and functions as a cut-off relay that cuts off the path that short-circuits the ground GND of the first inverter 200A22 to the ground.

[0362] Similarly, the seventh relay 200B7 is arranged between the second branch points 2BU, 2BV, 2BW and the ground GND of the second inverter 200B22, and has a parasitic diode DR7 that conducts current in the direction from the ground GND of the second inverter 200B22 toward the second winding group 100b, and functions as a cut-off relay that cuts off the path that short-circuits the ground GND of the second inverter 200B22.

[0363] The sixth relay 200A6 can be configured by connecting two semiconductor switch elements 6R in series, and similarly, the seventh relay 200B7 can be configured by connecting two semiconductor switch elements 7R in series.

[0364] Here, the two semiconductor switch elements 6R constituting the sixth relay 200A6 are each configured to have a parasitic diode DR6 that conducts a current in a direction from the ground GND of the first inverter 200A22 toward the first winding group 100a.

[0365] Similarly, the two semiconductor switch elements 7R constituting the seventh relay 200B7 are each configured to have a parasitic diode DR7 that conducts a current in a direction from the ground GND of the second inverter 200B22 toward the second winding group 100b.

[0366] In other words, the sixth relay 200A6 and the seventh relay 200B7 can include a first disconnecting relay and a second disconnecting relay connected in series.

[0367] also, Fig.17 The parasitic diodes DR11, DR12, and DR13 of the semiconductor switch elements 1RU, 1RV, and 1RW constituting the first relay 200A3 are set to be Figure 4 The first embodiment shown and Figure 8 The second embodiment shown is the opposite.

[0368] Right now, Fig.17The semiconductor switching elements 1RU, 1RV, and 1RW constituting the first relay 200A3 are configured in such a way that the drain becomes the first inverter 200A22 side and the source becomes the first winding group 100a side, and with respect to the directions of the parasitic diodes DR11, DR12, and DR13, the anode becomes the first winding group 100a side and the cathode becomes the first inverter 200A22 side.

[0369] In other words, in the third embodiment, the semiconductor switch elements 1RU, 1RV, 1RW constituting the first relay 200A3 include the parasitic diodes DR11, DR12, DR13 that conduct the current in the direction from the first winding group 100a toward the first inverter 200A22.

[0370] Likewise, Fig.17 The parasitic diodes DR21, DR22, and DR23 of the semiconductor switch elements 2RU, 2RV, and 2RW constituting the second relay 200B3 are set to be Figure 4 The first embodiment shown and Figure 8 The second embodiment shown is the opposite.

[0371] Right now, Fig.17 The semiconductor switching elements 2RU, 2RV, and 2RW constituting the second relay 200B3 are configured in such a way that the drain becomes the second inverter 200B22 side and the source becomes the second winding group 100b side, and with respect to the directions of the parasitic diodes DR21, DR22, and DR23, the anode becomes the second winding group 100b side and the cathode becomes the second inverter 200B22 side.

[0372] In other words, in the third embodiment, the semiconductor switch elements 2RU, 2RV, 2RW constituting the second relay 200B3 include the parasitic diodes DR21, DR22, DR23 that conduct the current in the direction from the second winding group 100b toward the second inverter 200B22.

[0373] As described in detail later, Fig.17 The sixth relay 200A6 and the seventh relay 200B7 function as cutoff relays for cutting off the short-circuit path to the ground GND of the first inverter 200A22 and the short-circuit path to the ground GND of the second inverter 200B22 instead of the first relay 200A3 and the second relay 200B3.

[0374] in addition, Fig.17 A normal control state is shown in which AC power is supplied from the first inverter 200A22 to the first winding group 100a, and AC power is supplied from the second inverter 200B22 to the second winding group 100b.

[0375] In a normal control state, the first inverter 200A22 and the second inverter 200B22 are PWM controlled, so the sixth relay 200A6 and the seventh relay 200B7 are maintained in an on state.

[0376] Fig.18 In the third embodiment, the control states of the semiconductor switch elements constituting the inverters 200A22, 200B22, 200C22 and the relays 200A3, 200B3, 200C3, 200C4, 200C5, 200A6, 200B7 are shown when a short-circuit fault occurs in the semiconductor switch element 1UL of the lower arm among the semiconductor switch elements 1UH, 1UL, 1VH, 1VL, 1WH, 1WL constituting the first inverter 200A22.

[0377] Here, it is assumed that the third inverter 200C22 supplies AC power to the first winding group 100a instead of the failed first inverter 200A22, and the second inverter 200B22 normally supplies AC power to the second winding group 100b.

[0378] Specifically, since the first inverter 200A22 fails, the PWM control of the first inverter 200A22 is stopped, and the semiconductor switching elements 1RU, 1RV, and 1RW constituting the first relay 200A3 are switched from the on state to the off state.

[0379] Furthermore, the semiconductor switch element 6R constituting the sixth relay 200A6 is switched from the on state to the off state.

[0380] On the other hand, since AC power is supplied from the third inverter 200C22 to the first winding group 100a, the semiconductor switching elements 3UH, 3UL, 3VH, 3VL, 3WH, and 3WL constituting the third inverter 200C22 are PWM-controlled.

[0381] Furthermore, the semiconductor switch elements 3RU1 , 3RV1 , and 3RW1 constituting the third relay 200C3 are switched from the OFF state to the ON state, and the semiconductor switch element 5R constituting the fifth relay 200C5 is also switched from the OFF state to the ON state.

[0382] On the other hand, the semiconductor switch elements 4RU1 , 4RV1 , and 4RW1 constituting the fourth relay 200C4 are maintained in the OFF state.

[0383] In such a control state, the AC current is supplied from the third inverter 200C22 to the first winding group 100a instead of the failed first inverter 200A22.

[0384] Here, even if the semiconductor switch elements 1RU, 1RV, 1RW constituting the first relay 200A3 are switched to the off state, the parasitic diodes DR11, DR12, DR13 allow the current to flow from the first winding group 100a toward the first inverter 200A22.

[0385] However, the semiconductor switch element 6R constituting the sixth relay 200A6 is controlled to be in the off state, and the parasitic diode DR6 of the semiconductor switch element 6R has its cathode set to the first inverter 200A22 side and its anode set to the ground GND side.

[0386] That is, the sixth relay 200A6 functions as a cutoff relay that cuts off the short-circuit path from the first inverter 200A22 to the ground GND by being controlled to be OFF.

[0387] Therefore, even if a short-circuit fault occurs in the semiconductor switching element 1UL constituting the first inverter 200A22, a short-circuit circuit to the ground is not formed via the semiconductor switching element 1UL.

[0388] Therefore, even if a short-circuit failure occurs in the lower arm of the first inverter 200A22, the first winding group 100a and the second winding group 100b can be normally controlled.

