JP2007228700A - Motor control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem that, when there occurs an offset error in a resolver, an electrical angle specified by the resolver is displaced from an actual electrical angle of a motor, a current fed to the motor is displaced from a d-axis, a q-axis component is fed to the motor, and thus output torque is generated at the motor. <P>SOLUTION: The charge of a capacitor 42 is fed to the motor 20 as the d-axis current. The number of revolutions of the motor 20 at that time is detected from an output of an angle sensor 22, and the offset error θ<SB>ofs</SB>of the angle sensor 22 is detected on the basis of the rotation state of the motor. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a motor control device that controls current supply to a motor in accordance with a motor drive command, and more particularly to a device that accurately detects a rotation angle of a rotor.

  Conventionally, an electric vehicle and a hybrid vehicle are known. In these vehicles, a motor is mounted and the vehicle is driven by the driving force of the motor. As this motor, a brushless AC motor is usually employed, and the motor is driven by converting DC power from the on-vehicle battery into AC current by an inverter. In particular, since an inverter is used, it is easy to control the output torque of the motor by controlling the drive current to the motor. Usually, the d-axis (excitation) current command and the q-axis (torque) current command are calculated according to the output torque command. Based on this, vector control for controlling the motor drive current is used.

  Here, in the motor drive control as described above, the motor drive current supplied to each phase stator is determined based on the rotor position (motor electrical angle). Therefore, it is necessary to detect the motor electrical angle by some means, and an angle sensor such as a resolver that detects the motor electrical angle by the current generated in the orthogonal coils is used, or the electrical angle is detected sensorlessly from the back electromotive force. .

  Among these methods, a method using a resolver is widely used because it does not require difficult processing and can easily detect an electrical angle.

  Here, when the resolver is used, the electrical angle with respect to the resolver is correctly detected and the output is obtained. However, if there is an error in the position where the resolver is attached, this becomes an offset error. The attachment position is set as accurately as possible, but the error cannot be reduced to 0, and a slight error is inevitable.

  On the other hand, although it is possible to measure the offset error of the resolver, it is necessary to measure the offset error for each resolver attached to each motor, which requires a large amount of work and is difficult to implement. It is.

  In addition, the slight error has little influence on the output torque and the like in the motor drive, and the measurement and correction work for the offset error is not normally performed.

Japanese Patent Laid-Open No. 10-262397

  Here, a capacitor is provided on the input side of the inverter in order to stabilize the inverter input voltage. When the vehicle stops running, that is, when the vehicle ignition is off, the electric charge stored in the capacitor is discharged in consideration of safety and the like. For this discharge, it is conceivable to use a resistance for discharging, but it is conceivable not to provide a resistance, but to cause a current to flow through the motor for discharging. In this case, it is preferable to discharge by supplying only the d-axis current to the motor so that the motor does not generate rotational torque.

  However, as described above, when there is an offset error in the resolver, the electrical angle specified by the resolver is deviated from the actual electrical angle of the motor, and accordingly, the current supplied to the motor is deviated from the d-axis. For this reason, the q-axis component is also supplied to the motor, and there is a problem that output torque is generated in the motor. And when a motor outputs a torque, a vibration may generate | occur | produce in a vehicle and there exists a request | requirement of wanting to prevent this.

  Note that the rotation angle sensor includes a Hall element, and the same problem occurs when this is used.

  The present invention is a motor control device that controls current supply to a motor in accordance with a motor drive command, and includes an electrical angle detection means that detects an electrical angle of the motor, and a current supplied to the motor in accordance with the detected motor angle. Current supply means for vector control for supplying electric current, and the electric angle according to the rotation state of the motor when the current supply means is controlling the supply current to the motor to supply only the d-axis current to the motor. Error detection means for detecting an error of the electrical angle detected by the detection means, and the electrical angle detected by the electrical angle detection means is corrected by the error detected by the error detection means.

  And a capacitor for holding a DC voltage, wherein the current supply means converts a DC output of the capacitor into a predetermined AC power and supplies the AC power to the motor, and the current supply means is provided when the motor is stopped. It is preferable that only the d-axis current is supplied to the motor to discharge the charge held in the capacitor, and the error detection means detects an error when discharging the capacitor charge.

  In addition, the error detection means has a map showing the relationship between the rotation state when only the d-axis current is supplied and the error in the rotation angle, and using this map, the error in the electrical angle detection means is calculated. It is preferable to detect.

  The electrical angle detection means is preferably a resolver.

