JP2008118750A - Servo controller and current detection method for servo controller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method that makes it possible to enhance the resolution of current detection and suppress vibration when a servo controller is at a stop. <P>SOLUTION: A current detection method is for a servo controller including a current detecting means by a ΔΣ type A/D converter. The servo controller includes a switching means 11 capable of switching the filtering time of a filter 10. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to a servo control device that drives a machine or the like with a servo motor and a current detection method for the control device.

Conventionally, due to magnetic saturation, the current control gain is lowered at low speeds to suppress current control instability (see, for example, Patent Document 1). Some elevators or the like switch the current resolution when the motor is stopped according to the loading situation (see, for example, Patent Document 2).
In FIG. 6, 7 is a current detection device, 8 is a comparator, 9 is a current control unit, 13 is a current control gain reduction unit, and the current control gain reduction unit 13 lowers the current control gain.
In FIG. 7, 24 is a current scale calculation unit, 26 is a current switch, 27 is an A / D converter, 28 is a three-phase / two-phase coordinate conversion, 29 is a current control unit, and a current switch according to the load. 26 and the current scale calculation unit 24 switch the current resolution.
Thus, in the conventional control apparatus, the procedure of lowering the current control gain at low speed or switching the current resolution in accordance with the load situation has been taken.
Japanese Patent Laying-Open No. 2003-189852 (page 7, FIG. 1) Japanese Patent No. 3310166 (page 6, FIG. 1)

In the conventional method, since the procedure of lowering the current control gain at low speed is taken, there is a problem that lowering the current control gain is vulnerable to load fluctuations. Further, in the case of Document 2, there is a problem that it is effective only when the load of the loading state fluctuates and is not effective because it depends on the load state at the time of stoppage.
The present invention has been made in view of such problems, and an object of the present invention is to provide a method capable of increasing the resolution of current detection during stop and suppressing vibration during stop.

In order to solve the above problem, the present invention is as follows.
According to the first aspect of the present invention, in the current detection method of the servo control device provided with current detection means by ΔΣ A / D conversion, the servo control device is provided with switching means for switching the filtering time of the filter. It is.
According to a second aspect of the present invention, the filter is switched so that the filtering time for current detection is lengthened when the motor is stopped and the filtering time for current detection is shortened when the motor is moved.
According to a third aspect of the present invention, the filter switching means performs the stop or movement state of the motor based on an encoder signal.
According to a fourth aspect of the present invention, in the servo control device provided with the current detection means by ΔΣ A / D conversion, the current detection filter is lengthened when the motor is stopped, and the current detection filter is set when the motor is moving. It is provided with switching means for shortening.
According to a fifth aspect of the present invention, there is provided a servo control device including a current detection means by ΔΣ A / D conversion, wherein the servo control device includes a switching means for switching between a speed control mode and a current control mode. It is.
According to a sixth aspect of the present invention, the servo control device is stopped by speed control and position control when the motor is stopped.
According to a seventh aspect of the invention, the switching means performs the stop or movement state of the motor based on an encoder signal.

According to the first to fourth aspects of the present invention, when the motor is stopped, the current detection filter can be lengthened to increase the resolution of the current detection, so that vibration during stop can be suppressed.
According to the invention described in claims 5 to 7, since current control is not performed when the motor is stopped, vibration at the resolution of the encoder can be suppressed, and vibration at the time of stop can be suppressed with a high-resolution encoder.

Hereinafter, specific examples of the method of the present invention will be described with reference to the drawings.

Although various functions and means are built in the actual servo control device, only the functions and means related to the present invention will be described and described in the figure.
FIG. 1 is a diagram showing the configuration of a servo control apparatus that implements the method of the present invention. In the figure, 1 is a microcomputer, 2 is a current amplifier, 3 is a base drive circuit, 4 is a power transistor module, 5 is a motor, 6 is an encoder, 7 is an encoder input circuit, 8 is a shunt resistor for current detection, and 9 is an A / A D converter 10 is a filter, 11 is a filter switching means.
The operation of the circuit configured as described above will be described with reference to FIG. First, the microcomputer 1 receives a position command or a speed command from an external controller or the like. In the case of position control, the position from the encoder 6 is input by the encoder input circuit 7 from the position command, the position feedback is subtracted, the position control is performed by applying the control gain, and the speed feedback is subtracted from the output speed command. Then, speed control is performed by applying a control gain. Then, the current amplifier 2 subtracts the current feedback from the output current command, and performs the current control by applying the control gain. The power transistor 4 is driven by the output of the current control through the base drive driving circuit 3 to control the motor 5. In the current feedback, the current of the motor 5 is detected as a voltage by the current detection shunt resistor 8. The voltage is converted into data by a ΔΣ A / D converter 9 and a filter 10 and current feedback is performed. Here, the ΔΣ method will be briefly described. The ΔΣ method is a method of converting an analog signal into a pulse density of a pulse train by feeding back an output to an input using an integrator and a comparator.
The pulse train density can be digitized by, for example, measuring a pulse train within a certain time with a counter or the like, and filtering this measured value with a filter 10 to produce data.
The filter 10 can change the resolution of the current feedback by changing the time constant of the filter with the filter switching means 11. When changing the resolution of the current feedback, the microcomputer 1 changes the current command commanded to the current amplifier 2 and the filter switching means 11.
As an example, when the filter is a moving average filter, if the time constant is increased, the pulse train density is averaged longer and measured. Although the pulse train density depends on the performance of the integrator, comparator, etc., the conversion speed is fast and fine, so it can be measured more finely if measured longer. By increasing the filter time constant in this way, the resolution can be increased.

