JP2001112300A - Motor control system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control the torque of a motor, without having to detect current to the motor. SOLUTION: This motor 11 is driven by the current outputted from a three- phase inverter 12, and the three-phase inverter 12 is controlled by a controller 13. The current command converting part 13a of the controller 13 converts the inputted torque command signal of the motor 11 into a motor current required to obtain its torque and outputs it to a voltage-computing part 13b. The voltage-computing part 13b computes applied voltages in the respective phases of the motor, respectively and outputs it to the three-phase inverter 12. The three-phase inverter 12 outputs respective computed applied voltages to the motor 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control system for a motor used as a drive source for an electric vehicle.

[0002]

2. Description of the Related Art A three-phase motor used as a drive source of an electric vehicle is generally disclosed in Japanese Patent Application Laid-Open No. H11-32499 and the like.
The feedback control is performed by the three-phase inverter of the type so that the motor torque and the like become constant. FIG. 2 shows an example of such a motor control system. In this motor control system, the motor 21 includes a three-phase inverter 22
Are controlled by the U-phase, V-phase, and W-phase winding currents output from the
It is controlled by a control device (CPU) 23. Two U-phase and V-phase winding currents output from the three-phase inverter 22 and supplied to the motor 21 are respectively detected by current sensors 24.

The control device 23 outputs three control signals for each winding current output from the three-phase inverter 12 based on the input torque command signal so that the motor 11 has a constant torque, for example. It is supposed to. The control device 23 includes a current command converter 23 that converts an input torque command signal into respective winding currents and outputs the current.
a, a current calculator 23c for calculating each winding current based on the detection result of each current sensor 24, and a voltage calculator 23b to which respective outputs of the current command converter 23a and the current calculator 23c are input. Have been.

[0004] A voltage calculation unit 23b is supplied with a winding current corresponding to the torque command signal from a current command conversion unit 23a. The current is also calculated by the current calculation unit 2.
3c. The voltage calculator 23b calculates a difference between the winding current corresponding to the torque command and the winding current output from the three-phase inverter 42, and outputs a voltage corresponding to the difference for each phase of the motor 21. Is calculated. Then, a signal corresponding to the obtained voltage of each phase is output to the three-phase inverter 22. The three-phase inverter 22, which is a power converter, outputs the U-phase, V-phase, and W-phase winding voltages of the motor 21 based on the voltage signals of the respective phases output from the voltage calculator 23b. Thereby, the motor 21
Is controlled to have a predetermined torque.

[0005]

In such feedback control, the winding current output from the three-phase inverter 22 is detected by the current sensor 24, and the current sensor 24
The control signal of the three-phase inverter 22 is calculated based on the winding current detected by the control circuit. For this reason, if the current sensor 24 fails, the torque control of the motor 21 may not be able to be performed.
In the case of a motor used as a drive source of an electric vehicle, there is a possibility that running may be disabled due to a failure of the current sensor 24.

An object of the present invention is to provide a motor control system capable of controlling a motor without detecting a current to the motor by a current sensor or the like. is there.

[0007]

SUMMARY OF THE INVENTION A motor control system according to the present invention is characterized in that, when a control command for a motor is given, means for calculating a motor current required to execute the control command is provided. Means for calculating respective applied voltages in each phase of the motor based on the motor current and the characteristics of the motor, and outputting the calculated applied voltages to each phase of the motor.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an example of an embodiment of a motor control system according to the present invention. In this control system, the torque of a three-phase motor 11 used as a drive source of an electric vehicle is controlled.

The three-phase motor 11 has a U (pulse amplitude modulation) type three-phase inverter
The three-phase inverter 12 is controlled by the winding currents of the three phases, the V phase and the W phase.
U) 13.

A torque command signal is input to the control device 13 as a control command signal for the motor 11. The input torque command signal is transmitted to the control device 13 in order to obtain the torque. A current command converter 13a for converting the motor current into a command signal corresponding to the required motor current;
Voltage calculation unit 13 that calculates the voltage of each phase of the phase, V phase, and W phase
b. Then, a control signal corresponding to the voltage of each phase calculated by the voltage calculation unit 13b is output to the three-phase inverter 12, which is a power converter.

