JPS6158488A - Control system of voice coil type linear motor - Google Patents

Abstract

PURPOSE:To correct the irregularity of the characteristic of a magnet and the influence due to an external force by measuring the influence of the distortion and the external force to the magnetic characteristic before starting an operation, obtaining the difference from an ideal value and storing it as a correction value in a memory. CONSTITUTION:An output A of a constant-voltage generator 1 is supplied through a power amplifier 4 to a voice coil motor VCM before starting the operation. On the other hand, a position signal PS fed back from a head is differentiated by differentiators 2, 3, converted into an acceleration C, and added to the output A. A current signal CRS flowed to the VCM at this time is converted by an A/D converter 11 into a digital signal, and a memory 12 stores the digital signal and a cylinder position signal CAR. The magnification of a multiplier 10 is corrected by the correction value F stored in the memory 12 at the operation time.

Description

[Detailed description of the invention] [Industrial field of application] Large 8g [113L+ m'; f chi 'X h 'i
ii +'f? F'+ H-h-L+ K2h j'
M n+'l? 11 control system, in particular, a voice coil type linear motor used for head positioning, that is, a voice coil that corrects magnetic field distortion occurring at the start, middle, and end of the operation of the voice coil motor (VOM), the influence of external force, etc. Regarding motor control method.

[Conventional technology and problems]

Positioning of the front and rear in the magnetic disk drive is performed by a VOM that moves in a straight line. Position control of the VCIM involves inputting device signals and speed signals from the head to the positioning circuit, and controlling the VOM based on the control signal from the control circuit.
Outputs drive signals and controls position. In this case, when the head is located at the outermost or innermost circumference of the disk cylinder, it is not affected by the effects of the lack of linearity in the magnetic properties of the VOM magnet, external forces such as wind pressure, or the effects of thrust from above the machine groove. This causes overshoot and undershoot in positioning, but as a countermeasure to this problem, it is generally corrected by a closed loop method using track servo.

However, these methods attempt to control the position while continuously feeding back the effects of the resulting magnetostriction and external force, and are not methods that measure in advance, obtain correction values, and use these values during actual operation.

[Means for solving problems]

The present invention measures the effects of the above-mentioned distortion of magnetic characteristics, external forces, etc. before the VOM starts an actual read/write operation,
The system calculates the difference value from the ideal value, stores it in memory as a correction value, and multiplies it during actual operation to obtain correct VOM operation. Voice coil type linear motor.

In the control system for the motor, the control circuit section includes a storage means for storing a difference value between a gain at a target speed and a gain at an actual speed, and a multiplier for correcting the actual speed based on the difference value. , Measure linearity such as magnetostriction and external force of the linear motor before starting operation, store the measured values in the storage means based on each cylinder address, and use the difference value stored in the memory during actual operation. The present invention is characterized in that the linear motor is corrected by multiplying by T in a multiplier.

〔Example〕

FIG. 1 is a block Pi1 diagram of a control circuit section of a device implementing the VOM control method according to the present invention. In FIG. 1, 1 is a constant voltage generation circuit, 2 and 3 are differentiating circuits, 4 is a power amplifier circuit, 5 is vau, 6 is a differential amplifier, 7 is a target speed generation circuit, 8 is an actual speed detection circuit, 9 is a differential circuit, 10
11 is an analog/digital converter, 12 is a memory, and 13 is a digital/analog converter.

Fig. 2 shows a part of the apparatus shown in Fig. 1, and shows a measurement circuit used to measure magnetostriction, external force, etc., and Fig. 6 shows a part of the apparatus shown in Fig. 1, in which the head reaches the target position. This is an operating circuit used when Figures 4 to 6 are the second
3 is a diagram for explaining the operation of the device shown in FIG. 3 and the device shown in FIG. 3. FIG. Further, FIG. 7 is a T graph showing changes in the magnetic flux density of the VOM magnet from the movable range of the VOM, that is, from the innermost circumference to the outermost circumference of the cylinder.

In such a configuration, how does the measurement circuit shown in FIG. 2 operate? This will be explained with reference to FIGS. 4 and 5. Furthermore, G.Y.
L=O indicates the innermost circumference of the cylinder, OY L = X/2 indicates the middle position of the cylinder, OYI == or the outermost circumference 2 of the cylinder, the arrow indicates the direction of travel of the head, and TI indicates the measurement interval. shall be indicated.

