JPS637177A - Capstan motor control system - Google Patents

Abstract

PURPOSE:To rapidly search an editing point by reversely rotating a motor when a speed set is altered from a high speed to a low speed to decelerate the speed, and releasing a brake when becoming a reference speed. CONSTITUTION:When the output of a shuttle speed generator 2 is altered from 5 times speed data to one times speed data, a capstan speed switching detector 12 detects it, and supplies its output signal to a brake circuit 11 and a signal selector 14. The brake circuit 11 switches the rotating direction of a capstan motor reversely, and the selector 14 selects the output of a brake voltage generator 15 to supply it to a capstan motor. When the rotating speed information of the motor becomes equal to the output of a reference speed information generator 13, a speed comparator 17 returns the rotating direction of the motor forward. Simultaneously, the selector 14 selects the output signal from a voltage amplifier 7.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a capstan motor control system in the shuttle mode of a VTR.

[Summary of the invention]

In the so-called shuttle mode of a VTR equipped with a variable speed playback function, when the speed setting value is changed, it is required to have as good followability as possible. However, due to the influence of the moment of inertia of the capstan motor, the coordination becomes poor especially when changing the speed from high speed to low speed. In order to solve this problem, the present invention provides a braking effect by reversing the rotational direction of the capstan motor at the moment the speed setting is switched from high speed to low speed. In addition, excessive braking is prevented by applying a brake voltage according to the actual capstan rotation speed. Further, the brake voltage is released when the speed drops to a speed equal to the speed setting value due to the brake voltage. Therefore, the rotational speed is rapidly reduced, speed response is improved, and cueing operations in editing operations using the variable speed playback function are facilitated.

[Conventional technology]

As a conventional technique, for example, there is a capstan motor control system in the shuttle mode of a VTR as shown in FIG. In this operation, an encoder pulse 1 generated by a rotary encoder connected to a dial for setting the shuttle speed is supplied to a shuttle speed data generator 2 to generate speed data corresponding to the rotation angle of the shuttle dial. This speed data is supplied to a speed setting reference pulse generator 5. A clock pulse 4 is input to the speed setting reference pulse 5, and the count number of the clock pulse is varied according to the speed data.

A speed setting reference pulse is generated and supplied to the speed detector 6. The speed detector 6 has a capstan TAOH obtained by a tachometer 10 attached to a capstan motor 9.
A signal is also provided to generate a frequency error signal of the capstan TAOH signal relative to the frequency of the speed setting reference pulse. This frequency error signal is applied to the error voltage amplifier 7. The signal is supplied to a capstan motor 9 via a motor drive amplifier 8 to control the rotation speed. In the example shown in FIG. 2, the capstan motor 9 is a three-phase brushless DC motor, and the rotation direction can be switched between forward and reverse directions by the output signal of the rotation direction command signal generator 3. That is, for example, if the shuttle dial is turned in the FWD (forward) direction, the output of the signal generator 3 will be at "O" level.If the capstan rotation is in the steady direction and the shuttle dial is turned in the REV (reverse) direction, the output of the signal generator 3 will be at "O" level. In this case, the output of the signal generator 3 is at the "1" level, and the rotating direction is reversed (rewinding direction).

The shuttle mode is indispensable for VTR editing work, and it is required to be able to advance and rewind the tape at variable speeds so that the beginning of nine editing points can be quickly found. Generally, the relationship between the shuttle dial and the tape feeding speed is 1/30 of the normal speed as the rotation angle increases from side to side.
, 1/20, 1/10.

The speed can be changed in stages, such as 1x speed and 3.5x speed.

[Problem that the invention seeks to solve]

The above-mentioned prior art has a high speed, e.g.
When the speed setting value is suddenly changed from double speed to low speed, for example, single speed, the rotational speed of the capstan motor is affected by inertia and therefore does not drop suddenly. Therefore, when performing editing work, there is a drawback that the cueing operation for one editing point cannot be performed quickly. In order to solve this drawback, it is an object of the present invention to improve the followability of the capstan motor control in the shuttle mode so that the cueing operation for one editing point can be performed quickly.

[Means for solving problems]

In order to achieve the above object, the present invention reverses the rotational direction of the capstan motor when the speed setting is changed from high speed to low speed in shuttle mode, thereby applying a braking effect so that the speed quickly decreases from high speed to low speed. give. If this brake is applied for too long, there is a risk that the capstan will stop rotating or will rotate in the opposite direction to the set rotation direction. Then, the reference speed information corresponding to the set shuttle speed is compared with the actual speed information of the capstan motor, and the brake is released when there is no difference. In addition, the brake voltage is set to apply the brake at a voltage proportional to the actual rotational speed of the capstan, thereby preventing the adverse effects of excessive braking.