The three-phase inverter 12 includes a voltage calculator 13b
Based on the control signal corresponding to the voltage of each phase calculated in the above, each high-voltage winding current corresponding to the U-phase, V-phase, and W-phase is output.

The control contents of the control device 13 will be specifically described. In the current command converter 13a of the control device 13, based on the input torque command, d
Command signals Id ^* and I of the motor current corresponding to the -q coordinate
q ^* are calculated and output to the voltage calculation unit 13b.

The voltage calculating section 13b receives the input motor current command signals Id ^* and Iq ^* and the characteristics of the motor 11,
That is, the command signals Vd ^* and Vq ^{* of the} voltage applied to each phase of the motor in the dq coordinates based on the winding resistance R, the rotation speed We, the induced voltage constant Ke, and the inductances Ld and Lq of the motor 11, respectively ^. Are calculated by the following equations (1) and (2), respectively.

Vd ^* = R · Id ^* −We · Lq · Iq ^* (1) Vq ^* = R · Iq ^* + (Ke + Ld · Id ^* ) · We (2)

As described above, when the command signals Vd ^* and Vq ^* of the applied voltage in the dq coordinates are calculated based on the equations (1) and (2), the voltage calculator 13b calculates
Based on the applied voltage commands Vd ^* and Vq ^* on the dq coordinates, the voltage command signals Vu, Vv, Vw applied to the U-phase, V-phase, and W-phase windings of the motor 11 are respectively described below. The calculation is performed based on the equations (3), (4), and (5).

Vu = (2/3) ^1/2 · (Vd ^* · cosθ−Vq ^* · sinθ) (3) Vv = (2/3) ^1/2 · ｛Vd ^* · cos (θ−2π / 3) −Vq ^* · sin (θ−2π / 3)｝ (4) Vw = −Vu−Vv (5)

When the voltage command signals Vu, Vv, and Vw applied to the U, V, and W phases of the motor 11 are calculated in the voltage calculator 13b, the voltage commands Vu are calculated. , Vv, Vw are output to the three-phase inverter 12, respectively. Then, the three-phase inverter 12 as a power converter sends a winding current corresponding to each of the voltages Vu, Vv, Vw to the motor 11 based on a control signal corresponding to each of the voltage command signals Vu, Vv, Vw.
Are output to the U, V, and W phases, respectively. As a result, the predetermined voltages Vu, Vv, Vw are applied to the respective windings of the motor 11, and the motor 11 is rotated so as to have a predetermined torque corresponding to the torque command signal. .

As described above, in the motor control system according to the present invention, the torque of the motor 11 can be controlled without detecting the current supplied from the three-phase inverter 12 to the motor 11 by the current sensor or the like. Therefore, the control system of the present invention can reduce the number of parts,
It is economical.

In the case where the current to the motor is detected by a current sensor and the torque of the motor is controlled, if the current sensor fails, the control contents of the control system of the present invention are the same. Thus, the torque control of the motor can be continued without using the current sensor.

In the above-described embodiment, the case of the torque control for controlling the motor to a predetermined torque has been described. A number control can be implemented.

[0021]

According to the motor control system of the present invention, since the motor can be controlled without using the current sensor, there is no need to worry about the failure of the current sensor. Further, also in a motor control system using a current sensor, when the current sensor fails, the motor can be controlled without any trouble. In addition, since the control of the motor can be performed without using a current sensor, the number of parts of the motor control system is reduced, which is economical.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an example of an embodiment of a motor control system according to the present invention.

FIG. 2 is a block diagram illustrating an example of a conventional motor control system.

[Explanation of symbols]

 Reference Signs List 11 motor 12 three-phase inverter 13 controller 13a current command converter 13b voltage calculator

Claims (1)

[Claims] When a control command to a motor is given, a motor current required to execute the control command is calculated, and the motor current is calculated based on the obtained motor current and motor characteristics. Means for calculating the applied voltage in each phase of each of the above, and outputting each of the calculated applied voltages to each of the phases of the motor.