JPH04103060A - Speed controller for rotating body - Google Patents

Abstract

PURPOSE:To prevent the jitters from being generated in a reproducing image by detecting a rotating speed of a rotating body by a speed detecting means, measuring a period of its detecting signal and setting it as a digital signal, applying it to a D/A converting circuit through a digital filter, and executing the speed control of a motor, based on an output of the D/A converting circuit. CONSTITUTION:A rotating speed of a rotating body 5 is detected by a speed detecting means 9, and a period of its detecting signal is outputted as a digital signal by a period measuring circuit 10. Subsequently, a signal of the period measuring circuit 10 is applied to a digital filter 31, and a fluctuation portion of a speed detecting signal corresponding to a rotating speed of the rotating body 5 and a rotating speed of the speed detecting means 9 is eliminated by the digital filter 31, the speed control of a motor 8 is executed. In such a way, generation of an uneven rotation caused by unevenness of a signal obtained from a speed information detector can be decreased, and a stable speed control can be realized.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a speed control device for a rotating body, particularly for controlling the speed of a rotating body such as a cylinder motor or a capstan motor of a video tape recorder. .

[Conventional technology]

In recent years, video tape recorders, especially camera-integrated video tape recorders, have been rapidly becoming smaller and lighter.

A cylinder motor speed control device used in this camera-integrated video tape recorder will be explained with reference to FIG. In this figure, a magnetic head 1.3 having the same azimuth angle and a magnetic head 2.4 having an opposite azimuth angle are mounted on a rotating cylinder 5 at an interval of 90°.
It is located along the circumference of the A magnetic tape 6 is wound around the rotating cylinder 5 by about 270 degrees in the direction of an arrow 7, and video signals are reproduced from the magnetic tape 6 by the magnetic heads 1-4.

Now, the rotating cylinder 5 is attached directly connected to the cylinder motor 8. A frequency generator (hereinafter referred to as FC) 9 having 8 teeth is attached to the cylinder motor 8, and during normal rotation, approximately 3607 signals are obtained from the FG 9, and this signal is given to the digital period measuring circuit 10. . The digital period measuring circuit 10 measures the period of this signal and outputs it as a digital signal.
1 is converted into an analog signal and sent to the cylinder motor 8.
Outputs a speed error signal according to the rotation speed.

On the other hand, a rotational phase detector (hereinafter referred to as PC) 12 for detecting the rotational phase of the cylinder motor 8 is provided. This P
Cl3 outputs a signal of about 457, and its output is given to the 1/3 frequency divider circuit 13. The 173 frequency divider circuit 13 divides the input signal to 1/3, that is, a signal with a period of approximately 66.6 Ns, and uses the 176 frequency divider as a reset signal.
It is applied to the frequency divider circuit 14 and the frequency divider 2 circuit 16. 176
The frequency dividing circuit 14 has FC9 applied to the clock input terminal, and P
A signal of approximately 60) tz synchronized with the output signal of Cl3 is transmitted to the delay circuit 15. The delay circuit 15 delays the input signal for a predetermined time, and its output is % as a clock signal.
The signal is applied to the frequency dividing circuit 16. The divide-by-2 circuit 16 uses this signal as a clock signal and transmits approximately 307 signals, which are phase-adjusted and synchronized with the output signal of the PCl3, to the digital phase measuring circuit 17. This speed control device also has a reference signal generation circuit 18. The digital phase measurement circuit F compares the phase with the reference signal of the reference signal generation circuit 18 and provides the phase error to the D/A conversion circuit 19. The D/A conversion circuit 19 converts this signal into an analog signal and transmits it to the mixing circuit 20.

The mixing circuit 20 mixes the speed system error signal and the phase system error signal, and drives the cylinder motor 8 via the motor drive circuit 21 to control its speed.

[Problem to be solved by the invention]

However, in such a conventional cylinder motor speed control device, if four heads are attached to the rotary cylinder 5 and the magnetic tape 6 is wound 270 degrees, it is possible to wind the magnetic tape 180 degrees using two ordinary heads. Compared to the conventional case, the diameter of the rotary cylinder 5 is 273 mm, which enables miniaturization, and is therefore widely used in camera-integrated VTRs. However, the number of rotations of the rotary cylinder 5 must also be increased by 1.5 times compared to a normal two-head type. In other words, in the NTSC system, it is approximately 45 rps (29.97 rps to be exact)
X1.5 = 44.955). Therefore, in a video tape recorder having a rotating cylinder using four heads, there is a problem in that jitter of 457 components is recognized in the reproduced image.

The present invention has been made in view of the problems encountered when controlling the speed of cylinder motors and capstan motors used in conventional camera-integrated VTRs, etc., and is a method that does not cause jitter in reproduced images. The technical problem is to provide a speed control device.

[Means for Solving the Problems] The present invention includes a motor, a rotating body connected to the motor and rotating at N rps, a speed detecting means for detecting the rotational speed of the rotating body and outputting an FHz signal, and a speed detecting means. A period measuring circuit that measures the period of the detection signal obtained by the means and outputs it as a digital signal, a digital filter to which the signal of the period measuring circuit is applied and has a characteristic of a transfer function H(z), and an analog converter for converting the output of the digital filter. The present invention is characterized in that it includes a D/A conversion circuit that converts the signal into a signal, and a motor drive circuit that controls the speed of the motor based on the output of the D/A conversion circuit.

[Effect]

According to the present invention having such characteristics, the rotational speed of the rotating body is detected by the speed detection means, and the period of the detection signal is outputted as a digital signal by the period measurement circuit. Then, the signal from the period measurement circuit is applied to a digital filter, and the variation in the speed detection signal corresponding to the rotation speed of the rotating body and the rotation speed of the speed detection means is removed by the digital filter, and the motor speed is controlled by the motor drive circuit. That's what I do.

