JPH0736129B2 - Position control offset adjustment method for servo circuit - Google Patents

Description

DETAILED DESCRIPTION [Table of Contents] Outline Industrial field of application Conventional technology (FIGS. 7, 8, and 9) Problem to be solved by the invention Means for solving the problem (FIG. 1) ) Operation Example (a) Description of configuration of one example (FIGS. 2 and 3) (b) Description of operation of one example (FIGS. 4, 5, and 6)
(C) Description of other embodiments Effect of the invention [Overview] In a servo circuit for positioning a servo target at a target position by speed control and position control, a position control offset adjusting method for removing an offset of a position control system. Concerning the above, regarding the purpose of automatically adjusting the circuit offset of the position control system without human intervention, the speed control unit that detects the actual speed of the servo target and controls the speed by the speed error from the target speed, and the servo A position control unit for position control by a position error signal obtained from a position signal of a target, a switching unit for switching and connecting the servo target to the speed control unit or the position control unit, and a main control unit for switching control of the switching unit. In the servo circuit which has the above-mentioned, and which is configured to switch from the speed control to the position control in the vicinity of the target position, the offset adjustment value given to the position control unit is changed to The method has a step of repeating the movement of a constant distance to measure the integrated value of the position signal at the time of position control at each offset adjustment value, and a step of setting the offset adjustment value that minimizes the integrated value as the optimum offset value.

[Industrial application field]

The present invention relates to a position control offset adjusting method for removing an offset of a position control system in a servo circuit that positions a servo target at a target position by speed control and position control.

Servo circuits are widely used for track positioning of a magnetic head of a magnetic disk device.

In such a servo circuit, if there is an offset in the analog circuit of the position control system, the position control cannot be performed smoothly, and therefore an offset adjustment technique for removing the offset is required.

[Conventional technology]

 FIG. 7 and FIG. 8 are explanatory views of the prior art.

In FIG. 7, reference numeral 1 is a servo target, and includes a voice coil motor 1a, a servo head 1b moved by the voice coil motor 1a, and a position signal generation circuit 1c for generating a position signal Ps from a read signal of the servo head 1b. Have

Reference numeral 2 denotes a speed detecting circuit, which detects the actual speed Vr from the position signal Ps and a detection current ic described later. That is, the speed detection circuit 2 is a circuit that obtains an actual speed signal by differentiating a known position signal, and adds a detection current ic in order to compensate the phase delay of the position signal Ps.

Reference numeral 3 denotes a measurement error detection circuit, which generates a speed error ΔV between a target speed Vc and an actual speed Vr, which will be described later, and controls the speed, and these constitute a speed control unit.

Reference numeral 4 denotes a position error detection circuit position control unit, which detects the position error signal ΔP from the position signal Ps and the detection current ic.
Is generated and the position is controlled. A method of creating the position error signal ΔP is also disclosed in Japanese Patent Laid-Open No. 63-9084. Further, the detection current ic is added for the purpose of compensating for the phase delay of the position signal Ps. Reference numeral 5 denotes a power amplifier and a switching unit, which has a changeover switch and a power amplifier, and controls the speed error detection circuit 3 or the position error detection circuit 4 by the coarse (speed control) / fine (position control) switching signal to serve as a servo target 1. The switch connection is made to.

6 is a main control unit, which is composed of a microprocessor,
Generate a target speed curve Vc according to the amount of movement,
The position of the servo target 1 is monitored by a track crossing pulse described later, and a switching signal from coarse to fine is generated near the target position.

Reference numeral 7 is a control current detection circuit, which detects the control current Is of the power amplifier 5 and generates a detection current signal ic, and 8 is a track crossing pulse generation circuit, which is a position signal Ps.
Generates a track crossing pulse from the main control unit 6
Is output to.

When the number of moving tracks (moving amount) is given, the main control unit 6 generates a target speed curve Vc according to the number of moving tracks, and drives the voice coil motor 1a by speed control to reach the vicinity of the target position. , The switching unit 5 is switched to the position control side, the position of the voice coil motor 1a is controlled, and the voice coil motor 1a is positioned on a desired track.

