Control device for electric motor and control method for electric motor

Abstract

A control device for an electric motor includes a first drive system including a first MCU and a first inverter, and a second drive system including a second MCU and a second inverter. The first MCU performs drive control of the electric motor through the first inverter, and performs fault diagnosis by energizing the first inverter. When a failure occurs in the first drive system, the second MCU performs drive control on the electric motor by means of a second inverter connected to a circuit connecting the first inverter and the electric motor, and performs failure diagnosis by energizing the second inverter. Furthermore, the first MCU performs a fault diagnosis of the first inverter when the second inverter is not energized in the second drive system, and the second MCU performs a fault diagnosis of the second inverter when the first inverter is not energized in the first drive system.

Description

Technical Field

[0001] The present invention relates to a control device for an electric motor and a control method for an electric motor. Background Art

[0002] In the electric power steering device of a vehicle, if the driving system of the electric motor that assists the steering force fails, the assistance of the steering force based on the electric motor will be suddenly lost. Therefore, as described in International Publication No. 2015 / 129271 (Patent Document 1), the driving system of the electric motor is multiplexed. Here, in the control of an electric motor such as an AC motor, in order to be able to arbitrarily change the rotation speed and output torque, an inverter composed of a plurality of semiconductor switching elements appropriately connected converts a DC current into an AC current, and supplies the AC current to the electric 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] In the inverter of the drive system, for example, by selectively operating the semiconductor switch element of the upper or lower section of the inverter, it is possible to diagnose whether the semiconductor switch element has a disconnection fault based on the voltage upstream of the inverter and the voltage between the terminals of the electric motor. In a control device with multiple drive systems, when executing diagnostic processing by starting each drive system, for example, due to a deviation in the execution time of the microcontroller unit, the inverters of each drive system sometimes energize the electric motor at the same time. In this case, since the AC current is supplied to the electric motor by the normal drive system, in the drive system where the semiconductor switch element has failed, it is mistakenly diagnosed that the semiconductor switch element is normal.

[0008] Therefore, an object of the present invention is to provide an electric motor control device and an electric motor control method in which a failure of each drive system is unlikely to be misdiagnosed even in a control device having multiple drive systems.

[0009] Means for solving problems

[0010] The control device of an electric motor for driving and controlling an electric motor having a multi-phase winding comprises: a first drive system including a first microcontroller unit and a first inverter composed of a plurality of semiconductor switch elements; and a second drive system including a second microcontroller unit and a second inverter composed of a plurality of semiconductor switch elements. The first microcontroller is configured to control the semiconductor switch elements of the first inverter, convert direct current into alternating current to drive and control the electric motor, and energize the plurality of semiconductor switch elements of the first inverter individually to perform fault diagnosis of the first inverter. The second inverter is connected to a circuit connecting the first inverter and the electric motor. The second microcontroller is configured to control the semiconductor switch elements of the second inverter, convert direct current into alternating current to drive and control the electric motor, and energize the plurality of semiconductor switch elements of the second inverter individually to perform fault diagnosis of the second inverter when a fault occurs in the first drive system. Moreover, the first microcontroller unit is configured to perform fault diagnosis of the first inverter when the multiple semiconductor switching elements of the second inverter are not powered on in the second drive system. In addition, the second microcontroller unit is configured to perform fault diagnosis of the second inverter when the multiple semiconductor switching elements of the first inverter are not powered on in the first drive system.

[0011] Effects of the Invention

[0012] According to the present invention, even in a control device in which the drive systems of an electric motor are multiplexed, it is possible to make it difficult for a failure of each drive system to be misdiagnosed. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is a schematic diagram showing an example of an electric power steering system.

[0014] Figure 2 This is a schematic diagram showing an example of a control system of an electric power steering system.

[0015] Figure 3 It is a schematic diagram showing an example of the internal structure of the first motor and the first control device of the electric motor.

[0016] Figure 4 This is a schematic diagram showing the entirety of an example of a control system for an electric motor.

[0017] Figure 5 This is a flowchart showing an example of the first diagnostic process executed by the first control device.

[0018] Figure 6 This is a flowchart showing an example of the first diagnostic process executed by the third control device.

[0019] Figure 7 This is a diagram for explaining the execution timing of diagnoses A and B in the first diagnostic process.

[0020] Figure 8 : is a flowchart showing an example of the second diagnostic process executed by the first control device.

[0021] Fig. 9 : is a flowchart showing an example of the second diagnostic process executed by the third control device.

[0022] Fig.10 This is a diagram for explaining the execution timing of diagnoses A and B by the second diagnostic process.

[0023] Fig.11 This is a flowchart showing an example of the third diagnostic process executed by the first control device.

[0024] Fig.12 This is a flowchart showing an example of the third diagnostic process executed by the third control device. DETAILED DESCRIPTION

[0025] Hereinafter, embodiments for implementing the present invention will be described in detail with reference to the drawings.

[0026] Figure 1 An example of an electric power steering system 100 mounted on a vehicle VH such as an automobile or a construction machine is shown. Figure 1 Fr represents the front of the vehicle.

[0027] The electric power steering system 100 includes a steering device 200 for steering the front wheels FW as steering wheels, and a reaction force device 400 for applying a reaction force torque to a steering wheel (steering wheel) SW operated by a driver of the vehicle VH. Figure 1 As can be easily understood, the steering wheel SW and the front wheels FW are not mechanically connected, and thus the electric power steering system 100 constitutes a steer-by-wire system. The electric power steering system 100 is not limited to a steer-by-wire system, and may be a known steering system in which the steering wheel SW and the front wheels FW are mechanically connected.

[0028] The steering device 200 includes an electric motor 220 for generating a steering force for steering the front wheel FW, a steering control device 240 for driving and controlling the electric motor 220, a steering mechanism 260, and a steering angle sensor 280 for detecting an actual steering angle (actual steering angle) of the front wheel FW.

[0029] The electric motor 220 is an AC motor with a multi-phase winding, for example, a three-phase brushless motor with a U-phase coil, a V-phase coil, and a W-phase coil, and has a rotation angle sensor 222 for detecting the rotation angle of the output shaft. Here, as the rotation angle sensor 222, for example, an encoder, a rotary transformer, etc. can be used. The steering control device 240 includes a microcontroller unit (MCU) having a built-in processor, a non-volatile memory, a volatile memory, an input / output circuit, and a communication circuit, and controls the driving of the electric motor 220 according to an application program stored in the non-volatile memory.

[0030] The steering mechanism 260 is a well-known mechanism that converts the rotational motion of the output shaft of the electric motor 220 into the linear motion of the steering rod 262. In this embodiment, a rack and pinion are used. The rotational driving force of the electric motor 220 is transmitted to the pinion shaft 266 via the speed reducer 264. On the other hand, the steering rod 262 has a rack 270 that is always meshed with a pinion 268 provided on the pinion shaft 266. When the pinion 268 rotates, the steering rod 262 moves horizontally in the left-right direction of the vehicle VH via the rack 270 meshing therewith, thereby changing the steering angle of the front wheel FW. In addition, the steering mechanism 260 is not limited to the rack and pinion, and may also be a mechanism using a ball screw, for example.

[0031] The steering device 200 converts the rotational motion of the electric motor 220 into the linear motion of the steering rod 262 via the speed reducer 264 , the pinion shaft 266 , the pinion 268 , and the rack 270 , and steers the front wheel FW to the left and right via the steering knuckle connected to the front end of the steering rod 262 .

