JPH0736132B2 - Servo circuit - Google Patents

Description

DETAILED DESCRIPTION [Table of Contents] Outline Industrial field of application Conventional technology (FIGS. 6 and 7) Problems to be solved by the invention (FIG. 8) Means for solving the problems (first Fig.) Action Embodiment (a) Description of one embodiment (Figs. 2, 3, and 4) (b) Description of another embodiment (Fig. 5) (c) Description of another embodiment Invention Effects of [Overview] Regarding a servo circuit that controls the speed of a servo target based on the error between the target speed and the actual speed, the purpose is to reduce the dull acceleration current during small differences and to shorten the speed control time. A target speed generation circuit that generates a target speed according to the amount of movement, a speed signal generation circuit that generates an actual speed from a position signal from the servo target, and the servo target based on an error between the target speed and the actual speed And a speed error generating circuit for controlling the speed According to the servo circuit that controls the deceleration after acceleration and positions it at the target position, an acceleration detection circuit that detects the acceleration in progress from the output of the speed error generation circuit is provided, and the speed error is detected by the acceleration detection signal of the acceleration detection circuit. The cutoff frequency of the generator circuit changes during acceleration and deceleration.

[Industrial application field]

The present invention relates to a servo circuit that controls a speed of a servo target based on an error between a target speed and an actual speed.

In magnetic disk devices and the like, a servo circuit is used for track positioning of a magnetic head.

In such a servo circuit, it is required to shorten the access time by shortening the time required for speed control.

[Conventional technology]

 FIG. 6 is an explanatory diagram of a conventional technique.

In the figure, reference numeral 1 denotes a magnetic disk mechanism as a servo target, which has a voice coil motor 1a, a carriage 1b on which a magnetic head 10 is mounted, and a magnetic disk 1c.

Reference numeral 2 is a position signal demodulation circuit, which detects the position signal from the servo information read by the servo head 10 on the servo surface of the magnetic disk 1c.
A demodulator of Ps, 3a is a target speed generation circuit, which generates a target speed Vc for positioning to a target position according to a movement amount from a main control unit (described later), 3b is a forward / forward
This is a reverse switching circuit, which switches and outputs the target speed in the forward direction or the target speed in the reverse direction from the target speed generation circuit 3a according to the FWD (forward) / RVS (reverse) switching signal of the main control section. .

Reference numeral 4 is a speed signal creating circuit, which creates an actual speed Vr from the position signal Ps and a current signal ic which will be described later. Reference numeral 5 is a speed error creating circuit, which determines a speed error ΔV between the target speed Vc and the actual speed Vr. Which generates a speed control current (signal), an amplifier 50 for generating a speed error ΔV, and a filter.
And 51.

6 is a position error creating circuit, which is a position signal Ps and a current signal
Generates a position error from ic and generates a position control signal. 7a is a coarse / fine switching unit. A speed error is created by a coarse (speed control) / fine (position control) switching signal from the main control unit. This is for switching from the speed control of the circuit 5 to the position control of the position error creating circuit 6.

7b is a power amplifier that amplifies the output of the switching unit 7a and drives the boil coil motor 1a of the magnetic disk mechanism 1. 7c is a current detection circuit that detects the drive current of the power amplifier 7b and outputs a current signal. This is what causes ic.

8 is a main control unit, which is composed of a microprocessor,
The position is detected according to the position signal Ps, and the target speed generation circuit 3a
The remaining movement amount is output to, the FWD / RVS switching signal is generated according to the forward / reverse direction, and the coarse / fine switching signal is generated near the target position.

In this servo circuit, speed control is performed up to the vicinity of the target position, and then position control is switched to position control at the target position.

By the way, the frequency characteristic of the servo target 1 is shown in FIG.
As shown in, it has a resonance point f ₂ .

The resonance point f ₂ is the torsional resonance point of the servo arm of the carriage 1b or the like of the servo target 1.