  According to the present invention, the error of the electrical angle detected by the electrical angle detection means is detected according to the rotation state of the motor when the supply current to the motor is controlled so that only the d-axis current is supplied to the motor. The detected electrical angle is corrected based on this. Therefore, only d-axis current can be supplied, and generation of rotational torque in the motor can be effectively prevented.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing the overall configuration of the system. In the case of a vehicle, first, an output torque command of the motor is determined from the accelerator opening, the vehicle speed, and the like. Based on this output torque command, d-axis and q-axis current commands id ^* and iq ^* are calculated in order to perform vector control.

The obtained d-axis current command id ^* and q-axis current command iq ^* are supplied to the subtractors 10d and 10q, where deviations Δid and Δiq from the current d-axis and q-axis current id and iq are obtained. . Based on the obtained deviations Δid and Δiq, the PI calculators 12d and 12q calculate the d-axis voltage command Vd and the q-axis voltage command Vq by the PI control calculation. That is, the d-axis and q-axis currents id and iq are corrected by the sum of the P feedback value obtained by multiplying the deviations Δid and Δiq by the P gain and the I feedback value obtained by multiplying the integral value of the deviations Δid and Δiq by the I gain. At the same time, this is converted into a voltage command to calculate the d-axis and q-axis voltage commands Vd and Vq.

  The calculated d-axis and q-axis voltage commands Vd and Vq are supplied to the coordinate conversion unit 14 and converted from the d and q axes to the three axes U, V and W. Motor drive voltage commands Vu, Vv, Vw are obtained. The obtained motor drive voltage commands Vu, Vv, Vw are converted into PWM control signals in the PWM converter 16. This conversion is performed, for example, by comparing the motor drive voltage commands Vu, Vv, Vw with a triangular wave having a predetermined frequency and determining the duty ratio of the PWM control signal. In this way, a PWM control signal for each phase is formed and supplied to the inverter 18.

  The inverter 18 receives a DC voltage from the battery 40 between the positive electrode bus and the negative electrode bus and converts it into a three-phase AC current. An arm formed by connecting two switching elements in series includes a positive electrode bus and a negative electrode bus. Three are connected in between, and the middle point of each arm is a three-phase output. Then, the two switching elements of each arm are complementarily turned on by the PWM control signal of each phase, whereby a motor driving current is output from the middle point of each arm. This motor drive current is supplied to the motor 20, and the motor 20 is driven with an output corresponding to the output torque command. A capacitor 42 for stabilizing the voltage is provided between the positive and negative buses of the inverter 18 on the DC voltage input side from the battery 40.

Here, the phase of the motor drive current is determined according to the electrical angle (rotor position) of the motor 20. Accordingly, an angle sensor (for example, a resolver) 22 is attached to the motor 20, and the rotor position (motor electrical angle) θ ₀ is detected.

The output θ ₀ of the angle sensor 22 is supplied to the correction unit 24 where the offset error θ _ofs is added to correct the electrical angle θ of the motor 20 (θ = θ ₀ + θ _ofs ). The corrected coordinate conversion unit 26 is supplied from the correction unit 24. The coordinate converter 26 is supplied with motor drive currents iv and iw supplied from the current sensors 28v and 28w, and these are coordinate-converted into d and q axes to calculate id and iq, which are described above. The current value is supplied to the subtracter 10 as the current d, q axis current id, iq.

  The electrical angle θ from the correction unit 24 is also supplied to the coordinate conversion unit 14, and the coordinate conversion unit 14 determines the phases of the motor drive voltage commands Vu, Vv, and Vw based on the electrical angle θ. During normal operation, the correction of the electrical angle in the correction unit 24 is not necessarily performed.

And in this embodiment, in order to detect offset error (theta) _ofs of the angle sensor 22, it has the following structures. When the offset error θ _ofs is detected, the initial value of the offset error θ _ofs is zero in the correction unit 24.

First, when the ignition of the vehicle is turned off, only the d-axis current is supplied to the motor 20 in order to discharge the charging charge of the capacitor provided on the input side of the inverter 18 (between the positive and negative buses of the inverter 18). Supply. Therefore, the predetermined value for a discharge as a d-axis current command id ^* (e.g. -50 A) is output, 0A is set as the q-axis current command iq ^*.

  Thus, if only the d-axis current is supplied to the motor 20, the motor rotation speed N should be zero. However, if there is an error in the electrical angle θ detected by the angle sensor 22, there is an error in the phase of the motor drive voltage commands Vu, Vv, Vw obtained by calculation in the coordinate conversion unit 14, and a q-axis current component is generated. As a result, rotational torque is generated in the motor 20. Therefore, vibration may occur in the vehicle.

