JPS63204421A - Control method for actuator - Google Patents

Abstract

PURPOSE:To shorten the access time and to stabilize the control for an actuator by setting the maximum speed at an early stage of working of the actuator and then controlling the working speed of the actuator based on the prescribed speed control characteristics at and after a set speed level. CONSTITUTION:The position of an actuator 6 is detected by a position detector 7 and converted into the access distance data by a shift distance detector 8 to be supplied to a CPU 1. The detection value of the circuit 7 is supplied to a speed detector 9 to be converted into the speed value and supplied to a comparator 10. The comparator 10 compares the speed detection value Vf with a reference speed Vref of a reference speed generating circuit 11 and sends the result of this comparison to the CPU 1. At the same time, the difference between the Vf and the Vref is supplied to gate circuits 2A and 2B via a speed error detecting circuit 12. Thus the gains K1 and K2 of a speed control loop are set. In such a constitution, the virtually shortest access time is obtained and the stable control is possible for the actuator 6 with the minimum influence of resonance of a mechanical system.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a control method for moving an actuator stopped at a certain position to a position an arbitrary distance away at high speed.

``Prior Art'' Conventionally, in an actuator (for example, a DC motor) applied to a head moving mechanism of a magnetic disk device, positioning control is performed by a control loop as shown in FIG.

That is, a control signal is supplied from the speed error detection circuit A to the power amplifier B, the power amplifier B drives the actuator C, the speed of the actuator C is detected by the speed detector, and the speed error detection circuit A drives the actuator C. The detected value Vr is fed back to the speed error detection circuit A, and the fed-back speed detected value r is compared with a reference speed value V ref to perform control so that the two coincide.

In addition, a calculation device (not shown) calculates the distance (access distance) between the current position and the target position, and
As shown by the solid line (a) in Figure 6, the standard speed curve corresponding to the access distance (for a certain access distance,
A curve or a straight line indicating the reference speed value V ref at each position during access is selected, and the V ref given by this curve is, for example, changed as the detected speed Vf as shown by the broken line (b) in Figure 6. In comparison, the drive current (2) of the actuator C is controlled differently as shown by the solid line (C) in FIG.

"Problems to be Solved by the Invention" By the way, there is a demand for reducing the time required for movement of magnetic disk heads.

In order to shorten this travel time, it is necessary to make the standard speed curve steeper and perform rapid acceleration/deceleration, but in order to perform rapid acceleration/deceleration, G = G IX G It is necessary to increase the total gain of the loop, which is defined as t There is a problem in that the total gain becomes abnormally high due to the influence, the loop oscillates, and predetermined control accuracy cannot be obtained.

The present invention was proposed in view of the above circumstances, and aims to provide a control method that shortens access time and prevents loop oscillation.

"One-shot means for solving problems" In order to achieve the above object, the present invention provides an access control method for moving an actuator stopped at a certain position by a predetermined access distance, when an access command is supplied. First, open-loop control is performed to drive the actuator at the maximum settable speed, and after the actuator speed approximately matches or exceeds the set value, the actuator is controlled according to the predetermined speed control characteristics. This is how I implemented closed-loop control.

"Operation" By performing the above control, first, the actuator moves at the maximum speed that it can exhibit, and then closed-loop control is performed to reduce the speed, and in this closed-loop control, the By reducing the gain, the stability of the control system can be improved.

"Embodiment" Hereinafter, an embodiment of a control device to which the method of the present invention is applied will be described with reference to FIGS. 1 to 4.

Reference numeral 1 in the figure is a CPU (central processing unit) as a control unit.
It is. Gate circuits 2A and 2B are connected in parallel to this CPUI, and the gate circuits 2A and 2B have amplifiers 3A and 3B whose gains are set to 1 and 1 (provided that >Kt). The outputs of these amplifiers 3A and 3B are connected to an OR circuit 4.

Further, the output of the OR circuit 5 is amplified by a power amplifier 5 and supplied to an actuator 6, and the actuator 6 drives a magnetic head (path shown).

