Electronic control device

Abstract

The present invention is provided with the following elements for each system: an inverter that supplies power to a winding; a power supply relay that interrupts power supply from a power supply to the inverter; and a motor relay that interrupts power supply from the inverter to the winding. For a first system, which is a system in which an abnormality has been detected, the inverter thereof is caused to stop the power supply to the winding, the power supply relay thereof is caused to interrupt the power supply to the inverter, and the motor relay is caused to interrupt the power supply to the winding. Furthermore for a second system, which is a system in which no abnormality has been detected, the inverter thereof is caused to continue the power supply to the winding when the rotation speed of a motor is not greater than a predetermined reference value for the rotation speed, and the inverter is caused to reduce the rotation speed of the motor when the rotation speed of the motor exceeds the reference value.

Description

Electronic control unit

[0001] The present disclosure relates to an electronic control device, for example, an electronic control device for a vehicle.

[0002] An electronic control device that controls motors in multiple systems continues to control the motors in the other systems when an abnormality occurs in one system. For example, a motor control device described in Patent Document 1 has a control function that turns on the upper or lower switching elements of the inverter in the abnormal system where an abnormality is detected, and also turns on the switching elements of the motor relay, when the motor rotation speed in the normal system where no abnormality is detected is equal to or greater than a predetermined rotation speed. Because a regenerative current path is formed in the inverter, the back electromotive force generated by the motor in the abnormal system is not regenerated to the power supply. This reduces the risk of damage to the switching elements due to an increase in power supply voltage.

[0003] Patent No. 6944657

[0004] However, the motor control device described in Patent Document 1 may be unable to control the switching elements of the motor relay and the inverter in the abnormal system depending on the location or state of the abnormality or failure. For example, if an abnormality occurs in the switching element drive circuit provided in the motor control device, the switching elements of the inverter or the motor relay in the abnormal system cannot be turned on. When the motor rotates at high speed, a voltage exceeding the withstand voltage of the switching elements is generated, leaving a risk of inverter failure.

[0005] A first aspect of the present disclosure is an electronic control device that drives and controls a motor having at least two systems of windings, the electronic control device including, for each system, an inverter that supplies power to the windings, a power supply relay that connects and disconnects the power supply from a power source to the inverter, and a motor relay that connects and disconnects the power supply from the inverter to the windings, a motor angle sensor that detects the rotational speed of the motor, and a drive system, wherein the drive system causes an inverter of a first system in which an abnormality has been detected to stop supplying power to the windings, causes the power supply relay to cut off the power supply to the inverter, and causes the motor relay to cut off the power supply to the windings, and when the rotational speed of the motor is equal to or lower than a predetermined reference value of rotational speed, causes an inverter of a second system in which no abnormality has been detected to continue supplying power to the windings, and when the rotational speed of the motor exceeds the reference value, causes the inverter to reduce the rotational speed of the motor.

[0006] According to the present disclosure, the motor current and the on / off state of the switching elements are controlled according to the motor rotation speed for the second system in which no abnormality is detected. Because the motor rotation speed is suppressed regardless of the fault state in the first system in which an abnormality is detected, the back electromotive force generated by the motor rotation is reduced. Therefore, the risk of inverter failure can be reduced or prevented.

[0007] It is a diagram showing a configuration example of an electric power steering device according to embodiment 1. It is a diagram showing a configuration example of an electric power steering device according to embodiment 2. It is a flowchart illustrating an operation example of a control unit according to embodiment 1.

[0008] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Common or corresponding elements in the various drawings are designated by the same reference numerals, and the description thereof will be incorporated unless otherwise specified. <Embodiment 1> First, embodiment 1 of the present disclosure will be described. FIG. 1 is a diagram illustrating an example of the hardware configuration of an electronic control device according to this embodiment. In the example of FIG. 1, the electronic control device is configured as a control unit CU1 for a vehicle. The control unit CU1 is applied to steering assistance using an electric power steering device PS1. In this application, steering assistance control is also referred to as assist control. The control unit CU1 includes power supply relays 13A and 13B, inverters 14A and 14B, motor relays 15A and 15B, a power supply circuit 1, an IG I / F circuit 2, a torque sensor I / F circuit 3, a CAN communication circuit 4, a CPU 5, drive circuits 12A and 12B, motor relay drive circuits 10A and 10B, power supply relay drive circuits 11A and 11B, and a motor angle sensor 16. The motor relay drive circuits 10A, 10B, the power relay drive circuits 11A, 11B, and the inverter drive circuits 12IA, 12IB of the drive circuits 12A, 12B constitute a drive system that controls the power relay 13, the inverter 14, and the motor relay 15 to drive the motor 17.

[0009] The control unit CU1 is connected to a power supply 20, an ignition mechanism IG21, a torque sensor 22, and a CANBUS 23 using connectors. The connectors are installed, for example, on the housing or board of the control unit CU1. The power supply 20 supplies power to the control unit CU1. The power supply 20 is, for example, a storage battery capable of supplying DC power. The positive electrode of the power supply 20 is connected to one end of a power supply circuit 1 of the control unit CU1. The negative electrode of the power supply 20 is connected to a potential reference point. The potential reference point is a reference point that provides a reference potential. The potential reference point corresponds to what is known as ground (GND). The control unit CU1 operates by consuming power supplied from the power supply 20. The power supply circuit 1 distributes the power supplied from the power supply 20 to each device in the control unit CU1.

[0010] The ignition mechanism IG21 is a switching mechanism that controls the activation (ON) or deactivation (OFF) of the vehicle's operating mechanisms. The vehicle's operating mechanisms include the electric power steering device PS1. The ignition mechanism IG21 outputs an ignition signal indicating activation or deactivation to the control unit CU1. The IG I / F (Ignition Interface) circuit 2 waits for an ignition signal input from the ignition mechanism IG21. When an ignition signal indicating activation is input while the control unit CU1 is not operating, the IG I / F circuit 2 activates the control unit CU1. The IG I / F circuit 2 activates the power supply circuit 1 to start supplying power to each device in the control unit CU1. Thereafter, the IG I / F circuit 2 causes the CPU 5 to start the activation process. When an ignition signal indicating deactivation is input while the control unit CU1 is operating, the IG I / F circuit 2 stops the operation of the control unit CU1. The IG I / F circuit 2 starts a shutdown process (shutdown) in the CPU 5. After the shutdown process is completed, the IG I / F circuit 2 stops the power supply circuit 1 to stop the power supply to each device in the control unit CU1.