As shown in FIG. 8, the position control unit 4 that performs this position control is a filter 40 that cuts high-frequency components of the position signal Ps.
, An amplifier 41 for amplifying the output of the filter 40, and a filter
An integrating circuit 42 for integrating the output of 40, a differentiating circuit 43 for differentiating the output of the filter 40 and the control current detection signal ic, and an amplifier
Position error generator 44 that generates a position (position) error signal from the outputs of 41, integration circuit 42, and differentiation circuit 43
And a resistor r ₁ for adjusting the offset of the differentiating circuit 43
had r ₄ .

Since such a position control system is composed of analog circuits, circuit offsets inevitably occur.

In particular, the offset of the current feedback system is large, and for example, the influence of the offset of the amplifier of the control current detection circuit 7 is large.

FIG. 9 is an explanatory diagram of a conventional technique.

If there is no circuit offset, as shown in Fig. 9 (A), after switching from coarse (speed control) to fine (position control), the position signal Ps immediately converges to 0 V, and after switching to fine, it remains constant for a certain period of time. Seek is completed by not exceeding the level (on-track level).

However, if there is a circuit offset, it is shown in FIG.
After switching to fine as shown in the figure, the position signal Ps gradually rises to correct the circuit offset, and seek is completed without being above a certain level for a certain time, but then a peak occurs and the on-track level is exceeded. It may happen.

When this exceeds the on-track level, it means that the servo target 1 is moved more than the on-track level.

In order to correct this circuit offset, especially the offset of the current feedback system, in the past, the position signal was observed with an oscilloscope while repeating the seek in a certain fixed interval, and the variable resistance
Humans were adjusting r ₄ (Fig. 8).

[Problems to be Solved by the Invention]

However, since humans make adjustments, there is a problem that adjustment variations due to individual differences and adjustment variations due to measuring instruments (oscilloscopes) and the like are likely to occur, and there is also a problem of cost increase due to measuring instruments and personnel costs.

Therefore, it is an object of the present invention to provide a position control offset automatic adjustment method for a servo circuit that can automatically adjust the circuit offset of the position control system without human intervention.

[Means for Solving the Problems]

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

As shown in FIG. 1, the present invention detects the actual speed of the servo target 1 and controls the speed based on the speed error from the target speed, and the position obtained from the position signal of the servo target 1. A position control unit 4 for position control by an error signal, a switching unit 5 for switching and connecting the servo target 1 to the speed aft units 2, 3 or the position control unit 4, and a main control unit 6 for switching control of the switching unit 5. In a servo circuit that has, and switches the speed control to the position control near the target position,
A step of changing an offset adjustment value given to the position control unit 4, repeating a movement of a fixed distance, and measuring an integrated value of a position signal at the time of position control at each offset adjustment value;
And a step of setting an offset adjustment value that minimizes the integrated value as an optimum offset value.

[Action]

The present invention, since the influence of the offset appears in the waveform of the position signal Ps in the position control as described above, while integrating the position signal in the position control while changing the offset value,
This is to find an offset value that minimizes the integrated value and try to adjust it.

That is, when the offset adjustment value is changed, the positional deviation amount changes, and feedback control is performed to reduce the positional deviation amount to zero. Therefore, the convergence pattern (differential value)
Changes. The offset adjustment value is adjusted so that the integrated value becomes the minimum.

Since the offset can be automatically adjusted, manual adjustment is not required, and there is no error and cost can be adjusted.

〔Example〕

(A) Description of Configuration of One Embodiment FIG. 2 is a configuration diagram of an embodiment of the present invention, and FIG. 3 is a configuration diagram of a position controller in the configuration of FIG.

In the figure, the same components as those shown in FIGS. 1, 7, and 9 are designated by the same symbols.

