JPS5996887A - Controlling method for rotating speed of servo motor - Google Patents

Abstract

PURPOSE:To enable to control the rotating speed of a servo motor at high speed time by dividing the frequency of a pulse which is generated from pulse generating means when the rotating speed becomes the prescribed value or higher and then supplying it to a microcomputer. CONSTITUTION:A rotating speed signal generated by a rotating speed generator 10 is converted by a D/A converter 2 from a digital signal to an analog signal, supplied through a motor drive circuit 3 to a servo motor 4, which starts rotating. Since a digital tachometer generator 5 is interlocked to the motor 4, a tachometer pulse which is proportional to the rotating speed of the motor 4, generated from the tachometer generator 5 is supplied to frequency dividers 6a, 6b, divided in frequency, supplied to a microcomputer 1, thereby accelerating the rotating speed of the motor 4, and enabling to control the rotating speed even if the period of the tachometer pulse becomes the period lower than that capable of being processed by the microcomputer.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for controlling the rotational speed of a servo motor, and particularly to a method for controlling the rotational speed of a servomotor by computer.

In general, it is desired that the motor that drives the capstan of a magnetic tape device has a short time from the start of rotation until the rated rotational speed is reached. However, if the rotation speed increases rapidly, slippage will occur between the capstan and the magnetic tape, and the magnetic tape will no longer be fed.
Motors for long-life applications like this are designed to prevent slippage.
It is necessary to perform fine rotation speed control.

For this reason, conventionally, a microcomputer used as a control device memorizes a rotation speed increase characteristic that does not cause the capstan to slip, and the control device supplies a rotation speed signal to the servo motor according to this rotation speed increase characteristic. It has become. A tacho generator used as a pulse generating means is linked to the servo motor and generates a number of tacho pulses proportional to the number of revolutions of the servo motor. This tacho pulse is supplied to the control device and compared with the rotation speed signal, and if the rotation speed of the servo motor is more or less than the rotation speed corresponding to the rotation speed signal, the control device generates a new rotation speed signal. . In this way, the servo motor is controlled to a rotation speed that does not cause the capstan and magnetic tape to slip, and rapidly reaches the rated rotation speed.

However, in such conventional devices, in order to perform fine rotational speed control, it is necessary to increase the number of tacho pulses to increase the resolution, but it is necessary to increase the resolution by increasing the number of tacho pulses, but it is difficult to use a servo motor for fast forwarding or rewinding magnetic tape. When operating at high speeds, the tacho pulse cycle becomes too short, making it impossible for the microcomputer to perform processing within the tacho pulse cycle, making it impossible to control the rotational speed.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a method for controlling the rotation speed of a servo motor, which allows the rotation speed to be controlled even when the rotation speed of the servo motor becomes high.

In order to achieve such an object, the present invention is such that when the rotational speed of the servo motor exceeds a predetermined value, the frequency of the pulse generated from the pulse generating means is divided and compared with the rotational speed signal. be. The present invention will be described in detail below using drawings showing embodiments.

The figure shows an embodiment in which the method of the present invention is applied to a servo motor that drives the carburetor of a magnetic tape device.

In the figure, 1 is a microcomputer used as a control device, 2 is a D/converter that converts the digital rotation speed signal supplied from the microcomputer 1 into an analog format, 3 is a motor drive circuit, and 4 is a servo motor. , 5 is a digital tacho generator used as a pulse generating means for generating a number of pulses proportional to the 40 rotational speed of the servo motor, and 6a and 6b are frequency dividers.

The microcomputer 1 includes an equally constrained rotation speed signal generator 10. It has a comparison section 112 and a frequency division signal generation section 12. The rotation speed signal generator 10 uses a magnetic tape (not shown) and carburetor methane to generate a rotation speed signal for driving the rotation speed of the servo motor 4 to the rated value in the shortest possible time without causing slippage. Furthermore, the generated rotational speed signal is adapted to change depending on the signal supplied to the terminal 10a. The comparator 11 compares the tacho pulse and the rotational speed signal, and when the number of pulses of the tachopulse differs from that corresponding to the rotational speed signal, it sends out a signal according to the degree of difference. When the number of pulses of the tacho pulse exceeds a predetermined value, that is, when the rotation speed of the servo motor 4 exceeds a predetermined value, the frequency division signal generating section 12 generates a frequency division signal from the terminal 12 &, and generates the frequency division signal from the terminal 12a. When the number of tacho pulses exceeds a predetermined value again while generating tacho pulses, a frequency division signal is also generated from the terminal 12b. Note that the comparator 11 operates in response to the frequency-divided tacho pulse when a frequency-divided signal is generated. Furthermore, when the frequency divider 6a, 6b is supplied with a division signal, the period of the supplied pulse is doubled, and when the division signal is not supplied, the frequency divider 6a, 6b outputs the supplied signal as is. There is.