[0011] The torque sensor 22 detects steering torque generated by the rotation of the steering wheel (not shown) and notifies the control unit CU1 of the detected steering torque. The torque sensor I / F (Interface) circuit 3 notifies the CPU 5 of the steering torque notified by the torque sensor 22. The CANBUS (Controller Area Network BUS) 23 is a communication path that connects multiple devices via a wired connection in accordance with the CAN standard so that various data can be communicated. The CAN standard is an example of a communication method defined by ISO 11898. The CANBUS 23 is capable of communication with other devices installed in the vehicle. The other devices may include various instruments that acquire vehicle information indicating the vehicle's driving status. Examples of the other devices include a speedometer, a lateral acceleration sensor, or a yaw rate sensor. The CAN communication circuit 4 connects the CPU 5 to the other devices via the CANBUS 23. The CAN communication circuit 4 relays communication between the CPU 5 and the other devices. The CAN communication circuit 4 can acquire vehicle information indicating the driving status of the vehicle from instruments inside the vehicle.

[0012] The motor 17 is a three-phase brushless motor with two three-phase windings. The motor 17 has multiple three-phase windings to ensure redundancy. In this application, the two three-phase windings are distinguished by being referred to as motor windings 17A and 17B. The motor windings 17A and 17B each include a U-phase winding, a V-phase winding, and a W-phase winding. Each motor winding is configured as a winding set by connecting the U-phase winding, the V-phase winding, and the W-phase winding. The motor windings may be connected in any of a star connection, a Y connection, or the like. In a star connection, the other ends of the U-phase winding, the V-phase winding, and the W-phase winding are all connected to a single node. In a Y connection, the other ends of each of the U-phase winding, the V-phase winding, and the W-phase winding are each connected to a single node. Therefore, a three-phase winding configured in a Y connection has three nodes. In either of the connection structures, AC power of the corresponding phase is supplied to one end of each phase winding, and one of the nodes or one of the ends of the winding is connected to a potential reference point.

[0013] Motor 17 includes one rotor. The rotor has a permanent magnet positioned so that the induced magnetic field generated by motor windings 17A and 17B reaches it. If motor 17 is a three-phase brushless motor, motor windings 17A and 17B each form a stator. Motor windings 17A and 17B generate an AC magnetic field using three-phase AC power supplied from inverter 14A, causing the rotor to rotate. In FIG. 1, U1, V1, and W1 represent the U-phase, V-phase, and W-phase of motor winding 17A, respectively. U2, V2, and W2 represent the U-phase, V-phase, and W-phase of motor winding 17B, respectively.

[0014] In the example of FIG. 1 , the rotor of the motor 17 engages with the steering mechanism of the electric power steering device PS1. The torque generated by the rotation of the rotor serves as an assist torque that assists the driver in steering. The steering mechanism controls the direction of the wheels of the vehicle using the assist torque. In this application, the rotation speed of the rotor of the motor 17 may be referred to as the rotation speed of the motor 17 or simply as the rotation speed. Note that this disclosure mainly focuses on the case where the motor 17 is a three-phase brushless motor, but is not limited to this. The motor 17 may also be a polyphase motor having polyphase windings of four or more phases.

[0015] The motor relay drive circuits 10A and 10B control the states of the motor relays 15A and 15B to an on / off state corresponding to the operating mode information notified by the CPU 5. The motor relay drive circuits 10A and 10B generate motor relay control signals indicating the corresponding on / off states and output the generated motor relay control signals to the motor relays 15A and 15B. For example, when the CPU 5 instructs the motor relay drive circuits 10A and 10B to operate in the normal mode, the motor relay drive circuits 10A and 10B set the motor relays 15A and 15B to the on state. The motor relay drive circuits 10A and 10B output motor relay control signals indicating an on command to the motor relays 15A and 15B. The CPU 5 notifies the motor relay drive circuit 10 associated with the abnormal system of the abnormal mode. In this case, the motor relay drive circuit 10 associated with the abnormal system sets the motor relay 15 to the off state. Therefore, the motor relay drive circuit 10 associated with the abnormal system outputs a motor relay control signal indicating an off command to the motor relay 15 associated with that system.

[0016] Next, an example configuration of the motor relay 15A will be described. The motor relay 15B has a similar configuration to the motor relay 15A, and therefore the description thereof will be incorporated herein. The motor relay 15A connects and disconnects the inverter 14A and the motor winding 17A in accordance with a motor relay control signal input from the motor relay drive circuit 10A. For example, when the motor relay control signal indicating an ON command is input from the motor relay drive circuit 10A, the motor relay 15A connects the inverter 14A and the motor winding 17A and supplies power supplied from the inverter 14A to the motor winding 17A. When the motor relay control signal indicating an OFF state is input from the motor relay drive circuit 10A, the motor relay 15A disconnects the inverter 14A and the motor winding 17A and cuts off the power supply from the inverter 14A.

[0017] The motor relay 15A includes a switching element for each phase. Each switching element electrically opens and closes a connection between one end and the other end in response to the voltage of an electrical signal applied to the base end. The switching element is, for example, a metal-oxide-semiconductor field-effect transistor (MOSFET). A MOSFET generally includes a source, a drain, and a gate. The source, drain, and gate correspond to one end, the other end, and the base end, respectively. The motor relay control signal indicating an ON command is indicated by a high voltage value significantly higher than the reference potential. The motor relay control signal indicating an OFF command is indicated by a low voltage value significantly lower than the high voltage value.