[0032] The reaction force device 400 includes a steering shaft 420 that rotates integrally with the steering wheel SW, an electric motor 440 that generates reaction force torque, a reaction force control device 460 that drives and controls the electric motor 440, and a steering angle sensor 480 that detects a steering angle that is an operation angle of the steering wheel SW. Here, the electric motor 440 is a three-phase brushless motor similar to the electric motor 220 of the steering device 200, and includes a rotation angle sensor 442 that detects a rotation angle of an output shaft. Similar to the steering control device 240 of the steering device 200, the reaction force control device 460 includes an MCU having a built-in processor, a nonvolatile memory, a volatile memory, an input / output circuit, a communication circuit, etc., and drives and controls the electric motor 440 in accordance with an application program stored in the nonvolatile memory.

[0033] The steering control device 240 of the steering device 200 compares the actual steering angle of the front wheel FW detected by the steering angle sensor 280 with the steering angle of the steering wheel SW detected by the steering angle sensor 480 of the reaction force device 400, and drives and controls the electric motor 220 of the steering device 200. In addition, the reaction force control device 460 of the reaction force device 400 obtains a target reaction force torque based on the steering angle of the steering wheel SW detected by the steering angle sensor 480, the vehicle speed, etc., and drives and controls the electric motor 440 based on the target reaction force torque.

[0034] Figure 2 An example of a control system of the electric power steering system 100 is shown.

[0035] In this embodiment, in order to consider the possibility of application to level 5 autonomous driving and prevent sudden loss of assistance caused by a failure, the electric motor 220 of the steering device 200 and the electric motor 440 of the reaction force device 400 become a dual redundant structure, and these control systems become a dual or triple redundant structure.

[0036] The electric motor 220 of the steering device 200 includes a first motor 224 having a winding composed of a U-phase coil, a V-phase coil, and a W-phase coil, and a second motor 226 having a winding composed of a U-phase coil, a V-phase coil, and a W-phase coil, which are housed in the same housing. In the steering device 200, the first motor 224 and the second motor 226 operate in parallel to steer the front wheels FW of the vehicle VH to the left and right.

[0037] The steering control device 240 includes a first control device 242 capable of driving and controlling the first motor 224, a second control device 244 capable of driving and controlling the second motor 226, and a third control device 246 capable of selectively driving and controlling the first motor 224 or the second motor 226. Therefore, the first control device 242 is connected to the first motor 224, the second control device 244 is connected to the second motor 226, and the third control device 246 is connected to the first motor 224 and the second motor 226, respectively. Here, the third control device 246 provides a backup function of driving and controlling the first motor 224 or the second motor 226 in place of the first control device 242 or the second control device 244 when any one of them fails. In addition, the first control device 242 and the second control device 244 are listed as an example of the first drive system, and the third control device 246 is listed as an example of the second drive system.

[0038] The first control device 242 includes an MCU 242A, a drive circuit 242B, and a motor relay 242C composed of a semiconductor switch element. The second control device 244 includes an MCU 244A, a drive circuit 244B, and a motor relay 244C composed of a semiconductor switch element. The third control device 246 includes an MCU 246A, a drive circuit 246B, and a first motor relay 246C and a second motor relay 246D composed of semiconductor switch elements. Here, it is also possible that among the MCU 242A of the first control device 242, the MCU 244A of the second control device 244, and the MCU 246A of the third control device 246, at least MCU 242A and 244A are multi-core processors. In the case where a dual-core processor is used as the multi-core processor, even if the first processor core as the main system fails, the drive control of the electric motor 220 can be continued by the second processor core as the backup system. In addition, MCU242A, 244A and 246A are electronic control devices with built-in processors, non-volatile memories, volatile memories, input / output circuits and communication circuits, and can also be called microcomputers, microcontrollers, control units, controllers, etc. In addition, MCU242A of the first control device 242 and MCU244A of the second control device 244 are listed as an example of a first microcontroller unit, and MCU246A of the third control device 246 is listed as an example of a second microcontroller unit.

[0039] The MCU242A of the first control device 242 outputs a control signal for controlling the AC current supplied to the first motor 224 to the drive circuit 242B. The drive circuit 242B of the first control device 242 includes a pre-driver and an inverter, and supplies the AC current to the first motor 224 via the motor relay 242C. Here, the inverter is a bridge circuit formed by appropriately combining a plurality of semiconductor switching elements, and each semiconductor switching element operates in response to an output signal of the pre-driver, and converts a DC current supplied from a DC power source such as a battery not shown in the figure into an AC current (the same applies below). The motor relay 242C of the first control device 242 is controlled by the MCU242A to be turned on and off, and selectively switches the connection and disconnection between the drive circuit 242B and the first motor 224.

[0040] The MCU 244A of the second control device 244 outputs a control signal for controlling the AC current supplied to the second motor 226 to the drive circuit 244B. The drive circuit 244B of the second control device 244 includes a pre-driver and an inverter, and supplies the AC current to the second motor 226 via the motor relay 244C. The motor relay 244C of the second control device 244 is controlled by the MCU 244A to be turned on and off, and selectively switches the connection and disconnection between the drive circuit 244B and the second motor 226.

[0041] The MCU246A of the third control device 246 outputs a control signal for controlling the AC current supplied to either the first motor 224 or the second motor 226 to the drive circuit 246B. The drive circuit 246B of the third control device 246 includes a pre-driver and an inverter, and supplies the AC current to the first motor 224 via the first motor relay 246C, or supplies the AC current to the second motor 226 via the second motor relay 246D. The first motor relay 246C of the third control device 246 is controlled by the MCU246A to be turned on and off, and selectively switches the connection and disconnection between the drive circuit 246B and the first motor 224. The second motor relay 246D of the third control device 246 is controlled by the MCU246A to be turned on and off, and selectively switches the connection and disconnection between the drive circuit 246B and the second motor 226.

[0042] When started by power-on, MCU242A of the first control device 242, MCU244A of the second control device 244, and MCU246A of the third control device 246 perform fault diagnosis of the drive circuits 242B, 244B, and 246B, and the motor relays 242C, 244C, 246C, and 246D.

[0043] Furthermore, if the drive circuit 242B of the first control device 242 fails, the MCU 242A of the first control device 242 turns off the motor relay 242C to disconnect the drive circuit 242B and the first motor 224, and notifies the third control device 246 of the occurrence of the failure. The MCU 246A of the third control device 246, which has been notified of the occurrence of the failure by the first control device 242, turns on the first motor relay 246C to connect the drive circuit 246B and the first motor 224. Therefore, if the first control device 242 fails, the third control device 246 can supply an AC current to the first motor 224 to perform drive control instead of the first control device 242.

[0044] If the drive circuit 244B of the second control device 244 fails, the MCU 244A of the second control device 244 turns off the motor relay 244C to disconnect the drive circuit 244B and the second motor 226, and notifies the third control device 246 of the occurrence of the failure. The MCU 246A of the third control device 246, which has been notified of the occurrence of the failure by the second control device 244, turns on the second motor relay 246D to connect the drive circuit 246B and the second motor 226. Therefore, if the second control device 244 fails, the third control device 246 can supply an AC current to the second motor 226 to perform drive control instead of the second control device 244.

[0045] If the drive circuit 246B of the third control device 246 fails, the MCU 246A of the third control device 246 disconnects the first motor relay 246C and the second motor relay 246D, respectively, disconnects the drive circuit 246B from the first motor 224 and the second motor 226, and notifies the first control device 242 and the second control device 244 of the failure. Therefore, the MCU 242A of the first control device 242 and the MCU 244A of the second control device 244 can recognize that the third control device 246 has failed.

[0046] Thus, in the steering device 200, even if any one of the first control device 242, the second control device 244, and the third control device 246 fails, the first motor 224 and the second motor 226 can be driven and controlled, and the steering of the front wheels FW by the steering device 200 can be continued. In addition, even if the first control device 242 or the second control device 244 fails, the third control device 246 can drive and control the first motor 224 or the second motor 226, and the steering of the front wheels FW by the steering device 200 can be continued. Therefore, in the steering device 200, for example, a sudden loss of assistance can be prevented.

