JPS63144469A - Magnetic disk device - Google Patents

Abstract

PURPOSE:To make the titled device small in size, high in capacity and in speed by using a self-calibration function to detect and compensate a DC offset of a driver circuit and a stationary external force exerted on a head carriage. CONSTITUTION:When a compensation signal of an output of a digital-analog converter DAC 8 is inputted while changing a value by a CPU 7, an output signal of a servo circuit 2 is offset so as to cancel a compensation signal and a head keeps positioning to an objective track. Then the output of a comparator 6 is supervised and a compensation signal at the boundary fixed to a high or low level for a prescribed time is obtained, and the center value of the output signal of a servo circuit 2 is obtained from the mean value from the boundary fixed to a high level and the boundary fixed to a low level and the compensation signal in the track is obtained. Moreover, calibration is applied for several tracks and the compensation signal is approximately calculated by a linear line with respect to the track, then the compensation signal in response to the objective track is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a head positioning control method for a magnetic disk device.

[Conventional technology]

The conventional head positioning control method for magnetic disk drives is as follows:
When positioning on the target track, head position information is reproduced by a position signal reproducing circuit, and after passing through a servo circuit, is input to a driver circuit of a hector carriage drive motor, thereby positioning the head. The servo circuit provides phase margin to the servo lube to stabilize it.
Adding the differentiated position signal and the position signal,
Configure a lead-lag filter. Additionally, the gain in the low range is increased to improve stiffness, and integration is performed to reduce the effects of steady disturbances and circuit offsets. Furthermore, in order to eliminate the influence of mechanical resonance that exists at several KH2, a notch filter or a second-order low-pass filter or the like is inserted.

When the head seeks between two tracks, the difference between the head speed signal (usually a signal obtained by differentiating the position signal) and the speed reference signal is input to the driver circuit of the head carriage drive motor to control the speed. ing.

Switching from speed control to positioning control on the target track is performed by detecting a position slightly in front of the target track, but if you consider the transient response of the head immediately after switching, an overshoot will occur, and after a finite period of time the target track will be lost. Within the positioning accuracy. The transient response is called the IJ song, and the finite time is called the IJ song.

During positioning control on the target track, if a steady external force is applied to the hector carriage due to the influence of the head lead wire or the lead wire of the head drive motor, a direct current force is applied to the motor due to the DC offset voltage of the driver circuit. Considering the case where the servo loop is added, since integration is performed, the gain in reducing the servo loop is high, and there is little effect on positioning accuracy. However, when the head settles immediately after a seek, the effects of steady external forces and DC offset appear, so some circuits are adjusted initially. The overshoot of settling may be large due to external forces or DC offset shadows, etc.) The tolerance for longer IJ time is large. Furthermore, when the head carriage is heavy, the influence of external force is relatively small.

[Problem that the invention seeks to solve]

However, in the above-mentioned conventional technology, due to the influence of the steady external force applied to the bed carriage of the magnetic disk device and the direct current offset of the circuit, the amount of settling overshoot and the increase in the settling time cannot be ignored. Furthermore, when adjusting the circuit initially, the number of circuit elements increases, such as by adding a trimmer resistor, and changes over time and temperature characteristics cannot be compensated for.

Therefore, the present invention is intended to solve these problems.The purpose of the present invention is to detect the influence of the steady external force applied to the head carriage and the DC offset of the circuit,
By providing a self-calibration function to compensate, good settling is achieved immediately after head seek,
The objective is to provide smaller, higher capacity, and faster magnetic disk drives.

[Means for solving problems]

The magnetic disk drive of the present invention includes a head carriage drive motor, a driver circuit that drives the motor, a position signal reproducing circuit that reproduces a position signal that provides head position information, and an integrated compensation for the position signal that is input to the driver circuit. The component is a servo circuit that compensates for the steady external force applied to the hector carriage, and a compensation signal that compensates for the DC offset of the driver circuit is input to the driver circuit in addition to the output signal of the servo circuit. In addition to the output signal of the servo circuit while changing the value sequentially, the value of the compensation signal that compensates for the steady external force and DC offset is determined by comparing the output signal of the servo circuit with a reference level using a comparator. It is characterized by having a calibration function, and the self-calibration function is calculated and stored in a CPU so that the value of the compensation signal can be set to a different value depending on the target track by executing the self-calibration function on a plurality of tracks on the magnetic disk. It is characterized by

〔Example〕

FIG. 1 is a block diagram of an embodiment of the present invention.

During head seek, 5W1 (analog switch 1) is on, SW2 (analog switch 2) and 5W3 (
Analog switch 6) is turned off. The difference between the speed signal reproduced by the speed signal generation circuit 6 and the speed reference signal managed by the 0PU7 and output by the DAO8 (digital-to-analog converter) is the difference between the speed signal reproduced by the speed signal generation circuit 6 and the speed reference signal output by the driver circuit 4.
The head carriage drive motor 5 converts the force into force to perform a seek operation. The force is integrated twice to become position information, which is reproduced by the position signal reproducing circuit 1, thereby forming a feedback loop.