[Effect]

As a result, when the shuttle speed setting is changed from a FWD high speed, such as 5x speed, to a FWD low speed, eg, 1x speed, the braking force is applied by switching the rotational direction of the capstan to the REV direction at the moment the set value is changed. This braking amount is a value proportional to the actual rotational speed of the capstan. Moreover, the period during which the brake is applied is the period until the actual rotation speed of the capstan falls to the set speed after the variable, in this case, 1x speed. Therefore, it is possible to quickly change the tape running speed from 5x speed to 1x speed, and improve the followability of the capstan motor.

〔Example〕

An embodiment of this invention will be explained with reference to FIG.

The configuration of FIG. 1 is the example of the conventional system shown in FIG.
17 is added. 11 switches the rotation direction of the capstan motor. Reference numeral 12 denotes a capstan speed switching detector which detects that the set value of the shuttle speed has been switched from high speed to low speed.

13 is a capstan reference speed pulse generator.

Generates a speed information signal according to the set shuttle speed. Reference numeral 14 denotes a signal selection circuit which normally selects a speed error signal and selects a brake voltage for a predetermined period from the moment the speed setting is switched from high speed to low speed. 15 is a brake voltage generator, 16 is a capstan speed detector, and 17 is a speed information comparator for comparing reference speed information and actual capstan speed information.

This operation will be explained below. F in shuttle mode
Taking as an example the case where the full speed is fixed in the WD direction 5, since it is set to FWD, the output of the capstan motor brake circuit 11 becomes 0'' level and is supplied to the motor drive amplifier 8, which rotates the capstan motor in the FWD direction. At this time, the signal selection circuit 14 selects the output signal of the speed error signal amplifier 7, and the speed of the capstan motor is controlled to be maintained at a speed five times the normal speed.

Next, a case will be described in which the speed setting value is changed from FWD 5x speed in the shuttle mode to, for example, FWD 1x speed as in the above example. First, the output of the shuttle speed data generator 2 changes from 5x speed data to 1x speed data. Capstan speed switching detector 12 detects this and supplies an output signal to brake circuit 11 and signal selection circuit 14. At this time, the output of the brake circuit 11 becomes "1" level, and the rotating direction of the capstan motor is switched to the REV direction. - On the other hand, the signal selection circuit 14 selects the output of the brake voltage generator 15 and supplies it to the capstan sode. Speed detector 16
The capstan TACH signal from the tachometer 10 is supplied to obtain capstan rotation speed information.

The output voltage of the brake voltage generator 15 is applied to the speed detector 1.
Generates a value proportional to the capstan rotation speed from 6. The output of the speed data generation circuit 5 is supplied to the reference speed information generator 13, and in the above example, reference speed information of 1x speed is obtained. This reference speed information and the actual capstan rotation speed information obtained by the speed detector 16 are compared by a speed comparator 17. That is, when the output of the reference speed information generator 13 and the output speed information of the speed detector 16 become equal, for example, a "0"' signal is outputted and supplied to the capstan speed switching detector 12. Add the output voltage to the capstan motor brake circuit 11 and change the rotation direction of the capstan motor from the REV direction to the FW direction.
Return to direction D. At the same time, the signal selection circuit 14 disconnects the brake voltage from the brake voltage generation circuit 15 and selects the output signal from the error voltage amplifier 7. That is, F″wD5w
D The moment the speed setting changes to 5x speed, the rotational direction of the capstan motor is reversed to give a braking effect to quickly reduce the speed, and when the speed drops to 1x speed, the rotational direction is returned to the FWD direction. In addition, excessive braking is prevented by setting the braking amount to a value that corresponds to the actual capstan speed.

〔effect〕

According to the present invention, the coordination of the capstan motor is improved when variable speed operation of tape running is performed in the shuttle mode in a VTR using a three-phase Plus DC motor as the capstan motor, thereby improving operability during editing work. has been improved and cueing can be done quickly.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of the present invention, and FIG. 2 is a block diagram showing a conventional embodiment.

Claims (1)

[Claims] 1. In the capstan motor control system of a VTR equipped with a variable speed playback function, a speed change detector is used to detect when the variable speed has been changed, and a reference speed that changes in proportion to the speed setting value. a pulse generator, a capstan speed detector that detects the rotational speed of the capstan, a brake voltage generator that generates a voltage to rapidly reduce the rotational speed of the capstan based on the output of the detector, and the speed switch. a capstan motor brake circuit that generates a signal for switching the rotation direction of the capstan motor based on the output of the detector; and a signal that selects either the capstan speed error voltage or the brake voltage based on the output of the speed switching detector. a selection circuit that compares the output of the reference speed pulse generator with the output of the capstan speed detector and outputs a predetermined output signal when the rotational speed of the capstan is equal to a value proportional to the speed setting value; and a speed information comparator that supplies the speed change detector to the speed information comparator, which reverses the rotation direction of the capstan motor at the moment the speed is switched from high speed to low speed in variable speed playback mode, and detects the actual rotation speed of the capstan motor. When it detects that the capstan speed has dropped to the set speed after switching, it returns the rotational direction of the capstan motor to its original direction and releases the brake voltage supply. A capstan motor control system characterized by: