JP2019097304A - Motor drive system - Google Patents

Abstract

To provide a motor drive system capable of determining presence/absence of demagnetization of a motor without substantially rotating the motor.SOLUTION: According to a motor drive system for driving an output shaft with a plurality of motors, there are provided a first motor for generating a rotation torque of the output shaft based on a first current; a second motor for generating the rotation torque of the output shaft based on a second current; a control unit for controlling the first current and the second current in such a manner that a rotation torque in a positive direction is made to be generated by the first motor and a rotation torque in an opposite direction is made to be generated by the second motor, and both the rotation torques are balanced to stop the output shaft when at least one of the first current and the second current has a predetermined reference current value or more; and a determination unit for determining that demagnetization is produced in either of the first motor and the second motor in a case where the output shaft cannot be stopped via current control by the control unit, or in a case where an absolute value difference between the first current and the second current when being able to stop the output shaft exceeds a predetermined threshold.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a motor drive system that drives one output shaft with a plurality of motors.

  For example, Patent Document 1 discloses a motor control system that determines a change in power supply voltage or current based on a back electromotive voltage generated by a motor to determine whether or not demagnetization occurs in the motor.

JP, 2015-076974, A

  In the technology described in Patent Document 1, a motor generates a counter electromotive voltage larger than the power supply voltage to determine the presence or absence of demagnetization of the motor. For this reason, in order to generate the required back electromotive force, it is necessary to rotate the motor at a considerably high speed.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a motor drive system capable of determining the presence or absence of demagnetization of a motor without substantially rotating the motor.

  In order to solve the above problems, one aspect of the present invention is a motor drive system in which one output shaft is driven by a plurality of motors, and a first of generating a rotational torque of the output shaft based on a first current. A motor, a second motor that generates rotational torque of the output shaft based on the second current, a rotational torque in the forward direction is generated in the first motor, and a rotational torque in the reverse direction is generated in the second motor And a control unit for controlling the first current and the second current so that the output shaft becomes stationary with both rotational torques being balanced when at least one of the first current and the second current is equal to or higher than a predetermined reference current value. If the output shaft can not be stopped by the current control of the control unit, or if the absolute value difference between the first current and the second current when the output shaft can be stopped exceeds the predetermined threshold, the first motor and the first motor Two mo Characterized in that it comprises a a determination unit demagnetization occurs in any of the coater, a.

  In the motor drive system according to this aspect, the first motor and the second motor perform control to generate rotational torque in mutually opposite directions with respect to the output shaft, and the state of the output shaft, the first current, and 2 Check the difference in absolute value from the current.

  According to this control, when demagnetization does not occur in any of the first motor and the second motor, the absolute value difference between the first current and the second current does not exceed the predetermined threshold value. The output shaft can be stopped at a predetermined reference current value or more. On the other hand, when demagnetization occurs in either the first motor or the second motor, the absolute value difference between the first current and the second current when the output shaft is stopped is a predetermined threshold value. If the controller performs current control, the output shaft can not be stopped. Therefore, it can be easily determined whether or not demagnetization occurs in the motor.

  According to the motor drive system of the present invention described above, the presence or absence of demagnetization of the motor can be determined without substantially rotating the motor (output shaft).

Schematic which shows the structure of the motor drive system which concerns on one Embodiment of this invention A flowchart showing the procedure of the demagnetization determination process executed by the motor drive system Diagram showing the relationship between the current value of each motor and the rotational torque of the output shaft Diagram showing the relationship between the current value of each motor and the rotational torque of the output shaft Diagram showing the relationship between the current value of each motor and the rotational torque of the output shaft

[Overview]
The motor drive system according to the present invention performs control to generate rotational torque in mutually opposite directions with respect to one output shaft by the first motor and the second motor, and the static / rotational state of the output shaft and Based on the difference in absolute value between the first current and the second current, it is determined whether or not demagnetization occurs in the motor. Thereby, the presence or absence of demagnetization of the motor can be determined without substantially rotating the motor (output shaft).

[System configuration]
FIG. 1 is a schematic view showing the configuration of a motor drive system 1 according to an embodiment of the present invention. In FIG. 1, a motor drive system 1 according to the present embodiment includes a first motor 11, a second motor 12, a first control unit 21, a second control unit 22, and a first current sensor. 31, a second current sensor 32, a rotation angle sensor 33, a demagnetization determination unit 34, an output shaft 40, and a battery 50.

  The first motor 11 is an electric motor that drives the battery 50 as a power supply. The first motor 11 generates a torque for rotating the output shaft 40 in a predetermined direction based on the current (hereinafter referred to as “first current”) supplied from the first control unit 21. For example, a three-phase DC motor can be used as the first motor 11.

  The second motor 12 is a motor that drives the battery 50 as a power supply. The second motor 12 generates torque for rotating the output shaft 40 in a predetermined direction based on the current (hereinafter referred to as “second current”) supplied from the second control unit 22. For example, a three-phase DC motor can be used as the second motor 12.

  The first control unit 21 is configured to control the first current supplied to the first motor 11 to cause the first motor 11 to generate torque that causes the output shaft 40 to rotate in a predetermined direction. For example, a three-phase bridge inverter circuit configured of six switching elements (MOS transistors or the like) can be used for the first control unit 21.

