JP7463024B2 - Control System - Google Patents

Description

The present invention relates to a system for use in a vehicle equipped with a battery and a drive motor that generates power for driving, and for controlling the drive motor.

Electric vehicles such as electric vehicles (EVs) and hybrid vehicles (HVs) are equipped with a vehicle control unit (VCU) and a motor control unit to control the drive motor that serves as the driving source for driving. Both the vehicle control unit and the motor control unit are equipped with a microcomputer (microcontroller).

The microcomputer in the vehicle control unit sets a target value for the motor torque based on the vehicle speed, etc., and inputs a torque command corresponding to the target value to the motor control unit via CAN (Controller Area Network) communication. The motor control unit further includes a high-voltage circuit including a boost converter and an inverter. The microcomputer in the motor control unit controls the operation of the high-voltage circuit based on the torque command input from the vehicle control unit. In the high-voltage circuit, the DC power output from the battery is boosted, and the boosted DC voltage is converted to an AC voltage. As a result, AC power corresponding to the target value of the motor torque is output from the high-voltage circuit, and the AC power is supplied to the drive motor.

In order to forcibly stop the drive motor if an abnormality occurs in such a control system, a motor shutdown circuit (MSDN circuit) is built into the control system. The motor shutdown circuit is configured, for example, by connecting a signal output circuit provided in the vehicle control unit to a high-voltage circuit via a dedicated signal line. When an abnormality occurs in the control system, a low-level MSDN signal is output from the signal output circuit, and the operation of the high-voltage circuit is forcibly stopped, thereby stopping the drive motor.

JP 2015-107786 A JP 2017-13705 A

To ensure vehicle safety, it is necessary to monitor for malfunctions of the motor shutdown circuit. For this reason, the vehicle control unit is provided with a monitoring circuit (a signal input circuit that inputs the MSDN signal output from the signal output circuit to the microcomputer) that allows the microcomputer to monitor the MSDN signal output from the signal output circuit, and providing this monitoring circuit is one of the factors that increases the cost of the control system.

The object of the present invention is to provide a control system that does not require a monitoring circuit.

In order to achieve the above object, a control system according to one aspect of the present invention is a system for controlling a drive motor mounted on a vehicle equipped with a battery and a drive motor that generates power for driving, and includes a motor control circuit having an inverter that converts DC power output from the battery into AC power and supplies the AC power converted by the inverter to the drive motor, a signal output circuit that selectively outputs an MSDN signal at one of a first level and a second level, an MSDN terminal to which the signal output circuit is connected via a signal line and to which the MSDN signal is input, a forced stop circuit that forcibly stops the operation of the motor control circuit when the input voltage level of the MSDN terminal is at the first level, and a controller that electrically separates the motor control circuit from the battery, and while a circuit voltage remains in the motor control circuit, causes the signal output circuit to output an MSDN signal at the first level, while executing discharge control of the motor control circuit to flow a current to the drive motor with the circuit voltage remaining in the motor control circuit, and determines that an abnormality has occurred if the circuit voltage drops as a result of the execution.

According to this configuration, the controller executes discharge control of the motor control circuit while outputting a first level MSDN signal from the signal output circuit in a state where a circuit voltage remains in the motor control circuit. In the discharge control, the motor control circuit is controlled so that a current flows to the drive motor with the circuit voltage remaining in the motor control circuit in a state where the battery and the motor control circuit are electrically disconnected.

When a first level MSDN signal is normally input to the MSDN terminal, the operation of the motor control circuit is forcibly stopped, so even if discharge control is executed, no current flows from the motor control circuit to the drive motor, and the circuit voltage remaining in the motor control circuit does not drop. Therefore, if the circuit voltage drops due to the execution of discharge control, it can be determined that an abnormality has occurred that prevents the input of a first level MSDN signal to the MSDN terminal.

This eliminates the need for the monitoring circuitry that was previously required, and by eliminating the monitoring circuitry, costs for the control system can be reduced.

The controller may be configured to execute discharge control while causing the signal output circuit to output a first level MSDN signal, and determine that an abnormality has occurred if the circuit voltage does not decrease when discharge control is executed, and to execute discharge control while causing the signal output circuit to output a second level MSDN signal, and determine that an abnormality has occurred if the circuit voltage does not decrease as a result of the execution.

When the second level MSDN signal is normally input to the MSDN terminal, when discharge control is executed, current flows from the motor control circuit to the drive motor, and the circuit voltage remaining in the motor control circuit drops. Therefore, if discharge control is executed while outputting the second level MSDN signal from the signal output circuit, and the circuit voltage does not drop, it can be determined that an abnormality has occurred that prevents the input of the second level MSDN signal to the MSDN terminal.

