JPH01102784A - Servo circuit for head positioning - Google Patents

Abstract

PURPOSE:To attach flexibility on a circuit by converting an analog speed signal to a digital value, generating a digital speed control signal depending on the digital value and remaining seek length and performing speed servo control by driving an actuator after converting the digital speed control signal to an analog value. CONSTITUTION:The speed servo control is performed by converting the analog speed signal to the digital value by an A/D converter 2, generating the digital speed control signal depending on the value and the remaining seek length by a microprocessor 1, and driving the actuator 8 after converting the digital speed control signal to the analog value by a D/A converter 3. In such a way, it is possible to apply the same circuit for a different kind of device only by changing firmware, and also, to attach the flexibility on a various kinds of speed servo systems.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a head positioning servo circuit for a magnetic disk drive, and more particularly to a speed servo control circuit for moving a magnetic head from one track position to another.

[Conventional technology]

The head positioning servo circuit of a magnetic disk device has two operating modes. There are two modes: a positioning mode for holding the head at a position, and a seek mode for performing a seek operation to move the head to a target cylinder. The part of the head positioning servo circuit used in the seek mode is called a speed servo control circuit.

The head positioning circuit can usually be represented by a block diagram as shown in FIG. In the positioning mode, the output of the position detector 5 is fed back via the compensation circuit 10. Switch 9 is an operation mode changeover switch. In the seek mode, the position control circuit loop is cut off by the switch 9, and the speed servo control circuit forms a closed loop. The target speed signal generation circuit 11 generates a set target value (target speed signal) for the head movement speed according to the remaining seek length, and the mixer 12 mixes this target speed signal with the speed signal output from the speed detector 6. Detect errors. The error amplifier 13 amplifies the speed error and drives the actuator 8 via the power amplifier 7 so that the moving speed of the magnetic head approaches the target value. As the magnetic head approaches the target position, the position signal output from the position detector 5 changes, the remaining seek length information is updated accordingly, and the target speed signal also changes accordingly. The target speed signal is normally designed to have a constant maximum value when the distance to the target (remaining seek length) is greater than a specified value, and to take a value approximately proportional to the 1/2 power of the distance when it is less than the specified value. be done. This is seek time (magnetic head movement time)
is derived from the conditions that minimize

[Problem that the invention seeks to solve]

The conventional speed servo control circuit described above is an analog circuit except for the target speed signal generation circuit section. Basically, it is linear feedback control, and circuit constants must be matched for each model. Therefore, it is not suitable for LSI integration, and even if it can be integrated into LSI, it would be difficult to use because circuit constants would have to be added externally to provide versatility. Furthermore, in order to perform advanced control such as feedforward, a separate circuit must be added for that purpose, which makes the circuit complicated.

The present invention solves the above-mentioned drawbacks and allows the same circuit to be used in different models of devices simply by changing the firmware, and by changing the firmware, the same circuit can perform not only linear control but also nonlinear control and feedforward control. The present invention attempts to provide a flexible speed servo control circuit.

[Means for solving problems]

A head positioning servo circuit of the present invention includes an AD converter, a DA converter, and a microprocessor means in a head positioning servo circuit for a magnetic disk device.
An analog speed signal is converted into a digital value by an AD converter, a digital speed control signal depending on the value and the remaining seek length is generated by a microprocessor, and the digital speed control signal is converted into an analog value by a DA converter. It is characterized by performing speed servo control by driving an actuator.

〔Example〕

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of an embodiment of the invention.

Referring to FIG. 1, there is an AD around the microprocessor 1.
Converter 2. DA converter 3. Remaining seek length counter 42 position detector5. and a speed detector 6 are arranged. When the microprocessor 1 receives a seek command, it first sets the initial value of the seek length in the remaining seek length counter 4.
Next, the operating mode of the servo circuit is switched from the positioning mode to the seek mode using the switch 9. The AD converter 2 converts the analog speed signal output from the speed detector 6 into a digital value. The microprocessor 1 has a table of target speed values corresponding to seek lengths at consecutive addresses in the memory. The microprocessor 1 refers to the table and sets the DA converter 3 to a value obtained by multiplying the difference between the target speed value corresponding to the remaining seek length at that time and the actual speed value obtained from the AD converter by a certain coefficient. repeat. As the head moves, the track crossing pulse output from the position detector 5 subtracts the remaining seek length counter 4. Remaining seek length is 1 (1/2) rack)
When the following happens, switch to positioning mode and end the seek.

The gain of the speed loop can be freely set by changing the coefficient multiplied by the speed difference using the microprocessor 1 program. In addition, in order to reduce power consumption, the circuit was changed to achieve so-called pan-pan control by setting values in the DA converter so that the power amplifier enters three states: saturated acceleration, saturated deceleration, and off, depending on the speed difference. You can do it without having to do it. Furthermore, feedforward control can also be performed by setting a value obtained by adding the planned acceleration value to the speed difference component in the DA converter.

[Effects of the Invention] As described above, the present invention has the advantage that the same circuit can be used in different types of devices simply by changing the firmware, and can be applied to various speed servo systems.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a block diagram showing a conventional head positioning servo circuit for a magnetic disk device. 1...Microprocessor, 2...AD
Converter, 3...DA converter, 4...
... Remaining seek length counter, 5 ... Position detector, 6 ... Speed detector, 7 ... Power amplifier, 8 ... Actuator, 9・・・・・・
Switch, 10... Compensation circuit, 11...
・Target speed signal generation circuit, 12...Mixer, 1
3...Error amplifier. Agent Patent Attorney Uchihara Ontai IYj! J Kaya 21!7

Claims (1)

[Claims] A head positioning servo circuit for a magnetic disk device includes an AD converter, a DA converter, and a microprocessor means, converts an analog speed signal into a digital value by the AD converter, and generates a digital speed depending on the digital value and the remaining seek length. A head positioning servo circuit characterized in that speed servo control is performed by generating a control signal by the microprocessor means and converting the digital speed control signal into an analog value by the DA converter to drive an actuator.