〔Example〕

FIG. 1 is a block diagram showing the configuration of a cylinder motor speed control device according to an embodiment of the present invention.

In this figure, the same parts as in the conventional example described above are given the same reference numerals, and detailed explanations are omitted. In this embodiment as well, magnetic heads 1.3 having the same azimuth angle are provided at symmetrical positions on the rotary cylinder 5, A magnetic head 2.4 having an azimuth angle in the opposite direction is provided at a position 90° apart from these. Then, the magnetic tape 6 is wound around the rotating cylinder 5 by about 270 degrees, and as it travels in the direction of the arrow 7, video signals are reproduced from the magnetic heads 1-4. Similarly to the conventional example described above, the cylinder motor 8 is equipped with Fe as the speed detection means.
2 is attached, and the signal from Fe2 is given to the digital period measuring circuit 10. The digital period measuring circuit 10 is F
The period of the signal e2 is output as a digital signal. Now, in this embodiment, the output of the digital period measuring circuit 10 is given to the digital filter circuit 31. As an example of the digital filter circuit 31 is shown in FIG. 2, an adder 41 is connected to the input terminal, and the addition output is fsiX
42 and a delay unit 43. The delay device 43 delays the input signal by one clock, and its delayed output is given to the adder 41 and a series connection of seven delay devices 44a to 44g. The output of the delay device 44g is sent to the subtracter 42
given to. The subtracter 42 subtracts the output of the delay device 44g from the output of the adder 41, and its output is given to the output terminal.

As is clear from the configuration of FIG. 2, this digital filter circuit 31 can be expressed by the following transfer function H(z).

-z Here, Fe2 has a frequency 3607 which is eight times the frequency of the rotating cylinder 50, 45 Hz, and the ratio is eight times that. - When fishing on a boat, assuming that the frequency of the rotating cylinder 5 is M rotations per second and the frequency of Fe2 is F, a digital filter circuit with a transfer function expressed by the following equation is used.

-Z-1 Now, when a 360 Hz signal is applied to this digital filter circuit 31, characteristics as shown in FIG. 3 are obtained. In other words, the gain is OdB near DC (near 07) and the gain does not decrease, and the gain is large at 45)tz, which is a harmonic of 45)[z (360/8Hz), 90Hz-... It has a characteristic of attenuation. Now, the output of this digital filter 31 is given to the D/A conversion circuit 11,
The signal is converted into an analog signal and applied to the mixing circuit 20.

On the other hand, the signal processing system of the PCl3 that detects the rotational phase of the cylinder motor 8 is similar to the conventional example described above, and the output signal of the PCl3 is divided into a frequency of 173 by the 173 frequency divider circuit 13, and , are transmitted to the IA frequency divider circuit 16. Then, the output of the 176 frequency divider circuit 14 is transmitted to the 2 frequency divider circuit 16 via the delay circuit 15, and the phase of the output and the reference signal of the reference signal generation circuit 18 is measured by the digital phase measuring circuit 17, and the D/A The signal is applied to the mixing circuit 20 via the conversion circuit 19. The mixing circuit 20 adds the velocity system error signal and the phase system error signal to obtain a mixed error signal,
The output is given to the motor drive circuit 21 to control the speed of the cylinder motor 8.

In this way, the speed-related error signal applied to the mixing circuit 20 does not have a component corresponding to the rotation speed of the rotary cylinder 5 and its harmonics, so it is possible to prevent uneven rotation due to uneven accuracy of Fe2.

〔Effect of the invention〕

As explained in detail above, according to the present invention, by inserting a digital filter into the speed control system of the cylinder motor, the frequency corresponding to the number of rotations and its harmonics are The components can be attenuated by digital filters. Therefore, the occurrence of rotational unevenness due to unevenness in the signal obtained from the speed information detector can be reduced, and stable speed control can be realized. Therefore, when the present invention is applied to a cylinder motor speed control circuit or a capstan motor speed control circuit, the reproduced image has less jitter (zink) corresponding to the rotational speed of the rotating cylinder, and the image quality is improved. You can also get the effect that you can.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a cylinder motor speed control device according to an embodiment of the present invention, FIG. 2 is a block diagram showing the configuration of a digital filter used in this embodiment, and FIG.
FIG. 4 is a characteristic diagram showing its frequency characteristics, and FIG. 4 is a block diagram showing the configuration of a conventional speed control device for a cylinder motor. 1 to 4---Magnetic head, 5---One rotation cylinder, 6---One magnetic tape, 8------
・Cylinder motor, 9--- Single frequency generator (FC
), 10----1-digital period measurement circuit,
11, 19---D/A conversion circuit,
12.--One rotation phase detector (PC), 17-.-
Digital phase measurement circuit, 20------1 mixing circuit, 21--1--Motor drive circuit, 31--
Digital filter circuit. Patent applicant Matsushita Electric Industrial Co., Ltd.

Claims (1)

[Claims] (1) A motor, a rotating body connected to the motor and rotating at Nrps, a speed detection means for detecting the rotational speed of the rotating body and outputting an FHz signal, and a detection signal obtained from the speed detection means. A period measurement circuit that measures the period and outputs it as a digital signal, and a transfer function H(z) given the signal of the period measurement circuit, H(z) = [1-＾-＾(＾F＾/＾N＾) )]/[1
-z^-^1]; and a D/A conversion circuit that converts the output of the digital filter into an analog signal, and the motor is controlled based on the output of the D/A conversion circuit. A speed control device for a rotating body, comprising: a motor drive circuit that controls the speed of a rotating body.