A control system according to another aspect of the present invention is a system for controlling the drive motor, used in a vehicle equipped with a battery and a drive motor that generates power for driving, and includes a motor control circuit having an inverter that converts DC power output from the battery into AC power and supplies the AC power converted by the inverter to the drive motor, a signal output circuit that selectively outputs an MSDN signal at one of a first level and a second level, an MSDN terminal to which the signal output circuit is connected via a signal line and to which the MSDN signal is input, a forced stop circuit that forcibly stops the operation of the motor control circuit when the input voltage level of the MSDN terminal is at the first level, and a controller that, when the drive motor is outputting motor torque, causes the signal output circuit to output an MSDN signal of the first level, and determines that an abnormality has occurred if the motor torque does not decrease below a predetermined level.

According to this configuration, the controller causes the signal output circuit to output a first level MSDN signal when the drive motor is outputting motor torque.

When a first level MSDN signal is normally input to the MSDN terminal, the operation of the motor control circuit is forcibly stopped, so that no current flows from the motor control circuit to the drive motor, and the motor torque output from the drive motor falls below a predetermined level. Therefore, if the motor torque does not fall below a predetermined level, it can be determined that an abnormality has occurred that prevents the input of a first level MSDN signal to the MSDN terminal.

This eliminates the need for the monitoring circuitry that was previously required, and by eliminating the monitoring circuitry, costs for the control system can be reduced.

The controller may be configured to output a first level MSDN signal from the signal output circuit and, if the motor torque falls below a predetermined level, output a second level MSDN signal from the signal output circuit and, if the motor torque does not return to above the predetermined level, determine that an abnormality has occurred.

When a second-level MSDN signal is normally input to the MSDN terminal, current flows from the motor control circuit to the drive motor, and the motor torque, which is less than a predetermined value, returns to a predetermined value or higher. Therefore, if the motor torque does not return to a predetermined value or higher when a second-level MSDN signal is output from the signal output circuit, it can be determined that an abnormality has occurred that prevents the input of a second-level MSDN signal to the MSDN terminal.

According to the present invention, the monitoring circuit can be eliminated. Therefore, by omitting the monitoring circuit, the cost of the control system can be reduced.

1 is a block diagram showing a configuration of a control system according to an embodiment of the present invention; 13 is a flowchart showing the flow of a first MSDN circuit monitoring process. 13 is a flowchart showing the flow of a second MSDN circuit monitoring process.

The following describes in detail an embodiment of the present invention with reference to the attached drawings.

<Control System>
FIG. 1 is a block diagram showing a configuration of a control system 1 according to an embodiment of the present invention.

The control system 1 is mounted, for example, on an electric vehicle (EV) that is equipped with a drive motor 2 as a driving source for running. The drive motor 2 is, for example, a permanent magnet synchronous motor (PMSM) that uses a permanent magnet in the rotor.

The control system 1 includes a vehicle control unit (VCU) 3 for overall control of the entire vehicle, and a motor control unit 4 for controlling the drive motor 2.

The vehicle control unit 3 and the motor control unit 4 are equipped with microcomputers (microcontrollers) 11 and 21, respectively. The microcomputers 11 and 21 each have a built-in CPU, non-volatile memory such as a flash memory, and volatile memory such as a dynamic random access memory (DRAM). In addition, the vehicle control unit 3 and the motor control unit 4 each have a CAN transceiver 12 and 22, respectively, to enable two-way data communication between them using the CAN (Controller Area Network) communication protocol.

The motor control unit 4 further includes a high-voltage circuit 23 that supplies a drive current to the drive motor 2. The high-voltage circuit 23 includes a boost converter that boosts DC power, and an inverter that converts the boosted DC power by the boost converter into AC power. The inverter has a bridge circuit configuration in which two IGBT (Insulated Gate Bipolar Transistor) series circuits are provided for each of the U, V, and W phases, and these series circuits are connected in parallel between the positive wiring 24 and the negative wiring 25.

The electric vehicle is equipped with a battery 5 consisting of a battery pack made up of multiple secondary batteries. A positive wire 24 and a negative wire 25 are connected to the positive and negative terminals of the battery 5, respectively. Switches 26 and 27 are provided in the positive wire 24 and the negative wire 25, respectively, and the battery 5 and the high-voltage circuit 23 are electrically connected/disconnected by turning on/off the switches 26 and 27. In addition, a smoothing capacitor (not shown) is provided between the bridge circuit consisting of six IGBTs and the switches 26 and 27, between the positive wire 24 and the negative wire 25.