Therefore, the output θ ₀ of the angle sensor 22 at the time of discharging is supplied to the rotation speed calculation unit 30 where the motor rotation speed N is calculated. The calculated motor rotation speed N is supplied to the subtractor 32. The subtracter 32 subtracts N = 0, which is the target motor rotation speed at that time, from the motor rotation speed N (N = N), and supplies the deviation N to the PI calculation section 34. The PI calculator 34 multiplies the deviation N by the P gain to calculate the P feedback value, and also multiplies the deviation N by the I gain to calculate the I feedback value, and adds these to add an electrical angle offset error θ. _ofs is calculated.

That is, the offset error θ _ofs is calculated by θ _ofs = P gain × (actual rotational speed N−rotational speed command 0) + I gain × Σ (actual rotational speed−rotational speed command 0).

The calculated offset error θ _ofs is supplied to the correction unit 24, and the offset error θ _ofs in the correction unit 24 is changed to a new value. Then, based on the new electrical angle θ = θ _o + θ _ofs in the correction unit 24, the motor drive current is controlled and this is repeated.

By sequentially changing the offset error θ _ofs by such processing, the offset error θ _ofs converges to a predetermined value and the motor rotation speed N converges to 0 as shown in FIG. The offset error θ _ofs obtained in this way is stored in the correction unit 24, and is used at the normal time and when the capacitor 42 is charged and discharged from the next time.

In this way, when discharging the capacitor charge when the ignition is off, the motor electrical angle θ = θ _o + θ _ofs corrected by the correction unit 24 is used, so that torque generation in the motor 20 is suppressed and vibration is generated. Can be prevented. That is, if the electrical angle detected by the angle sensor 22 is deviated, as shown in FIG. 3, the d-axis and q-axis, which are the premise of the calculation indicated by the solid line, deviate from the correct d-axis and q-axis indicated by the broken line. End up. Thereby, rotational torque is generated in the motor 20 by the d-axis current.

In the present embodiment, by correcting the electrical angle with the offset error θ _ofs , the d-axis and q-axis that are the premise of the calculation can be brought close to the correct one.

The offset error θ _ofs is caused by an attachment error and does not basically change, but the above-described correction operation may be repeated at an appropriate frequency.

  FIG. 4 is another embodiment, and the output of the rotation speed calculation unit 30 is supplied to the memory 36. As shown in Table 1, the memory 36 stores the relationship between the rotational speed and the offset error (shift angle).

That is, the relationship between (i) rotation direction, (ii) rotation speed, and (iii) deviation angle when the discharge current is shifted from the d-axis is obtained in advance by experiment and stored in the memory 36. Therefore, by reading out the corresponding deviation angle from the memory 36 based on the motor rotation speed N when only the d-axis current is caused to flow by the discharge current, and supplying this to the correction unit 24 as the offset error θ _ofs , the correction unit offset error theta _ofs in can be corrected to the correct value.

It is a figure which shows the structure of embodiment. It is a figure explaining the operation _| movement which _{calculates |} requires offset error (theta) _ofs . It is a figure which shows the shift | offset | difference of d axis and q axis. It is a figure which shows the structure of another embodiment.

Explanation of symbols

  10, 32 subtractor 12, 34 PI calculator, 14, 26 coordinate converter, 16 PWM converter, 18 inverter, 20 motor, 22 angle sensor, 24 corrector, 28 current sensor, 30 rotation speed calculator, 36 Memory, 40 battery, 42 capacitor.

Claims (4)

A motor control device that controls current supply to a motor in response to a motor drive command,
Electrical angle detection means for detecting the electrical angle of the motor;
Current supply means for vector control for supplying current to the motor according to the motor drive command and the detected electrical angle;
The current supply means detects an error in the electrical angle detected by the electrical angle detection means according to the rotation state of the motor when the supply current to the motor is controlled so that only the d-axis current is supplied to the motor. Error detection means for
Have
An electric angle detected by the electric angle detecting means is corrected by an error detected by the error detecting means. The motor control device according to claim 1,
Having a capacitor to hold the DC voltage,
The current supply means converts the direct current output of the capacitor into predetermined alternating current power and supplies it to the motor,
The current supply means discharges the electric charge held in the capacitor by supplying only the d-axis current to the motor when the motor is stopped.
The motor control apparatus according to claim 1, wherein the error detection means detects an error when discharging the electric charge of the capacitor. The motor control device according to claim 1 or 2,
The error detection means has a map showing the relationship between the rotation state when only the d-axis current is supplied and the error in the rotation angle, and detects an error in the electrical angle detection means using this map. The motor control apparatus characterized by the above-mentioned. In the motor control device according to any one of claims 1 to 3,
The motor control device according to claim 1, wherein the electrical angle detection means is a resolver.

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