JPH01298560A - Reel motor controller - Google Patents

Abstract

PURPOSE:To eliminate such analog circuits as an electric current detecting amplifier and an adder circuit, etc., and hence to reduce the scale of circuits by making a software for a microcomputer or a digital circuit processed by estimating the acceleration of a capstan, converting this acceleration into torque value and adding the torque value to a reel motor driving signal. CONSTITUTION:A counter-electromotive voltage of a capstan motor 1 can be measured from an output signal of a rotation detecting device provided in relation to the capstan motor 1. When a digital signal corresponding to the counter-electromotive voltage out of digital signals corresponding to a voltage to be impressed on the capstan motor 1 is subtraction-processed by a subtraction circuit 32, an effective voltage for the capstan motor 1 can be obtained. This voltage is digitally converted into acceleration by a multiplication circuit 35, and the acceleration is digitally converted into torque value by a multiplication circuit 36, so as to add each digital signal for driving the reel motors 12S and 12T respectively. Consequently, the need for analog circuits is eliminated, and the tape tension can be kept constant in consideration of the acceleration of the capstan.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a reel motor control device applied to a VTR.

[Summary of the invention]

In this invention, a digital signal corresponding to the voltage applied to the capstan motor is subtracted from a back electromotive force obtained from the rotation speed of the capstan motor and the corresponding digital signal, and the subtracted output is multiplied by a predetermined coefficient. As a result, the acceleration of the capstan motor is determined, and the acceleration is added to the signal that drives the reel motor. Analog circuits such as a capstan current detection circuit and an acceleration addition circuit can be omitted, and the circuit size can be reduced ( can.

[Conventional technology]

A VTR is provided with a reel servo circuit to keep the tape tension run constant. FIG. 2 shows an example of a conventional capstan servo circuit and a reel servo circuit. In FIG. 2, ■ indicates a capstan motor. A magnetic rotation detection device 2 in conjunction with the capstan motor 1
is provided, and the rotation detection device 2 is connected to the capstan motor 1.
A detection signal with a frequency proportional to the rotation speed is generated. This detection signal is supplied to the speed detection circuit 3. In the speed detection circuit 3, a speed servo signal corresponding to the difference between the set speed and the detected speed is formed, and this speed servo signal is supplied to the capstan phase servo circuit 4 and the capstan search servo circuit 5.

A phase detection signal from a phase detection circuit 8 is supplied to the capstan phase servo circuit 4 . This phase detection signal is
It is generated from a control signal reproduced by a fixed head 6 and passed through an amplifier 7. The capstan phase servo circuit 4 generates a servo signal for rotating the capstan motor 1 at a predetermined speed and a predetermined phase.

During a search operation in which the capstan and pinch roller contact each other and the tape is fed at high speed, no phase servo operation is performed and only speed servo operation is performed, so a capstan search servo circuit 5 is provided for the search operation. It is being

Digital servo signals are generated from the capstan phase servo circuit 4 and capstan search servo circuit 5, respectively, and one of the servo signals is selected by the switch circuit 9 depending on the operating state. The servo signal passed through the switch circuit 9 is converted into an analog drive signal by the D/A converter 10. This drive signal is supplied to the capstan motor 1 via the drive amplifier 11, and the capstan motor 1 is driven by voltage.

In FIG. 2, 12 indicates a reel motor.

A magnetic rotation detection device 13 in conjunction with the reel motor 12
is provided. A detection signal from this rotation detection device 13 is supplied to a radius calculation circuit 14. The detection signal from the rotation detection device 13 is also supplied to the radius calculation circuit 14 . The radius calculation circuit 14 calculates the tape winding diameter of the reel. That is, the tape winding diameter is calculated from the amount by which the tape has advanced (the number of revolutions of the capstan motor 1) and the number of revolutions of the reel. The output signal of the radius calculation circuit 14 is supplied to the reel servo circuit 15 and also to the inertia calculation circuit 16. The inertia calculation circuit 16 calculates the tape density (predetermined value)
The inertia of the reel is calculated by adding the mass of the part where the tape is not wound to the value obtained by multiplying by the tape winding diameter. The output signal of the inertia calculation circuit 16 is supplied to the reel servo circuit 15.