  The second control unit 22 is configured to control the second current supplied to the second motor 12 so as to cause the second motor 12 to generate torque for rotating the output shaft 40 in a predetermined direction. For example, a three-phase bridge inverter circuit configured of six switching elements (MOS transistors or the like) can be used as the second control unit 22.

  The first control unit 21 and the second control unit 22 normally generate the first current and the second current for generating the torque for rotating the output shaft 40 in the same direction. It supplies the second motor 12. On the other hand, the first control unit 21 and the second control unit 22 respectively generate torque (see the arrow in FIG. 1) for rotating the output shaft 40 in opposite directions in the demagnetization determination process described later. The first current and the second current are supplied to the first motor 11 and the second motor 12.

  The first current sensor 31 is configured to detect a first current supplied to the first motor 11 by the first control unit 21. The value of the first current detected by the first current sensor 31 is output to the demagnetization determination unit 34.

  The second current sensor 32 is configured to detect a second current supplied to the second motor 12 by the second controller 22. The value of the second current detected by the second current sensor 32 is output to the demagnetization determination unit 34.

  The rotation angle sensor 33 is provided in the vicinity of the output shaft 40 and is configured to detect the rotation angle of the output shaft 40. The rotation angle of the output shaft 40 detected by the rotation angle sensor 33 is output to the demagnetization determination unit 34.

  The demagnetization determination unit 34 inputs the value of the first current from the first current sensor 31, the value of the second current from the second current sensor 32, and the rotation angle of the output shaft 40 from the rotation angle sensor 33. Do. Then, the demagnetization determination unit 34 executes demagnetization determination processing described later based on the value of the first current, the value of the second current, and the rotation angle of the output shaft 40.

  The first control unit 21 and the second control unit 22 described above correspond to the “control unit” in the claims. The first current sensor 31, the second current sensor 32, the rotation angle sensor 33, and the demagnetization determination unit 34 correspond to the "determination unit" in the claims.

  Typically, all or part of first control unit 21, second control unit 22, demagnetization determination unit 34, and central processing unit (CPU: Central Processing Unit), memory, and input and output It can be configured as an electronic control unit (ECU) including an interface. In the electronic control unit, the CPU reads and executes a program stored in the memory to realize the above-described predetermined function.

[Demagnetization determination processing]
Next, the process performed by the motor drive system 1 according to the embodiment of the present invention will be described with further reference to FIGS. 2, 3A, 3B, and 3C. FIG. 2 is a flowchart showing the procedure of the demagnetization determination process performed by the motor drive system 1. 3A, 3B, and 3C are diagrams showing the relationship between the current values of the first current and the second current, and the rotational torque of the output shaft 40. FIG.

  Step S201: It is determined whether or not there is an electrical failure in the motor drive system 1. The electrical failure is a failure not caused by the demagnetization of the motor, such as an abnormality of a current sensor or an abnormality of an inverter circuit. If there is no electrical failure in the system (step S201, none), the process proceeds to step S202. On the other hand, when there is an electrical failure in the system (Step S201, Yes), a driver or the like is notified that there is an electrical failure in motor drive system 1 using a predetermined method, and this demagnetization is performed. The determination process ends.

  Step S202: It is determined whether the first motor 11 and the second motor 12 are both overheated. The non-overheated state is a state in which the temperature of the motor has not reached a predetermined upper limit temperature at which driving can not be performed. For example, a state in which there is a certain margin to the upper limit temperature can be made. If the motor is not overheated (step S202, none), the process proceeds to step S203. On the other hand, when the motor is overheated (Yes in step S202), a predetermined method is used to notify the driver or the like that at least one of the first motor 11 and the second motor 12 is overheated. Then, the present demagnetization determination processing ends.

  Step S203: The supply of the first current for generating the torque for rotating the output shaft 40 in the positive direction is started to the first motor 11. The supply of the second current that generates the torque for rotating the output shaft 40 in the reverse direction to the second motor 12 is started. When current supply to each motor is started, the process proceeds to step S204.

  Step S204: It is determined whether or not the value of the first current is equal to or greater than a predetermined reference current, or the value of the second current is equal to or greater than the predetermined reference current. The reference current value can be set based on, for example, the driving force of the output shaft 40 required for the motor drive system 1. If at least one of the first current value and the second current value is greater than or equal to the reference current value (Yes in step S204), the process proceeds to step S208 because the condition for performing the demagnetization determination is satisfied. On the other hand, when at least one of the first current value and the second current value is not greater than or equal to the reference current value (No in step S204), the process proceeds to step S205 because the condition for performing the demagnetization determination does not hold. .

  Step S205: It is determined whether the output shaft 40 is stationary. For example, when the rotation angle of the output shaft 40 does not change even after a predetermined time has elapsed, it can be determined in the system that the rotation torques of both motors are balanced and stationary. If the output shaft 40 is stationary (Yes at Step S205), the process proceeds to Step S206. On the other hand, if the output shaft 40 is not stationary (No at Step S205), the process proceeds to Step S207.

