JPS6129234B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a motor positioning device for driving a load at high speed and in steps, and more particularly to a hunting prevention circuit in a motor positioning device for driving a tape winding frame of a magnetic recording/reproducing device.

For example, a digital servo system is often used in a positioning device for a motor that drives a rotating head of a magnetic recording/reproducing device. An example of this type of device is shown in FIG. In the figure, 1 is a load such as a tape winding frame of a magnetic recording/reproducing device, and 2 is a load 1.
3 is a position detector that detects the rotational displacement of the motor 2 as a digital quantity; 4 is a direction discriminator that determines the rotational direction of the motor 2 based on the detection signal from the position detector 3;
5 is a comparator that compares the control input signal with the signal from the direction discriminator 4 to determine the positional deviation, 6 is a DA converter that converts the positional deviation from a digital quantity to an analog quantity, and 7 is used to suppress an increase in motor inertia. 8 is a power amplifier. The above-mentioned positioning of the load 1 directly connected to the motor 2 is performed by detecting the rotational displacement of the motor 2 as a digital amount by the position detector 3, feeding back this rotational displacement amount to the comparator 5, and comparing it with the control input signal. Find the position deviation,
This positional deviation is applied to the motor 1 via the phase compensation circuit 7 and the power amplifier 8, and the rotation of the motor 2 is controlled while driving.

In the above-mentioned motor positioning device, high accuracy and high speed may be achieved. In such a case, when the amount of rotational displacement of the motor 2 quantized by the position detector 3 is applied to the phase compensation circuit 7 via the DA converter 6, the output signal from the phase compensation circuit 7 As shown in FIG. 2, quantization noise occurs. This quantization noise has caused a phenomenon in which the motor cannot be stopped stably (hunting phenomenon). This quantization noise contains a frequency component that is the same as or close to the resonant frequency of the motor 2 shaft, which is set higher than the bandwidth of the normal servo circuit, so it may cause the motor 2 shaft to resonate. . Furthermore, in order to achieve higher accuracy and higher speed of the device, the control loop gain and natural frequency of the device also increase, resulting in drawbacks such as hunting or axial resonance of the motor 2 being likely to occur.

The present invention has been made based on the above-mentioned matters, and is a motor positioning device that requires high precision and high speed, and is capable of preventing hunting without impairing the high precision and high speed of the control system. The purpose is to provide a prevention circuit.

While the motor is in operation, both high precision and high speed are required for control purposes, but when the motor is stopped, only high precision and high speed are not required. Specifically, after the motor enters the stopped state, the motor correction current for correcting the error does not need to respond to fast changes in frequency. On the other hand, if the motor can respond in the opposite direction, the motor may not be able to stop stably.

The present invention is characterized by detecting the rotational position of a load coupled to a motor, and feeding back this rotational position as a digital quantity to the input side.
In the motor positioning device, the positional deviation between the rotational position amount and the motor control input is applied as a deviation control input to the motor via a control system including a DA converter, a phase compensation circuit, and a power amplifier. The control system includes a first control system including a quantization noise removal function, a second control system not including a quantization noise removal function, and a switch means operated by an information signal regarding the rotation of the motor. The hunting prevention circuit is characterized in that the switch means is operated to select the first control system when the motor is stopped.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 3 shows a control circuit of a motor positioning device including an example of the circuit of the present invention, and in the figure, the same reference numerals as in FIG. 1 indicate the same parts. 9 is a low-pass filter provided in series between the phase compensation circuit 7 and the power amplifier 8, and this low-pass filter 9 functions to remove quantization noise including high frequency components unrelated to control characteristics. do.

When the amount of rotational displacement of the motor 2 quantized by the position detector 3 is applied to the phase compensation circuit 7 via the DA converter 6, the motor control signal that becomes the output signal from the phase compensation circuit 7 is If quantization noise is included, this quantization noise is removed by the low-pass filter 9. Therefore, motor 2
Since a control signal that does not include quantization noise larger than the bandwidth included in the control signal for the motor 2 is applied to the motor 2, the shaft of the motor 2 is accurately controlled without causing resonance. In addition, when the motor 2 is stopped, the control is mainly to reduce the steady-state deviation, so the control in conventional equipment, that is, the control that generates the manipulated variable that takes into account the speed of change of the deviation, results in unnecessary amplification of noise. However, the present invention can also improve this point.

FIG. 4 shows a control circuit for a motor positioning device having another example of the circuit of the present invention, and in this figure, the same reference numerals as in FIG. 3 are the same parts.
In this embodiment, the phase compensation circuit 7 is connected to the low pass filter 9 in conjunction with the stopped state and the operating state of the motor 2.
The low-pass filter 9 may be connected to the power amplifier 8 via the low-pass filter 9, or may be connected to the power amplifier 8 without passing through the low-pass filter 9. That is, a low-pass filter 9 is provided in parallel between the phase compensation circuit 7 and the power amplifier 8 via a switch 10, and the switch 10 is switched by a signal 11 indicating information on the stopped state of the motor 2. 7 is connected to a power amplifier 8 through only a low pass filter 9. This makes it possible to remove the quantization noise that tends to occur when the motor 2 is stopped.

FIG. 5 shows a control circuit for a motor positioning device having still another example of the circuit of the present invention, and in this figure, the same parts as those in FIG. 4 are denoted by the same symbols. In this embodiment, a switch 10 is provided at the input part of the differential circuit constituting the phase compensation circuit 7 without using the low-pass filter 9, and the switch 10 is turned on by a signal 11 that informs information of the stopped state of the motor 2. This is what I did.

With this configuration, the above-mentioned fourth
It is possible to exhibit the same effect as the embodiment shown in the figure. Furthermore, according to this embodiment, the low-pass filter 9 is not required, so the circuit configuration is simplified.

As detailed above, the present invention provides a motor positioning device that requires high precision and high speed with a hunting prevention circuit to prevent hunting that occurs in the motor positioning device described above. resonance and its positioning control can be improved.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing a control circuit of a conventional motor positioning device, Fig. 2 is a diagram showing a motor control signal including quantization noise in the conventional device, and Figs. 3 to 5 are diagrams showing an implementation of the circuit of the present invention. FIG. 3 shows a control circuit of a motor positioning device with an example; 1... Load, 2... Motor, 3... Position detector, 5... Comparator, 6... DA converter, 7... Phase compensation circuit, 8... Power amplifier, 9... Low pass filter, 10...Switch.

Claims (1)

[Claims] 1. Detecting the rotational position of a load coupled to a motor,
This rotational position is fed back to the input side as a digital quantity, and the positional deviation between this rotational position quantity and the motor control input is input as a deviation control input to the motor via a control system including a DA converter, a phase compensation circuit, and a power amplifier. In the motor positioning device, the control system includes a first control system including a quantization noise removal function, a second control system not including a quantization noise removal function, and a control system related to rotation of the motor. 1. A hunting prevention circuit comprising: switch means operated by an information signal, said switch means being operated to select a first control system when the motor is stopped. 2. The hunting prevention circuit according to claim 1, wherein the first control system is constructed by connecting a phase compensation circuit and a quantization noise removal means in series. 3. The hunting prevention circuit according to claim 1, wherein the first control system is configured by blocking a differential circuit within the phase compensation circuit.