JPS5829180A - Positioning device for magnetic head - Google Patents

Abstract

PURPOSE:To compensate the effect on a positioning control system so that the transient time can not be prolonged and error due to the dispersion of a spring through a force cancelling the spring force with a control means, by correcting the dispersion of the spring force after detection. CONSTITUTION:A CPU3 stores a displacement (x), a spring force F, and a correction term alpha due to dispersion of a spring. The CPU3 reads out the spring force F corresponding to an objective position, calculates the difference of distance between the present position and the objective, and objective speed information is loaded to a register 2. This information is converted into an objective speed signal at a converter 6 and outputted to a summing amplifier 8. A differentiation circuit 4 forms a speed signal from a position signal of a position detector 12 and outputs the signal to the amplifier 8. The amplifier 8 subtracts both the signals to accelerate a carriage 11 accordingly. When a head crosses a track, a cylinder pulse S is given to the CPU3. The speed control is performed with the similar operation.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic head positioning device in a magnetic disk drive.

Some recent magnetic disk scissor holders are equipped with springs so that the carriage returns to a predetermined position when the power is turned off. In this magnetic disk drive, spring force is always acting on the carriage, so compensation for this is required. In conventional magnetic disk drives, the influence of spring force is compensated for by inserting a low-frequency integrator into the control system that positions and holds the magnetic head on the track.

However, if the time constant of this low-frequency integrator is made too small,
The closed loop of the control system is likely to oscillate, so the time constant tube must be set to a fairly large value. If the time constant is increased, there is a drawback that the transition time becomes longer when switching from speed control to control for positioning and holding the magnetic head on a track. So we removed these shortcomings,
A magnetic head positioning device has been proposed that can compensate for the influence of a spring on a magnetic head positioning control system so that the transition time does not become long.

Specifically, the force F generated by the spring attached to the carriage is expressed by the formula p' = z kX, where the spring constant is 1 and displacement is X, and this formula is used to correspond to the target track position. I am trying to find the spring force F.

That is, the value of Paneka corresponding to the position of the target rack is determined using the above formula and stored in the memory. When the head moves onto the target track, position control is switched to position the head on the target track.

Then, the prepared panel value is D/A converted and added to the head position signal so as to cancel out the spring panel value, so that the head can be positioned on the target track. Therefore, in the above proposal, as a method of compensating for the influence exerted by the spring on the magnetic head positioning control system, the transient time can be shortened and the response characteristics can be significantly improved compared to the conventional method of using a low-frequency integrator. .

However, due to manufacturing problems of the springs, the possibility of variations in individual springs was taken into consideration, and there was still room for improvement.

Jin's MA IIi was created in view of the above circumstances, and can compensate for the influence of springs on the magnetic head positioning control system so that the transient time does not become long, and also compensates for errors due to spring variations. The object of the present invention is to provide a magnetic head positioning device that can perform the following steps.

Hereinafter, referring to the drawings, one embodiment of the present invention is a phase compensation circuit, 2 is a register, 3 is a microprocessor, and 4 is a differential circuit. Reference numerals 5 and 7 indicate analog switches, and reference numeral 6 indicates a DA converter. Reference numeral 8 indicates a summing amplifier, reference numeral 9 indicates an a-power amplifier, and reference numeral 10 indicates a motor. Reference numeral rx designates a carriage, on which a not-shown siren head and a read/write head are attached.

Although not shown, a spring is attached to the carriage II so that the carriage II returns to a predetermined position when the power is turned off. Reference numeral 12 indicates a position detector, which receives a position signal P from the data read from a magnetic disk (not shown) by the serge head and a position signal P from the head.

The analog-to-digital converter indicated by numeral 12 outputs the cylinder pulse S generated every time the cylinder crosses the top of the cylinder, and converts the position error signal Q, which is the output signal of the analog switch 5, from analog to digital. The generated data is supplied to the microprocessor 3.

Next, the operation of the above embodiment will be explained. As shown in FIG. 2, springs used in magnetic disk drives vary linearly in spring force with respect to displacement xK. Since it is necessary that the spring force always act on the carriage 11, the spring is attached with a slight load Ff from its free state. However, when the spring is actually installed, due to manufacturing variations in the spring, the force F of the spring against the displacement
will be different. Even in this case, the slope of the straight line is almost constant, and if the spring constant is k, it can be considered that only α in the formula IP e=kX+α changes. In addition, this variation in springs is unique to springs and hardly changes for a single device.
In this embodiment, it will be explained that the correction is performed during a 7-first seek operation to position the head at the initial position of the track after the power is turned on.

Note that, of course, the correction may be performed any number of times to correct for temperature changes, changes over time, etc., and the correction may be performed at any track address.

On the other hand, three microprocessors, a FROM (not shown)
RA
M (random access memory) and ROM (
Built-in read-only memory). Above FRO
In M, the force F is stored as a first table in correspondence with each position X based on the spring constant k. That is, the force F corresponding to the average spring displacement X is stored. This FROM K Fi
, the value of α, which is a correction term due to variations in each spring in the equation p = m kX+α, is stored as a correction table.

First, when the magnetic head is positioned at the initial position of the magnetic disk, that is, the '0'' track, at fC, the microprocessor 3 converts the value of the device error signal Q made up of the analog switch 6 into digital form using the A-D converter IJ. Read the converted value.

Then, the microprocessor 3 reads out the value of the correction term α from the correction table stored in the FROM according to this read value, and uses this read value and each of the tables stored in the FROM. data is added and stored in the RAM as a new second table. That is, the table $2 in this RAM stores the spring force F' corresponding to the displacement xK to each target track position, taking spring variations into consideration.

After such preparations are made, when a target track is specified by the host system, the microprocessor jti applies the spring force F corresponding to the position of the target track to the above RA.
The second table stored in M is read out and stored in a register (not shown) in the microprocessor 3. Then, the microprocessor 3Fi calculates the distance difference between the track where the head is currently located and the target track, and loads into the register 2 target speed information corresponding to a target speed signal corresponding to this distance difference.

This can be realized by the microprocessor 3 storing target speed information corresponding to the distance difference in the FROM in advance.

The target speed information stored in the register 2 is provided to the DA converter 6. The DA converter 6 converts the signal into a target speed signal and outputs it to the summing amplifier 8 . On the other hand, the differentiating circuit 4 is
A speed signal is created by differentiating the signal given from the position detector 12 and output to the summing amplifier 8 via the analog switch 7. Also, at this time, the analog switch 51f
, turned off. The summing amplifier 8 subtracts the input target speed signal and speed signal. The signal Fi obtained from the summing amplifier 8 is converted into a current by the power amplifier 9, and further converted into force by the motor IO. Therefore, the motor 10 applies acceleration to the carriage 11 according to the output signal of the summing amplifier 8. Each time the head is moved by the carriage 11 and crosses a track on the way, a cylinder pulse S is applied to the microprocessor 3. When the microprocessor 3 receives this cylinder pulse S, it calculates a new distance difference from the target track and loads the target speed information into the register 2. Hereafter, by the above-mentioned action of Mr. Hikama, Ki f rre
Performs v-speed longitudinal control.

When the head moves onto the target track, analog switch 1 is set to ff l, analog switch 5 is set to 0! 1, and the position control is switched to positioning the head on the target track. As a result, the phase compensation circuit 1, the analog switch 5, the summing amplifier @gs power amplifier 9, the motor 10. Carriage X1. Position control is performed in a closed loop formed by position detector I2. microprocessor 3
loads the spring force F, which has been previously read from the second table and stored in a register (not shown), into register 2. This spring force is converted into voltage by a DA converter. This voltage is converted into power via a summing amplifier 8, a power amplifier 9, and a power output IO. Since this force exactly cancels out the spring force, the head can be accurately positioned on the target track. If no force is applied to offset the spring force, a voltage corresponding to the spring force will be generated at the output of the analog switch 5. This is because the head is displaced from the target track by the spring force fc by the voltage. By applying a voltage that cancels out the spring force, taking into account the above-mentioned variations in each spring, the head can be positioned on the target track without positional deviation. Therefore, at this time, the voltage applied from the phase compensation circuit I to the summing amplifier 8 via the analog switch 5 becomes O(V).

In addition, in the above embodiment, after reading the value of the correction term α in 2F=kx+α from the correction table stored in FROM, a new table for wJ2 is stored in RAM. The value of the correction term α is stored in a register, and when the target track is specified, the FRO
Read out the spring force that does not take spring variations into account from the @1 table stored in M, and correct it by adding the value stored in the register above to the read -10 = spring force.
It is also possible to do so.

As described above, according to the present invention, the influence of the spring on the magnetic head positioning control system can be compensated for so that the transient time does not become long, and the magnetic head positioning system can also compensate for the error in the spring parallax Φ. We can provide the following equipment.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of an embodiment of the present invention, FIG. 2 is a diagram showing force with respect to spring displacement, and FIG. 3 is a diagram showing errors due to spring variations. I...Phase compensation circuit, 2...Register, 3...!
Microprocessor, 4... Differential circuit, 5. F--analog switch, DA converter, 8-summing amplifier, 9-power amplifier, 10-motor, 11
... Carriage, 12... Position detector, 13...
A-D converter. Canter Agent Patent Attorney Suzue Takehiko 11-

Claims (1)

[Claims] In a magnetic disk drive provided with a spring so that the magnetic head returns to a predetermined position when the power is turned off, a means for detecting a zero value of variation in the spring force inherent in the spring, and a method for positioning the magnetic head on a target track. The positioning device for the pad of the spring is corrected based on the value of the detected spring force variation.