Reference numeral 9 denotes an integrator, which is turned on by the main controller (hereinafter referred to as MPU) 6 and which is a switch 90 for passing the position signal Ps.
And an absolute value circuit 91 for converting the position signal Ps from the switch 90 into an absolute value, and an integrating circuit 92 for integrating the output of the absolute value circuit 91.
And an analog / digital converter (ADC) 93 for converting the analog output of the integrating circuit 92 into a digital value.

62 is an offset register for storing the offset value L, 63 is an integrating circuit register for storing the integrating circuit, 64 is a work register, and various measured values FWD, RVS, T ₁ , T ₂ , T ₃ , and A are stored.

In FIG. 3, 45 is a digital / analog converter (referred to as DAC), which is connected to the resistor r ₂ and converts the digital offset value from the MPU 6 into an analog offset amount and sets the offset of the differentiation circuit 43. is there.

(B) Description of Operation of One Embodiment FIG. 4 is a flow chart of adjustment processing of one embodiment of the present invention, FIG. 5 is a flow chart of determination of forward / reverse offset adjustment value of FIG. 4, and FIG. FIG. 5 is a flow chart of an integral sampling process of FIG. 5.

Incidentally, FIG. 5 is a subroutine of the flow of FIG. 4, and FIG. 6 is a subroutine of the flow of FIG.

First, the overall adjustment process will be described with reference to FIG.

MPU6 resets various registers at the start of adjustment.

Next, the MPU 6 executes a subroutine described later with reference to FIG. 5, determines the offset adjustment value L in the forward direction, and sets the determined offset adjustment value L in “FWD” of the register 64.
To store.

The MPU 6 further executes a subroutine described later in FIG. 5 to determine the offset adjustment value L in the reverse direction,
The determined offset adjustment value L is stored in “RVS” of the register 64.

Next, the MPU6 calculates the average of "FWS" and "RVS" in the register 64, sets the average value in the register 62 as "L",
Output.

Next, the offset adjustment value determination process will be described with reference to FIG.

First, the MPU 6 sets “3” in the integration count I of the register 63. That is, the integration is performed 3 times.

The MPU 6 sets the offset adjustment value L in the register 62 and outputs “L” to the DAC 45 of the position control unit 4.

Then, the MPU 6 executes an integral sampling subroutine described later in FIG. 6, obtains the integral value of the position signal Ps in the register A, and stores it in the register Ti (i = 4-I).

At this time, this routine is repeated a plurality of times to average the integrated values.

Next, the MPU 6 updates L of the register 62 to (L + X),
The number of integration times I in the register 63 is updated to (I-1). However, X is a predetermined displacement amount. This value is not a value that is directly related to the offset adjustment process, and is only necessary for changing the offset adjustment value at equal intervals.

The MPU 6 checks whether the integration count I of the register 63 is "0", and if it is not "0", returns to the step.

On the other hand, if I = 0, the integration operation is completed three times, and the integrated values T ₁ , T ₂ , and T ₃ are obtained, and the current gain is (L +
3X).

First, the MPU 6 compares the first-time integrated value T ₁ with the second-time integrated value T ₂ .

If T ₁ ≧ T ₂ is not satisfied, that is, T ₁ <T ₂ , the offset L is (L−4X), that is, L = L + 3X, because a minimal value cannot be obtained because the increase is monotonic with respect to the increasing change of the offset L. For (L
-X) and return to step.

On the other hand, if T ₁ ≧ T ₂ , the second integrated value T ₂ and the third integrated value T ₃ are compared.

If T ₃ ≧ T ₂ is not satisfied, that is, T ₃ <T ₂ , the offset L is (L−2X), that is, L = (L + 3X), because a minimal value cannot be obtained because of a monotonic decrease with respect to an increasing change in the offset L. ), Increase to (L + X) and return to step.

On the contrary, if T ₃ ≧ T ₂ , the relationship of T ₁ ≧ T ₂ ≦ T ₃ is established, and T ₂ ≧ T ₂
Is a minimum value, the gain of T ₂ is (L−2X) = (L +
X), store the value in the register 64 as the offset determination value "FWD" in the forward direction, and return.

