JP2687062B2 - Motor control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor control device for adjusting an offset of a motor current.

[0002]

2. Description of the Related Art Japanese Patent Laid-Open No. 63-274390 discloses a conventional controller for adjusting an offset of a motor current.
Alternatively, a structure as shown in JP-A-2-123969 is known.

FIG. 8 is a block diagram showing an outline of such a conventional technique. Reference numeral 1 denotes a torque command signal T ^* and a current command signal I ^* (indicating a vector amount, based on an output from a magnetic pole position detecting portion described later, The same shall apply hereafter). 2 is a current control section that converts a current signal into a voltage signal based on the current command signal I ^* and outputs the voltage signal.
3 is a pulse width modulation (PWM) based on a voltage command signal V ^* (indicating a vector amount, the same applies to the following).
And a sub-harmonic PWM section 4 for performing an inverter section for converting a direct current into an alternating current based on a switching function S (indicating a vector quantity, the same applies to the following).
5 is an electric motor which is a load driven by the output signal of the inverter unit 4, 6a, 6b a current detector for detecting an output current of the inverter unit 4, 7 current detector 6a, 6b output signal v _v a, v _u AD converter for converting the digital signals, 8 output signals _i lv of the AD converter 7, _{i lu}
The current offset compensating unit 10 is an encoder, and 11 is an encoder. The current feedback amount I ₂ (indicating a vector amount, the same applies to the following) is created by subtracting the offset compensation amount from the current offset compensating unit. It is a magnetic pole position detection unit that is controlled by the output of 10 to detect the magnetic pole position θ and output it to the current command creation unit 1. The current command generator 1, the current controller 2, and the current offset compensator 8 compose a controller 9 including an MPU, and the controller 9 outputs an inverter stop signal to the inverter unit 4. In addition, the inverter unit 4
Therefore, i _u , _iv , and i _w are output to the load 5 as a result of applying a voltage according to the switching function S.

Here, each signal is expressed by the following equation.
The offset compensation amount I _o is the output i of the AD converter when the inverter is stopped by the inverter stop signal.
It is a value held by sampling and holding _lu and i _lv , respectively.

[0005]

(Equation 1)

With such a configuration, the current detectors 6a, 6b
As a description will be given of a case where a Hall CT (Hall Current Lance) is used as the Hall element, the Hall elements are arranged as shown in FIG. Reference numeral 13 is a core formed by laminating silicon steel sheets, 14 is a winding wound around the core 13 with a number of turns N, 15 is a Hall element arranged in the gap 13A of the core 13, and 16 is an amplifier connected to the Hall element 15. Is.

Such a Hall CT converts a current into a voltage and outputs it in the process as shown in FIG.

Since the core 13 forming the current detectors 6a and 6b has a hysteresis characteristic as shown in FIG. 11, the current detectors 6a and 6b are not operated when the inverter unit 4 is not operating.
When the output of 6b is sampled and held via the AD converter 7 (hereinafter referred to as a holding operation), the following operation is performed.

That is, since the magnetic flux density (residual magnetic flux density Br) remains in the core 13 due to the current flowing in the core 13, the current detectors 6a and 6b are as follows even if the inverter unit 4 is not operating. Output a voltage Vo. However, Voff: The voltage Vo during the holding operation is held by the offset voltage generated by the Hall element amplifier.

[0010]

In the conventional motor control device, since the voltage Vr is included in the held voltage Vo, a DC component corresponding to the voltage Vr is superimposed on the current during operation, resulting in a large torque ripple. There is a problem of becoming.

FIG. 12 is a time chart for explaining this situation. It is assumed that the current i changes as time elapses as shown in FIG.
Considering on the hysteresis loop of 3, deceleration (period)
In, the locus shown in FIG. 13 is drawn. Therefore, during the constant speed operation period (period), the current O
Is ideally the origin. This means that the voltage Vo held by the holding operation includes an error with respect to the desired value by Vr corresponding to the residual magnetic flux density, and as a result, the torque ripple becomes large.

Next, considering the acceleration period (period), the trajectory on the hysteresis loop line is as shown in FIG. Therefore, the point corresponding to the current O in the constant speed operation period (period) thereafter is point C in FIG. Thus, the point corresponding to the current O on the hysteresis line is the current flow.
It depends on the one , so it cannot be determined unconditionally, but it is thought that it is almost the origin on average. Therefore, inclusion of Vr in the voltage Vo held in the holding operation results in superposition of a DC component corresponding to the voltage Vr on the current, leading to an increase in torque ripple.