[0047] The electric motor 440 of the reaction force device 400 includes a first motor 444 having a winding composed of a U-phase coil, a V-phase coil, and a W-phase coil, and a second motor 446 having a winding composed of a U-phase coil, a V-phase coil, and a W-phase coil, which are housed in the same housing. The first motor 444 and the second motor 446 of the reaction force device 400 operate in parallel to impart a reaction torque to the steering wheel SW of the vehicle VH.

[0048] The reaction force control device 460 includes a first control device 462 capable of driving and controlling the first motor 444 and a second control device 464 capable of driving and controlling the second motor 446. Therefore, the first control device 462 is connected to the first motor 444, and the second control device 464 is connected to the second motor 446.

[0049] The first control device 462 includes an MCU 462A, a drive circuit 462B, and a motor relay 462C formed of a semiconductor switch element. The second control device 464 includes an MCU 464A, a drive circuit 464B, and a motor relay 464C formed of a semiconductor switch element.

[0050] The MCU 462A of the first control device 462 outputs a control signal for controlling the AC current supplied to the first motor 444 to the drive circuit 462B. The drive circuit 462B of the first control device 462 includes a pre-driver and an inverter, and supplies the AC current to the first motor 444 via the motor relay 462C. The motor relay 462C of the first control device 462 is controlled by the MCU 462A to be turned on and off, and selectively switches the connection and disconnection between the drive circuit 462B and the first motor 444.

[0051] The MCU464A of the second control device 464 outputs a control signal for controlling the AC current supplied to the second motor 446 to the drive circuit 464B. The drive circuit 464B of the second control device 464 includes a pre-driver and an inverter, and supplies the AC current to the second motor 446 via the motor relay 464C. The motor relay 464C of the second control device 464 is controlled by the MCU464A to be turned on and off, and selectively switches the connection and disconnection between the drive circuit 464B and the second motor 446.

[0052] In addition, similar to the steering control device 240, the reaction force device 400 may include a third control device in addition to the first control device 462 and the second control device 464. Furthermore, the third control device may be configured to control the supply of AC current to the first motor 444 when a failure occurs in the first control device 462, and to control the supply of AC current to the second motor 446 when a failure occurs in the second control device 464.

[0053] Here, the details of the steering control device 240 for driving and controlling the electric motor 220 of the steering device 200 are described. The first control device 242 and the second control device 244 have the same structure, and the structure of the third control device 246 is the same as the first control device 242 and the second control device 244 except that two motor relays are provided, so only the first control device 242 is described. Therefore, it is assumed that the second control device 244 and the third control device 246 are described by describing the first control device 242. In addition, the same reference numerals as the structural elements of the first control device 242 are marked for the structural elements of the second control device 244 and the third control device 246. In addition, the reaction force control device 460 of the reaction force device 400 for driving and controlling the electric motor 440 is the same as the steering control device 240 of the steering device 200, so its detailed description is omitted.

[0054] Figure 3 An example of the internal structure of the first motor 224 and the first control device 242 of the electric motor 220 is shown.

[0055] The first motor 224 includes a stator 224S having a substantially cylindrical shape in which a U-phase coil 224U, a V-phase coil 224V, and a W-phase coil 224W are connected in a star shape and wound, and a rotor 224R rotatably arranged on the inner circumference of the stator 224S. A rotary drive shaft (not shown) of the rotor 224R protrudes outward from an axial end of the stator 224S, and an input shaft of the speed reducer 264 of the steering device 200 is connected to the protruding portion.

[0056] The first control device 242 includes, in addition to the above-mentioned MCU 242A, drive circuit 242B, and motor relay 242C, a power relay 242D that selectively connects and disconnects the positive terminal PT of a DC power source such as a battery and the drive circuit 242B. The drive circuit 242B has a pre-driver 242B1 and an inverter 242B2. The inverter 242B2 is a three-phase bridge circuit formed by appropriately connecting semiconductor switch elements SW1 to SW6 such as P-channel MOSFET (Metal Oxide Semiconductor Field Effect Transistor: Metal Oxide Semiconductor Field Effect Transistor) with a parasitic diode (return diode). Here, the semiconductor switch elements SW1 to SW6 are not limited to P-channel MOSFETs, but may also be N-channel MOSFETs, IGPTs (Insulated Gate Bipolar Transistors: Insulated Gate Bipolar Transistors), etc. (the same applies below). In addition, the inverter 242B2 of the first control device 242 is listed as an example of the first inverter.

[0057] Specifically, inverter 242B2 includes a U-phase arm including semiconductor switching elements SW1 and SW2 connected in series, a V-phase arm including semiconductor switching elements SW3 and SW4 connected in series, and a W-phase arm including semiconductor switching elements SW5 and SW6 connected in series.

[0058] In the U-phase arm, the source of the upper semiconductor switch element SW1 is connected to the positive terminal PT of the DC power supply via the power relay 242D, the drain of the upper semiconductor switch element SW1 is connected to the source of the lower semiconductor switch element SW2, and the drain of the lower semiconductor switch element SW2 is connected to the negative terminal MT of the DC power supply. In addition, the circuit between the upper semiconductor switch element SW1 and the lower semiconductor switch element SW2 is connected to the U-phase coil 224U of the first motor 224 via the U-phase drive line 242U.

[0059] In the V-phase arm, the source of the upper semiconductor switch element SW3 is connected to the positive terminal PT of the DC power supply via the power relay 242D, the drain of the upper semiconductor switch element SW3 is connected to the source of the lower semiconductor switch element SW4, and the drain of the lower semiconductor switch element SW4 is connected to the negative terminal MT of the DC power supply. In addition, the circuit between the upper semiconductor switch element SW3 and the lower semiconductor switch element SW4 is connected to the V-phase coil 224V of the first motor 224 via the V-phase drive line 242V.

[0060] In the W-phase arm, the source of the upper semiconductor switch element SW5 is connected to the positive terminal PT of the DC power supply via the power relay 242D, the drain of the upper semiconductor switch element SW5 is connected to the source of the lower semiconductor switch element SW6, and the drain of the lower semiconductor switch element SW6 is connected to the negative terminal MT of the DC power supply. In addition, the circuit between the upper semiconductor switch element SW5 and the lower semiconductor switch element SW6 is connected to the W-phase coil 224W of the first motor 224 via the W-phase drive line 242W.

[0061] A motor relay 242C is disposed in the middle of the U-phase drive line 242U, the V-phase drive line 242V, and the W-phase drive line 242W that connect the inverter 242B2 and the first motor 224, and selectively connects or disconnects them. Figure 3 As can be seen, the motor relay 242C includes a U-phase relay 242C1 that selectively connects or disconnects the U-phase drive line 242U, a V-phase relay 242C2 that selectively connects or disconnects the V-phase drive line 242V, and a W-phase relay 242C3 that selectively connects or disconnects the W-phase drive line 242W. The U-phase relay 242C1, the V-phase relay 242C2, and the W-phase relay 242C3 are composed of P-channel MOSFETs having parasitic diodes, and operate in the same state according to instructions from the MCU 242A.

[0062] In addition, a capacitor 242E having a predetermined capacitance is arranged in a branch path branched from the circuit connecting the inverter 242B2 and the power supply relay 242D and connected to the negative terminal MT of the DC power supply. The capacitor 242E is charged during the operation of the power supply relay 242D, and is used to diagnose whether the inverter 242B2 and the motor relay 242C have an open circuit (open) (disconnection) fault when the first control device 242 is started, as described in detail later.

