JP2692117B2 - Multi-actuator speed control circuit - Google Patents

Description

The present invention relates to a positioning control circuit for an actuator used in a magnetic disk device, an optical disk device or the like, and more particularly to a multi-actuator speed control circuit for independently controlling a plurality of actuators. Is.

[Conventional technology]

Conventionally, as a multi-actuator speed control circuit of this type, there is a control circuit which is provided with a slew rate limiting circuit and removes a high-frequency signal component which causes a displacement of other actuators from a drive current of each actuator (for example, Japanese Patent Publication No. 61-120215). FIG. 3 is a waveform diagram showing the operation of the conventional example, 13 is the target speed signal, 14 is the actual speed signal, and 17 is the actuator drive current.

[Problems to be solved by the invention]

In the conventional multi-actuator speed control circuit described above, the slew rate limiting circuit is connected between the speed control signal generation circuit and the power amplifier, so the output waveform of the speed control signal generation circuit and the output waveform of the slate rate control circuit, that is, the power. There is a drawback that the input waveform of the amplifier is not the same waveform. Further, the slew rate limitation means that the followability is deteriorated, and there is a drawback that a seek error occurs in the worst case.

[Means for solving the problem]

The multi-actuator speed control circuit of the present invention includes an actuator and a movable body composed of a carriage, a head, and the like moved by the actuator, compares the current speed of the movable body with a target speed, and finds the difference between them. A multi-actuator speed control circuit for accelerating or decelerating the movable body to stop it at a target position by supplying a drive current to the actuator until it disappears, which is a DA converter for converting the number of moving tracks from a digital amount to an analog amount. A nonlinear processing circuit for converting the output of the DA converter into an appropriate target speed signal, an electronic tachometer for obtaining an actual speed signal, and a speed error amplifier for obtaining an error signal between the target speed signal and the actual speed signal. , A comparator for comparing the output of the speed error amplifier with a reference potential, and the actual speed at the input terminal An analog switch that is supplied with a signal and is opened and closed by the output of the comparator, and is connected between the output terminal of the analog switch and the input terminal of the non-linear processing circuit and has an opposite polarity to the output signal of the DA converter. It has an RC filter that passes a signal.

〔Example〕

Next, the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of one embodiment of the present invention. From the seek logic, the desired number of tracks to be moved by the actuator 6 is set in the track address counter 1. The content of the track address counter 1 is 1 for the actuator 6.
1 by the track pulse generator 9 every time the track moves
The track pulses 20 transmitted one by one are subtracted by one, and become zero by the track pulse generated immediately before the target track. The output of track address counter 1 is DA
The converter 2 converts the digital signal into an analog signal, and the non-linear processing circuit 3 converts it into a desired target speed signal 13. The difference signal between the target speed signal 13 and the actual speed signal 14 is amplified by the speed error amplifier 4 and input to the power amplifier 5. Then, a drive current is passed through the actuator 6 to accelerate it. The actual speed signal 14 is accelerated until it coincides with the target speed signal 13, and then, the actuator 6 moves toward the desired track according to the target speed signal 13. The power amplifier 5 sends a maximum current to the actuator 6 in the acceleration region regardless of the speed error signal. In the conventional speed loop in which the desired number of tracks and the target speed 13 correspond one-to-one, the current sharply changes when transitioning from the acceleration region to the deceleration region. In this case, there is a drawback that the driving force for the actuator that is moving at high speed is transmitted as a disturbance to another actuator that is performing position tracking control via the support function of the actuator, which may cause head position deviation.

In the present invention, a unipolar speed signal is applied to the input terminal of the non-linear processing circuit 3 improved as follows through the analog switch 11 and the RC filter 19. The analog switch 11 is closed when the actuator 6 starts moving. Then, when the movement starts and the movement speed becomes faster and the difference from the target speed matches or becomes within a certain range, the analog switch 11
Opens. The opening / closing control of the analog switch 11 is performed by detecting a difference between the target speed signal 13 and the actual speed signal 14, that is, a so-called speed error signal. When the analog switch 11 is closed, the absorption current of the DA converter 2 and the reverse polarity current are RC filter.
It flows through 19 into the non-linear processing circuit 3 from the unipolar speed signal side. As a result, the target speed signal 13 is
The level is smaller than when 11 is open. When the speed error signal enters a certain range, the analog switch 11 opens, so that the unipolar speed signal is not input to the nonlinear processing circuit 3 and the target speed signal 13 becomes large. In this case, if the RC filter 19 is not connected, the target speed signal 13 suddenly changes, the actuator drive current also suddenly changes, and the phenomenon as described above occurs, but in the present invention, since the RC filter 19 is connected, the characteristics of the filter The current flowing into the non-linear processing circuit 3 gradually changes in accordance with the above. Therefore, the target speed signal 13 gradually increases, and the actuator drive current also changes gently. This is shown in FIGS. 2A and 2B.

〔The invention's effect〕

As described above, the present invention has the effect of gently changing the target speed signal by changing the inflow current of the non-linear processing circuit by the charge accumulated in the capacitor of the RC filter. Also, because the target speed signal changes slowly, the actuator drive current does not change suddenly when shifting from the acceleration state to the deceleration state, so there is no disturbance to other actuators during position tracking control, and a head position deviation occurs. There is an effect that does not let you.

[Brief description of the drawings]

FIG. 1 is a block diagram of one embodiment of the present invention, and FIG.
FIG. 3 is a waveform diagram showing the operation of the figure, and FIG. 3 is a waveform diagram showing the operation of the conventional example. 1 ... Track address counter, 2 ... DA converter, 3
...... Non-linear processing circuit, 4 …… Velocity error amplifier, 5 …… Power amplifier, 6 …… Actuator, 7 …… Position signal reproduction circuit, 8 …… Electronic tachometer, 9 …… Track pulse generator, 10 …… Comparison Instrument, 11 …… Analog switch, 12 ……
Rectifier circuit, 13 …… Target speed signal, 14 …… Actual speed signal,
15 …… Analog switch open / close signal, 16 …… Speed error signal, 17 …… Actuator drive current, 18 …… Circuit of the present invention, 19 …… RC filter, 20 …… Track pulse.

Claims (1)

(57) [Claims] 1. An actuator and a movable body composed of a carriage, a head, etc., which is moved by the actuator, compares the current speed of the movable body with a target speed, and sets the actuator until the difference disappears. In a multi-actuator speed control circuit for accelerating or decelerating the movable body by supplying a driving current to stop at a target position, a DA converter for converting the number of moving tracks from a digital amount to an analog amount, and the DA converter A non-linear processing circuit that converts the output to an appropriate target speed signal,
An electronic tachometer for obtaining an actual speed signal, a speed error amplifier for obtaining an error signal between the target speed signal and the actual speed signal, a comparator for comparing the output of the speed error amplifier with a certain reference potential, and the input terminal as described above. An analog switch that is supplied with an actual speed signal and is opened and closed by the output of the comparator,
A multi-actuator speed control including an RC filter connected between an output terminal of the analog switch and an input terminal of the non-linear processing circuit, the RC filter passing a signal having a polarity opposite to that of the output signal of the DA converter. circuit.