[0389] Fig.19 It is shown that in the third embodiment, when the first inverter 200A22 supplies AC power to the first winding group 100a and the second inverter 200B22 supplies AC power to the second winding group 100b, even if a short-circuit fault occurs in the semiconductor switch element 3UL of the lower arm of the third inverter 200C22, a short-circuit circuit to the ground will not be formed through the semiconductor switch element 3UL.

[0390] When the first inverter 200A22 supplies AC power to the first winding group 100a and the second inverter 200B22 supplies AC power to the second winding group 100b, the semiconductor switch elements 3RU1, 3RV1, 3RW1 constituting the third relay 200C3 and the semiconductor switch elements 4RU1, 4RV1, 4RW1 constituting the fourth relay 200C4 are maintained in the off state.

[0391] However, the parasitic diodes DR311, DR321, DR331, DR411, DR421, and DR431 included in the semiconductor switch elements 3RU1, 3RV1, 3RW1, 4RU1, 4RV1, and 4RW1 have cathodes on the third inverter 200C22 side and anodes on the motor 100 side.

[0392] Therefore, the current supplied to the first winding group 100a and the second winding group 100b can flow into the third inverter 200C22 through the parasitic diodes DR311, DR321, DR331, DR411, DR421, and DR431.

[0393] However, the semiconductor switch element 5R constituting the fifth relay 200C5 is held in the off state, and the parasitic diode DR5 of the semiconductor switch element 5R has its cathode directed toward the third inverter 200C22 and its anode directed toward the ground GND.

[0394] Therefore, the semiconductor switch element 5R (and the parasitic diode DR5 ) functions as a cutoff relay that cuts off the short-circuit path to the ground, and a short-circuit circuit to the ground is not formed via the semiconductor switch element 3UL in which the short-circuit failure has occurred.

[0395] Therefore, even if the semiconductor switching element of the lower arm of the third inverter 200C22 short-circuits, the output current of the first inverter 200A22 and the output current of the second inverter 200B22 can be prevented from being short-circuited to the ground via the short-circuited semiconductor switching element.

[0396] Therefore, even if a short-circuit failure occurs in the semiconductor switching element of the lower arm of the third inverter 200C22, the control of the first winding group 100a and the second winding group 100b can be continued normally.

[0397] "Fourth Implementation Method"

[0398] Fig. 20 It is a block diagram showing a detailed structure of a motor control device 200 according to a fourth embodiment.

[0399] Fig. 20 The motor control device 200 and Figure 7 The motor control device 200 shown is different only in that the fifth relay 200C5 is omitted and an eighth relay 200C8 is provided instead.

[0400] Therefore, in Fig. 20 In, with Figure 7 The same elements are denoted by the same reference numerals, and detailed descriptions thereof are omitted.

[0401] The eighth relay 200C8 is disposed between the third branch points 3BU, 3BV, 3BW and the third inverter 200C22, and is controlled to be turned on and off by the third MCU 200C1 of the third control device 200C.

[0402] Fig.21 It is shown Fig. 20Detailed circuit diagram of the inverters 200A22, 200B22, 200C22 and relays 200A3, 200B3, 200C3, 200C4, 200C8 shown.

[0403] In addition, Fig.21 In, with Figure 8 The same elements are denoted by the same reference numerals, and detailed descriptions thereof are omitted.

[0404] The eighth relay 200C8 is constituted by semiconductor switching elements 8RU, 8RV, 8RW respectively arranged on the third drive lines 3DU, 3DV, 3DW between the first inverter 200A22 and the third branch points 3BU, 3BV, 3BW.

[0405] The semiconductor switch elements 8RU, 8RV, 8RW are arranged so that their drains are on the third branch points 3BU, 3BV, 3BW side (the motor 100 side) and their sources are on the third inverter 200C22 side.

[0406] Furthermore, regarding the orientation of the parasitic diodes DR81, DR82, and DR83 of the semiconductor switch elements 8RU, 8RV, and 8RW, the cathodes are on the third branch points 3BU, 3BV, and 3BW sides, and the anodes are on the third inverter 200C22 side.

[0407] That is, the semiconductor switch elements 8RU, 8RV, 8RW constituting the eighth relay 200C8 include parasitic diodes DR81, DR82, DR83 that conduct the current in the direction from the third inverter 200C22 toward the third branch points 3BU, 3BV, 3BW.

[0408] The eighth relay 200C8 described above is provided as a cutoff relay in place of the fifth relay 200C5 arranged between the third inverter 200C22 and the ground GND in the second embodiment.

[0409] Furthermore, the eighth relay 200C8 includes parasitic diodes DR81, DR82, and DR83 that conduct a current from the ground GND of the third inverter 200C22 toward the first winding group 100a and the second winding group 100b.

[0410] According to such a structure, when the first inverter 200A22 supplies AC power to the first winding group 100a and the second inverter 200B22 supplies AC power to the second winding group 100b, when a short-circuit fault occurs in the semiconductor switch element 3UL of the lower arm of the third inverter 200C22, the formation of a short-circuit circuit to the ground through the semiconductor switch element 3UL can be avoided.

[0411] like Fig.21As shown, when the PWM control of the third inverter 200C22 is stopped, the semiconductor switching elements 3RU1, 3RV1, 3RW1 constituting the third relay 200C3, the semiconductor switching elements 4RU1, 4RV1, 4RW1 constituting the fourth relay 200C4, and the semiconductor switching elements 8RU, 8RV, 8RW constituting the eighth relay 200C8 are all maintained in the off state.

[0412] Here, the parasitic diodes of the semiconductor switch elements 3RU1, 3RV1, 3RW1 constituting the third relay 200C3 and the semiconductor switch elements 4RU1, 4RV1, 4RW1 constituting the fourth relay 200C4 can conduct current in the direction toward the third branch points 3BU, 3BV, 3BW.

[0413] However, the parasitic diodes DR81, DR82, DR83 of the semiconductor switch elements 8RU, 8RV, 8RW constituting the eighth relay 200C8 block the current from the third branch points 3BU, 3BV, 3BW to the third inverter 200C22.

[0414] Therefore, even if the semiconductor switch element 3UL of the lower arm of the third inverter 200C22 short-circuits, the output current of the first inverter 200A22 and the output current of the second inverter 200B22 are prevented from being short-circuited to the ground through the semiconductor switch element 3UL by the eighth relay 200C8.

[0415] Therefore, even if a short-circuit failure occurs in the semiconductor switching element 3UL of the lower arm of the third inverter 200C22, the first winding group 100a and the second winding group 100b can be normally controlled.

[0416] "Motor Control Process"

[0417] Hereinafter, one aspect of the control process of the motor 100 by the above-mentioned motor control device 200 will be described.