[0063] Moreover, if Figure 4As shown, the first control device 242, the second control device 244, and the third control device 246 thus configured are connected to the electric motor 220 to control the driving thereof. That is, the inverter 242B2 of the first control device 242 is connected to the U-phase coil 224U, the V-phase coil 224V, and the W-phase coil 224W of the first motor 224 of the electric motor 220 via the motor relay 242C. The inverter 244B2 of the second control device 244 is connected to the U-phase coil 226U, the V-phase coil 226V, and the W-phase coil 226W of the second motor 226 of the electric motor 220 via the motor relay 244C. In addition, the inverter 246B2 of the third control device 246 is connected to the U-phase drive line 242U, the V-phase drive line 242V, and the W-phase drive line 242W connecting the first control device 242 and the first motor 224 of the electric motor 220 via the first motor relay 246C. Furthermore, the inverter 246B2 of the third control device 246 is connected to the U-phase drive line 244U, the V-phase drive line 244V, and the W-phase drive line 244W connecting the second control device 244 and the second motor 226 of the electric motor 220 via the second motor relay 246D. In short, the third control device 246 is connected in such a manner that when any one of the first control device 242 or the second control device 244 fails, the drive control of the first motor 224 or the second motor 226 of the electric motor 220 continues. In addition, the inverter 244B2 of the second control device 244 is listed as an example of the first inverter, and the inverter 246B2 of the third control device 246 is listed as an example of the second inverter.

[0064] Here, a diagnostic method for the inverter 242B2 and the motor relay 242C executed when the first control device 242 is started by power-on is described. In addition, the diagnostic method for the first control device 242 is described below, but the second control device 244 and the third control device 246 can also diagnose the inverters 244B2 and 246B2, and the motor relays 244C, 246C, and 246D, respectively, based on the same principle.

[0065] When the first control device 242 is started, in order to prevent the current of the DC power supply from flowing downstream due to a short circuit failure of the inverter 242B2, the diagnosis is performed in a state where the power supply relay 242D is disconnected. At this time, since the terminal voltage of the first motor 224 is used as a diagnostic parameter, the motor relay 242C is operated and the inverter 242B2 is connected to the first motor 224. In addition, since the current is not supplied from the DC power supply, the charge accumulated in the capacitor 242E is used to diagnose the inverter 242B2.

[0066] First, MCU242A operates the semiconductor switch elements SW2, SW4, and SW6 of the lower stage of inverter 242B2 for a predetermined time via pre-driver 242B1. Then, MCU242A compares the terminal voltage V0 of capacitor 242E with the terminal voltage V1 of first motor 224 for U-phase arm, V-phase arm, and W-phase arm, respectively, and diagnoses whether the semiconductor switch elements SW1, SW3, and SW5 of the upper stage of inverter 242B2 have short-circuit faults.

[0067] If the semiconductor switch elements SW1, SW3, and SW5 of the upper section of the inverter 242B2 are normal, the current supplied from the capacitor 242E flows through the parasitic diodes of the semiconductor switch elements SW1, SW3, and SW5 of the upper section. At this time, a voltage drop is generated by the parasitic diodes of the semiconductor switch elements SW1, SW3, and SW5 of the upper section. If the voltage drop is represented by Vf, the correlation relationship of V0-V1=2*Vf holds. Therefore, if V0-V1=2*Vf is achieved when the semiconductor switch elements SW2, SW4, and SW6 of the lower section of the inverter 242B2 are operated, the MCU242A can diagnose that the semiconductor switch elements SW1, SW3, and SW5 of the upper section are normal.

[0068] On the other hand, if the semiconductor switch elements SW1, SW3, and SW5 of the upper stage of the inverter 242B2 are short-circuited, the current supplied from the capacitor 242E flows through the semiconductor switch elements SW1, SW3, and SW5 of the upper stage, and becomes V0-V1 = Vf. Therefore, if V0-V1 = Vf when the semiconductor switch elements SW2, SW4, and SW6 of the lower stage of the inverter 242B2 are operated, the MCU 242A can diagnose that the semiconductor switch elements SW1, SW3, and SW5 of the upper stage are short-circuited.

[0069] Next, MCU242A operates the semiconductor switch elements SW1, SW3, and SW5 of the upper stage of the inverter 242B2 for a predetermined time via the pre-driver 242B1. Then, MCU242A compares the terminal voltage V0 of the capacitor 242E with the terminal voltage V1 of the first motor 224 for the U-phase arm, the V-phase arm, and the W-phase arm, respectively, and diagnoses whether the semiconductor switch elements SW2, SW4, and SW6 of the lower stage of the inverter 242B2 have a short-circuit fault.

[0070] If the semiconductor switch elements SW2, SW4, and SW6 of the lower stage of the inverter 242B2 are normal, the current supplied from the capacitor 242E flows through the parasitic diode of the motor relay 242C. If the voltage drop equivalent to this is expressed as Vf, the correlation relationship of V0-V1=Vf holds. Therefore, if V0-V1=Vf, that is, V1=V0-Vf, is achieved when the semiconductor switch elements SW1, SW3, and SW5 of the upper stage of the inverter 242B2 are operated, the MCU 242A can diagnose that the semiconductor switch elements SW2, SW4, and SW6 of the lower stage are normal.

[0071] On the other hand, if a short-circuit fault occurs in the semiconductor switch elements SW2, SW4, and SW6 of the lower stage of the inverter 242B2, the current supplied from the capacitor 242E flows through the semiconductor switch elements SW2, SW4, and SW6 of the lower stage, and V0 = 0. Therefore, if V0-V1 = Vf, that is, V1 = -Vf, when the semiconductor switch elements SW1, SW3, and SW5 of the upper stage of the inverter 242B2 are operated, the MCU 242A can diagnose that the semiconductor switch elements SW2, SW4, and SW6 of the lower stage have a short-circuit fault.

[0072] In addition, if an open-circuit fault occurs in the semiconductor switch elements SW1, SW3, and SW5 of the upper stage of the inverter 242B2, V1=0, so MCU242A can diagnose that an open-circuit fault occurs in the semiconductor switch elements SW1, SW3, and SW5 of the upper stage. Further, if an open-circuit fault occurs in the motor relay 242C when the semiconductor switch elements SW1, SW3, and SW5 of the upper stage of the inverter 242B2 are operated, V1=0, so MCU242A can also diagnose whether an open-circuit fault occurs in the motor relay 242C at the same time.

[0073] Therefore, by executing the application program that realizes the above principle, MCU242A can diagnose whether the semiconductor switch elements SW1 to SW6 of inverter 242B2 and U-phase relay 242C1, V-phase relay 242C2 and W-phase relay 242C3 of motor relay 242C have open circuit faults or short circuit faults. In addition, MCU242A can first operate the semiconductor switch elements SW1, SW3 and SW5 of the upper stage of inverter 242B2 to perform fault diagnosis, and then operate the semiconductor switch elements SW2, SW4 and SW6 of the lower stage of inverter 242B2 to perform fault diagnosis.

[0074] However, if the inverter and motor relay faults are diagnosed simultaneously in the first control device 242 and the third control device 246, or the second control device 244 and the third control device 246, the following undesirable situation may occur. In the following description, it is assumed that an open circuit fault occurs in any of the semiconductor switch elements SW1, SW3, and SW5 of the upper stage of the inverter 242B2 of the first control device 242, on the premise that the inverter fault diagnosis of the first control device 242 and the third control device 246 is performed.

[0075] In the first control device 242 and the third control device 246, if the semiconductor switch elements SW1, SW3, and SW5 of the upper stage are turned on at the same time, an open circuit failure occurs in the semiconductor switch elements SW1, SW3, and SW5 of the upper stage in the first control device 242, so the current supplied from the capacitor 242E does not flow. Therefore, in the first control device 242, the terminal voltage V1 of the first motor 224 of the electric motor 220 becomes 0. However, in the third control device 246, the inverter 246B2 does not fail, so the current flows through the parasitic diodes of the semiconductor switch elements SW2, SW4, and SW6 of the lower stage and the semiconductor switch elements SW1, SW3, and SW5 of the upper stage, and the terminal voltage of the first motor 224 of the electric motor 220 becomes Vf. Therefore, in the fault diagnosis of the first control device 242, due to the third control device 246, the terminal voltage of the first motor 224 of the electric motor 220 becomes Vf, and the correlation relationship of V0-V1=Vf is established, and it is erroneously diagnosed as normal.