The reel servo circuit 15 is supplied with an output signal from a tension sensor 17 for detecting tape tension. A digital servo signal from the reel servo circuit 15 is supplied to the D/A converter 18.
An analog glue servo signal from the reel motor 12 is supplied to the reel motor 12 via an adder circuit 19 and a drive amplifier 20.

The reel motor 12 is current-driven for torque control.

When the tape is transferred by rolling contact between the capstan and the pinch roller, acceleration or deceleration of the capstan causes disturbance to the reel servo system. Due to its own inertia, the tensilan sensor 17
There was a problem in that the tape could not follow the rapid acceleration and deceleration of the capstan, causing the tape to loosen and excessive tension to occur.

Therefore, a detection resistor 21 is connected in series with the capstan motor l, and a current detection amplifier 22 is connected to the connection point between the capstan motor l and the detection resistor 21.
2, a detection signal proportional to the acceleration of the capstan motor 1 is obtained. When the capstan motor 1 has a sufficiently small load other than its own inertia, the drive current is proportional to the acceleration. The output signal of the current detection amplifier 22 is converted into a torque value by the current torque conversion circuit 23, and added to the reel servo signal in the addition circuit 19. The current-torque conversion circuit 23 is supplied with signals obtained by the radius calculation circuit 14 and the inertia calculation circuit 16, respectively.

Although FIG. 1 only shows the configuration of one of the take-up reel motor and the supply reel motor, in reality, the reel servo signal is supplied to both reel motors.

[Problem to be solved by the invention]

In the above-mentioned reel motor control device, the servo signal is formed by digital processing at the stage before the D/A converter 18, but the acceleration of the capstan motor 1 is detected,
The configuration (current detection amplifier 22, current torque conversion circuit 23, addition circuit 19) for adding this acceleration to the reel servo signal was configured with an analog circuit. Therefore, there was a problem that the circuit scale became large.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a reel motor control device whose circuit scale is smaller than that of the prior art by digitally performing the process of adding the acceleration of the capstan to the reel servo signal.

[Means to solve the problem]

In this invention, a digital signal corresponding to the voltage applied to the capstan motor is subtracted from a back electromotive force obtained from the rotation speed of the capstan motor and the corresponding digital signal, and the subtracted output is multiplied by a predetermined coefficient. As a result, the acceleration of the capstan motor is determined, and the acceleration is added to the signal that drives the reel motor.

[Effect]

The back electromotive voltage of the capstan motor can be measured from the output signal of a rotation detection device provided in association with the capstan motor. By subtracting the digital signal corresponding to the back electromotive force from the digital signal corresponding to the voltage applied to the capstan motor, the effective voltage of the capstan motor can be determined. This voltage is digitally converted to acceleration, and the acceleration is digitally converted to a torque value and added to the digital signal that drives the reel motor. Therefore, the tape tension can be made constant while taking into account the acceleration of the capstan, without requiring any analog circuitry.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. In Figure 1, the components surrounded by broken lines are:
It represents the software processing of a microcomputer as functional blocks.

A capstan motor indicated by 1 is voltage driven by the output of a drive amplifier 11. In the drive amplifier 11,
A driving voltage converted into an analog signal by the D/A converter 10 is supplied. The D/A converter 10 is supplied with a signal from the capstan phase servo circuit selected by the switch circuit 9 or a signal from the capstan search servo circuit as in the conventional case. A multiplier circuit 31 multiplies a digital signal (output signal of the switch circuit 9) corresponding to the voltage applied to the capstan motor l by a coefficient of 1.

The output signal of the multiplication circuit 31 is supplied to the subtraction circuit 32.