A indicates a voltage waveform at the output A of the constant voltage generation circuit 1, and the constant voltage is input to the power amplifier circuit 4 at the subsequent stage. A power amplifier circuit is a type of voltage-current conversion circuit, and can obtain an output current proportional to an input voltage. Therefore, if the input voltage is constant, a constant current can be obtained from the output. Since such a constant current flows through the VOM, the actuator can perform uniform acceleration interlocking. Is B the waveform at output B of differentiator circuit 2? As shown, Kakeru! When a position signal (ps) is input from a head subjected to IrIJ, a differential circuit (Δx
)2, the target speed and the actual speed A when there is no magnetostriction, external force, etc. overlap. Note that vertical @V indicates speed. In the sections D1 and I)2 where distortion occurs, Dl is considered to be due to magnetostriction at the end of the magnet, and Dl is considered to be affected by external force, thrust, etc. O is the output waveform of the differentiating circuit 3, and indicates the acceleration α obtained by differentiating the velocity shown in B with respect to time T0 In this case, the solid line is the actual acceleration 2 when the position signal (ps) is not input, that is, when there is no feedback
, and the acceleration changes in sections D1 and Dl. D is a voltage waveform at the input of the power amplifier circuit 4,
The power amplifier 4 uses the compensated values in the sections D1 and Dl.
Enter. As a result, from the output of power amplifier 4, VO
A current can be passed that causes constant acceleration to M. E indicates the output of the differential amplifier B, and the thus corrected undercurrent sensitivity signal (OR3) is input to the subsequent analog-to-digital converter (A/D) 11, where it is digitally converted and sent to the memory (MEM) 12. become old.

In this case, the memory 12 is given a cylinder address OAR for each cylinder. F is multiplier-1 after being converted from digital to analog during actual operation.
Indicates the magnification added to 0.

In Figure 5, the cylinder position is intermediate 0YL=X/2
In the measurement section 2 from 2 to the outermost circumference oyr+=x, correction is shown for the case where the head moves in the direction of the arrow. A-IP indicates the same position as in FIG. As is clear from the figure, the concept is exactly the same as that in Figure 4, and the current sensitivity signal (ORS) shown in E is A/D converted and written to the memory 12, and corrected as shown in A during actual operation. A multiplier is added to the multiplier.

FIG. 6(cL) shows that the fourth
Figure CF) and Figure 5 (with Takumi's track correction,
2. The operating characteristics of the operating circuit shown in FIG. 5 are softer than those in the case where such correction was not made. Cylinder position g OY L = X 1 to 0YL
In the seek operation in the section = show.

Further, J indicates the output waveform of the multiplier 10, and the dotted line indicates the case where gain correction is performed by the multiplier. FIG. 6(b) shows the details of the P part of (α),
The center 0 indicates the on-track position, and L is the distance indicating the deviation from the target track.

Moreover, all the curves show the waveforms at J, of which the solid line shows the case where there is no gain correction by the multiplier 10, and the dotted line shows the case where there is correction of the gain magnification. As is clear from the figure, if there is no correction, the velocity will be O at a position that deviates from the target track by the distance, so a voltage will be applied in the opposite direction to reach the position where the distance is 0, following a trajectory. In other words, an overshoot occurred in positioning.

Figure 7 shows the strong magnetic field recursion from the innermost circumference 0LY=:O of the cylinder to the outermost circumference OLY:X! The relationship between shame and correction curvework 1 is shown, Dl, D2. By performing correction 2 as in step 1 for the distortion of the magnetic flux density B at D3, the current applied to VOH can be compensated.

〔Effect of the invention〕

As explained above, in order to correct the VOM magnet glide linearity and external force, turn on the switch swOB before operation, measure the magnet glide linearity and external force, store the correction values for each cylinder in memory, and switch swOB during operation.
W1 and sw2: 2 are read from the memory after they are turned on, multiplied by a correction value using a multiplier, and applied to the VOM, so it is possible to correct for variations in magnet characteristics, the influence of external forces, etc. before actual operation. can.

[Brief explanation of drawings]

1 is a block diagram of a control circuit section of an apparatus implementing a control method as an embodiment of the present invention; FIG. 2 is a block diagram of a measuring circuit showing a part of the apparatus of FIG. 1; The figure shows an operation circuit showing a part of the apparatus shown in FIG. 1, FIGS. 4 and 5 are diagrams explaining the operation of the circuit shown in FIG. 2, and FIGS. and FIG. 7 are diagrams showing changes in magnetic field strength and external force from the innermost circumference to the outermost circumference of the cylinder, and a correction curve 2 thereof. (Explanation of symbols) 1... constant voltage generation circuit, 2, 3... differentiating circuit, 4
...Power increase circuit 11, 5...Voice coil motor, 6...Differential amplifier, 7...Target speed generation circuit, 8
...Actual speed detection circuit, 9...Difference circuit, 10...
・Multiplier-111...A/D converter, 12・
...Memory, 16...D/A converter.

Claims (1)

[Claims] 1. In a control method for a voice coil type linear motor for head positioning in a control circuit section of a magnetic disk device, the control circuit section includes a storage means for storing a difference value between a gain at a target speed and a gain at an actual speed; and a multiplier that corrects the actual speed based on the difference value,
Measure the linearity of the linear motor such as magnetostriction and external force before starting operation, store the measured values in the storage means based on each cylinder address, and multiply the difference value stored in the memory during actual operation. 1. A control method for a voice coil type linear motor, characterized in that the voice coil type linear motor is corrected by multiplying the voice coil type linear motor in a device.