JPH0145839B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a motor control device for controlling the speed of a DC motor.

Conventionally, when controlling the rotational speed of a DC motor stably and accurately, two control systems are provided: a speed control system that applies negative feedback to the rotational speed, and a phase control system that applies negative feedback to the rotational phase. Highly accurate rotation was obtained by adding the signals, comparing the added detection signal with a certain fixed reference level, and correcting it. The frequency pull range of the control system using this method is approximately determined by the addition amount of the phase system, and if the addition amount of the phase system is increased to widen the pull range, damping of the control system will worsen and hunting phenomenon will occur in the motor. It may cause. Therefore, in the above method, 10
A pull-in range of only around % could be obtained. However, in the conventional rotation speed control of record players, etc., the rotation speed required of the motor, such as 33r.pm and 45r.pm, is about two or three values, and each rotation speed is changed by a switch etc. The fixed reference level to be compared or the time constant of the frequency-voltage converter used in the speed detector may also be changed at the same time.
Rather, in many cases, high precision and long-term stable rotation at a constant rotation speed after the switching is desired. On the other hand, in devices that require high-density recording such as video discs, in order to effectively utilize the recording surface and achieve stable recording and playback characteristics, information including synchronization signals is kept constant at any radial position. There is a demand for constant relative velocity recording that performs recording and reproduction at a recording density of . In this constant relative velocity recording, the information unit represented by the synchronization signal is recorded on the disk surface (recording medium) at a somewhat uniform length, so it is recorded from the inner circumference to the outer circumference (or vice versa). As the recording position changes continuously, the rotational speed of the turntable motor that rotates the disk, which is the recording medium, is required to change continuously and stably. This rotational speed is determined by the rotational speed of the motor in ω (rad/sec), the radius at which the recording head is located at that time in χ (mm), and the required relative speed as V.
(mm/sec), it becomes a continuous function expressed as ω=V/χ.

Also, during playback, the turntable motor, which is controlled to keep the synchronization signal recorded on the disk at a constant frequency, responds to changes in the playback position, as expressed by the above equation, just like the turntable motor for recording. As a result, the rotation speed changes continuously, but in order for the pick-up device that reads information to be sent at a constant track pitch, the rotation speed of the motor that drives the pick-up device in the radial direction must be controlled by the reduction ratio of the device. It is required to change the rotation speed continuously and stably in synchronization with the turntable motor at a predetermined rotation speed. The same applies to the recording apparatus described above, in which the feed motor is continuously changed in synchronization with the turntable motor.

The present invention has been made in view of the above points, and its purpose is to enable a DC motor to rotate continuously and stably at a required number of rotations in synchronization with an input frequency. The purpose of the present invention is to provide a motor control device that has a significantly improved rotational speed pull-in range.

The present invention will be explained below with reference to Examples.

FIG. 1 shows continuous changes in the rotational speed of the turntable for constant relative velocity recording shown in the example of the above equation. The horizontal axis represents the radial position χ, and the vertical axis represents the rotational speed ω.