FIG. 2 is a flowchart showing a current detection method. The method of the present invention will be described step by step with reference to this figure.
First, in step 21, it is confirmed whether the motor is stopped. When the motor is stopped, the filter setting is lengthened using the filter switching 11 in step 22. In other words, the filtering time is set to 18 μs, and the current feedback resolution is set to about 12 bits to finely control. If the motor is not stopped, the filter switching 11 is set to normal filter setting in step 23. That is, the filtering time is set to 5 μs and the current feedback resolution is normally controlled with about 8 bits. In step 24, the current is input through the filter and the A / D converter that have been set.
Thus, since the filter of the A / D converter is lengthened while the motor is stopped, the resolution of the current feedback can be changed, and the vibration at the time of stopping can be suppressed by controlling the small current. In other words, if the load disturbance or the like is small at the time of stopping, a transient response as at the time of moving is not required. Therefore, even when the response is slightly reduced by lengthening the filter, vibration at the time of stopping can be suppressed. The current amplifier 2 may be performed by the microcomputer 1.

Next, a second embodiment of the present invention will be described. The configuration is shown in FIG. Since the operation is the same as that of the first embodiment, the description thereof is omitted. The current feedback is switched by the current detection shunt resistor 8, the A / D converter 9, and the filter 10 without being switched.
FIG. 5 is a control block diagram of current control. In the figure, 51 is current control, 52 and 54 are motors, power conversion, and 53 is a voltage command conversion constant. When the motor is stopped, it is switched to the lower side, the current command is converted into a voltage command by the voltage command conversion constant 53, and the current flows through the motor by the motor and power conversion 54. However, since there is no current control, current flows through the motor, torque is generated, and when it appears as speed, it is suppressed by speed control.
FIG. 4 is a flowchart showing a current control method. The method of the present invention will be described step by step with reference to this figure.
First, in step 41, it is confirmed whether or not the motor is stopped. If the motor is stopped, the current command is converted to a voltage command in step 42 and the motor is stopped without current control. In this case, since current control is not used, the motor is stopped by speed control. Since the speed control is stopped, the speed control is required to have a high resolution and a high response, but there is no fluctuation due to the current resolution. If the motor is not stopped, the motor is controlled in step 43 by normal current control.

  In this way, current control while the motor is stopped is eliminated, so control without regard to the resolution of current feedback can suppress vibration during stop, etc.In other words, if the load disturbance is small during stop, Since a transient response is not required, if the resolution of the speed control is high and the response of the speed control is high, the current control can be supplemented by the speed control. Can do it. The current amplifier 2 may be performed by the microcomputer 1.

The block diagram which shows the structure of the servo control apparatus which applies the method of this invention The flowchart which shows the process sequence of the principal part of this invention. The block diagram which shows the structure of the servo control apparatus to which the 2nd method of this invention is applied. The flowchart which shows the process sequence of the 2nd method of this invention. Current control block diagram showing processing of the second method of the present invention The figure which shows the structure of the current control apparatus to which the conventional method is applied The figure which shows the structure of the current control apparatus to which the conventional 2nd method is applied.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Microcomputer 2 Current amplifier 3 Base drive circuit 4 Power transistor module 5 Motor 6 Encoder 7 Input circuit 8 Current detection shunt resistor 9 A / D converter 10 Filter 11 Filter switching 51 Current control 52, 54 Motor, Power conversion 53 Voltage Command conversion constant

Claims (7)

In a current detection method of a servo control device provided with current detection means by a ΔΣ A / D converter,
The servo control device comprises a switching means for switching a filtering time of a filter of the A / D converter, wherein the servo control device has a current detection method.   2. The current detection method for a servo control device according to claim 1, wherein the filter is switched so that the filtering time for current detection is lengthened when the motor is stopped and the filtering time for current detection is shortened when the motor is moved.   2. The current detection method for a servo control device according to claim 1, wherein the filter switching unit performs the stop or movement state of the motor based on an encoder signal. In a servo control device having a current detection means by ΔΣ A / D conversion,
A servo control device comprising switching means for lengthening a current detection filter when the motor is stopped and shortening a current detection filter when the motor is moving. In a servo control device having a current detection means by ΔΣ A / D conversion,
The servo control device comprises a switching means for switching between a speed control mode and a current control mode.   6. The servo control device according to claim 5, wherein the servo control device is stopped by speed control and position control when the motor is stopped.   6. The servo control apparatus according to claim 5, wherein the switching unit performs the stop or movement state of the motor based on an encoder signal.

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