[0076] Therefore, in the present embodiment, the fault diagnosis of one of the first control device 242 and the third control device 246 is performed when the semiconductor switch elements SW1 to SW6 of the inverter 242B2 and 246B2 of the other of them are not energized. In short, for the MCU242A of the first control device 242, the fault diagnosis is performed when the semiconductor switch elements SW1 to SW6 of the inverter 246B2 are not energized in the third control device 246. On the other hand, for the MCU246A of the third control device 246, the fault diagnosis is performed when the semiconductor switch elements SW1 to SW6 of the inverter 242B2 are not energized in the first control device 242. The control to realize such a feature is described in detail below. In addition, the first control device 242 and the third control device 246 that drive and control the first motor 224 of the electric motor 220 are described below, but the processing can of course also be applied to the second control device 244 and the third control device 246 that drive and control the second motor 226 of the electric motor 220.

[0077] 《First Implementation Mode》

[0078] Figure 5 An example of the first diagnostic process executed by the MCU 242A of the first control device 242 when the first control device 242 is activated is shown. The first diagnostic process is executed in accordance with the application program stored in the nonvolatile memory of the MCU 242A (the same applies hereinafter).

[0079] In step 10 ( Figure 5 In the process (hereinafter referred to as "S10"), MCU 242A reads, for example, the voltage V0 between the terminals of capacitor 242E from a voltage sensor.

[0080] In step 11, MCU242A determines whether the voltage V0 between the terminals of capacitor 242E is normal, that is, whether the diagnosis of inverter 242B2 and motor relay 242C can be performed by the charge accumulated in capacitor 242E. Then, if MCU242A determines that the voltage V0 between the terminals is normal (Yes), the process proceeds to step 12. On the other hand, if MCU242A determines that the voltage V0 between the terminals is abnormal, that is, the diagnosis of inverter 242B2 and motor relay 242C cannot be performed by the charge accumulated in capacitor 242E (No), the process proceeds to step 21.

[0081] In step 12, MCU242A operates the semiconductor switch elements SW2, SW4 and SW6 of the lower stage of inverter 242B2 via pre-driver 242B1 for a predetermined time, and performs "diagnosis A" for diagnosing whether the semiconductor switch elements SW1, SW3 and SW5 of the upper stage have a short-circuit fault. In addition, since the details of the diagnostic processing have been explained, the details will not be further explained below. If necessary, please refer to the previous description.

[0082] In step 13, MCU242A transmits (notifies) the diagnosis result of diagnosis A to MCU246A of third control device 246. Therefore, MCU246A of third control device 246 receiving the diagnosis result of diagnosis A from first control device 242 can recognize that diagnosis A in first control device 242 is completed.

[0083] In step 14, MCU242A determines whether the diagnosis result of diagnosis A is received from the third control device 246. In short, it determines whether diagnosis A is completed in the third control device 246. Then, if MCU242A determines that the diagnosis result of diagnosis A is received (Yes), the process proceeds to step 15. On the other hand, if MCU242A determines that the diagnosis result of diagnosis A is not received (No), the determination process of step 14 is repeatedly performed again. In short, in step 14, MCU242A waits until diagnosis A is completed in the third control device 246.

[0084] In step 15, MCU242A operates the semiconductor switch elements SW1, SW3, and SW5 of the upper stage of inverter 242B2 via pre-driver 242B1 for a predetermined time, and performs "diagnosis B" for diagnosing whether the semiconductor switch elements SW2, SW4, and SW6 of the lower stage and the motor relay 242C have short-circuit faults, and whether the semiconductor switch elements SW2, SW4, and SW6 of the lower stage have open-circuit faults. In addition, since the details of the diagnostic processing have been explained, the details will not be further explained below. If necessary, please refer to the previous explanation.

[0085] In step 16, MCU242A transmits the diagnosis result of diagnosis B to MCU246A of third control device 246. Therefore, MCU246A of third control device 246 receiving the diagnosis result of diagnosis B from first control device 242 can recognize that diagnosis B in first control device 242 is completed.

[0086] In step 17, MCU242A determines whether the diagnosis result of diagnosis B is received from the third control device 246. In short, it determines whether diagnosis B is completed in the third control device 246. Then, if MCU242A determines that the diagnosis result of diagnosis B is received (Yes), the process proceeds to step 18. On the other hand, if MCU242A determines that the diagnosis result of diagnosis B is not received (No), the determination process of step 17 is repeatedly performed again. In short, in step 17, MCU242A waits until diagnosis B is completed in the third control device 246.

[0087] In step 18, MCU242A determines whether at least one of the inverter 242B2 and the motor relay 242C of the first control device 242 is faulty based on the diagnosis results of diagnosis A and diagnosis B in the first control device 242. Then, if MCU242A determines that at least one of the inverter 242B2 and the motor relay 242C is faulty (Yes), the process proceeds to step 19. On the other hand, if MCU242A determines that neither the inverter 242B2 nor the motor relay 242C is faulty (No), the process proceeds to step 21.

[0088] In step 19, since a fault has occurred in the first control device 242, the MCU 242A disconnects the motor relay 242C in preparation for handing over the drive control of the first motor 224 to the third control device 246. Therefore, in the first control device 242, the drive circuit 242B is disconnected from the first motor 224, and the first control device 242 can no longer drive and control the first motor 224.

[0089] In step 20, the first control device 242 no longer needs to drive and control the first motor 224, so in order to suppress the consumption of the DC power supply, the MCU242A transfers the operation mode to the low power mode. Here, in the low power mode, it is considered that only the wake-up function that is activated in response to the start signal from the outside is operated (the same below). In addition, instead of transferring the operation mode to the low power mode, the MCU242A can also stop the first control device 242 (the same below).

[0090] In step 21, since the voltage V0 between the terminals of the capacitor 242E is abnormal and the diagnosis cannot be performed, or no failure occurs in the first control device 242, the MCU 242A transfers to the normal control for driving and controlling the first motor 224 of the electric motor 220. In addition, the normal control also includes the failsafe treatment assumed in the first control device 242 (the same applies below).

[0091] Figure 6 An example of the first diagnostic process executed by MCU246A of the third control device 246 when the third control device 246 is activated is shown. In addition, the first diagnostic process is executed in accordance with the application program stored in the non-volatile memory of MCU246A. In addition, for the same process as the first diagnostic process in the first control device 242, its description is simplified for the purpose of avoiding repeated description (the same below). Please refer to the previous description if necessary.

[0092] In step 30 , MCU 246A reads the inter-terminal voltage V0 of capacitor 246E.

[0093] In step 31, MCU246A determines whether the inter-terminal voltage V0 of capacitor 246E is normal. Then, if MCU246A determines that the inter-terminal voltage V0 is normal (Yes), the process proceeds to step 32. On the other hand, if MCU246A determines that the inter-terminal voltage V0 is not normal (No), the process proceeds to step 41.

[0094] In step 32, MCU246A determines whether the diagnosis result of diagnosis A is received from the first control device 242, in short, whether diagnosis A is completed in the first control device 242. Then, if MCU246A determines that the diagnosis result of diagnosis A is received (Yes), the process proceeds to step 33. On the other hand, if MCU246A determines that the diagnosis result of diagnosis A is not received (No), the determination process of step 32 is repeatedly performed again. In short, in step 32, MCU246A waits until diagnosis A is completed in the first control device 242.