[0018] The power relay drive circuits 11A and 11B each control the state of the power relays 13A and 13B to an on / off state corresponding to the operating mode information notified by the CPU 5. The power relay drive circuits 11A and 11B each generate a power relay control signal indicating the corresponding on / off state and output the generated power relay control signal to the power relays 13A and 13B. For example, when the CPU 5 instructs the power relay drive circuits 11A and 11B to operate in the normal mode, the power relay drive circuits 11A and 11B each set the state of the power relays 13A and 13B to the on state. The power relay drive circuits 11A and 11B each output a power relay control signal indicating an on command to the power relays 13A and 13B. The CPU 5 notifies the power relay drive circuit 11 associated with the abnormal system of the abnormal mode. In this case, the power relay drive circuit 11 associated with the abnormal system sets the state of the power relay 13 to the off state. Therefore, the power relay drive circuit 11 associated with the abnormal system outputs a power relay control signal indicating an off command to the power relay 13 associated with that system.

[0019] Next, an example configuration of the power relay 13A will be described. The power relay 13B has a similar configuration to the power relay 13A, and therefore its description will be incorporated herein. The power relay 13A connects and disconnects the power source 20 and the inverter 14A in accordance with a power relay control signal input from the power relay drive circuit 11A. For example, when a power relay control signal indicating an ON command is input from the power relay drive circuit 11A, the power relay 13A connects the power source 20 and the inverter 14A and supplies power supplied from the power source 20 to the inverter 14A. When a power relay control signal indicating an OFF command is input from the power relay drive circuit 11A, the power relay 13A disconnects the connection between the power source 20 and the inverter 14A and interrupts the power supply from the power source 20. The power relay 13A has two switching elements connected in series. The number of switching elements included in the power relay 13A may be one or three or more. However, by connecting a plurality of switching elements in series in the power supply relay 13A, the voltage applied to the entire power supply relay 13 is distributed among the plurality of switching elements based on the electrical resistance of each element, thereby ensuring a sufficient withstand voltage.

[0020] Next, an example configuration of the inverter 14A will be described. The inverter 14B has a similar configuration to the inverter 14A, and therefore the description thereof will be incorporated herein. The inverter 14A includes an upper-stage switching element group 14UA, a lower-stage switching element group 14DA, and a resistor element group 14RA. The upper-stage switching element group 14UA is also referred to as the "upper arm," and the lower-stage switching element group 14DA is also referred to as the "lower arm." The upper-stage switching element group 14UA includes one switching element per phase, for a total of three switching elements. Hereinafter, the individual switching elements belonging to the upper-stage switching element group 14UA may be referred to as "upper-stage switching elements." The lower-stage switching element group 14DA includes one switching element per phase, for a total of three switching elements. Hereinafter, the individual switching elements belonging to the lower-stage switching element group 14DA may be referred to as "lower-stage switching elements." The resistor element group 14RA includes one resistor element per phase, for a total of three resistor elements.

[0021] One end of the upper-stage switching element is connected to the other end of the power supply relay 13A common to all phases. The other end of the upper-stage switching element is connected to one end of the lower-stage switching element corresponding to each phase and one end of the motor relay 15A. One end of the lower-stage switching element is connected to the other end of the upper-stage switching element corresponding to each phase and one end of the motor relay 15A. The other end of the lower-stage switching element is connected to one end of the resistor element corresponding to each phase. One end of the resistor element is connected to the other end of the lower-stage switching element corresponding to each phase. The other ends of the resistor elements are all connected to the potential reference point.

[0022] From another perspective, the inverter 14A has a group of circuit elements, each of which has an upper-stage switching element, a lower-stage switching element, and a resistor connected in series for each phase. This group of circuit elements is also referred to as a "leg." For each phase, a node between the other end of the upper-stage switching element and one end of the lower-stage switching element is connected to one end of the motor winding 17A via a motor relay 15A. The upper-stage switching element and the lower-stage switching element connect and disconnect one end of each element in accordance with a switching signal input to their respective base ends from the drive circuit 12A. When the upper-stage switching element for a given phase closes both ends in response to an ON command and the corresponding lower-stage switching element opens both ends in response to an OFF command, power supplied from the power supply relay 13A is supplied to the motor winding 17A via the motor relay 15A. When the upper-stage switching element opens both ends in response to an OFF command and the corresponding lower-stage switching element closes both ends in response to an ON command, the potential at the other end of the upper-stage switching element approaches the reference potential. Therefore, inverter 14A supplies an AC current whose voltage fluctuates periodically to motor winding 17A via motor relay 15A based on a switching signal that periodically repeats on and off commands at different phases for each phase.

[0023] Next, a configuration example of the drive circuit 12A will be described. The drive circuit 12B has a similar configuration to the drive circuit 12A, and therefore its description will be incorporated herein. The drive circuit 12A includes an inverter drive circuit 12IA, a motor current detection circuit 12MA, and an abnormality detection unit 12AA. The inverter drive circuit 12IA of the drive circuit 12 associated with the normal system supplies three-phase AC power to the motor windings 17A in accordance with a current control variable notified to the inverter 14A by the CPU 5. Based on the rotation speed and rotation angle of the motor 17 notified to the CPU 5, the inverter drive circuit 12IA converts the notified control variable into a voltage command value on a three-phase coordinate system using a known conversion method. For each set of stages and phases of the inverter 14A, the inverter drive circuit 12IA generates a PWM (Pulse Width Modulation) signal as a switching signal based on the voltage command value of the corresponding phase. The PWM signal is a binary signal that alternates between a first value and a second value at a predetermined carrier wave period.