When the frequency of the speed control signal appears up to the band covering such a resonance point, mechanical vibration appears during seek (movement) operation, improving the floating stability of the magnetic head 10 and the stability after fine switching. I can't hope.

Therefore, the frequency band of the amplifier 50 of the speed error detection circuit 5 is determined by the time constant of the resistor and the capacitor of the filter 51, and its cutoff frequency f ₁ shown in FIG. 7 (B) is f ₂
It is necessary to make it smaller, for example, f ₂ = 2f _{1 to} 1.5f ₁
I was trying.

[Problems to be Solved by the Invention]

However, in recent years, there has been a demand for faster access time, and a seek with one difference, as shown in FIG.
The current cycle for acceleration and deceleration of the speed control signal is approaching the cutoff frequency f ₁ .

Therefore, as indicated by the solid line in FIG. 8, the current waveform, particularly the current waveform at the time of acceleration is blunted, and the current cannot flow any more as indicated by the dotted line.

Since it is difficult to raise the resonance point f ₂ of the mechanical characteristics, it has been difficult to reduce the speed control time.

Therefore, it is an object of the present invention to provide a servo circuit capable of reducing the dullness of the acceleration current at the time of a small difference and shortening the speed control time.

[Means for Solving the Problems]

 FIG. 1 is a principle diagram of the present invention.

The present invention, as shown in FIG. 1, includes a target speed generating circuit 3a for generating a target speed according to a moving amount and a speed signal generating circuit 4 for generating an actual speed from a position signal from the servo target 1.
And a speed error generation circuit 5 for controlling the speed of the servo target 1 based on the error between the target speed and the actual speed,
In the servo circuit that controls the deceleration after acceleration according to the movement amount and positions it at the target position, the acceleration detection circuit 9 for detecting the acceleration in progress from the output of the speed error detection circuit 5 is provided, and the acceleration detection circuit 9 is in progress. The cutoff frequency of the speed error generating circuit 5 is changed by the detection signal during acceleration and during deceleration.

[Action]

1 (B) and 1 (C) are diagrams for explaining the operation of the present invention, in which the upper stage shows a cut-off frequency characteristic diagram and the lower stage shows a current waveform diagram.

According to the present invention, the cutoff frequency during acceleration is infinite (shown by the dotted line in the cutoff frequency characteristic diagram of FIG. 1B) or large f ₁ ′ (cutoff frequency characteristic diagram of FIG. 1C). It shows). During deceleration, as shown in the cutoff frequency characteristic diagrams of FIGS. 1 (B) and (C), a small f ₁
And This reduces the rounding of the acceleration current during acceleration as shown by the solid line in the current waveform diagrams of FIGS. 1 (B) and (C).

During acceleration, the power amplifier does not work as a current source, and the power amplifier inputs a sufficiently large voltage so that the power supply voltage is applied to the motor. In this state, the accelerating current only increases, and it is equal to that the servo control is not applied. That is, since the servo loop is equal to the broken state, the vibration signal from the position signal is not amplified by the servo circuit and is not input to the power amplifier. In other words, vibration induction by the loop does not occur. Therefore, even if the cutoff frequency is infinite or large, vibration of the mechanism (servo target) is less likely to occur, and it is better to increase the cutoff frequency to reduce the dull acceleration current and shorten the acceleration period. .

As a result, as shown by the solid line in the current waveform charts in the lower part of FIGS. 1 (B) and 1 (C), the acceleration time is shortened as compared with the conventional dotted line, and the speed control time can be shortened.

Further, during deceleration, the cutoff frequency is returned to f ₁ , so that mechanical vibration does not occur as a whole.

〔Example〕

(A) Description of an Embodiment FIG. 2 is a configuration diagram of an embodiment of the present invention, and FIG. 3 is a configuration diagram of a main part of the configuration of FIG.

In the figure, the same components as those shown in FIGS. 1 and 6 are designated by the same symbols.

In the figure, the filter 51 is composed of a resistor R, a parallel circuit of a switch SW and a capacitor C.