[0095] In step 33 , MCU 246A performs diagnosis A.

[0096] In step 34, MCU246A transmits the diagnosis result of diagnosis A to MCU242A of first control device 242. Therefore, MCU242A of first control device 242 receiving the diagnosis result of diagnosis A from third control device 246 can recognize that diagnosis A in third control device 246 is completed.

[0097] In step 35, MCU246A determines whether the diagnosis result of diagnosis B is received from the first control device 242, in short, whether diagnosis B is completed in the first control device 242. Then, if MCU246A determines that the diagnosis result of diagnosis B is received (Yes), the process proceeds to step 36. On the other hand, if MCU246A determines that the diagnosis result of diagnosis B is not received (No), the determination process of step 35 is repeatedly executed again. In short, in step 35, MCU246A waits until diagnosis B is completed in the first control device 242.

[0098] In step 36 , MCU 246A performs diagnosis B.

[0099] In step 37, MCU246A transmits the diagnosis result of diagnosis B to MCU242A of first control device 242. Therefore, MCU242A of first control device 242 receiving the diagnosis result of diagnosis B from third control device 246 can recognize that diagnosis B in third control device 246 is completed.

[0100] In step 38, MCU246A determines whether at least one of the inverter 242B2 and the motor relay 242C of the first control device 242 is faulty based on the diagnosis results of diagnosis A and diagnosis B received from the first control device 242. Then, if MCU246A determines that a fault has occurred in the first control device 242 (Yes), the process proceeds to step 39. On the other hand, if MCU246A determines that no fault has occurred in the first control device 242 (No), the process proceeds to step 41.

[0101] In step 39, since a failure occurs in the first control device 242, the MCU 246A turns on the first motor relay 246C in order to take over the drive control of the first motor 224 of the electric motor 220 from the first control device 242. Therefore, by turning on the first motor relay 246C, the drive circuit 246B of the third control device 246 is connected to the first motor 224, and the third control device 246 can drive and control the first motor 224.

[0102] In step 40, MCU 246A starts driving control of first motor 224 of electric motor 220. In short, since first control device 242 fails to drive first motor 224, third control device 246 takes over driving control of first motor 224 for backup.

[0103] In step 41, since the voltage V0 between the terminals of the capacitor 242E is abnormal and the diagnosis cannot be performed, or there is no failure in the first control device 242, the MCU 246A shifts the operation mode to the low power mode in order to suppress the consumption of the DC power supply. In addition, the MCU 246A may stop the third control device 246 instead of shifting the operation mode to the low power mode (the same applies below).

[0104] like Figure 7 As shown, according to the first diagnostic processing, after the start signal is turned on and the diagnosis of hardware and the like is completed, before the fault diagnosis is performed by MCU246A of the third control device 246, MCU242A of the first control device 242 performs diagnosis A and B. That is, if the start signal is turned on and the diagnosis of hardware and the like is completed, diagnosis A is first performed in the first control device 242. While diagnosis A is being performed in the first control device 242, the third control device 246 is on standby. Then, if diagnosis A is completed in the first control device 242, diagnosis A is performed in the third control device 246. While diagnosis A is being performed in the third control device 246, the first control device 242 is on standby.

[0105] If the diagnosis A is completed in the third control device 246, the diagnosis B is executed in the first control device 242. During the execution of the diagnosis B in the first control device 242, the third control device 246 is on standby. Then, if the diagnosis B is completed in the first control device 242, the diagnosis B is executed in the third control device 246. During the execution of the diagnosis B in the third control device 246, the first control device 242 is on standby. Afterwards, when the diagnosis B in the third control device 246 is completed, if the first control device 242 has not failed, the first control device 242 is transferred to the normal control of driving the first motor 224, and the third control device 246 is transferred to the low power mode. On the other hand, if a failure occurs in the first control device 242, the first control device 242 is disconnected from the first motor 224, and the third control device 246 is connected to the first motor 224, and the third control device 246 takes over the driving control of the first motor 224.

[0106] In the first control device 242 and the third control device 246, as shown in FIG. Figure 7 It can be easily understood that diagnosis A and diagnosis B are not performed at the same time. Therefore, in the first control device 242 and the third control device 246, the semiconductor switch elements SW1 to SW6 of the inverters 242B2 and 246B2 do not operate at the same time. Therefore, the AC current is not supplied from the first control device 242 and the third control device 246 to the first motor 224 at the same time, and it is possible to avoid misdiagnosis of whether the inverters 242B2 and 246B2 and the motor relays 242C, 246C and 246D are faulty.

[0107] Second Implementation Method

[0108] Figure 8 An example of the second diagnostic process executed by the MCU 242A of the first control device 242 when the first control device 242 is activated is shown.

[0109] In step 50 , MCU 242A reads the inter-terminal voltage V0 of capacitor 242E.

[0110] In step 51, MCU242A determines whether the inter-terminal voltage V0 of capacitor 242E is normal. Then, if MCU242A determines that the inter-terminal voltage V0 is normal (Yes), the process proceeds to step 52. On the other hand, if MCU242A determines that the inter-terminal voltage V0 is not normal (No), the process proceeds to step 58.

[0111] In step 52, MCU242A determines whether the diagnosis results of diagnosis A and B are received from the third control device 246. Then, if MCU242A determines that the diagnosis results of diagnosis A and B are received (Yes), the process proceeds to step 53. On the other hand, if MCU242A determines that the diagnosis results of diagnosis A and B are not received (No), the determination process of step 52 is executed again. In short, in step 52, MCU242A waits until the diagnosis result is received from the third control device 246.

[0112] In step 53 , MCU 242A executes diagnosis A and B successively.

[0113] In step 54, MCU242A transmits the diagnosis results of diagnosis A and B to MCU246A of third control device 246. Therefore, MCU246A of third control device 246, which receives the diagnosis results, can recognize that diagnosis A and B in first control device 242 are completed.

[0114] In step 55, MCU242A determines whether at least one of the inverter 242B2 and the motor relay 242C of the first control device 242 is faulty based on the diagnostic results of the diagnoses A and B in the first control device 242. Then, if MCU242A determines that the first control device 242 is faulty (Yes), the process proceeds to step 56. On the other hand, if MCU242A determines that the first control device 242 is not faulty (No), the process proceeds to step 58.

[0115] In step 56 , since a failure has occurred in the first control device 242 , the MCU 242A turns off the motor relay 242C in preparation for handing over the drive control of the first motor 224 to the third control device 246 .

[0116] In step 57 , since the first control device 242 cannot drive and control the first motor 224 , the MCU 242A shifts the operation mode to the low power mode in order to suppress consumption of the DC power supply.

[0117] In step 58 , since the charge of the capacitor 242E cannot be used to perform the diagnoses A and B, or the first control device 242 is normal, the MCU 242A shifts to normal control for driving and controlling the first motor 224 .

[0118] Fig. 9 An example of the second diagnostic process executed by MCU 246A of third control device 246 when third control device 246 is activated is shown.

[0119] In step 60 , MCU 246A reads the inter-terminal voltage V0 of capacitor 246E.

[0120] In step 61, MCU246A determines whether the inter-terminal voltage V0 of capacitor 246E is normal. Then, if MCU246A determines that the inter-terminal voltage V0 is normal (Yes), the process proceeds to step 62. On the other hand, if MCU246A determines that the inter-terminal voltage V0 is not normal (No), the process proceeds to step 68.

[0121] In step 62 , MCU 246A executes diagnosis A and B successively.

[0122] In step 63, MCU246A transmits the diagnosis results of diagnosis A and B to MCU242A of first control device 242. Therefore, MCU242A of first control device 242, which receives the diagnosis results of third control device 246, can recognize that diagnosis A and B in third control device 246 are completed.