  Step S206: If the output shaft 40 is at rest, the current values of both the first current and the second current are increased together. After the current value is increased together, the process returns to step S204.

  Step S207: If the output shaft 40 is not stationary, either one of the first current and the second current is increased. Specifically, the current value of the motor with the smaller rotational torque is increased so that the rotation of the output shaft 40 stops. For example, if the output shaft 40 is rotating in the forward direction, the second current is increased to increase the rotational torque in the reverse direction. After increasing one of the current values, the process returns to step S204.

  Step S208: It is determined whether or not the output shaft 40 is at rest in a state in which the condition for performing the demagnetization determination is satisfied. The determination of rest is as described above. If the output shaft 40 is stationary (Yes at step S208), the process proceeds to step S209. On the other hand, when the output shaft 40 is not stationary (No in step S208), it is determined that there is demagnetization of the motor (abnormality). Specifically, it is determined that demagnetization occurs in the motor that generates rotational torque in the direction opposite to the direction in which the output shaft 40 is rotating. Then, when the determination is made, the present demagnetization determination processing ends.

  For example, as shown in FIG. 3C, if there is a difference between the rotational torque generated by the second current and the rotational torque generated by the first current of the reference current no matter how much the current amount is increased, the output shaft 40 is positive. It will keep rotating in the direction. Therefore, in this case, when a predetermined rotation angle is detected by the rotation angle sensor 33, it can be determined that the motor is demagnetized (abnormal).

  Step S209: If the output shaft 40 is stationary, it is determined whether the absolute value of the current value difference obtained by subtracting the value of the second current from the value of the first current is less than a predetermined threshold value. . The threshold is a threshold for determining the difference between the first current and the second current, and is appropriately set based on the required standard of the motor drive system 1 or the like. If the absolute value of the current value difference is less than the threshold (Yes at step S209), it is determined that the motor does not demagnetize (normal) (see FIG. 3A). On the other hand, when the absolute value of the current value difference is equal to or more than the threshold (No in step S209), it is determined that the motor demagnetization is present (abnormal). Specifically, it is determined that the demagnetization occurs in the motor that is passing the current having a large value. Then, when the determination is made, the present demagnetization determination processing ends.

  For example, as shown in FIG. 3B, even if the rotational torque of each motor is balanced and the output shaft 40 is stationary, if there is a large deviation in the current value flowing to generate the rotational torque, the motor drive system The overall efficiency will be degraded. Therefore, in this case, it is possible to determine that there is demagnetization (abnormality) of the motor when the current value difference which is equal to or greater than the threshold value is detected through the first current sensor 31 and the second current sensor 32. .

[Operation / effect]
As described above, according to the motor drive system 1 according to the embodiment of the present invention, the first motor 11 and the second motor 12 generate rotational torque in mutually opposite directions with respect to the output shaft 40. Control is performed to confirm the state of the output shaft 40 and the difference in absolute value between the first current and the second current.

  According to this control, when demagnetization does not occur in any of the first motor 11 and the second motor 12, the absolute value difference between the first current and the second current exceeds a predetermined threshold value. Therefore, the output shaft 40 can be stopped at a predetermined reference current value or more. Therefore, it is possible to easily determine that demagnetization does not occur in the motor without substantially rotating the output shaft.

  On the other hand, when demagnetization occurs in any of the first motor 11 and the second motor 12, the absolute value difference between the first current and the second current when the output shaft 40 is stopped is Even if the first threshold value is exceeded or the first control unit 21 and the second control unit 22 perform current control, the output shaft 40 can not be stopped. Therefore, it is possible to easily determine that demagnetization occurs in the motor without substantially rotating the output shaft.

  In the above embodiment, although the motor drive system 1 including two of the first motor 11 and the second motor 12 has been described, the demagnetization described above is similarly applied to a system including three or more motors. Determination processing can be applied. When a plurality of three or more motors are provided, one of the plurality of motors is caused to perform the processing of the first motor 11 and the second motor 12 described above, so that either one of the plurality of motors can be operated. It can be determined that demagnetization has occurred.

  The present invention is applicable to a motor drive system that drives one output shaft with a plurality of motors.

DESCRIPTION OF SYMBOLS 1 motor drive system 11 1st motor 12 2nd motor 21 1st control part 22 2nd control part 31 1st current sensor 32 2nd current sensor 33 rotation angle sensor 34 demagnetization determination part 40 output shaft 50 battery

Claims (1)

A motor drive system for driving one output shaft with a plurality of motors,
A first motor that generates a rotational torque of the output shaft based on a first current;
A second motor that generates a rotational torque of the output shaft based on a second current;
Rotational torque in the forward direction is generated in the first motor, and rotation torque in the opposite direction is generated in the second motor, and at least one of the first current and the second current is a predetermined reference current. A control unit configured to control the first current and the second current such that the rotational torques of both are in balance with each other and the output shaft is stopped;
When the output shaft can not be stopped by the current control of the control unit, or when the absolute value difference between the first current and the second current when the output shaft can be stopped exceeds the predetermined threshold value, And a determination unit that determines that demagnetization occurs in any of the first motor and the second motor,
Motor drive system.

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