90 is a comparator, the output of the amplifier 50 (speed error current)
VCMCRT is sliced to zero volt and speed slice signal VSL is output, and 91 is an inverting circuit.
It reverses VSL.

Reference numerals 92 and 93 each have a 3-input AND gate, and generate a "high" level output only when all 3 inputs are at a "high" level. The AND gate 92 is a forward from the main control unit (referred to as MPU) 6. A high level AND between the movement signal * MvF, the capture velocity signal * CVL generated when the actual speed from the MPU6 is below a certain level, and the output of the comparator 90. The AND gate 93 is the reverse movement from the MPU6. The signal * MvR, the capture velocity signal * CVL from the MPU 6, and the output of the inverting circuit 91 are set to high level AND.

Reference numeral 94 is an OR gate, which takes the OR of the outputs of the AND gates 92 and 93, and 95 is an inverting circuit, which inverts the output of the OR gate 94 and generates the acceleration end signal EAC.

Reference numeral 96 is a flip-flop, which is cleared by an access start * ASP from the MPU 6, is inverted with the acceleration end signal EAC as a clock, and generates an accelerating signal SKA from the output.

FIG. 4 is a waveform diagram of essential parts of one embodiment of the present invention.

When moving forward, MPU6 is the target speed generator circuit.
The target velocity FwVc in the forward direction is generated from 3a, the MPU 6 generates the forward movement signal * MvF, and when the velocity of the small difference is small, the capture velocity signal * CVL is generated from the actual velocity Vr.

In the speed error creating circuit 5, the speed error between the target speed FwVc and the actual speed Vr is taken by the amplifier 50, and the speed error signal ΔV
To occur.

At this time, the acceleration detection circuit 9 is generated by the access start signal * ASP generated at the seek (access) start.
Since the flip-flop 96 of is cleared, a high level acceleration signal SKA is generated from the output.

This turns off the switch SW of the filter 51,
The cutoff frequency of the amplifier 50 becomes infinite, and the speed error signal ΔV rises rapidly.

Since the speed error signal ΔV is sliced to zero volts by the comparator 90, a high level speed slice signal VSL is generated when the speed error signal ΔV is positive.

Therefore, a high level output is generated from the AND gate 92, and the low level acceleration end signal EAC is generated via the OR gate 94 and the inverting circuit 95.

When the speed error signal ΔV becomes zero, the speed slice signal VSL of the comparator 90 becomes low level, the output of the AND gate 92 becomes low level, and the acceleration end signal EAC becomes high level via the OR gate 94 and the inverting circuit 95. The flip-flop 96 is inverted by using this change point as a clock, and the output accelerating signal SKA is set to low level.

Therefore, the switch SW of the filter 51 is turned on and the amplifier 50
The cutoff frequency of is f ₁ .

Therefore, in the subsequent deceleration period, the speed error signal ΔV is band-limited at the cutoff frequency f ₁ .

As a result, the current VCMCRT flowing through the voice coil motor 1a via the power amplifier 7b becomes as shown in FIG. 4, and the acceleration period rises substantially linearly.

On the other hand, in reverse movement, the MPU6 starts the access start signal * AS when starting the access for one difference.
The target speed generating circuit 3a generates the target speed RvVc in the reverse direction, the reverse movement signal * MvR, and the capture velocity signal * CVL.

In the speed error creating circuit 5, a speed error between the target speed RvVc and the actual speed Vr is taken and a speed error signal ΔV is generated.

At this time, the flip-flop 96 of the acceleration detection circuit 9 is cleared by the access start signal * ASP, so that the high-acceleration signal SKA is generated from the output.

As a result, the switch SW of the filter 51 is turned off, the cutoff frequency of the amplifier 50 is made infinite, and the speed error signal ΔV is rapidly raised.

The speed error signal ΔV is sliced to zero volts by the comparator 90, and when the speed error signal ΔV is negative, the low level speed slice signal VSL is generated.