[0123] In step 64, MCU246A determines whether the diagnosis results of diagnosis A and B are received from the first control device 242. Then, if MCU246A determines that the diagnosis results are received from the first control device 242 (Yes), the process proceeds to step 65. On the other hand, if MCU246A determines that the diagnosis results are not received from the first control device 242 (No), the determination process of step 64 is executed again. In short, in step 64, MCU246A waits until the diagnosis A and B in the first control device 242 are completed.

[0124] In step 65, MCU246A determines whether at least one of the inverter 242B2 and the motor relay 242C of the first control device 242 is faulty based on the diagnosis results of the diagnosis A and B received from the first control device 242. Then, if MCU246A determines that the first control device 242 is faulty (Yes), the process proceeds to step 66. On the other hand, if MCU246A determines that the first control device 242 is not faulty (No), the process proceeds to step 68.

[0125] In step 66 , since a failure has occurred in the first control device 242 , the MCU 246A turns on the first motor relay 246C in order to take over the drive control of the first motor 224 of the electric motor 220 from the first control device 242 .

[0126] In step 67 , the MCU 246A starts driving control of the first motor 224 of the electric motor 220 .

[0127] In step 68 , since diagnoses A and B cannot be executed by the charge accumulated in capacitor 246E or first control device 242 has not failed, MCU 246A shifts the operation mode to the low power mode in order to suppress consumption of the DC power supply.

[0128] According to the second diagnosis process, unlike the first diagnosis process, Fig.10 As shown, before the fault diagnosis of the inverter 242B2 is performed by the MCU242A of the first control device 242, the MCU246A of the third control device 246 continuously executes the diagnosis A and B. That is, in the second diagnostic process, unlike the first diagnostic process, first, the diagnosis A and B in the third control device 246 are continuously executed, during which the first control device 242 is on standby. Then, if the diagnosis A and B in the third control device 246 are completed, the diagnosis A and B in the first control device 242 are continuously executed, during which the third control device 246 is on standby. Therefore, the number of messages sent and received between the first control device 242 and the third control device 246 is reduced, and the execution time can be shortened accordingly.

[0129] In the first control device 242 and the third control device 246, as shown in FIG. Fig.10 It is easy to understand that diagnosis A and diagnosis B are not performed at the same time. Therefore, in the first control device 242 and the third control device 246, the semiconductor switch elements SW1 to SW6 of the inverters 242B2 and 246B2 do not operate at the same time. Therefore, the AC current is not supplied from the first control device 242 and the third control device 246 to the first motor 224 at the same time, and it is possible to avoid misdiagnosis of whether the inverters 242B2 and 246B2, and the motor relays 242C, 246C, and 246D are faulty. In addition, other functions and effects are the same as those of the first embodiment, so their description is omitted to avoid repeated description. If necessary, please refer to the description of the first embodiment.

[0130] 《Third Implementation Mode》

[0131] Fig.11 An example of the third diagnostic process executed by the MCU 242A of the first control device 242 when the first control device 242 is activated is shown.

[0132] In step 70 , MCU 242A reads the inter-terminal voltage V0 of capacitor 242E.

[0133] In step 71, MCU242A determines whether the inter-terminal voltage V0 of capacitor 242E is normal. Then, if MCU242A determines that the inter-terminal voltage V0 is normal (Yes), the process proceeds to step 72. On the other hand, if MCU242A determines that the inter-terminal voltage V0 is not normal (No), the process proceeds to step 79.

[0134] In step 72, MCU242A, for example, uses a timer function to determine whether a predetermined standby time has passed since the start of the third diagnostic process. Here, the predetermined standby time is the maximum time required to complete the diagnoses A and B in the third control device 246, and can be appropriately set, for example, in consideration of the processing capacity of the third control device 246, the ability to send and receive messages, etc. Then, if MCU242A determines that the predetermined standby time has passed (Yes), the process proceeds to step 74. On the other hand, if MCU242A determines that the predetermined standby time has not passed (No), the process proceeds to step 73.

[0135] In step 73, MCU242A determines whether the diagnosis results of diagnosis A and B are received from the third control device 246. Then, if MCU242A determines that the diagnosis result is received from the third control device 246 (Yes), the process proceeds to step 74. On the other hand, if MCU242A determines that the diagnosis result is not received from the third control device 246 (No), the process returns to step 72.

[0136] In step 74 , MCU 242A executes diagnosis A and B successively.

[0137] In step 75 , MCU 242A transmits the diagnosis results of diagnoses A and B to MCU 246A of the third control device 246 .

[0138] In step 76, MCU242A determines whether at least one of the inverter 242B2 and the motor relay 242C of the first control device 242 has a fault based on the diagnostic results of the diagnoses A and B in the first control device 242. Then, if MCU242A determines that a fault has occurred in the first control device 242 (Yes), the process proceeds to step 77. On the other hand, if MCU242A determines that no fault has occurred in the first control device 242 (No), the process proceeds to step 79.

[0139] In step 77 , since a failure has occurred in the first control device 242 , the MCU 242A turns off the motor relay 242C in preparation for handing over the drive control of the first motor 224 to the third control device 246 .

[0140] In step 78 , since the first control device 242 cannot drive and control the first motor 224 , the MCU 242A shifts the operation mode to the low power mode in order to suppress consumption of the DC power supply.

[0141] In step 79 , since the diagnoses A and B cannot be executed by the charge accumulated in the capacitor 242E or the first control device 242 is normal, the MCU 242A shifts to normal control for driving and controlling the first motor 224 of the electric motor 220 .

[0142] Fig.12 An example of the third diagnostic process executed by the MCU 246A of the third control device 246 when the third control device 246 is activated is shown.

[0143] In step 80 , MCU 246A reads the inter-terminal voltage V0 of capacitor 246E.

[0144] In step 81, MCU246A determines whether the inter-terminal voltage V0 of capacitor 246E is normal. Then, if MCU246A determines that the inter-terminal voltage V0 is normal (Yes), the process proceeds to step 82. On the other hand, if MCU246A determines that the inter-terminal voltage V0 is not normal (No), the process proceeds to step 89.

[0145] In step 82 , MCU 246A executes diagnosis A and B successively.

[0146] In step 83 , MCU 246A transmits the diagnosis results of diagnoses A and B to MCU 242A of first control device 242 .

[0147] In step 84, MCU246A, for example, uses a timer function to determine whether a predetermined standby time has passed since the start of the third diagnostic process. Here, the predetermined standby time is the maximum time required for the first control device 242 to complete the diagnosis A and B, and can be appropriately set, for example, in consideration of the processing capacity of the first control device 242, the ability to send and receive messages, etc. Then, if MCU246A determines that the predetermined standby time has passed (Yes), the process proceeds to step 86. On the other hand, if MCU242A determines that the predetermined standby time has not passed (No), the process proceeds to step 85.

[0148] In step 85, MCU246A determines whether the diagnosis results of diagnosis A and B are received from the first control device 242. Then, if MCU246A determines that the diagnosis results are received from the first control device 242 (Yes), the process proceeds to step 86. On the other hand, if MCU246A determines that the diagnosis results are not received from the first control device 242 (No), the process returns to step 84.

[0149] In step 86, MCU246A determines whether at least one of the inverter 242B2 and the motor relay 242C of the first control device 242 has a fault based on the diagnosis result received from the first control device 242. Then, if MCU246A determines that the first control device 242 has a fault (Yes), the process proceeds to step 87. On the other hand, if MCU246A determines that the first control device 242 has not a fault (No), the process proceeds to step 89.

[0150] In step 87 , since the first control device 242 has failed, the MCU 246A turns on the first motor relay 246C in order to take over the drive control of the first motor 224 of the electric motor 220 from the first control device 242 .