The position of the actuator 6 is detected by a position detector 7, and the detected value of the position detector 7 is further supplied to a movement distance (access distance) detector 8, where it is converted into access distance data and A/D converted. and is supplied to the CPUI. Further, the position detection circuit 7
The detected value is converted into a speed value by being multiplied by the speed detection value 9 and subjected to arithmetic processing such as differentiation, and the output of this speed detector 9 is inputted to a comparator circuit 1O. Then, the comparison circuit IO compares the speed detection value vr and the speed Vrer, and transmits the comparison result to the CPU.
It is designed to supply to I. Note that the reference speed V
rer is supplied to the comparator circuit IO by the standard speed generation circuit 11 which receives data from the memory within the CPUI. Furthermore, the detected speed value vr of the speed detector 9 is supplied to a speed error detection circuit 12, and in this speed error detection circuit 12, the reference ω speed and the reference impregnation speed V ref supplied from the variation generation circuit 11 are input. An error Δ■ is detected, and V to this error is supplied to the two gate circuits and 2B, respectively.

Next, signal processing in the control loop will be explained.

The position detection circuit 7 is a circuit having a mechanism such as a means for reading servo data of a magnetic disk or a rotary (analog) encoder that operates in conjunction with the actuator 6, and the detection signal of the position detection circuit 7 is shows a change as shown in FIG. 3(a). That is, it shows a triangular waveform that crosses zero at every access distance corresponding to the track pitch A of the magnetic disk and takes positive and negative values in proportion to the moving distance of the head. Then, the movement detection circuit 7 detects zero-crossing points in the waveform shown in FIG.
Outputs a pulse as shown in figure (b). In other words, a pulse is output every time one track is moved, and this pulse is sent to the CPU.
It is counted by I. And C
In the PUI, the remaining access distance (residual distance) is recognized by setting the distance to be moved as an initial value and decrementing a count value each time the pulse is supplied. Then, based on the calculated residual distance, the reference speed generating circuit 1 outputs an analog waveform indicating the track number, as shown in FIG. 3(C).

On the other hand, the position detection circuit 7 receives an input signal as shown in FIG. 3(a) into a sawtooth waveform as shown in FIG. 3(d).
If the differential value is positive, the waveform is inverted; if the differential value is negative, it is converted to a non-inverted waveform). Then, depending on the level of this signal, the position within one track is recognized, and furthermore, a signal indicating the track position (Fig. 3 (c)
), the residual value of the access distance is obtained.

Furthermore, the comparison circuit 10 compares the drill speed V rer supplied from the reference speed generation circuit 11 and the detected speed Vf supplied from the speed detector 9, and determines that V r > V r
When ef is established, a logic signal of "1" is output.

Next, the operation of the control loop and the control method according to the present invention will be explained with reference to the flowchart of FIG.

Note that SPn in the following description indicates the n-th step in the flowchart.

Start Control starts by supplying an access command.

SPI: Distance between the current position and the target point, i.e., access distance Xs (Xs = X 4 in the illustrated example)
and the preset second specified distance (Kitei distance)
From l, the calculation ΔXs=(Xs/2)X, -X3 is executed and the calculation result ΔXs is set.

SF3: Set access distance Xs.

Open loop control is performed in which a speed signal (current value shown in Figure 2) is supplied to drive the SP3 near actuator at the maximum speed, and thereby the actuator 6 is accelerated to approach the supplied maximum speed signal. Then, the speed of the actuator 6 is increased with the maximum achievable acceleration.

SP4': Operate the gate circuits 2A and 2B of the speed control loop to set the loop gain to a position where a (large gain) can be obtained.

SF3: Determine whether the access distance Xs is greater than the first specified distance, and if YES, go to SF3, rv o
In this case, proceed to 5P20.

SF3: It is determined whether the moving distance Xr of the head is greater than the above-mentioned ΔXs, and if YES, the process proceeds to the next SF3. In other words, the intermediate point (Xs/
2) Proceed to the next SF3 on the condition that the point is a certain distance (X, ) before the point (the point at distance X3 from the target point in FIG. 2).

SF3: As in the conventional example, based on the speed error signal supplied from the speed error detection circuit 12, the actuator 6 is decelerated while performing closed loop control to reduce the speed error. Note that this closed loop control is
In reality, the control is close to open loop control.

That is, by setting the current vehicle speed V ref to a value smaller than the deceleration capacity of the actuator (motor), control close to open-loop control can be performed.

SF3: Movement speed ■r is the reference speed V at the current position
It is determined whether the value has decreased to the point where it can be considered to match rer (or not), and if YES is the condition, the process proceeds to the next SF3.