When the torque ripple becomes large in this way, speed unevenness increases during speed control, and accurate positioning becomes difficult during position control, which causes problems in control of the electric motor.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a control device for an electric motor that reduces torque ripple during operation.

[0015]

In order to achieve the above object, the present invention provides a voltage signal based on a current command signal.
Signal for converting into a signal and outputting it, power amplifying means for applying a voltage according to the output of the current controlling portion to the electric motor, and detecting current supplied from the power amplifying means to the electric motor. a current detector, a current offset compensation unit for compensating the offset value included in the output of the current detector, a control device of an electric motor and a motor driven by said power amplifying means, the alternating signal decays with time The above power increase
And degaussing signal command unit supplied to the current detector than the width means, and a switch for supplying to the next stage by switching signal based on the output signal and the current signal of the degaussing signal command unit is provided, this By switching the switch, the power consumption can be increased.
Degaussing the output from the current controller sent to the width means
It is characterized in that it is adapted to be switched between a driving mode and a driving mode .

[0016]

[Operation] A demagnetization signal command unit for supplying an alternating signal that decays with time to the current detector is provided with a switch, and an alternating signal is supplied from the demagnetization signal command unit to the current detector via the switch before performing the holding operation. To do. As a result, the degaussing operation is performed and the residual magnetic flux density of the core forming the current detector is set to 0, so that the torque ripple during operation can be reduced.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a first embodiment of a motor control device according to the present invention. 1 is a current command creating section, 2 is a current control section, 3 is a subharmonic PWM section, 4 is an inverter section, and 5 is an inverter section. An electric motor as a load, 6a and 6b are current detectors composed of cores, 7 is an AD converter, 8 is a current offset compensation unit, 9 is a control unit composed of an MPU (microprocessor unit), 10 is an encoder, 11 is a magnetic pole position In the detection unit, each of the above units has the same configuration as the conventional configuration of FIG. 8 and performs the same operation.

Reference numeral 18 denotes a degaussing current command generator for generating a degaussing signal _Ie ^* (which indicates a vector amount, and the same applies to the following), which is an alternating signal that decays with time.
19 is a degaussing signal I _{e *} or switch for supplying switching the current command signal I ^* Kano any of the signals from the current command production unit 1 to the current controller ^2, from the degaussing current command generating section 18 is there.

FIG. 2 is a block diagram showing the specific configuration of FIG. 1, in which the control unit 9 has a CPU 9A and each of input / output ports 9B to 9H. Sub-harmonic PWM section 3
Has a PWM circuit 3A and a digital carrier (triangular wave) generation circuit 3B. The inverter unit 4 has a large number of transistors 4T and diodes 4D. The AD converter 7 has a multiplexer and is configured to convert the outputs i _lu and i _lv of the current detector in time series. The electric motor as the load 5 is composed of a synchronous motor with a permanent magnet (DC non-commutator motor).

FIG. 3 is a flow chart showing the operation of the first embodiment, which comprises steps a to p.
The calculation of V ^* is calculated from the equations (8-2) to (8-6) shown with reference to FIG. The section A shows the degaussing operation, the section B shows the holding operation, and the section C shows the driving operation. Further, FIG. 4 shows each operation in a time chart.

In FIG. 1, a degaussing current command generator 18 is provided.
The degaussing signal I _e ^* generated by the following equation is expressed by the following equation.

[0022]

(Equation 2)

Next, the degaussing operation, the holding operation, and the operation operation in this embodiment will be described. (A) Degaussing operation In FIG. 1, the switch 19 is switched to the degaussing current command generating unit 18 on the side, and the inverter stop signal output from the control unit 9 to the inverter unit 4 is made inactive as shown in FIG. , Operates the inverter unit 4. Here, by setting the degaussing signal I _e ^* so as to satisfy the equation (1-1), it is possible to flow an alternating current such as i _u in FIG. 4 that decays with time in the current detectors 6a and 6b. it can. As a result, the locus on the hysteresis loop line becomes as shown in FIG. 5, and changes in the order of to. in this case,
It is preferable that the frequency of the alternating current is as high as possible, because the rotor of the electric motor that is the load 5 cannot follow it, and the rotor does not move.