In the motor control unit 4, the microcomputer 21 controls the gate drive circuit (not shown), and the signal (voltage) supplied from the gate drive circuit to the gate of each IGBT of the inverter is switched between high and low levels, turning each IGBT on and off. The drive motor 2 is supplied with AC power from the high voltage circuit 23 according to the on/off state of the IGBT.

In order to forcibly stop the drive motor 2 if an abnormality occurs in the control system 1, the control system 1 incorporates a motor shutdown circuit (MSDN circuit) 6. The motor shutdown circuit 6 is provided in the vehicle control unit 3 and includes a signal output circuit 31 that outputs an MSDN signal, and a forced stop circuit 32 that is provided in the motor control unit 4 and forcibly stops the operation of the high voltage circuit 23. The motor control unit 4 is provided with an MSDN terminal 33, and the signal output terminal of the signal output circuit 31 is connected to the MSDN terminal 33 via a dedicated signal line 34.

The forced stop circuit 32 is provided with an AND circuit 35 corresponding to each IGBT of the inverter. A signal output from the gate drive circuit to the IGBT corresponding to the AND circuit 35 is input to one first input terminal of the AND circuit 35, and the other second input terminal is connected to the MSDN terminal 33 by wiring. The output terminal of the AND circuit 35 is connected to the gate of the IGBT corresponding to the AND circuit 35 by wiring.

When the control system 1 is operating normally, the microcomputer 21 of the vehicle control unit 3 controls the signal output circuit 31, and the signal output circuit 31 outputs a high-level MSDN signal. The MSDN signal output from the signal output circuit 31 is input to the MSDN terminal 33 via the signal line 34, and is input from the MSDN terminal 33 to the second input terminals of all the AND circuits 35 via wiring. Therefore, when the MSDN signal is at a high level, the signal input from the output terminal of the AND circuit 35 to the gate of the IGBT of the inverter switches between a high level and a low level depending on whether the signal input from the gate drive circuit to the first input terminal of each AND circuit 35 is at a high level or a low level.

The microcomputer 11 of the vehicle control unit 3 sets a target value for the motor torque based on the vehicle speed and accelerator opening of the electric vehicle, and transmits a torque command corresponding to the target value to the microcomputer 21 of the motor control unit 4 via CAN communication. Based on the torque command received from the vehicle control unit 3, the microcomputer 21 of the motor control unit 4 controls the gate drive circuit to switch the signal output from the gate drive circuit to the inverter of the high voltage circuit 23 between high and low levels. As a result, the signal supplied to the gate of each IGBT of the inverter switches between high and low levels, and AC power corresponding to the target value of the motor torque is supplied from the high voltage circuit 23 to the drive motor 2.

When an abnormality occurs in the control system 1, the microcomputer 21 of the vehicle control unit 3 controls the signal output circuit 31, and the signal output circuit 31 outputs a low-level MSDN signal. When this low-level MSDN signal is input to the MSDN terminal 33 via the signal line 34, and is input from the MSDN terminal 33 to the second input terminals of all the AND circuits 35 via wiring, the signals input from the output terminals of all the AND circuits 35 to the gates of the IGBTs become low level, regardless of whether the signal input from the gate drive circuit to the first input terminal of the AND circuit 35 is high level or low level. As a result, the operation of the high voltage circuit 23 is forcibly stopped, and the drive motor 2 is stopped. Also, if a break occurs in the signal line 34, the potential of the MSDN terminal 33 becomes low level, so that the operation of the high voltage circuit 23 is forcibly stopped, and the drive motor 2 is stopped.

<MSDN circuit monitoring process 1>
FIG. 2 is a flowchart showing the flow of the first MSDN circuit monitoring process.

The first MSDN circuit monitoring process is a process for determining whether the motor shutdown circuit 6 is normal or abnormal, and is executed by the microcomputer 11 of the vehicle control unit 3 and the microcomputer 21 of the motor control unit 4 in cooperation with each other when the control system 1 is stopped. During execution of the MSDN circuit monitoring process, communication is constantly performed between the microcomputer 11 of the vehicle control unit 3 and the microcomputer 21 of the motor control unit 4.

In the MSDN monitoring process, first, in the vehicle control unit 3, the MSDN signal output from the signal output circuit 31 is switched from high level to low level (step S11).