[0024] More specifically, the inverter drive circuit 12IA generates a carrier wave whose waveform repeats at predetermined carrier wave periods. The carrier wave is, for example, a triangular wave. The inverter drive circuit 12IA normalizes the voltage command value for each phase so that the range of the voltage command value is equal to the range of the signal value representing the carrier wave. The inverter drive circuit 12IA generates a switching signal representing an ON command or an OFF command for each phase based on the normalized voltage command value and the signal value of the carrier wave. During a period in which the voltage command value for each phase is greater than the signal value of the carrier wave, the inverter drive circuit 12IA sets the value of the upper switching signal to a value representing an ON command (e.g., 1) and the value of the lower switching signal to a value representing an OFF command (e.g., 0). The inverter drive circuit 12IA generates a switching signal representing the set value for each set of stages and phases and outputs the generated switching signal to the inverter 14A.

[0025] The CPU 5 may notify the inverter drive circuit 12I of the drive circuit 12 associated with the normal system of operation mode information indicating a reduced current mode, a regenerative braking mode, or a reverse rotation mode. These individual operation modes will also be described in the description of the operation of the CPU 5. When the CPU 5 notifies the inverter drive circuit 12I of an operation mode indicating a reduced current mode, the inverter drive circuit 12I calculates a reduced control amount by multiplying the current control amount (corresponding to the assist current value) notified by the CPU 5 by a predetermined gain (e.g., 0.3 to 0.5 times) less than 1. The inverter drive circuit 12I generates a switching signal based on the reduced control amount instead of the control amount notified by the CPU 5. The inverter drive circuit 12I outputs the generated switching signal to the inverter 14 of that system. This reduces the assist current supplied to the motor 17.

[0026] When the CPU 5 notifies the inverter drive circuit 12I of an operating mode indicating the regenerative braking mode, the inverter drive circuit 12I generates, for example, a switching signal indicating an OFF state for each phase in the upper row and a switching signal indicating an ON state for each phase in the lower row. Alternatively, the inverter drive circuit 12I may generate a switching signal indicating an ON state for each phase in the upper row and a switching signal indicating an OFF state for each phase in the lower row. The inverter drive circuit 12I outputs the generated switching signals to the inverter 14 of that system.

[0027] The inverter drive circuit 12I of the drive circuit 12 associated with the normal system may be notified by the CPU 5 of operation mode information indicating the reverse rotation mode. In this case, the inverter drive circuit 12I shifts the phase of the switching signal so as to reverse the phase sequence of the three-phase AC power. The inverter drive circuit 12I exchanges the output phases of any two of the three-phase switching signals. For example, the inverter drive circuit 12I exchanges the V and W phases among the U, V, and W phases, and outputs the U-phase switching signal, the W-phase switching signal before the exchange as the V-phase switching signal after the exchange, and the V-phase switching signal before the exchange as the W-phase switching signal before the exchange to the inverter 14.

[0028] The inverter drive circuit 12I operating in the reduced current mode, regenerative braking mode, or reverse rotation mode may receive operation mode information indicating the normal mode from the CPU 5. In this case, the inverter drive circuit 12I returns to the normal mode and generates switching signals related to normal assist control. Note that the inverter drive circuit 12I of the drive circuit 12 related to the abnormal system may receive operation mode information indicating the abnormal mode from the CPU 5. In this case, the inverter drive circuit 12I sets the switching elements of the inverters 14 for all phase-stage sets to the OFF state. Therefore, the inverter drive circuit 12I outputs switching signals indicating OFF commands to the inverters 14 of that system for all phase-stage sets.

[0029] The motor current detection circuit 12MA detects the current supplied from the inverter 14A to the motor winding 17A via the motor relay 15A as the motor current for each phase. The motor current detection circuit 12MA detects the voltage generated across the resistor element provided in the inverter 14A. The detected voltage corresponds to the motor terminal voltage generated in the motor winding 17A. This voltage is also proportional to the current value of the current flowing through the resistor element. Therefore, if the resistance value of the resistor element and the resistance value of the motor winding 17A are known, the detected voltage can be considered as the motor current. The motor current detection circuit 12MA outputs the detected motor current for each phase to the CPU 5.

[0030] The abnormality detection unit 12AA monitors the operating status of the inverter 14A and detects any abnormalities in operation. For example, the abnormality detection unit 12AA detects the motor current for each phase, similar to the motor current detection circuit 12MA, and determines whether an abnormality has occurred based on whether the detected motor current is within a predetermined reference range. Here, whether an excessively high or low current has occurred for each phase is detected. The abnormality detection unit 12AA may also calculate the sum of the motor currents for all phases and determine whether an abnormality has occurred based on whether the calculated sum is within a predetermined tolerance range. Ideally, the sum of the motor currents is always zero, so it is possible to detect whether the motor currents are balanced among multiple phases. When an abnormality is detected, the abnormality detection unit 12AA notifies the CPU 5 of abnormality detection information indicating the abnormality.

[0031] The CPU 5 constitutes the computer system of the control unit CU1. The CPU 5 executes various processes for realizing and controlling the functions of the control unit CU1 according to commands written in a pre-installed program. The CPU 5 controls steering assistance (assist control) and operation modes. For example, the CPU 5 monitors input of abnormality detection information from the drive circuits 12A and 12B. The CPU 5 determines the operation mode for the system of the drive circuits 12A and 12B to which no abnormality detection information is input as the normal mode. In this application, the system in which no abnormality is detected is sometimes referred to as the "normal system." If no abnormality detection information is input from either the drive circuits 12A or 12B, both systems are determined to be normal systems, and the operation mode for each system is determined to be the normal mode. The CPU 5 executes assist control for the system related to the normal mode.

[0032] When performing assist control, the CPU 5 calculates a control amount for supplying power to the motor windings of the motor 17 based on the steering torque and vehicle information. The CPU 5 calculates a target torque based on the steering torque and vehicle information according to a known steering assist control method. The CPU 5 receives the steering torque from the torque sensor 22 via the torque sensor I / F circuit 3. The CPU 5 calculates a control amount of current for the motor windings 17A, 17B using a known calculation method so as to reduce the difference between the target torque and the steering torque. The CPU 5 may use any method, such as MTPA (Maximum Torque Per Ampere) control or MTPV (Maximum Torque Per Flux) control. The CPU 5 outputs the calculated control amount to the drive circuit 12 associated with that system.