The operation of the device configured as described above is as follows. The rotation speed signal generated by the rotation speed signal generator 10 is
/A converter 2 converts the digital signal into an analog signal, which is then sent to the servo motor 4 via the motor drive circuit 3.
The servo motor 4 starts rotating.

Since the digital tachometer generator 5 is linked to the servo motor 4, this digital tachometer generator 5
A tacho pulse generated from the servo motor 40 and proportional to the rotation speed of the servo motor is supplied to the frequency divider 61L. Immediately after the servo motor 4 starts rotating, the rotational speed is low, so the frequency division signal generating section 12 does not generate a frequency division signal. For this reason, the frequency divider (
ia, (ib is the i
Since the digital tacho generator 5 operates to output a t ratio, the tacho pulse output from the digital tacho generator 5 is supplied to the comparator 11 without being frequency-divided. It is determined whether or not the number of rotational speed signals corresponding to the number of rotational speed signals generated is generated, and if there is a difference, a signal corresponding to the amount of difference is output. In order to increase the rotation speed of the servo motor 4, the rotation speed signal generating section 10 generates a rotation speed signal that changes every moment according to predetermined characteristics. At this time, if the comparison section 11 determines that the rotation speed of the servo motor 4 is different from that corresponding to the rotation speed signal, the comparison section 11
1 outputs a signal according to the amount of difference, so the rotation speed signal generator 10 outputs a rotation speed signal corrected in accordance with the supplied signal. As a result, when the rotation speed of the servo motor 4 is too fast, the rotation speed decreases, and when it is too slow, the rotation speed increases, and the rotation speed of the servo motor 4 increases according to a predetermined characteristic.

When the rotational speed of the servo motor 4 rises to a certain degree and reaches a predetermined value or more, the frequency division signal generating section 12 generates a division signal from the output terminal 12&, and supplies this frequency division signal to the division device 6a and the comparison section 11. do. As a result, the tacho pulse is divided by frequency divider 6
The frequency is divided by 1L, the period is doubled, and the signal is supplied to the comparator 11. Since the comparator 11 is also supplied with the frequency-divided signal,
The comparator 11 performs a comparison operation after determining that the tacho pulse has been frequency-divided.

When the rotational speed of the servo motor 4 increases further as during rewinding, the division signal generator 12 also generates a frequency division signal from the output terminal 12b, so the tacho pulse is frequency-divided by the division divider 5m and also by the frequency divider 6b. However, since the signal is divided, the period is quadrupled and the signal is supplied to the comparator 11.

In this way, by dividing the frequency of the tacho pulse and supplying it to the microcomputer 1, the rotation speed of the servo monitor 4 increases, and even if the period of the tacho pulse becomes less than the period that the microcomputer 1 can process, the rotation speed can be controlled. can be done.

As explained above, the method according to the present invention divides the frequency of the pulses generated from the nox pulse generator when the rotational speed of the servo motor exceeds a predetermined value, and then processes the pulses using a control device such as a computer. This makes it possible to process pulses that are shorter than the processing cycle of the control device, and it is possible to control the rotation speed slightly outside the rise and fall characteristics without reducing the resolution of the pulse generation means. At the same time, it is also possible to control the rotational speed at high speeds, which has the effect of enabling stable control over a wide speed range.

[Brief explanation of the drawing]

The figure is a block diagram showing an embodiment of a rotation speed control device constructed by applying the servo motor control method according to the present invention. 10am・Microcomputer, 2・・・/A converter, 3・・・Motor drive circuit, 4・・・・Servo motor, 5・・Digital tacho generator, 5a,
5b... Frequency divider, 10... Rotation speed signal generator,
11... Comparison section, 12... Frequency division signal generation section. Patent Applicant Oki Univac Co., Ltd. Agent Kazuko Yamakawa (and 1 other person) □l

Claims (1)

[Claims] The rotation speed of the servo motor is determined by comparing the rotation speed signal generated from the control device that controls the rotation speed of the servo motor with the pulse signal from the pulse generator that generates pulses proportional to the rotation speed of the servo motor. In a method for controlling the rotation speed of a servo motor to a predetermined rotation speed, when the rotation speed of the servo motor exceeds a predetermined rotation speed, the control device divides a pulse signal into a signal and a rotation speed signal. A servo motor rotation speed control method characterized by controlling the rotation speed of a servo motor by comparison.