Next, the motor control unit 4 executes discharge control (step S12). In the discharge control, the switches 26 and 27 are turned off, and the battery 5 and the high voltage circuit 23 are electrically disconnected. In this state, the gate drive circuit is controlled so that a current flows to the drive motor 2 with the circuit voltage remaining in the high voltage circuit 23, that is, the charging voltage of the smoothing capacitor, and the signal input from the gate drive circuit to the inverter of the high voltage circuit 23 is switched between high and low levels.

After the discharge control is executed, the motor control unit 4 checks the circuit voltage of the high voltage circuit 23 (step S13). If the circuit voltage of the high voltage circuit 23 has not decreased due to the execution of the discharge control (YES in step S14), the motor control unit 4 continues to execute the discharge control, while the MSDN signal output from the signal output circuit 31 in the vehicle control unit 3 is switched from low level to high level (step S15).

When the motor control unit 4 detects a drop in the circuit voltage of the high voltage circuit 23 in response to the MSDN signal being switched from low to high (YES in step S16), the vehicle control unit 3 determines that the control system 1 is operating normally (step S17), and the MSDN circuit monitoring process is terminated.

On the other hand, if a drop in the circuit voltage of the high voltage circuit 23 is confirmed when discharge control is executed with the MSDN signal at a low level (NO in step S14), or if the circuit voltage of the high voltage circuit 23 does not drop in response to the MSDN signal being switched from a low level to a high level (NO in step S16), the vehicle control unit 3 determines that an abnormality has occurred in the control system 1 (step S18). Then, fail-safe control (F/S control) is executed (step S19), and the MSDN circuit monitoring process is terminated.

<Action and effect>
As described above, with the circuit voltage remaining in the high voltage circuit 23, a low-level MSDN signal is output from the signal output circuit 31, and discharge control of the high voltage circuit 23 is executed. In the discharge control, with the battery 5 and the high voltage circuit 23 electrically separated, the high voltage circuit 23 is controlled so as to cause a current to flow to the drive motor 2 with the circuit voltage remaining in the high voltage circuit 23.

When a low-level MSDN signal is normally input to the MSDN terminal 33, the operation of the high-voltage circuit 23 is forcibly stopped, so even if discharge control is executed, no current flows from the high-voltage circuit 23 to the drive motor 2, and the circuit voltage remaining in the high-voltage circuit 23 does not decrease. Therefore, if the circuit voltage decreases due to the execution of discharge control, it can be determined that an abnormality has occurred that prevents the input of a low-level MSDN signal to the MSDN terminal 33.

In addition, if the circuit voltage does not drop when discharge control is executed while a low-level MSDN signal is output from the signal output circuit 31, a high-level MSDN signal is output from the signal output circuit 31 and discharge control is executed.

When a high-level MSDN signal is normally input to the MSDN terminal 33, when discharge control is executed, current flows from the high-voltage circuit 23 to the drive motor 2, and the circuit voltage remaining in the high-voltage circuit 23 drops. Therefore, if discharge control is executed while a high-level MSDN signal is output from the signal output circuit 31, and the circuit voltage does not drop, it can be determined that an abnormality has occurred that prevents a high-level MSDN signal from being input to the MSDN terminal 33.

This eliminates the need for the monitoring circuitry that was previously required, and by eliminating the monitoring circuitry, costs for the control system can be reduced.

<MSDN circuit monitoring process 2>
FIG. 3 is a flowchart showing the flow of the second MSDN circuit monitoring process.

The second MSDN circuit monitoring process is executed by the microcomputer 11 of the vehicle control unit 3 and the microcomputer 21 of the motor control unit 4 in cooperation with each other when the electric vehicle is decelerating (coasting, regenerative driving) without the accelerator being operated, that is, when the electric vehicle is decelerating with the accelerator released. During execution of this MSDN circuit monitoring process, communication is constantly performed between the microcomputer 11 of the vehicle control unit 3 and the microcomputer 21 of the motor control unit 4.

In the MSDN circuit monitoring process, first, the motor control unit 4 determines whether the motor torque of the drive motor 2 is within a predetermined range (step S21). The predetermined range is, for example, a range of motor torque in which the driver of the electric vehicle does not feel a deceleration shock even if the drive motor 2 stops (the motor torque drops to 0), and is, for example, a range of less than a few Nm. The predetermined range may be fixed, or may be variably set according to a map that uses the vehicle speed and the gradient (inclination) of the road surface on which the electric vehicle is located.

If the motor torque of the drive motor 2 is not within the predetermined range (NO in step S21), the MSDN circuit monitoring process is terminated and the MSDN circuit monitoring process is executed again after a predetermined control period has elapsed.