[0033] When abnormality detection information is input from one of the drive circuits 12A and 12B, the CPU 5 determines the operating mode of the system that received the abnormality detection information as the abnormal mode. In this application, the system in which the abnormality is detected may be referred to as the "abnormal system." The CPU 5 determines the system corresponding to the drive circuit 12 that received the abnormality detection information as the abnormal system, and determines the system corresponding to the drive circuit 12 that did not receive the abnormality detection information as the normal system. The CPU 5 may also obtain the abnormality detection information of the inverter 14 from another device. In this case, the drive circuits 12A and 12B may omit the abnormality detection units 12AA and 12AB (described below). For example, the control unit CU1 may be equipped with a dedicated abnormality detection circuit.

[0034] The CPU 5 stops assist control for the abnormal system. The CPU 5 notifies the motor relay drive circuit 10 corresponding to the abnormal system among the motor relay drive circuits 10A, 10B, the motor relay drive circuit 10 corresponding to the abnormal system among the power supply relay drive circuits 11A, 11B, and the drive circuit 12 corresponding to the abnormal system among the power supply relay drive circuits 11 and drive circuits 12A, 12B of operation mode information indicating the abnormal mode. This allows the power supply relay drive circuit 11 corresponding to the abnormal system to control the switching state of the power supply relay 13 to the off state, and the motor relay drive circuit 10 to control the switching state of the motor relay 15 to the off state. The drive circuit 12 corresponding to the abnormal system controls the switching states of all switching elements provided in the inverter 14 of that system to the off state.

[0035] If an abnormality is detected in any of the systems, the CPU 5 controls the operating mode of the assist control for the normal system using the drive circuit 12 based on the motor rotation speed. In the example of FIG. 1 , the CPU 5 has the function of a motor rotation speed / motor rotation direction discrimination unit 5M and acquires information on the rotation speed and rotation direction of the motor 17. Information on the rotation angle of the rotor of the motor 17 is input to the motor rotation speed / motor rotation direction discrimination unit 5M from the motor angle sensor 16. The motor rotation speed / motor rotation direction discrimination unit 5M calculates the rotation speed and rotation direction of the motor 17 per unit time based on the input rotation angle information. The rotation speed per unit time corresponds to the rotation speed. The motor rotation speed / motor rotation direction discrimination unit 5M calculates the rotation speed by subtracting the next most recent rotation angle from the most recent input rotation angle and dividing the resulting difference by the rotation angle sampling period. The motor rotation speed / motor rotation direction discrimination unit 5M can determine the rotation direction based on whether the calculated rotation speed is a positive value. Note that the CPU 5 may acquire information on the rotation speed and rotation direction of the motor 17 from another device. In this case, the function of the motor rotation speed / motor rotation direction determining section 5M can be omitted from the CPU 5. As another device, for example, the control unit CU1 may be provided with a rotation speed sensor instead of the motor angle sensor 16.

[0036] The CPU 5 determines whether the rotation speed of the motor 17 exceeds a predetermined reference value. If the predetermined reference value is exceeded, the CPU 5 reduces the rotation speed of the motor 17 for the drive circuit 12 associated with the normal system. The reference value for the rotation speed is preset in the drive circuit 12 as a rotation speed that generates a back electromotive force in the motor 17, causing the voltages applied to the circuit elements, such as the power supply relays 13A and 13B, the inverters 14A and 14B, and the motor relays 15A and 15B, to be lower than their withstand voltages. The reference value may be a fixed value or a value with hysteresis. For example, the reference value for the rotation speed used to determine whether to reduce the assist current may be smaller than the reference value for the rotation speed used to determine whether to cancel the reduction in the assist current (described below).

[0037] More specifically, the CPU 5 causes the drive circuit 12 to execute one of the following processes: (1) Reduce the assist current supplied from the inverter 14 to the motor windings. (Current reduction mode) The CPU 5 notifies the drive circuit 12 of the normal system of operation mode information indicating the current reduction mode. As described above, a reduced assist current is supplied from the drive circuit 12 to the motor 17. By reducing the assist current, the rotation speed of the motor 17 decreases, thereby suppressing the back electromotive force induced by the rotation. Since the voltage applied to the power supply relay 13, inverter 14, and motor relay 15 of the normal system decreases, voltages exceeding their withstand voltages are no longer applied to the switching elements provided therein. This prevents damage to the switching elements.

[0038] (2) The potentials of each phase applied from the inverter 14 to the motor windings are all set to the reference potential. (Regenerative Braking Mode) The CPU 5 notifies the drive circuit 12 of the normal system of operation mode information indicating regenerative braking mode. In the inverter 14 of the normal system, the states of the upper-stage switching elements 14U (described below) for each phase are controlled to the OFF state, and the states of the lower-stage switching elements 14D (described below) for each phase are controlled to the ON state based on the switching signals input from the drive circuit 12. In this case, the motor windings of each phase related to the normal system are connected to the potential reference point via the motor relay 15 and the resistor group 14RB (described below). Therefore, a regenerative current path is formed by the motor relay 15 and the lower-stage switching elements of the inverter 14. The electromagnetic brake acts based on the back electromotive force generated by the rotation of the motor 17, reducing the rotational speed of the motor 17.

[0039] Alternatively, instead of the above (2), the CPU 5 may (2') set the potentials of each phase applied from the inverter 14 to the motor windings to the power supply voltage. In this case, the CPU 5 also notifies the drive circuit 12 of the normal system of operation mode information indicating the regenerative braking mode. However, in the inverter 14 of the normal system, the upper-stage switching elements 14U are controlled to the ON state for each phase, and the lower-stage switching elements 14D are controlled to the OFF state for each phase, based on the switching signals input from the drive circuit 12. In this case, the motor windings of the normal system are connected to the power supply 20 via the motor relay 15 and the power supply relay 13 for each phase. Therefore, a regenerative current path is formed by the motor relay 15 and the upper-stage switching elements of the inverter 14. In this case, the electromagnetic brake is applied based on the back electromotive force generated by the rotation of the motor 17, thereby reducing the rotational speed of the motor 17.