[0418] Figure 22-Figure 25 The flowchart shows the control process implemented by the first control device 200A (first MCU200A1) and the second control device 200B (second MCU200B1). Figure 26-Figure 29 The flowchart shows a control process implemented by the third control device 200C (third MCU 200C1).

[0419] Figure 22-Figure 29The control process shown in the flowchart includes a process of supplying AC power to the first winding group 100a and the second winding group 100b through one of the normal driving circuits when a failure occurs in the first driving circuit 200A2 or the second driving circuit 200B2 (hereinafter also referred to as a failure-time driving process).

[0420] Furthermore, in the fault-time driving process, a process of switching the driving circuit that supplies AC power to the first winding group 100a and the second winding group 100b (hereinafter also referred to as a driving switching process) is performed.

[0421] Through the above-described drive switching process, it is possible to suppress a temperature increase of the semiconductor switching elements constituting the inverter while continuing to drive the motor 100 , thereby protecting the semiconductor switching elements.

[0422] in addition, Figure 22-Figure 25 The control process shown in the flowchart is a control process common to the first control device 200A and the second control device 200B.

[0423] Therefore, the control process implemented by the first control device 200A will be described below as a representative example, and the description of the control process implemented by the second control device 200B will be omitted.

[0424] Fig. 22 as well as Fig.23 The flowchart shows a main routine of the control process based on the first control device 200A.

[0425] When the first control device 200A (first MCU 200A1) is started by turning on the ignition switch 260 as a main switch for driving and stopping the vehicle 1 in step S801, the first control device 200A (first MCU 200A1) acquires information on the target direction steering angle of the front wheels 2L, 2R in the next step S802.

[0426] Furthermore, in step S803 , the first control device 200A acquires the output signal of the motor rotation angle sensor 101 , and obtains the rotation angle of the motor 100 based on the acquired output signal.

[0427] Furthermore, in step S804 , the first control device 200A obtains the drive current of the motor 100 based on the output of a current sensor (not shown).

[0428] Next, in step S805 , the first control device 200A diagnoses the presence or absence of a fault in the drive system including the first winding group 100 a of the first drive circuit 200A2 .

[0429] The failure mode includes a short-circuit failure of the semiconductor switching element constituting the first inverter 200A22 and the like.

[0430] Then, in step S806, the first control device 200A determines whether the occurrence of a failure is detected.

[0431] Here, when the first control device 200A detects the occurrence of a failure, the process proceeds from step S806 to step S807.

[0432] In step S807, the first control device 200A transmits information indicating that the supply of AC power from the first inverter 200A22 to the first winding group 100a is stopped due to the occurrence of the failure to the other systems (the second control device 200A and the third control device 200C).

[0433] Then, in step S808, the first control device 200A stops the PWM control of the first inverter 200A22.

[0434] Furthermore, in step S809, the first control device 200A controls all of the semiconductor switch elements 1RU, 1RV, and 1RW constituting the first relay 200A3 (in other words, the phase relays of the first winding group 100a) to be turned off.

[0435] In the case of the motor control device 200 of the third embodiment provided with the sixth relay 200A6 and the seventh relay 200B7, when the first control device 200A controls the first relay 200A3 to be OFF in step S809, the sixth relay 200A6 is also controlled to be OFF.

[0436] After the first control device 200A controls the first relay 200A3 to be turned off in step S809, the first control device 200A controls the power supply relay 13 that disconnects and connects the power supply path from the first battery 11 to the first inverter 200A22 to be turned off in step S810.

[0437] On the other hand, when the drive system of the first winding group 100a is normal, the first control device 200A proceeds from step S806 to step S811.

[0438] In step S811, the first control device 200A determines whether or not there is a request to switch the drive circuit for the drive switching process.

[0439] Although described in detail later, the first control device 200A determines the presence or absence of a request to switch the drive circuit based on the accumulated drive time of the first inverter 200A22, the estimated temperature of the semiconductor switching element constituting the first inverter 200A22, and the like.

[0440] Then, when the first control device 200A determines that a request for switching the drive circuit has been generated, it raises a drive switching determination flag FDS to 1 and stores information on the request for executing the drive switching process.

[0441] Next, in step S812, the first control device 200A transmits drive stop information (in other words, information related to drive switching determination) based on the drive circuit switching request to other systems.

[0442] Furthermore, in step S813, the first control device 200A determines whether the third inverter 200C22 is being driven in a standby manner.

[0443] Then, if the third inverter 200C22 is being driven, the first control device 200A proceeds to step S815 to stop the PWM control of the first inverter 200A22.

[0444] Furthermore, in step S816, the first control device 200A controls all of the semiconductor switching elements 1RU, 1RV, and 1RW constituting the first relay 200A3 as the phase relay of the first winding group 100a to be turned off.

[0445] On the other hand, when the third inverter 200C22 is not being driven, the first control device 200A proceeds from step S813 to step S814 to determine whether the drive switching determination flag FDS is set to zero.

[0446] The drive switching determination flag FDS is a flag indicating whether the inverter switching instruction is set. The drive switching determination flag FDS=1 indicates that the inverter supplying AC power to the motor 100 is instructed to switch, in other words, the drive switching request is set.

[0447] Here, when the drive switching determination flag is set to 1 and the inverter supplying AC power to the motor 100 is instructed to be switched, the first control device 200A proceeds to step S815.

[0448] Then, the first control device 200A stops the PWM control of the first inverter 200A22 in step S815, and further controls all the semiconductor switch elements 1RU, 1RV, and 1RW constituting the first relay 200A3 to be turned off in step S816.

[0449] On the other hand, when the driving state of the motor 100 is not based on the third inverter 200C22, and the drive switching determination flag is set to zero and the inverter switching request is not set, the first control device 200A enters step S817, and then performs PWM control on the first inverter 200A22, thereby supplying AC power from the first inverter 200A22 to the motor 100.

[0450] In step S817 , the first control device 200A obtains the steering angle of the front wheels 2L, 2R based on the output signal of the steering angle detection device 400 .

[0451] Next, in step S818, the first control device 200A feeds back the steering angle of the front wheels 2L, 2R obtained based on the output signal of the steering angle detection device 400 to the target value side, thereby comparing the actual steering angle with the target steering angle.

[0452] Furthermore, in step S819, the first control device 200A obtains a target motor torque for bringing the actual steering angle closer to the target steering angle based on the control deviation which is the difference between the actual steering angle and the target steering angle.

[0453] Furthermore, in step S820, the first control device 200A obtains a d-axis current command value and a q-axis current command value corresponding to the target motor torque.

[0454] Then, in step S821, the first control device 200A performs vector control.