SF3: Operate gate circuits 2A and 2B to set the gain of the speed control loop to 2 (reduce the gain).

s p 10: Similarly to SP7, the actuator 6 is driven while controlling to reduce the speed error based on the speed error signal, and the process proceeds to the next 5 PII.

On the other hand, if it is determined No in SP5, 5P20: Proceed to the next 5P21 on the condition that the moving speed vr exceeds the reference speed Vrer.

5P21: Gate circuit 2A by command from CPUI
・2B is operated and the speed loop gain is set to 2.

5P22: Based on the speed error signal, the reference speed Vref
The actuator 6 is driven while controlling to minimize the speed error by decelerating the moving speed Vf that exceeds the above value, and then proceeding to the next 5 PII.

S P 11+ Has the access been completed, that is, whether the difference between the pulse count value shown in FIG. 3(b) and the set access distance becomes zero? 11.
The process ends on the condition of YES.

That is, by the above control operation, in response to the access command, the actuator 6 is first driven at the maximum realizable speed, and then, when the access distance is larger than the first specified pressure MXI, the actuator 6 is driven with a large loop gain. Closed-loop control (so-called bang-bang control, which is close to open-loop control) is performed until the target point is reached, and then, after approaching the target point, control is performed by switching to a small loop gain. Further, when the access distance is smaller than the first specified distance, the moving speed V of the actuator 6 which is under open loop control to operate at the maximum speed.
On the condition that f is accelerated to exceed the reference speed Vref at the moving position, the control state is immediately switched to a control state with a small loop gain, and closed loop control is performed.

According to the above control, when the access distance is larger than the first specified distance The loop gain is made smaller after the access distance approaches a certain point, and on the other hand, when the access distance is small, the closed loop control in the state where the loop gain is large is omitted and control with a small loop gain is immediately performed. It is possible to satisfy the contradictory demands of shortening access time and improving positioning accuracy.

In addition, in the above control, the distance X3 from the target point of the point at which the actuator is switched from the acceleration state to the deceleration state
is, X 3-(X 4/2) X +=(Xs/2)
-X.

The second specified distance x1 applied to specify this X3 indicates the distance between the point where the speed becomes 0 when decelerating from the maximum speed to the maximum deceleration and the target point. ing.

Furthermore, X2, which indicates the point at which bang-bang control is switched to general closed-loop control, is naturally set so that X2>XI with respect to X+.

Also, the transition conditions from open-loop control to closed-loop control (S P 6 and 5P20), or
The conditions for switching the loop gain (SF3) are not necessarily limited to the above-mentioned example, but the point is that the actuator must access a point slightly in front of a specific target point at maximum speed in the middle of the movement range of the actuator. After reaching that point, normal closed-loop control may be performed.

"Effects of the Invention" As is clear from the above explanation, the present invention performs maximum speed control at the initial stage of actuator operation, and then performs normal closed-loop control. A so-called bang-bang control is performed in which the actuator is driven at maximum speed, and the target position can be reached in almost the shortest time, and the control is executed from slightly in front of the target. By setting the loop gain in closed-loop control to a small value, it is possible to perform stable control that is less susceptible to resonance of the mechanical system.

[Brief explanation of the drawing]

1 to 4 show an embodiment of a control device to which the present invention is applied. FIG. 1 is a block diagram of a control loop, and FIG. 2 is a relationship between moving distance, speed, and control current. Figure 3 is an output waveform diagram, Figure 4 is a flowchart of control operation, Figures 5 and 6 are examples of a control device to which the conventional method is applied, and Figure 5 is a block diagram. ,
FIG. 6 is a chart showing the relationship between moving distance, speed, and control current. l...CPU, 2A/2B...Gate circuit, 3A/3B...Amplifier, 6...
Actuator, 7...Position detection circuit, 8...
...Movement distance detector, 9...Speed detector,
! 0... Comparison circuit, 11... Reference speed generation circuit, 12... Speed error detection circuit.

Claims (1)

[Claims] In an access control method that moves an actuator that is stopped at a certain position by a predetermined access distance, when an access command is supplied, open loop control is first performed to drive the actuator at the maximum achievable speed, and the actuator 1. A method for controlling an actuator, comprising: controlling the actuator in a closed loop according to predetermined speed control characteristics after the access speed of the actuator reaches a speed that substantially matches or exceeds a set value.