Therefore, a high level output is generated from the AND gate 93, and the low level acceleration end signal EAC is generated via the OR gate 94 and the inverting circuit 95.

When the speed error signal ΔV becomes zero, the speed slice signal VSL of the comparator 90 becomes high level, the output of the AND gate 93 becomes low level, and the acceleration end signal EAC becomes high level via the OR gate 94 and the inverting circuit 95. Then, the flip-flop 96 is inverted with this change point as a clock, and the output accelerating signal SKA is set to the low level.

Therefore, the switch SW of the filter 51 is turned off and the amplifier 50
The cutoff frequency of is f ₁ .

Therefore, during the deceleration period, the speed error signal ΔV is band-limited at the cutoff frequency f ₁ .

As a result, the current VCMCRT flowing through the voice coil motor 1a via the power amplifier 7b rises substantially linearly during the acceleration period as shown in FIG.

Thus, in 1 difference seek, the switch SW of the filter 51 is turned off by the access start signal, the cutoff frequency becomes infinite, and the switch SW is turned on by the end of acceleration, and the cutoff frequency is the capacitor C and the resistance. It becomes f ₁ determined by R.

(B) Description of Other Actual Speed FIG. 5 is another explanatory drawing of the actual speed of the present invention.

In the figure, the same components as those shown in FIGS. 1, 2, 3, and 6 are designated by the same symbols.

In this embodiment, the filter 51 includes a resistor R and a capacitor.
It is composed of a parallel circuit of C1, a switch SW, and a capacitor C2.

Therefore, when the switch SW is on, the cutoff frequency changes to f ₁ as shown in FIG. 1C, and when the switch SW is off, the cutoff frequency changes to f ₂ .

Due to the same operation as in Fig. 2 and Fig. 3, in 1 difference seek, the switch SW is accelerating during acceleration.
It is turned off by SKA, the cutoff frequency becomes f ₂ ,
The rounding of the acceleration signal is reduced, the switch SW turns on during deceleration, and the cutoff frequency becomes f ₁ .

In this example, since the band is limited even during acceleration, there is no fear of mechanical vibration, but the accelerating current is more dull and the accelerating time is longer than that in FIG.

(C) Description of Another Embodiment Although the magnetic disk device has been described as an example in the above embodiment, the present invention can be applied to other devices as well, and it is possible to move a desired distance.
The cutoff frequency can be changed.

Although the present invention has been described with reference to the embodiments, the present invention can be variously modified according to the gist of the present invention, and these modifications are not excluded from the present invention.

〔The invention's effect〕

As described above, according to the present invention, it is possible to reduce the dullness of the acceleration current during short-distance movement and to shorten the speed control time.

[Brief description of drawings]

 FIG. 1 is a principle diagram of the present invention, FIG. 2 is a configuration diagram of an embodiment of the present invention, FIG. 3 is a configuration diagram of an essential part of the configuration of FIG. 2, and FIG. FIG. 5 is an explanatory view of another embodiment of the present invention, FIGS. 6 and 7 are explanatory views of a conventional technique, and FIG. 8 is an explanatory view of problems of the conventional technique. In the figure, 1 ... Servo object, 3a ... Target speed generation circuit, 4 ... Speed signal generation circuit, 5 ... Speed error generation circuit, 9 ... Acceleration detection circuit.

Claims (1)

[Claims] 1. A target speed generation circuit (3a) for generating a target speed according to a movement amount, a speed signal generation circuit (4) for generating an actual speed from a position signal from a servo target (1), and the target. A servo having a speed error generation circuit (5) for controlling the speed of the servo target (1) based on the error between the speed and the actual speed, and performing deceleration control after acceleration according to the movement amount to position the servo at a target position. The circuit is provided with an acceleration detection circuit (9) for detecting acceleration from the output of the speed error detection circuit (5), and the speed error generation circuit (5) is detected by the acceleration detection signal of the acceleration detection circuit (9). The servo circuit characterized in that the cutoff frequency of) changes during acceleration and during deceleration.