[0040] (3) The inverter 14 reverses the phase sequence of the AC power supplied to the motor windings. (Reverse Mode) Here, the CPU 5 notifies the drive circuit 12 of the normal system of operation mode information indicating the reverse mode. Because the motor windings are supplied with three-phase AC power with reversed phases, the induced magnetic field generates torque in the direction opposite to the direction of rotation. This causes the rotation speed of the motor 17 to decrease. Note that when the rotation speed of the motor 17 decreases below a reference value, the CPU 5 cancels the processing applied among the above (1) to (3) and returns to normal assist control. Here, the CPU 5 notifies the drive circuit 12 of the normal system of operation mode information indicating the normal mode.

[0041] The CPU 5 may sequentially attempt the above processes (1), (2), and (3). For example, after attempting a process of a certain order (e.g., (1)), the CPU 5 may determine whether the rotational speed of the motor 17 has decreased to or below a reference value. If the rotational speed has not decreased to or below the reference value, the CPU 5 may proceed to the next process (e.g., (2)). The braking force applied to the motor 17 increases in the order of (1), (2), and (3), thereby reducing the impact of braking on the steering feel. Conversely, the CPU 5 may sequentially attempt the above processes (3), (2), and (1). In this case, the rotational speed of the motor 17 in the normal system can be reduced earlier. Note that the reference values ​​of the rotational speed used to determine whether to perform processes (1), (2), and (3) may increase in the order of (1), (2), and (3). Thus, the higher the rotational speed of the motor 17, the stronger the braking force acting thereon, resulting in an earlier reduction in the rotational speed. The lower the rotational speed, the less the impact on the steering feel, thereby reducing the sense of discomfort felt by the driver.

[0042] The drive circuits 12A, 12B notify the CPU 5 of information about the currents of the respective parts of the inverters 14A, 14B. For example, the CPU 5 is notified of the current value for each phase supplied from the inverter 14A to the motor winding 17A. The CPU 5 is notified of the current value for each phase supplied from the inverter 14B to the motor winding 17B. For example, when a current inquiry command is input from another device, the CPU 5 may output the current value for each of the notified combinations of system and phase as a response to the current inquiry command.

[0043] Next, an example of the operation of the control unit CU1 according to this embodiment will be described. FIG. 3 is a flowchart showing an example of the operation of the control unit CU1 according to this embodiment. (Step S02) The control unit CU1 starts operation when an ignition signal indicating activation is input. The CPU 5 receives torque sensor information from the torque sensor 22 and vehicle information from the CANBUS 23. (Step S04) The CPU 5 calculates an assist current value to be supplied to the motor windings 17A, 17B based on the torque sensor information and the vehicle information. The assist current value corresponds to a current value required to generate an assist torque by rotating the motor 17. The assist torque corresponds to a torque adjustment amount for providing a target torque based on the steering torque and the vehicle information.

[0044] (Step S06) CPU 5 performs assist control based on the calculated assist current value. Here, CPU 5 notifies drive circuits 12A and 12B of the assist current value for motor windings 17A and 17B. Drive circuits 12A and 12B generate switching signals for supplying three-phase AC power having the assist current values ​​notified by CPU 5. Drive circuits 12A and 12B output the generated switching signals to inverters 14A and 14B. In accordance with the switching signals input from drive circuits 12A and 12B, inverters 14A and 14B supply three-phase AC power to motor windings 17A and 17B via motor relays 15A and 15B. Motor windings 17A and 17B rotate the rotors by an induced magnetic field based on the three-phase AC power supplied from drive circuits 12A and 12B.

[0045] (Step S08) The drive circuits 12A, 12B monitor the operating conditions of the inverters 14A, 14B, respectively, and determine whether an abnormality has occurred. If an abnormality is detected in one of the inverters 14A, 14B (YES in step S08), the drive circuit 12 associated with the system in which the inverter abnormality occurred outputs abnormality detection information indicating the abnormality detection to the CPU 5. Thereafter, the process proceeds to step S10. If no abnormality is detected (NO in step S08), the process returns to step S02. Thus, the assist control continues until an abnormality occurs in one of the inverters 14A, 14B.

[0046] (Step S10) The CPU 5 outputs operation mode information indicating the abnormal mode to the motor relay drive circuit 10, power supply relay drive circuit 11, and drive circuit 12 associated with the abnormal system. As a result, the motor relay drive circuit 10, power supply relay drive circuit 11, and drive circuit 12 associated with the abnormal system issue OFF commands to the motor relay 15, power supply relay 13, and inverter 14, respectively. Assist control continues for the normal system in which no abnormality has occurred.

[0047] (Step S12) The CPU 5 starts monitoring the rotation speed (rotational speed) and rotation direction of the motor 17 of the normal system based on the rotation angle information input from the motor angle sensor 16. (Step S14) The CPU 5 determines whether the rotation speed of the motor 17 exceeds a predetermined reference value for the rotation speed. If it exceeds the predetermined reference value (YES in step S14), the process proceeds to step S16. If it is determined that the rotation speed of the motor 17 is equal to or less than the reference value (NO in step S14), the process returns to step S12. (Step S16) The CPU 5 reduces the current value of the assist current supplied from the inverter 14 to the drive circuit 12 of the normal system. Here, the CPU 5 notifies the drive circuit 12 of the normal system of operation mode information indicating the current reduction mode.

[0048] (Step S18) The CPU 5 determines whether the rotation speed of the motor 17 still exceeds the reference value. If the rotation speed of the motor 17 exceeds the reference value (YES in step S18), the process proceeds to step S20. If it is determined that the rotation speed of the motor 17 is equal to or less than the reference value (NO in step S18), the process proceeds to step S28. (Step S20) The CPU 5 turns off the upper switching elements of all phases and turns on the lower switching elements of all phases in the inverter 14 of the drive circuit 12 of the normal system. Here, the CPU 5 notifies the drive circuit 12 of the normal system of operation mode information indicating the regenerative braking mode.