FIG. 2 shows a block diagram of one embodiment of the invention. 1 is a frequency oscillator, which is a device that continuously generates a frequency of a function required by the motor 2 to be controlled. The output of the frequency oscillator 1 is applicable even when only one value is output, such as a crystal oscillator, and it is also applicable to the rotation detector of the turntable motor, which requires synchronization, in cases such as the reproduction feed motor mentioned above. Frequency output is desirable for configuration. 3 is a frequency divider that divides the output of the frequency oscillator 1 into an integer, and 4 is a frequency-voltage converter that converts the divided frequency into a voltage level. 5 is a rotation detector that generates a frequency proportional to the rotation of the motor 2 to be controlled; the frequency of this rotation detector 5 is divided into integer parts by a frequency divider 6;
The frequency-to-voltage converter converts the voltage into a voltage proportional to the rotational speed. It is preferable for the frequency-voltage converters 4 and 7 to have the same configuration and characteristics in order to correct nonlinearity in temperature characteristics and conversion characteristics.
Furthermore, it is better if the frequency to be handled is the same or an integer multiple, and therefore the frequency dividers 3 and 6 are configured to be adjustable. The output A of the frequency-voltage converter 7 is a rotational speed signal of the motor 2, and the output B of the frequency-voltage converter 4 corresponds to the speed reference level of the rotational speed, and is compared with the voltage comparator 8. , adder 9
After superimposing the phase signal, the signal is supplied to the motor 2 through an amplifier 10. The outputs of each of the frequency dividers 3 and 6 are subjected to phase-to-voltage conversion by a phase comparator 11, and the output voltage of the frequency-to-voltage converter 4 controls the amount of signal applied to the adder 9. After being adjusted by the gain control circuit 12, the adder 9 adds it to the speed signal. Note that the addition point may be placed after the frequency-voltage converter 7. Furthermore, if necessary, a low-pass filter, a phase compensation filter, etc. may be inserted into the loop. The amount of addition of the phase signal is adjusted by the gain control circuit 12 because the kinetic energy of the motor 2 and the detection gain of the speed system and phase system change depending on the rotation speed, so the amount of addition of the speed signal and the phase signal is corrected. This is because the response of the control system is more stable, and as a result, stable and highly accurate rotation speed control can be achieved over a wide rotation speed range. In the embodiment, the amount of addition is adjusted by changing the slope of the reference trapezoidal wave of the phase comparator 1 shown in FIG. 3a by the output B of the frequency-voltage converter 4 as shown in FIG. 3b. . FIG. 3c shows the sampling pulse produced by the output of frequency divider 6. With this configuration, the DC component of the output level of the phase comparator 11 shown in FIG. 3d is kept constant, and only the gain of the error component can be adjusted.

When controlling a motor synchronously with the output reference frequency, the present invention converts the frequency into voltage using a frequency-voltage converter that converts the input reference frequency into voltage, and a detector that generates a frequency proportional to the rotation of the motor. The motor is equipped with a frequency-voltage converter, and the rotation error is detected by comparing the outputs of the two frequency-voltage converters, and the rotation speed of the motor is controlled through an amplifier, so the rotation speed changes continuously. Even when controlled by a fixed speed standard, it is possible to obtain a stable and highly accurate motor rotation speed over a wide rotation speed range more than 10 times that of a fixed speed standard. Further, the gain adjustment of a phase control system that makes the output gain of the phase comparison circuit between the reference frequency and the frequency of the detector variable by the output of a frequency-voltage converter that converts the input reference frequency into voltage. By adding a circuit, speed system and phase system detection can be made independent, and suitable control characteristics can be obtained by adjusting the amount of addition, and by selecting the configuration of the frequency-voltage converter (for example, sample The cut-off frequency of the hold type) control system can be raised, and the design of the filter to be inserted into the loop can be easily designed.

[Brief explanation of drawings]

Fig. 1 is a characteristic diagram of the change in rotation speed when the rotation speed of the motor is continuously changed, Fig. 2 is a configuration diagram of an embodiment of the present invention, and Figs. 3 a to d are time charts of each part of the same. be. 1 is a frequency oscillator, 2 is a motor, 3 is a frequency divider, 4 is a frequency-voltage converter, 5 is a rotation detector,
6 is a frequency divider, 7 is a frequency-voltage converter, 8 is a voltage comparator, 9 is an adder, 10 is an amplifier, 11 is a phase comparator, and 12 is a gain control circuit.

Claims (1)

[Claims] 1 A frequency-voltage converter that converts an input reference frequency signal for synchronizing a motor into a voltage, and a frequency-voltage converter that converts a signal from a detector that generates a signal with a frequency proportional to the number of rotations of the motor into a voltage. The rotation speed error is detected by comparing the outputs of the two frequency-voltage converters, and the rotation speed of the motor is controlled through an amplifier, and the reference frequency signal and the output signal of the detector are detected. and a gain adjustment circuit of a phase control system that makes the output gain of the phase comparison circuit variable by the output of a frequency-voltage converter that converts the input reference frequency signal into voltage. A motor control device characterized in that the phase of the motor is controlled by the output of a gain control circuit.