[0455] In detail, the first control device 200A implements a 3-phase → 2-phase conversion of converting the actual currents Iu, Iv, and Iw of each 3 phase into d-axis actual current and q-axis actual current, and then calculates the d-axis voltage command value Vd and the q-axis voltage command value Vq based on the d-axis current command value and the q-axis current command value corresponding to the target motor torque and the deviation from the d-axis actual current and the q-axis actual current.

[0456] Next, in step S822, the first control device 200A converts the d-axis voltage command value Vd and the q-axis voltage command value Vq into three-phase command voltages Vu, Vv, and Vw based on the rotation angle of the motor 100, and calculates the duty ratio of the PWM control based on the three-phase command voltages Vu, Vv, and Vw.

[0457] Next, in step S823 , the first control device 200A turns on the power supply relay 13 .

[0458] Furthermore, in step S824, the first control device 200A controls all of the semiconductor switch elements 1RU, 1RV, and 1RW constituting the first relay 200A3 as a phase relay to be turned on.

[0459] Then, in step S825, the first control device 200A outputs a control pulse for on-off control of each semiconductor switching element of the first inverter 200A22 to the first pre-driver 200A21 by PWM based on the three-phase command voltages Vu, Vv, and Vw.

[0460] After the first control device 200A completes the processing in steps S810, S816, and S825, the process proceeds to step S826 to determine whether the ignition switch 260 has been switched from on to off.

[0461] Then, if the ignition switch 260 is kept in the on state, the first control device 200A returns to step S802 and repeats the control process of step S802 to step S825.

[0462] On the other hand, when the ignition switch 260 is switched from on to off, the first control device 200A ends the control process of steps S802 to S825 described above.

[0463] Fig.24 1 is a flowchart showing details of the processing content in step S811, that is, a subroutine of the processing for determining whether or not there is a request to switch the drive circuit.

[0464] In addition, as a method, Fig.24 The determination process shown in the flowchart of FIG. 1 shows the drive switching determination based on the accumulated drive time.

[0465] First, in step S851, the first control device 200A determines whether the output current of the first inverter 200A22 is equal to or greater than a predetermined value CTH.

[0466] In other words, the first control device 200A determines in step S851 whether AC power is being supplied from the first inverter 200A22 to the first winding group 100a and whether the semiconductor switching element of the first inverter 200A22 is generating heat.

[0467] Here, if it is determined that the output current of the first inverter 200A22 is equal to or greater than the predetermined value CTH, the first control device 200A proceeds to step S852 and performs update processing to increase the measurement counter MC for measuring the cumulative drive time of the first inverter 200A22 by 1 from the current value.

[0468] On the other hand, if it is determined that the output current of the first inverter 200A22 is smaller than the predetermined value CTH, the first control device 200A proceeds to step S853 to determine whether the measurement counter MC has become equal to or smaller than zero.

[0469] Then, when the measurement counter MC becomes equal to or less than zero, the first control device 200A resets the measurement counter MC to zero in step S854.

[0470] On the other hand, when the measurement counter MC is greater than zero, the first control device 200A performs an update process of subtracting 1 from the current value of the measurement counter MC in step S855.

[0471] That is, if the output current of the first inverter 200A22 is equal to or greater than the predetermined value CTH, the measurement counter MC is incremented by 1 in each execution cycle of this subroutine.

[0472] On the other hand, when the output current of the first inverter 200A22 is smaller than the predetermined value CTH, the measurement counter MC is decremented by 1 with zero being the lower limit for each execution cycle of this subroutine.

[0473] Therefore, the value of the measurement counter MC indicates the cumulative time in which the output current of the first inverter 200A22 is equal to or greater than the predetermined value CTH, in other words, the cumulative driving time as the accumulation of the driving time of the first inverter 200A22.

[0474] In step S852, the first control device 200A performs an update process for increasing the measurement counter MC by 1 from the current value, and then proceeds to step S856.

[0475] In step S856, the first control device 200A determines whether a failure has been detected in the second control device 200B or the third control device 200C as the other system, based on the failure information acquired from the second control device 200B or the third control device 200C.

[0476] When no fault is detected in the second control device 200B and the third control device 200C, the first control device 200A proceeds to step S857 to reset the drive switching determination flag FDS to zero, thereby saving information indicating that no switching request for the inverter (drive circuit) is generated.

[0477] That is, when the first control device 200A, the second control device 200B, and the third control device 200C are all normal, the first inverter 200A22 supplies AC power to the first winding group 100a, and the second inverter 200B22 supplies AC power to the second winding group 100b.

[0478] Furthermore, after resetting the measurement counter MC to zero in step S854, the first control device 200A also proceeds to step S857 to reset the drive switching determination flag FDS to zero.

[0479] That is, when resetting the measurement counter MC to zero, the first control device 200A determines that the accumulated drive time of the first inverter 200A22 is short and there is no need to switch the inverter (drive circuit) under the current situation, and resets the drive switching determination flag FDS to zero.

[0480] On the other hand, when the first control device 200A determines in step S856 that a failure has been detected in the second control device 200B or the third control device 200C, the process proceeds to step S858 to determine whether the measurement counter MC has reached or exceeded a predetermined value MCH.

[0481] Then, when the measuring counter MC becomes greater than the specified value MCH (in other words, when the accumulated driving time of the first inverter 200A22 becomes greater than the set time), the first control device 200A enters step S859, and saves information indicating the state of a switching request for the inverter (drive circuit) by setting the drive switching determination flag FDS to 1.

[0482] Fig.25 The flowchart is another aspect of the process of determining whether or not there is a request to switch the drive circuit.

[0483] Here, the first control device 200A estimates the temperature of the semiconductor switching element (MOS-FET) constituting the first inverter 200A22, and performs drive switching determination based on the temperature estimation value of the semiconductor switching element.

[0484] In step S871 , the first control device 200A detects the temperature of the first control device 200A (specifically, the temperature of the substrate where the first control device 200A is mounted) based on an output signal of a temperature sensor (not shown).

[0485] Next, in step S872, the first control device 200A performs a process of integrating the current value of the drive current output by the first inverter 200A22.

[0486] Then, in step S873, the first control device 200A estimates the temperature rise of the semiconductor switching element (MOS-FET) constituting the first inverter 200A22 based on the integrated current value.

[0487] In the next step S874, the first control device 200A obtains the temperature of the semiconductor switching element constituting the first inverter 200A22 (the estimated temperature of the FET).

[0488] Specifically, the first control device 200A adds the temperature rise estimated value obtained in step S873 to the temperature of the first control device 200A detected in step S871 to estimate the temperature of the semiconductor switching elements constituting the first inverter 200A22.

[0489] Next, in step S875, the first control device 200A determines whether the estimated temperature of the semiconductor switching element constituting the first inverter 200A22 is equal to or higher than a predetermined value TSH.