[0049] (Step S22) The CPU 5 determines whether the rotation speed of the motor 17 still exceeds the reference value. If the rotation speed of the motor 17 exceeds the reference value (YES in step S22), the process proceeds to step S24. If the rotation speed of the motor 17 is determined to be equal to or less than the reference value (NO in step S22), the process proceeds to step S28. (Step S24) The CPU 5 causes the inverter 14 of the normal system to supply an assist current to the motor windings so that the rotation direction of the motor 17 is reversed. That is, the CPU 5 causes the inverter 14 to reverse the phase sequence of the AC power supplied to the motor windings. Here, the CPU 5 notifies the normal system drive circuit 12 of operation mode information indicating the reverse rotation mode.

[0050] (Step S26) The CPU 5 determines whether the rotation speed of the motor 17 still exceeds the reference value. If the rotation speed of the motor 17 exceeds the reference value (NO in step S26), the process returns to step S24. If the rotation speed of the motor 17 is determined to be equal to or less than the reference value (YES in step S26), the process proceeds to step S28. (Step S28) The CPU 5 returns the operation mode of the drive circuit 12 of the normal system to normal assist control. Here, the CPU 5 notifies the drive circuit 12 of the normal system of operation mode information indicating the normal mode. When the drive circuit 12 of the normal system is notified of the operation mode information indicating the normal mode by the CPU 5, the inverter 14 supplies three-phase AC current to the motor windings based on the current control value for normal assist control.

[0051] As described above, in this embodiment, the inverter 14 in the normal system is controlled to suppress the rotation of the motor 17. Therefore, regardless of the state of the fault in the abnormal system, the risk of damage to the switching elements due to excessive back electromotive force that may be generated by the high-speed rotation of the motor 17 can be avoided or reduced.

[0052] Second Embodiment Next, a second embodiment of the present disclosure will be described. Fig. 2 is a diagram showing an example of the hardware configuration of an electronic control device according to this embodiment. In the example of Fig. 2, the electronic control device is configured as a control unit CU2 for a vehicle. The control unit CU2 is applied to steering assistance by an electric power steering device PS2. The following description will mainly focus on differences from the first embodiment.

[0053] The control unit CU2 includes power supply circuits 1A, 1B, IG I / F circuits 2A, 2B, torque sensor I / F circuits 3A, 3B, CAN communication circuits 4A, 4B, CPUs 5A, 5B, motor relay drive circuits 10A, 10B, power relay drive circuits 11A, 11B, drive circuits 12A, 12B, power relays 13A, 13B, inverters 14A, 14B, motor relays 15A, 15B, and motor angle sensors 16A, 16B. The control unit CU2 can be considered to include a drive system for controlling AC power supplied to the motor windings for each system. The drive system for motor winding 17A includes at least CPU 5A, motor relay drive circuit 10A, power relay drive circuit 11A, and inverter drive circuit 12IA. The drive system for motor winding 17B includes at least CPU 5B, motor relay drive circuit 10B, power relay drive circuit 11B, and inverter drive circuit 12IB.

[0054] Power supplies 20A, 20B, IGs 21A, 21B, torque sensors 22A, 22B, and CANBUS 23A, 23B are connected to control unit CU2. Power supply circuits 1A, 1B supply power from power supplies 20A, 20B to CPUs 5A, 5B and various devices in systems common to CPUs 5A, 5B. IG I / F circuits 2A, 2B wait for ignition signals from IG 21A, IG 21B, respectively. IG I / F circuits 2A, 2B control whether or not devices in their own systems operate in accordance with the ignition signals input thereto.

[0055] Torque sensor I / F circuits 3A and 3B notify CPUs 5A and 5B of steering torques input from torque sensors 22A and 22B, respectively. CAN communication circuits 4A and 4B relay communications between CPUs 5A and 5B and other devices in the vehicle cabin using CANBUS 23A and 23B. Motor angle sensors 16A and 16B detect the rotation angle of motor 17, respectively.

[0056] The CPUs 5A and 5B each include a motor rotation speed / motor rotation direction discrimination unit 5MA and 5MB. The motor rotation speed / motor rotation direction discrimination unit 5MA and 5MB receive the rotor rotation angle corresponding to the motor windings 17A and 17B from the motor angle sensors 16A and 16B, respectively. The motor rotation speed / motor rotation direction discrimination unit 5MA and 5MB calculate the amount of rotation based on the notified rotation angle and determine the rotation direction based on the calculated rotation speed. The CPUs 5A and 5B wait for input of abnormality detection information from the drive circuits 12A and 12B, respectively. The CPUs 5A and 5B determine the operating mode of their own system based on whether or not the abnormality detection information has been input. The CPUs 5A and 5B share the acquired information acquired about their own system and the control information obtained by control with other units.

[0057] For example, the CPUs 5A and 5B notify the CPUs 5B and 5A of the abnormality detection information of their own systems. Therefore, the CPUs 5A and 5B can obtain the acquired information and control information of the other systems. The CPUs 5A and 5B stop the assist control when their own systems are abnormal and execute the assist control when their own systems are normal. When their own systems are normal, the CPUs 5A and 5B control the operation mode of the assist control using the drive circuits 12A and 12B based on the motor rotation speed.

[0058] Each of the CPUs 5A and 5B executes steps S02 to S08 in FIG. 3 for its own system. Then, in step S10, the CPU associated with the normal system (e.g., CPU 5A) controls the switching states of all switching elements included in the power supply relay 13, inverter 14, and motor relay 15 associated with the abnormal system to the OFF state. Then, the CPU associated with the normal system executes steps S12 to S28. In this embodiment, too, the rotation of the motor 17 is suppressed by controlling the inverter 14 of the normal system. Therefore, regardless of the fault state in the abnormal system, the risk of damage to the switching elements due to excessive back electromotive force that may be generated by the high-speed rotation of the motor 17 can be avoided or reduced.