(B) Holding Operation First, as shown in FIG. 4, the inverter stop signal is activated to stop the inverter section 4 while keeping the switch 19 on the side in FIG. Next, the output Vo of the current detectors 6a and 6b is sampled and held as shown in FIG. This value is the offset compensation amount Io.

(C) Driving Operation In FIG. 1, the switch 19 is provided on the side of the current command preparing section 1
Then, the inverter stop signal is made inactive to operate the inverter section 4 as shown in FIG. In this case, the offset voltage of the outputs of the current detectors 6a and 6b can be canceled by subtracting the offset compensation amount Io held in the holding operation (B) from the outputs of the current detectors 6a and 6b.

Therefore, according to the operation of the present embodiment as described above, the current detector 6a,
Since the residual magnetic flux density Br of the core 13 forming 6b can be set to 0, the torque ripple during operation can be reduced. As a result, speed unevenness is reduced during speed control of the electric motor, and accurate positioning is facilitated during position control, so that the electric motor can be smoothly controlled.

FIG. 6 shows a second embodiment of the present invention, which is different from the first embodiment in FIG. 1 in that the current offset compensating section 8 is provided on the current command preparing section 1 side. is there. In the second embodiment, the output signal I ₂ ^* from the current offset compensator 8 is set as in the following equation.

[0028]

(Equation 3)

Then, the current offset is canceled by adding the held value to the current command signal I ^* .

FIG. 7 shows a third embodiment of the present invention, in which a degaussing voltage command generator 20 is provided as compared with the first embodiment of FIG. Then, the degaussing signal V _e ^* from the degaussing voltage command generator 20 is set according to the following equation.

[0031]

(Equation 4)

Then, the degaussing operation is performed by passing an alternating current that decays with time through the current detectors 6a and 6b.

Also in the second and third embodiments as described above, the same effects as in the first embodiment can be obtained with only a difference in the configuration. The present invention can be applied to a DC motor, an induction motor, a reactance AC generator, etc., and the same effects as those of the present embodiment can be obtained.

[0034]

As described above, according to the present invention, since the demagnetizing operation is performed by supplying the alternating current signal, which decays with time, to the current detector from the power amplifying means, it is possible to adjust the offset of the electric motor current. As a result, the torque ripple during operation can be reduced. Moreover, power
Amplification means doubles as demagnetization current supply means, making the device compact
And cost reduction.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a first embodiment of a motor control device according to the present invention.

FIG. 2 is a block diagram showing a specific configuration of FIG.

FIG. 3 is a flowchart illustrating the operation of the first embodiment.

FIG. 4 is a time chart explaining the operation of the first embodiment.

FIG. 5 is a hysteresis characteristic diagram for explaining the operation of the first embodiment.

FIG. 6 is a block diagram showing a second embodiment of the present invention.

FIG. 7 is a block diagram showing a third embodiment of the present invention.

FIG. 8 is a block diagram showing a conventional example.

FIG. 9 is an explanatory diagram of a Hall CT used as a current detector of a motor control device.

10 is an explanatory diagram of the operation of the Hall CT in FIG.

FIG. 11 is a hysteresis characteristic diagram illustrating a conventional problem.

FIG. 12 is a time chart illustrating a conventional problem.

FIG. 13 is a hysteresis characteristic diagram illustrating a conventional problem.

FIG. 14 is a hysteresis characteristic diagram illustrating a conventional problem.

[Explanation of symbols]

 1 Current Command Creation Section 2 Current Control Section 4 Inverter Section 5 Load (Motor) 6a, 6b Current Detector 8 Current Offset Compensation Section 9 Control Section 18 Demagnetization Current Command Generation Section 19 Switch 20 Demagnetization Voltage Command Generation Section

Claims (1)

(57) [Claims] 1. A current control unit that converts a current signal into a voltage signal based on a current command signal and outputs the voltage signal, a power amplification unit that applies a voltage according to the output of the current control unit to a motor, and > a current detector for detecting a current supplied to the motor from the power amplifying means, and the current offset compensation unit for compensating the offset value included in the output of the current detector, and a motor driven by said power amplifying means In the provided motor control device, an alternating signal that decays with time is used to increase the power.
And degaussing signal command unit supplied to the current detector than the width means, and a switch for supplying to the next stage by switching signal based on the output signal and the current signal of the degaussing signal command unit is provided, this By switching the switch, the power consumption can be increased.
Degaussing the output from the current controller sent to the width means
A control device for an electric motor, which is configured to be switched between a driving mode and a driving mode .