The subtraction circuit 32 is supplied with the output signal of the multiplication circuit 33. The zero multiplication circuit 33 multiplies the digital signal from the terminal 34 corresponding to the measured speed of the capstan motor 1 by a constant by 2. The speed of the capstan motor l can be measured by a magnetic rotation sensing device.
The value of the output signal of the multiplier circuit 33 is the value of the output signal of the capstan motor 1.
corresponds to the back electromotive force of The output signal of the subtraction circuit 32 is therefore a digital signal corresponding to the effective voltage applied to the capstan motor 1.

The output signal of the subtraction circuit 32 is supplied to a multiplication circuit 35, and the coefficient is multiplied by three. This multiplier circuit 35 is a circuit that converts an effective voltage into acceleration A, and the coefficient 3 corresponds to the reciprocal of the resistance value of the capstan motor 1 and the current-acceleration conversion coefficient.

2. The output signal of the multiplication circuit 35 represents the acceleration A, and the above-mentioned coefficient Kl. 3 can be determined experimentally.

Acceleration A from the multiplication circuit 35 is supplied to the multiplication circuit 36. This multiplier circuit 36 is a circuit that converts current into torque. The division circuit 3T performs the calculation of (J/R), and the output signal of the division circuit 37 is supplied to the multiplication circuit 36. Here, J is the reel inertia and R is the reel radius. The reel radius R means the tape winding diameter, and can be determined from the relationship between the rotation speed of the capstan motor and the rotation speed of the reel. The reel inertia J can be determined by determining the inertia of the tape-wound portion from the reel radius and tape density, and then adding the inertia of the tape-unwound portion.

In the multiplier circuit 36, a calculation of (J/R)XA is performed, and a torque value is generated from the multiplier circuit 36. This torque value is supplied to adder circuits 19T and 193. Addition circuit 19T
is supplied with the torque value of the take-up reel motor 12T from the terminal 38T, and the adder circuit 193 is supplied with the torque value of the take-up side reel motor 12T from the terminal 38T.
The torque value of the supply side reel motor 12S is supplied from. These torque values do not take into account capstan acceleration and are generated from the reel servo circuit. The output signals of adder circuits 19T and 193 are sent to D/A converters 18, respectively.
It is supplied to T and 183 and converted into an analog value. The output signals of these D/A converters 18T and 18S are supplied to drive amplifiers 20T and 20S, respectively, and the take-up side reel motor 12T and supply side reel motor 12S are current-driven by the output signals of the drive amplifiers 20T and 203. .

By considering the acceleration of the capstan, even if the capstan accelerates or decelerates, the tape will not loosen or
This prevents excessive tension from being applied to the tape.

〔Effect of the invention〕

In this invention, the acceleration of the capstan is estimated, and
Since the process of converting this acceleration into a torque value and adding the torque value to the reel motor drive signal is performed by microcomputer software or digital circuits, analog circuits such as current detection amplifiers and adder circuits can be omitted. , the circuit scale can be reduced.

[Brief Description of the Drawings] Fig. 1 is a functional block diagram of an embodiment of the present invention;
The figure is a block diagram of a conventional reel motor control device to which the present invention can be applied. Explanation of main symbols in the drawings 1: Capstan motor, 2: Rotation detection device, 12T;
Take-up side reel motor; 12S: supply side reel motor; 19T, 19S: addition circuit; 32: subtraction circuit; 36: multiplication circuit for current-torque conversion. Agent Patent Attorney Tadashi Sugiura Tomoichi Kuhn T Shiitari Figure 1

Claims (1)

[Claims] Subtraction processing is performed between a digital signal corresponding to the voltage applied to the capstan motor and a digital signal corresponding to the back electromotive force obtained from the rotational speed of the capstan motor, and a predetermined coefficient is applied to the subtracted output. A reel motor control device, characterized in that the acceleration of the capstan motor is determined by multiplying by , and the acceleration is added to a digital signal for driving the reel motor.