[0490] When the estimated temperature of the semiconductor switching element constituting the first inverter 200A22 is lower than the predetermined value TSH, the first control device 200A proceeds to step S876 to determine whether the value of the measurement counter MC is equal to or lower than zero.

[0491] Then, if the value of the measurement counter MC is equal to or less than zero, the first control device 200A resets the measurement counter MC to zero in step S877.

[0492] On the other hand, when the value of the measurement counter MC is greater than zero, the first control device 200A performs an update process of subtracting 1 from the current value of the measurement counter MC in step S878.

[0493] In addition, when the estimated temperature of the semiconductor switching elements constituting the first inverter 200A22 is above the specified value TSH, the first control device 200A determines in step S879 whether a fault is detected in the second control device 200B or the third control device 200C which are other systems based on the fault information obtained from the second control device 200B and the third control device 200C.

[0494] Here, when the first control device 200A does not detect a failure in other systems, the process proceeds to step S880 to reset the drive switching determination flag FDS to zero.

[0495] Furthermore, after resetting the measurement counter MC to zero in step S877, the first control device 200A also proceeds to step S880 to reset the drive switching determination flag FDS to zero.

[0496] On the other hand, when the first control device 200A determines in step S879 that a failure has been detected in another system, the process proceeds to step S881 to perform an update process of increasing the measurement counter MC by 1 from the current value.

[0497] Next, in step S882, the first control device 200A determines whether the measurement counter MC is equal to or greater than a predetermined value MCH.

[0498] Then, when the measurement counter MC is equal to or greater than the predetermined value MCH, the first control device 200A proceeds to step S883, and sets the drive switching determination flag FDS to 1, thereby storing information indicating that a switching request for the inverter (drive circuit) has been generated.

[0499] In addition, when the measurement counter MC is smaller than the predetermined value MCH, the first control device 200A directly terminates this subroutine.

[0500] Fig.26 1 is a flowchart showing a main routine of a control process by the third control device 200C (third MCU 200C1 ).

[0501] in addition, Fig.26 The processing contents in each step of step S901 to step S906 of the flowchart are the same as Fig. 22 Steps S801 to S806 of the flowchart are the same, so detailed description is omitted.

[0502] When the third control device 200C detects a failure in step S906, the process proceeds to step S907 to transmit information indicating that a failure has occurred in the third control device 200C and supply of AC power from the third inverter 200C22 is stopped to the first control device 200A and the second control device 200B as other systems.

[0503] Next, in step S908, the third control device 200C stops the PWM control of the third inverter 200C22.

[0504] Furthermore, in the next step S909, the third control device 200C controls the third relay 200C3 (first switching relay) and the fourth relay 200C4 (second switching relay) to be turned off.

[0505] Furthermore, in step S910, the third control device 200C controls the cutoff relay for cutting off the ground short-circuit path and the inflow of the drive current to be turned off.

[0506] For example, in the first embodiment, the disconnecting relays whose opening control is performed by the third control device 200C in step S910 are the semiconductor switch elements 3RU2, 3RV2, 3RW2 constituting the third relay 200C3 and the semiconductor switch elements 4RU2, 4RV2, 4RW2 constituting the fourth relay 200C4.

[0507] That is, in the case of the first embodiment, the third relay 200C3 and the fourth relay 200C4 have a function as a switching relay and a function as a disconnecting relay.

[0508] In the second embodiment and the third embodiment, the cutoff relay that is controlled to be turned off by the third control device 200C in step S910 is the fifth relay 200C5 (semiconductor switch element 5R).

[0509] In the fourth embodiment, the cutoff relay that is controlled to be turned off by the third control device 200C in step S910 is the eighth relay 200C8 (semiconductor switch elements 8RU, 8RV, 8RW).

[0510] After the third control device 200C performs the OFF control of the cutoff relay in step S910 , it controls the power supply relay 15 and the power supply relay 16 to be OFF in step S911 .

[0511] On the other hand, when the third control device 200C determines in step S906 that there is no failure, the process proceeds to step S912 to perform a drive switching determination.

[0512] The drive switching determination performed in the above-mentioned step S912 will be described in detail later.

[0513] Next, in step S913, the third control device 200C transmits information on driving and stopping of the third drive circuit 200C2 (third inverter 200C22) to the first control device 200A and the second control device 200B.

[0514] Furthermore, in step S914, the third control device 200C determines whether the first drive circuit 200A2 (first inverter 200A22) is being driven based on the information transmitted from the first control device 200A.

[0515] Here, when the third control device 200C is not driving the first drive circuit 200A2 (first inverter 200A22), the process proceeds to step S915 to determine whether the second drive circuit 200B2 (second inverter 200B22) is being driven based on the information sent from the second control device 200B.

[0516] Then, if at least one of the first drive circuit 200A2 and the second drive circuit 200B2 is being driven, the third control device 200C performs the same processing as steps S908 to S910 in steps S917 to S919, thereby stopping the driving of the third drive circuit 200C2.

[0517] On the other hand, when the first drive circuit 200A2 and the second drive circuit 200B2 are in the driving stop state, the third control device 200C proceeds to step S916 to determine whether the drive switching determination flag FDS is zero.

[0518] Here, when the drive switching determination flag FDS is 1 and a request is generated to switch from drive based on the third drive circuit 200C2 (third inverter 200C22) to drive based on other systems, the third control device 200C stops the drive based on the third drive circuit 200C2 (third inverter 200C22) by implementing the processing of steps S917 to S919.

[0519] When the drive switching determination flag FDS is zero and there is no request to switch from drive by the third drive circuit 200C2 (third inverter 200C22) to drive by another system, the third control device 200C performs each process of step S920 to step S929.

[0520] In addition, the third control device 200C performs the same operations as those described above in each of steps S920 to S929 and steps S920 to S926. Fig.23 The processing from step S817 to step S823 of the flowchart is the same as that of the flowchart, so the detailed description is omitted here.

[0521] In step S927, the third control device 200C controls the third relay 200C3 and the fourth relay 200C4, which correspond to the phase relays being driven by the third inverter 200C22, to be turned on.

[0522] Furthermore, in the next step S928, the third control device 200C controls the cutoff relay that is the target of the off control in the above-mentioned step S910 to be turned on.

[0523] Then, in the next step S929, the third control device 200C outputs a control pulse for on-off control of each semiconductor switching element of the third inverter 200C22 to the third pre-driver 200C21 by PWM based on the three-phase command voltages Vu, Vv, and Vw.

[0524] After the third control device 200C completes the processing in each of steps S911, S919, and S929, the process proceeds to step S930 to determine whether the ignition switch 260 has been switched from on to off.