The reverse direction offset determination value "RVS" is similarly obtained by performing reverse direction integral sampling in steps.

Next, the integral sampling process will be described with reference to FIG.

(I) The MPU 6 starts forward seek for the planned amount of difference.

(Ii) The MPU 6 determines whether or not the speed control is completed. When the speed control is completed, the MPU 6 issues an integration start, turns on the switch 90, and operates the integration circuit 92.

Therefore, the integrator circuit 92 starts integrating the position signal Ps from the end of the speed control, as shown in FIG.

(Iii) In this way, after the speed control is switched to the position control, the on-track signal continues for a certain period of time to determine that the seek has ended.

After a predetermined time, the integration start signal is turned off, the switch 90 is turned off, the integration circuit 92 is deactivated, and the integration is completed.

Therefore, the integration period is as shown in FIG.

(Iv) After the integration period ends, the MPU 6 samples the integrated value from the ADC 93 and stores it in the register 64 as “A”.

Then, a reverse seek is performed by the predetermined amount and the process returns.

The above flow is the integral sampling process in the forward direction, but in the case of the reverse direction, the forward seek is set to the reverse seek in step (i), and the step (iv) is performed.
Just change reverse seek to forward seek with
The rest is the same.

In this way, there may be a difference in the offset between the forward direction and the reverse direction, so as shown in FIG. 4, the offset adjustment values in both directions are determined and the average value is used as the automatic offset adjustment value.

Further, since the offset value that minimizes the integrated value of the position signal is determined, an appropriate offset adjustment value can be obtained.

(C) Description of Other Embodiments In the above-mentioned embodiments, the servo object is the magnetic disk device, but it may be another device or the MPU 6 may perform the integrating operation without providing the integrating portion. .

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, the present invention has the following effects.

Seek is repeated while changing the offset, the integrated value of the position signal Ps at each offset is measured, and the offset value that minimizes the integrated value is determined, so the circuit offset of the position control system is automatically adjusted to the optimum value. it can.

Since the optimum offset values in the forward direction and the reverse direction are obtained and the average value thereof is used as the offset value, it is possible to automatically adjust to the optimum offset value in both the forward direction and the reverse direction.

[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 a position control unit in the configuration of FIG. 2, and FIG. 4 is an adjustment of an embodiment of the present invention. Processing flow chart, FIG. 5 is a flow chart of offset adjustment value determination processing in FIG. 4, FIG. 6 is a flow chart of integral sampling processing in FIG. 5, FIG. 7, FIG. 8 and FIG. It is a figure. In the figure, 1 ... Servo object, 2 ... Speed detection circuit, 3 ... Speed error detection circuit, 4 ... Position error detection circuit, 5 ... Switching unit, 6 ... Main control unit.

Claims (1)

[Claims] 1. A speed control unit (2, for detecting an actual speed of a servo target (1) and controlling the speed by a target speed and a speed error.
3), a position control unit (4) for position control by a position error signal obtained from the position signal of the servo target (1), and the speed control unit (2, 3) or position control of the servo target (1). A switching unit (5) that is switch-connected to the unit (4) and a main control unit (6) that controls switching of the switching unit (5) are provided, and speed control is switched to position control in the vicinity of the target position. In the servo circuit described above, the main control unit (6) changes the offset adjustment value given to the position control unit (4) and repeats the movement of a fixed distance in the forward direction and the reverse direction. The step of measuring the integrated value of the position signal and the step of obtaining the offset adjustment value in the movement in the forward direction and the offset adjustment value in the movement in the reverse direction where the integrated value is the minimum And a step of obtaining an average value of the offset adjustment value in the movement in the forward direction and the offset adjustment value in the movement in the reverse direction that minimizes the integrated value, and setting it as an optimum offset value. Position control offset adjustment method for servo circuit.