[0059] The control units CU1 and CU2 according to the embodiments of the present disclosure may be configured with dedicated hardware or may include a general-purpose computer system. A computer system generally includes a processor and a storage medium. The processor may read a program non-temporarily stored in advance in the storage medium and execute the read program to implement the functions of each component of the control units CU1 and CU2 in cooperation with the storage medium and other hardware. The motor 17 and motor angle sensor 16 may be omitted from the control units CU1 and CU2, and may be provided separately from the control units CU1 and CU2 in the electric power steering devices PS1 and PS2. While the above description illustrates an example in which the control units CU1 and CU2 are applied to an electric power steering device for a vehicle, the present disclosure is not limited to this. The control units CU1 and CU2 may also be applied to equipment and structures that use motors as power sources, such as railcars, bicycles, elevators, robots, and conveyors.

[0060] As described above, the electronic control device (e.g., control units CU1, CU2) according to the present disclosure is an electronic control device that drives and controls a motor 17 having at least two systems of windings (e.g., motor windings 17A, 17B), and includes, for each system, inverters 14A, 14B that supply power to the windings, power supply relays 13A, 13B that connect and disconnect the power supply from power sources 20, 20A, 20B to the inverters, and motor relays 15A, 15B that connect and disconnect the power supply from the inverters to the windings, a motor angle sensor 16 that detects the rotational speed of the motor 17, and a drive system (e.g., CPUs 5, 5A, 5B, motor relay drive circuits 10A, 10B, power supply relay drive circuits 11A, 11B, and inverter drive circuits 12IA, 12IB). The drive system stops the power supply to the windings of the inverter of the first system (e.g., the abnormal system) in which an abnormality is detected in inverters 14A, 14B, causes the power supply relay to cut off the power supply to the inverter, and causes the motor relay to cut off the power supply to the windings. When the rotation speed of motor 17 is equal to or lower than a predetermined rotation speed reference value, the drive system continues the power supply to the windings of the inverter of the second system (e.g., the normal system) in which no abnormality is detected in the inverter. When the rotation speed of motor 17 exceeds the reference value, the drive system causes the inverter of the second system to reduce the rotation speed of motor 17. With this configuration, the power supply to the windings of the first system in which an abnormality is detected in the inverter is stopped and the power supply to the windings of the second system in which no abnormality is detected in the inverter is continued. When the rotation speed of motor 17 is high, the drive system reduces the rotation speed of motor 17. This reduces the back electromotive force that may be generated by the rotation of motor 17, thereby avoiding or reducing the possibility of a voltage exceeding the withstand voltage being applied to the switching elements of the inverter. Therefore, the risk of damaging the inverter can be avoided or reduced.

[0061] The above electronic control device may be realized as follows. The drive system may reduce the amount of power supplied to the windings of the inverter of the second system when the rotational speed of the motor 17 exceeds a reference value. The drive system may disconnect the inverter of the second system from the power supply relay and connect it to the potential reference point when the rotational speed of the motor 17 exceeds the reference value. The drive system may connect the inverter of the second system to the power supply relay and disconnect it from the potential reference point when the rotational speed of the motor 17 exceeds the reference value. The drive system may reverse the phase sequence of the power supplied to the windings of the inverter of the second system when the rotational speed of the motor 17 exceeds the reference value. The above electronic control device may include a power supply, a motor angle sensor, and a processor for each system. The drive system may share inverter abnormality detection information between the systems.

[0062] According to the electronic control device according to the present disclosure, the risk of inverter failure can be reduced or prevented.

[0063] CU1, CU2... control unit, PS1, PS2... electric power steering device, 1, 1A, 1B... power supply circuit, 2, 2A, 2B... IG I / F circuit, 3, 3A, 3B... torque sensor I / F circuit, 4, 4A, 4B... CAN communication circuit, 5, 5A, 5B... CPU, 10A, 10B... motor relay drive circuit, 11A, 11B... power supply relay drive circuit, 12A, 12B... drive circuit, 13A, 13B... power supply relay, 14A, 14B... inverter, 15A, 15B... motor relay, 16, 16A, 16B... motor angle sensor, 17... motor, 20, 20A, 20B... power supply, 21, 21A, 21B... ignition mechanism IG, 22, 22A, 22B... torque sensor, 23, 23A, 23B... CAN BUS

Claims

1. An electronic control device for driving and controlling a motor having at least two systems of windings, comprising: an inverter for supplying power to the windings, a power supply relay for connecting and disconnecting the power supply from a power source to the inverter, and a motor relay for connecting and disconnecting the power supply from the inverter to the windings, for each system; a motor angle sensor for detecting the rotational speed of the motor; and a drive system, wherein the drive system causes the inverter of a first system in which an abnormality has been detected to stop supplying power to the windings, causes the power supply relay to cut off the power supply to the inverter and causes the motor relay to cut off the power supply to the windings, causes the inverter of a second system in which no abnormality has been detected to continue supplying power to the windings when the rotational speed of the motor is equal to or lower than a predetermined reference value of rotational speed, and causes the inverter to reduce the rotational speed of the motor when the rotational speed of the motor exceeds the reference value.

2. The electronic control device according to claim 1, wherein the drive system reduces the amount of power supplied to the winding of the inverter of the second system when the rotational speed of the motor exceeds the reference value.

3. The electronic control device according to claim 1, wherein the drive system disconnects the second inverter from the power supply relay and connects it to a potential reference point when the rotational speed of the motor exceeds the reference value.

4. The electronic control device according to claim 1, wherein the drive system connects the second system inverter to the power supply relay and cuts off the connection to the potential reference point when the rotational speed of the motor exceeds the reference value.

5. The electronic control device according to claim 1, wherein the drive system reverses the phase sequence of the power supplied to the windings by the inverter of the second system when the rotational speed of the motor exceeds the reference value.

6. The electronic control device according to claim 1, wherein the power supply, the motor angle sensor, and the drive system are provided for each of the systems.

7. The electronic control device according to claim 6, wherein the drive system shares the abnormality detection information of the inverter between systems.

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