[0525] Then, while the ignition switch 260 is kept in the on state, the third control device 200C returns to step S902 and repeats the control process of step S902 to step S929.

[0526] On the other hand, when the ignition switch 260 is switched from on to off, the third control device 200C ends the control process of steps S902 to S929 described above.

[0527] Fig.28 It is shown Fig.26 1 is a flowchart of the details of the processing content in step S912 of the flowchart, that is, a flowchart of the subroutine of the drive switching determination.

[0528] Furthermore, as one method of determining the drive switching, Fig.28 The flowchart of FIG. 1 shows the drive switching determination based on the accumulated drive time.

[0529] First, in step S951, the third control device 200C determines whether the output current of the third inverter 200C22 is equal to or greater than a predetermined value CTH.

[0530] Here, if it is determined that the output current of the third inverter 200C22 is equal to or greater than the predetermined value CTH, the third control device 200C proceeds to step S952 to perform an update process for increasing the measurement counter MC for measuring the cumulative drive time of the third inverter 200C22 by 1 from the current value.

[0531] On the other hand, if it is determined that the output current of the third inverter 200C22 is smaller than the predetermined value CTH, the third control device 200C proceeds to step S953 to determine whether the measurement counter MC has become equal to or smaller than zero.

[0532] Then, when the measurement counter MC becomes equal to or less than zero, the third control device 200C resets the measurement counter MC to zero in step S954, and then resets the drive switching determination flag FDS to zero in step S956.

[0533] Furthermore, when the measurement counter MC is greater than zero, the third control device 200C performs an update process of subtracting 1 from the current value of the measurement counter MC in step S955.

[0534] In step S952, the third control device 200C performs an update process for increasing the measurement counter MC by 1 from the current value, and then proceeds to step S957.

[0535] In step S957, the third control device 200C determines whether a failure of any one of the first drive circuit 200A2 and the second drive circuit 200B2 has been detected.

[0536] When the third control device 200C detects a fault in either the first drive circuit 200A2 or the second drive circuit 200B2, that is, when the normal drive system is a dual system including the third drive circuit 200C2 and is capable of switching the supply of AC power to the first winding group 100a and the second winding group 100b, the process proceeds to step S958.

[0537] In step S958, the third control device 200C determines whether the measurement counter MC is equal to or greater than a predetermined value MCH.

[0538] Then, when the measurement counter MC is equal to or greater than the predetermined value MCH, the third control device 200C proceeds to step S959 and sets the drive switching determination flag FDS to 1, thereby storing information indicating that a switching request for the inverter (drive circuit) has been generated.

[0539] On the other hand, when the measurement counter MC is smaller than the predetermined value MCH, the third control device 200C does not perform the process of setting the drive switching determination flag FDS and terminates this subroutine.

[0540] In addition, in step S957, the third control device 200C enters step S959 and sets the drive switching determination flag FDS to 1 when it is determined that neither the first drive circuit 200A2 nor the second drive circuit 200B2 is in a faulty state, that is, when it is determined that both the first drive circuit 200A2 and the second drive circuit 200B2 are normal, or when both the first drive circuit 200A2 and the second drive circuit 200B2 are faulty.

[0541] Therefore, when the first drive circuit 200A2 and the second drive circuit 200B2 fail and the drive stops, even if a switching request is generated from the drive based on the third drive circuit 200C2, the drive switching determination flag FDS is immediately set to 1 because there is no normal drive circuit that drives the motor 100 instead of the third drive circuit 200C2.

[0542] In addition, if the first drive circuit 200A2 and the second drive circuit 200B2 are normal, it is sufficient to return to the standard state in which the first drive circuit 200A2 drives the first inverter 200A22 and the second drive circuit 200B2 drives the second inverter 200B22, so the drive switching determination flag FDS is immediately set to 1.

[0543] Fig.29 The flow chart shows Fig.26 Another manner of the drive switching determination in step S912 of the flowchart.

[0544] Here, the third control device 200C estimates the temperature of the semiconductor switching element (MOS-FET) constituting the third inverter 200C22, and performs drive switching determination based on the temperature estimation value of the semiconductor switching element.

[0545] in addition, Fig.29 The processing in each step of step S971-step S979 is the same as Fig.25 Compared with steps S871 to S878 and step S880, the processing is different in that the processing is based on the third control device 200C and the object of temperature estimation is the semiconductor switching element constituting the third inverter 200C22, but the processing content is the same.

[0546] Therefore, the detailed description of the processing contents in each step from step S971 to step S979 is omitted.

[0547] When the third control device 200C determines in step S975 that the estimated temperature of the semiconductor switching elements constituting the third inverter 200C22 is equal to or higher than the predetermined value TSH, the process proceeds to step S980.

[0548] In step S980 , the third control device 200C determines whether a failure of any one of the first drive circuit 200A2 and the second drive circuit 200B2 has been detected.

[0549] When the third control device 200C detects a fault in either the first drive circuit 200A2 or the second drive circuit 200B2, that is, when the normal drive system is a dual system including the third drive circuit 200C2 and is capable of switching the supply of AC power to the first winding group 100a and the second winding group 100b, the process proceeds to step S981.

[0550] In step S981, the third control device 200C performs an update process of increasing the measurement counter MC by 1 from the current value.

[0551] Thereafter, the third control device 200C proceeds to step S982 to determine whether the measurement counter MC has reached or exceeded a predetermined value MCH.

[0552] Then, when the measurement counter MC is equal to or greater than the predetermined value MCH, the third control device 200C proceeds to step S983, and sets the drive switching determination flag FDS to 1, thereby storing information indicating that a switching request for the inverter (drive circuit) has been generated.

[0553] On the other hand, when the measurement counter MC is smaller than the predetermined value MCH, the third control device 200C does not perform the process of setting the drive switching determination flag FDS, but directly terminates the present subroutine.

[0554] In addition, in step S980, the third control device 200C enters step S983 and sets the drive switching determination flag FDS to 1 when it is determined that neither the first drive circuit 200A2 nor the second drive circuit 200B2 is in a faulty state, that is, when it is determined that both the first drive circuit 200A2 and the second drive circuit 200B2 are normal, or when both the first drive circuit 200A2 and the second drive circuit 200B2 are faulty.

[0555] The motor control device 200 according to the first embodiment to the fourth embodiment will be described below. Figure 22-Figure 29 The flowchart shows the control status of the relay and the inverter when the control process is executed.

[0556] For example, in the motor control device 200 of the second embodiment, if Fig. 9 As shown, when the first inverter 200A22 fails and AC power is supplied from the second inverter 200B22 to the first winding group 100a and the second winding group 100b, the accumulated driving time of the second inverter 200B22 exceeds the set time, or the estimated temperature of the FET of the second inverter 200B22 continues to exceed the set temperature, the second control device 200B raises the drive switching determination flag FDS to 1.