[0151] In step 88 , the MCU 246A starts driving control of the first motor 224 .

[0152] In step 89 , since diagnoses A and B cannot be executed by the charge accumulated in capacitor 246E or first control device 242 is normal, MCU 246A shifts the operation mode to the low power mode in order to suppress consumption of the DC power supply.

[0153] According to the third diagnostic processing, in addition to the action and effect of the second diagnostic processing, the first control device 242 and the third control device 246 start their subsequent processing, such as inverter fault diagnosis, when the diagnostic result is not notified from the other party even after a prescribed standby time from the start. Therefore, even if the diagnostic result cannot be sent or received for some reason, the execution of diagnoses A and B, or the determination of whether the first control device 242 has a fault, etc. are performed. Therefore, even in a situation where the diagnostic result cannot be sent or received, the fault diagnosis of the inverter and the motor relay can be performed. In addition, other actions and effects are the same as those of the second diagnostic processing, so their description is omitted to avoid repeated description.

[0154] In addition, those skilled in the art can easily understand that new embodiments can be generated by omitting part of the technical ideas of the various above-mentioned embodiments, appropriately combining part of them, or replacing part of them with known technologies.

[0155] For example, the control object of the proposed technology is not limited to the steering device 200, but may be the reaction force device 400 or a known vehicle-mounted system. In addition, the electric motor 220 is not limited to a three-phase brushless motor, but may be an electric motor having any multi-phase winding.

[0156] Description of Reference Numerals

[0157] 220…electric motor; 224…first motor; 226…second motor; 242…first control device (first drive system); 242A…MCU (first micro control unit); 242B2…inverter (first inverter); 242C…motor relay (relay); 244…second control device (first drive system); 244A…MCU (first micro control unit); 244B2…inverter (first inverter); 244C…motor relay (relay); 246…third control device (second drive system); 246A…MCU (second micro control unit); 246B2…inverter (second inverter); 246C…first motor relay (relay); 246D…second motor relay (relay); SW1~SW6…semiconductor switching elements.

Claims

1. A control device for an electric motor, comprising: a first drive system, comprising: a first microcontroller unit and a first inverter composed of a plurality of semiconductor switch elements, wherein the first microcontroller unit controls the semiconductor switch elements of the first inverter to convert direct current into alternating current, drives and controls an electric motor having a multi-phase winding, and individually energizes the plurality of semiconductor switch elements of the first inverter to perform a fault diagnosis of the first inverter; and The second drive system is configured to include a second microcontroller unit and a second inverter composed of a plurality of semiconductor switch elements, wherein the second inverter is connected to a circuit connecting the first inverter and the electric motor, and when a fault occurs in the first drive system, the second microcontroller unit controls the semiconductor switch elements of the second inverter to convert a direct current into an alternating current to drive and control the electric motor, and individually energizes the plurality of semiconductor switch elements of the second inverter to perform fault diagnosis of the second inverter. The first micro control unit is configured to perform a fault diagnosis of the first inverter when the plurality of semiconductor switching elements of the second inverter are not energized in the second drive system. The second micro control unit is configured to perform a fault diagnosis of the second inverter when the plurality of semiconductor switching elements of the first inverter are not energized in the first drive system.

2. The control device for an electric motor according to claim 1, wherein: The first micro control unit is configured to perform a fault diagnosis of the first inverter before a fault diagnosis of the second inverter is performed by the second micro control unit.

3. The control device for an electric motor according to claim 2, wherein: The second micro control unit is configured to execute a fault diagnosis of the second inverter when a fault diagnosis result of the first inverter is notified from the first micro control unit.

4. The control device for an electric motor according to claim 3, wherein: The second micro control unit is configured to execute a fault diagnosis of the second inverter when no fault diagnosis result of the first inverter is notified from the first micro control unit even after a predetermined waiting time has elapsed since startup.

5. The control device for an electric motor according to claim 1, wherein: The second micro control unit is configured to perform a fault diagnosis of the second inverter before the fault diagnosis of the first inverter is performed by the first micro control unit.

6. The control device for the electric motor according to claim 5, wherein: The first micro control unit is configured to execute a fault diagnosis of the first inverter when a fault diagnosis result of the second inverter is notified from the second micro control unit.

7. The control device for an electric motor according to claim 6, wherein: The first micro control unit is configured to execute a fault diagnosis of the first inverter when no fault diagnosis result of the second inverter is notified from the second micro control unit even after a predetermined waiting time has elapsed since startup.

8. The control device for an electric motor according to claim 1, wherein: The first drive system further comprises: a relay including a semiconductor switching element for opening and closing a circuit connecting the first inverter and the electric motor, The first micro control unit is configured to simultaneously perform a fault diagnosis of the relay when performing a fault diagnosis of the first inverter by operating the semiconductor switching element at the upper stage of the first inverter for a predetermined time.

9. The control device for an electric motor according to claim 1, wherein: The second drive system further comprises: a relay composed of a semiconductor switching element for opening and closing a circuit connecting the second inverter and the electric motor, The second micro control unit is configured to simultaneously perform a fault diagnosis of the relay when performing a fault diagnosis of the second inverter by operating the semiconductor switching element at the upper stage of the second inverter for a predetermined time.

10. The control device for an electric motor according to claim 1, wherein: The first drive system further comprises: a power relay for opening and closing a circuit connecting the first inverter and a positive terminal of a DC power source; and A capacitor is arranged in a branch path branched from a circuit connecting the power relay and the positive terminal of the DC power supply and connected to the negative terminal of the DC power supply, The first micro control unit is configured to turn off the power supply relay and perform a fault diagnosis of the first inverter based on a voltage between terminals of the capacitor and a voltage between terminals of the electric motor.

11. The control device for an electric motor according to claim 1, wherein: The second drive system also has: a power relay that opens and closes a circuit connecting the second inverter and a positive terminal of a DC power source; and A capacitor is arranged in a branch path branched from a circuit connecting the power relay and the positive terminal of the DC power supply and connected to the negative terminal of the DC power supply, The second micro control unit is configured to turn off the power supply relay and perform a fault diagnosis of the second inverter based on a voltage between terminals of the capacitor and a voltage between terminals of the electric motor.

12. The control device for an electric motor according to claim 1, wherein: The second micro control unit is configured to shift the operation mode to the low power mode when the fault diagnosis result of the first inverter notified from the first micro control unit is normal.

13. The control device for an electric motor according to claim 1, wherein: The first micro control unit and the second micro control unit are configured to respectively perform fault diagnosis of the first inverter and the second inverter when the first drive system and the second drive system are started.

14. A method for controlling an electric motor, wherein a control device for the electric motor controls the electric motor, the control device for the electric motor comprising: a first drive system, comprising: a first microcontroller unit and a first inverter composed of a plurality of semiconductor switch elements, wherein the first microcontroller unit controls the semiconductor switch elements of the first inverter to convert direct current into alternating current, drives and controls an electric motor having a multi-phase winding, and individually energizes the plurality of semiconductor switch elements of the first inverter to perform a fault diagnosis of the first inverter; and The second drive system is configured to include a second microcontroller unit and a second inverter composed of a plurality of semiconductor switch elements, wherein the second inverter is connected to a circuit connecting the first inverter and the electric motor, and when a fault occurs in the first drive system, the second microcontroller unit controls the semiconductor switch elements of the second inverter to convert a direct current into an alternating current to drive and control the electric motor, and individually energizes the plurality of semiconductor switch elements of the second inverter to perform fault diagnosis of the second inverter. The first micro control unit performs a fault diagnosis of the first inverter when the plurality of semiconductor switching elements of the second inverter are not powered on in the second drive system. The second micro control unit performs a fault diagnosis of the second inverter when the plurality of semiconductor switching elements of the first inverter are not energized in the first drive system.

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