If the motor torque of the drive motor 2 is within the predetermined range (YES in step S21), the MSDN signal output from the signal output circuit 31 in the vehicle control unit 3 is switched from high level to low level (step S22).

Next, the motor control unit 4 checks the motor torque of the drive motor 2 (step S23) and determines whether the motor torque has fallen below a predetermined value, for example to zero (step S24).

If the motor torque has fallen below a predetermined level (YES in step S24), the MSDN signal output from the signal output circuit 31 in the vehicle control unit 3 is switched from low level to high level (step S25).

When the motor control unit 4 confirms that the motor torque of the drive motor 2 has returned from less than a predetermined level to a predetermined level or higher in response to the MSDN signal being switched from low to high (YES in step S26), the vehicle control unit 3 determines that the control system 1 is operating normally (step S27), and the MSDN circuit monitoring process is terminated.

On the other hand, if the motor torque of the drive motor 2 does not fall below a predetermined level in response to the MSDN signal being switched from high to low (NO in step S24), or if the motor torque of the drive motor 2 does not return from below a predetermined level to above a predetermined level in response to the MSDN signal being switched from low to high (NO in step S26), the vehicle control unit 3 determines that an abnormality has occurred in the control system 1 (step S28). Then, fail-safe control (F/S control) is executed (step S29), and the MSDN circuit monitoring process is terminated.

<Action and effect>
As described above, when the drive motor 2 is outputting motor torque, the signal output circuit 31 outputs a low-level MSDN signal.

When a low-level MSDN signal is normally input to the MSDN terminal 33, the operation of the high-voltage circuit 23 is forcibly stopped, so that no current flows from the high-voltage circuit 23 to the drive motor 2, and the motor torque output from the drive motor 2 falls below a predetermined level. Therefore, if the motor torque does not fall below a predetermined level, it can be determined that an abnormality has occurred that prevents the input of a low-level MSDN signal to the MSDN terminal 33.

In addition, when the motor torque falls below a predetermined level in response to the output of a low-level MSDN signal from the signal output circuit 31, a high-level MSDN signal is output from the signal output circuit 31.

When a high-level MSDN signal is normally input to the MSDN terminal 33, current flows from the high voltage circuit 23 to the drive motor 2, and the motor torque, which is less than a predetermined value, returns to a predetermined value or higher. Therefore, if a high-level MSDN signal is output from the signal output circuit 31 and the motor torque does not return to a predetermined value or higher, it can be determined that an abnormality has occurred that prevents a high-level MSDN signal from being input to the MSDN terminal 33.

This eliminates the need for the monitoring circuitry that was previously required, and by eliminating the monitoring circuitry, costs for the control system can be reduced.

<Modification>
Although one embodiment of the present invention has been described above, the present invention can be embodied in other forms.

For example, in the above embodiment, the control system 1 is mounted on an electric vehicle, but the control system 1 may also be mounted on a hybrid vehicle (HV) that is equipped with a drive motor as a driving source for running.

In addition, various design modifications can be made to the above-mentioned configuration within the scope of the claims.

1: Control system 2: Drive motor 5: Battery 11, 21: Microcomputer (controller)
23: High voltage circuit (motor control circuit)
31: Signal output circuit 32: Forced stop circuit 33: MSDN terminal 34: Signal line

Claims (2)

A system for use in a vehicle equipped with a battery and a drive motor that generates power for driving, the system controlling the drive motor,
a motor control circuit having an inverter for converting DC power output from the battery into AC power, the motor control circuit supplying the AC power converted by the inverter to the drive motor;
a signal output circuit for selectively outputting an MSDN signal of one of a first level and a second level;
an MSDN terminal to which the signal output circuit is connected via a signal line and to which the MSDN signal is input;
a forced stop circuit that forcibly stops the operation of the motor control circuit when the input voltage level of the MSDN terminal is the first level;
a controller that, when the vehicle is decelerating and the drive motor is outputting a motor torque within a predetermined range, causes the signal output circuit to output the MSDN signal at the first level, and determines that an abnormality has occurred if the motor torque does not decrease below a predetermined level ;
A control system in which the predetermined range is variably set according to a map that uses the vehicle speed and the gradient of the road surface on which the vehicle is located . The control system of claim 1, wherein the controller causes the signal output circuit to output the MSDN signal at the second level when the motor torque falls below the predetermined level, and determines that an abnormality has occurred when the motor torque does not return to the predetermined level or higher.

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