[0557] Then, the second control device 200B raises the drive switching determination flag FDS to 1 by entering Fig.23 Steps S815 and S816 of the flowchart are executed, thereby stopping the supply of AC power from the second inverter 200B22 to the first winding group 100a and the second winding group 100b.

[0558] If the supply of AC power from the second inverter 200B22 to the first winding group 100a and the second winding group 100b is stopped, the third control device 200C executes Fig. 27 The processing after step S920 of the flowchart is switched to a state where the third inverter 200C22 supplies AC power to the first winding group 100a and the second winding group 100b (see Fig.10 ).

[0559] That is, the third control device 200C controls both the third relay 200C3 and the fourth relay 200C4 to be turned on, and starts PWM control of the third inverter 200C22, thereby supplying AC power from the third inverter 200C22 to the first winding group 100a and the second winding group 100b.

[0560] Then, if the driving by the third inverter 200C22 continues and the third control device 200C raises the driving switching determination flag FDS to 1, the driving of the third inverter 200C22 is stopped, and instead, the state is switched to the state where the second inverter 200B22 supplies AC power to the first winding group 100a and the second winding group 100b (see Fig. 9 ).

[0561] Thus, even if the first inverter 200A22 fails, the supply of AC power to the first winding group 100a and the second winding group 100b can continue, and a temperature increase of semiconductor switching elements constituting the inverter of the drive motor 100 can be suppressed.

[0562] Similarly, in the motor control device 200 of the first embodiment, Figure 6 As shown, the case where a failure occurs in the first inverter 200A22 is described.

[0563] Here, if the accumulated driving time of the second inverter 200B22 exceeds the set time or the estimated temperature of the FET of the second inverter 200B22 exceeds the set temperature while AC power is supplied from the second inverter 200B22 to the first winding group 100a and the second winding group 100b, the second control device 200B will raise the drive switching determination flag FDS to 1, stop the PWM control of the second inverter 200B22, and control the second relay 200B3 to be disconnected.

[0564] At this time, the third control device 200C controls both the third relay 200C3 and the fourth relay 200C4 to be turned on, and starts PWM control of the third inverter 200C22, thereby supplying AC power from the third inverter 200C22 to the first winding group 100a and the second winding group 100b.

[0565] That is, even in the first embodiment, when a fault occurs in the first inverter 200A22, the state in which AC power is supplied from the second inverter 200B22 to the first winding group 100a and the second winding group 100b and the state in which AC power is supplied from the third inverter 200C22 to the first winding group 100a and the second winding group 100b are switched alternately.

[0566] In addition, Fig.17In the motor control device 200 of the third embodiment shown, for example, when a failure occurs in the first inverter 200A22, if the second relay 200B3 is controlled to be turned on and the second inverter 200B22 is PWM controlled, and on the other hand, the third relay 200C3 and the fourth relay 200C4 are all controlled to be turned on, AC power can be supplied from the second inverter 200B22 to the first winding group 100a and the second winding group 100b.

[0567] In such a state, if the accumulated driving time of the second inverter 200B22 exceeds the set time, or the estimated temperature of the FET of the second inverter 200B22 exceeds the set temperature, the second control device 200B will raise the drive switching determination flag FDS to 1, stop the PWM control of the second inverter 200B22, and control the second relay 200B3 to be disconnected.

[0568] Here, the third control device 200C keeps the third relay 200C3 and the fourth relay 200C4 all controlled to be in the on state, and starts PWM control of the third inverter 200C22, thereby replacing the second inverter 200B22 and supplying AC power from the third inverter 200C22 to the first winding group 100a and the second winding group 100b.

[0569] In addition, even in Fig.21 In the motor control device of the fourth embodiment shown, for example, when a failure occurs in the first inverter 200A22, if the second relay 200B3 is controlled to be turned on and the second inverter 200B22 is PWM controlled, on the other hand, if the third relay 200C3 and the fourth relay 200C4 are all controlled to be turned on, AC power can also be supplied from the second inverter 200B22 to the first winding group 100a and the second winding group 100b.

[0570] In such a state, if the accumulated driving time of the second inverter 200B22 exceeds the set time, or the estimated temperature of the FET of the second inverter 200B22 exceeds the set temperature, the second control device 200B will raise the drive switching determination flag FDS to 1, stop the PWM control of the second inverter 200B22, and control the second relay 200B3 to be disconnected.

[0571] Here, the third control device 200C maintains the third relay 200C3 and the fourth relay 200C4 all controlled to be in the on state, and further controls the eighth relay 200C8 to be on, and then starts PWM control of the third inverter 200C22, thereby replacing the second inverter 200B22, and supplying AC power from the third inverter 200C22 to the first winding group 100a and the second winding group 100b.

[0572] In this way, when a failure occurs in either the first drive circuit 200A2 or the second drive circuit 200B2, the motor control device 200 alternately switches to a state in which the motor 100 is driven only by the normal drive circuit in the first drive circuit 200A2 or the second drive circuit 200B2, and a state in which the motor 100 is driven only by the third drive circuit 200C2.

[0573] Thus, even when a failure occurs in either the first drive circuit 200A2 or the second drive circuit 200B2, the motor 100 can continue to be driven while suppressing a temperature rise in the semiconductor switching element (FET) constituting the inverter that drives the motor 100.

[0574] The technical concepts described in the above embodiments can be used in combination as appropriate unless there is any contradiction.

[0575] Furthermore, although the contents of the present invention have been specifically described with reference to the preferred embodiments, it is needless to say that a person skilled in the art can adopt various modified aspects based on the basic technical idea and teachings of the present invention.

[0576] For example, the steer-by-wire system may be a system including a backup mechanism that mechanically couples the steering wheel 500 and the front wheels 2L, 2R via a clutch or the like.

[0577] The steering device is not limited to the steer-by-wire device, but may be an electric power steering device in which a steering wheel and steering wheels (front wheels) are mechanically coupled and a motor for generating a steering force is provided.

[0578] Furthermore, the semiconductor switching element constituting the relay is not limited to the MOSFET, and an IGBT (Insulated Gate Bipolar Transistor) or the like can be used.

[0579] Furthermore, the motor control device 200 may include four (4 systems) or more control devices including an MCU, a drive circuit, and a relay.

[0580] Furthermore, when the MCU constituting the control device is multi-core, the plurality of processor cores can monitor each other's operations.

[0581] Moreover, for example, when an abnormality occurs in the first processor core of the first processor core and the second processor core constituting the dual core, the drive control of the motor (actuator) can be continued by the second processor core. In addition, the monitoring of the pre-driver, inverter, and power supply can be continued by the second processor core.

[0582] Description of Reference Numerals

[0583] 100…motor, 100a…first winding group (first multi-phase winding group), 100b…second winding group (second multi-phase winding group), 200…motor control device, 200A…first control device (control unit), 200A22…first inverter, 200A6…sixth relay (cut-off relay), 200B…second control device (control unit), 200B22…second inverter, 200B7…seventh relay (cut-off relay), 200C…third control device (control unit), 200C22…third inverter, 200C5…fifth relay (cut-off relay), 200 0A3…first relay (phase relay, cut-off relay), 200B3…second relay (phase relay, cut-off relay), 200C3…third relay, 200C4…fourth relay, 1000…direction control system, 2000…direction control device, 3RU2, 3RV2, 3RW2…semiconductor switching element (cut-off relay), 4RU2, 4RV2, 4RW2…semiconductor switching element (cut-off relay), 1BU, 1BV, 1BW…first branch point, 2BU, 2BV, 2BW…second branch point, 3BU, 3BV, 3BW…third branch point.

Claims

1. A motor control device for controlling a motor having a first multi-phase winding group and a second multi-phase winding group, the motor control device comprising: a first inverter connected to the first multi-phase winding group and supplying AC power to the first multi-phase winding group; a second inverter connected to the second multi-phase winding group and supplying AC power to the second multi-phase winding group; a third inverter connected to a first branch point between the first multi-phase winding group and the first inverter, and connected to a second branch point between the second multi-phase winding group and the second inverter, and capable of supplying AC power to the first multi-phase winding group or the second multi-phase winding group; a switching relay capable of switching between power on and power off, the switching relay comprising a first switching relay disposed between the first branch point and the third inverter, and a second switching relay disposed between the second branch point and the third inverter, the first switching relay and the second switching relay having a diode for conducting a current in a direction from the motor toward the third inverter; a cut-off relay capable of switching between power on and power off, the cut-off relay being arranged between the first branch point and the ground and between the second branch point and the ground, and having a diode for conducting a current in a direction from the ground toward the motor; as well as The control unit controls the first inverter, the second inverter, the third inverter, the switching relay, and the cutoff relay.

2. The motor control device according to claim 1, wherein: The cutoff relay is arranged between the first branch point and a third branch point, and between the second branch point and a third branch point, wherein the third branch point branches from between the third inverter and the first branch point toward the second branch point.

3. The motor control device according to claim 1, wherein: The cutoff relay is arranged between the third inverter and ground.

4. The motor control device according to claim 3, wherein: The cutoff relay includes a first cutoff relay and a second cutoff relay connected in series.

5. The motor control device according to claim 3, wherein: When the control unit detects a failure of the first inverter, all of the switching relays are turned on to drive the motor via either the second inverter or the third inverter.

6. The motor control device according to claim 5, wherein: The control unit switches between driving of the motor by the second inverter and driving of the motor by the third inverter according to a temperature of the second inverter and a temperature of the third inverter.

7. The motor control device according to claim 5, wherein: The control unit switches between driving of the motor by the second inverter and driving of the motor by the third inverter according to driving time of the motor by the second inverter and driving time of the motor by the third inverter.

8. The motor control device according to claim 1, wherein: The cutoff relay is arranged between the first inverter and the ground, and between the second inverter and the ground.

9. The motor control device according to claim 8, wherein: The cutoff relay includes a first cutoff relay and a second cutoff relay connected in series.

10. The motor control device according to claim 1, wherein: The cutoff relay is arranged between the first inverter and the first branch point and between the second inverter and the second branch point.

11. The motor control device according to claim 1, wherein: When the control unit detects a failure of the first inverter, it turns off the cutoff relay and turns on the first switching relay to supply AC power from the third inverter to the first multi-phase winding group.

12. The motor control device according to claim 1, wherein: The control unit turns off the cutoff relay and the switching relay when a failure of a switching element of a lower arm of the third inverter is detected.

13. The motor control device according to claim 1, wherein: When the control unit detects a failure of the switching element of the lower arm of the third inverter and a failure of the first switching relay, the control unit turns off the cutoff relay and the switching relay, and further stops the operation of either the first inverter or the second inverter.

14. The motor control device according to claim 1, wherein: The control unit stops the operation of either the first inverter or the second inverter when detecting a failure of the first switching relay and a failure of the second switching relay.

15. The motor control device according to claim 1, wherein: The switching relay and the disconnecting relay are formed of semiconductor switching elements having parasitic diodes.

16. A motor device comprising: A motor having a first multi-phase winding group and a second multi-phase winding group; and A motor control device controls the motor, the motor control device comprising: a first inverter connected to the first multi-phase winding group and supplying AC power to the first multi-phase winding group; a second inverter connected to the second multi-phase winding group and supplying AC power to the second multi-phase winding group; a third inverter connected to a first branch point between the first multi-phase winding group and the first inverter, and connected to a second branch point between the second multi-phase winding group and the second inverter, and capable of supplying AC power to the first multi-phase winding group or the second multi-phase winding group; a switching relay capable of switching between power on and power off, the switching relay comprising a first switching relay disposed between the first branch point and the third inverter, and a second switching relay disposed between the second branch point and the third inverter, the first switching relay and the second switching relay having a diode for conducting a current in a direction from the motor toward the third inverter; a cut-off relay capable of switching between power on and power off, the cut-off relay being arranged between the first branch point and the ground and between the second branch point and the ground, and having a diode for conducting a current in a direction from the ground toward the motor; as well as The control unit controls the first inverter, the second inverter, the third inverter, the switching relay, and the cutoff relay.

17. A steering system comprising: A steering device having a motor with a first multi-phase winding group and a second multi-phase winding group, and capable of steering a steering wheel of a vehicle according to an output of the motor; as well as A motor control device controls the motor, the motor control device comprising: a first inverter connected to the first multi-phase winding group and supplying AC power to the first multi-phase winding group; a second inverter connected to the second multi-phase winding group and supplying AC power to the second multi-phase winding group; a third inverter connected to a first branch point between the first multi-phase winding group and the first inverter, and connected to a second branch point between the second multi-phase winding group and the second inverter, and capable of supplying AC power to the first multi-phase winding group or the second multi-phase winding group; a switching relay capable of switching between power on and power off, the switching relay comprising a first switching relay disposed between the first branch point and the third inverter, and a second switching relay disposed between the second branch point and the third inverter, the first switching relay and the second switching relay having a diode for conducting a current in a direction from the motor toward the third inverter; a cut-off relay capable of switching between power on and power off, the cut-off relay being arranged between the first branch point and the ground and between the second branch point and the ground, and having a diode for conducting a current in a direction from the ground toward the motor; as well as The control unit controls the first inverter, the second inverter, the third inverter, the switching relay, and the cutoff relay.

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