During positioning control to position on the target track, S
Wl is off and SW2 and SW3 are on. The position signal reproduced by the position signal reproduction circuit 1 is sent to the servo circuit 2.
DA'l:! is managed by 0PU7. It is added to the compensation signal outputted at 8 and inputted to the driver circuit 4,
This is converted into force by the head carriage drive motor 5, integrated twice, and fed back as position information to form a servo loop. The compensation signal is a signal for compensating the steady external force applied to the head carriage and the DC offset of the driver circuit 4. The value of the compensation signal is determined by the self-calibration function described later, and C! Managed and stored in PU7. Servo circuit 2 includes a differentiation circuit that differentiates the position signal in order to provide phase margin and stability to the servo loop, and a differentiation circuit that increases the gain in the low range to improve stiffness and reduce the effects of steady disturbances and circuit offset. The output of the servo circuit 2 is the sum of the position signal itself, the output of the differentiation circuit, and the output of the integration circuit. Usually, such a servo configuration is called "P" control.

During self-calibration, the analog switch is turned on and off during positioning control, and the head uses the reference level, which is one input of the zero comparator 6 positioned on the target track, in a servo loop. When fixed at the center level (level where the driver circuit 4 human force is zero and no force is applied to the hector carriage drive motor 5), if the steady external force applied to the head carriage and the DC offset of the driver circuit 4 are zero, the servo The humbalator output, which is the difference between the circuit output signal and the reference level, repeats high and low outputs at extremely short time intervals. This is because the output signal of the servo circuit 2 fluctuates around the reference level because disturbances such as track fluctuations of the magnetic disk are constantly applied and the servo loop is configured so that the head follows these disturbances. Figure 2 shows this situation. In Figure 2 (A), the output signal of the servo circuit 2 swings around the reference level, so the output signal of the comparator 6 has high and low levels. Return the comb randomly. If a steady external force applied to the head carriage or an offset of the driver circuit 4 is applied in a negative direction with respect to the center level of the servo loop, the output of the servo circuit 2 will be affected by the external force and the DC offset due to the effect of the integrator of the servo circuit 2. Gives an output offset in the positive direction to cancel out. If the offset value is small, it will be as shown in FIG. 2 (Bl), and if it is large, it will be as shown in FIG. 2 (C), and the output of the comparator 6 is fixed at high.

If the offset is to the opposite side, as shown in Fig. 2 (D), if you input the compensation signal of the output of DAO8 without changing the value in 0PU7, the output signal of servo circuit 2 will cancel the compensation signal. is offset and the head continues positioning to the target track. In other words, depending on the value of the compensation signal, the output of the converter 6 may be randomly repeated high or low, or may be fixed high or low. Monitor the output of comparator 6 while sequentially changing the value of the compensation signal,
Find the value of the compensation signal at the boundary that is fixed at high or low for a certain period of time, and calculate the center value of the output signal of the servo circuit 2 from the average value of the boundary at which it is fixed at high or the boundary at which it is fixed at low. Then, the value of the compensation signal on that track is found. Furthermore, by performing the above calibration on several tracks and approximating the value of the compensation signal using a straight line or the like with respect to the track, a compensation signal corresponding to the target track can be obtained. Figure 3 shows the settling immediately after seek. Figure 3 (A) shows the case when the steady external force applied to the head carriage and the DC offset of the driver circuit 4 are compensated, and Figure 3 (B) l (0) shows the case without compensation. (B
) is when an external force is applied in the theta direction, and (0) is when an external force is applied in the opposite direction to the seek direction. ◎ [Effects of the Invention] As described above, according to the present invention, the steady external force applied to the head carriage and The DC offset of the driver circuit is detected and compensated for by the self-calibration function. There is no need to initially adjust the magnetic disk drive, and changes over time and temperature characteristics can be compensated for, resulting in good settling immediately after head seek. By realizing this, it has the effect of providing smaller size, higher capacity, and higher speed of the magnetic disk device.

[Brief explanation of the drawing]

FIG. 1 is a main block diagram showing an embodiment of a magnetic disk device of the present invention. FIG. 2 is a diagram illustrating an embodiment of the magnetic disk device of the present invention, and FIG. 3 is a diagram showing the relationship between the output signal of the servo circuit, the reference level, and the output signal of the comparator. FIG. 3 is a diagram illustrating settling immediately after a seek in an embodiment of the apparatus. Applicant Seiko Epson Co., Ltd. Agent Patent Attorney Tsutomu Mogami et al. 19” −−7゜・−
,/Koshi IXl Radar/Uneshun 2nd Ward

Claims (2)

[Claims] (1) A head carriage drive motor, a driver circuit that drives the motor, a position signal reproducing circuit that reproduces a position signal that provides head position information, and a servo circuit that integrates the position signal and inputs it to the driver circuit. In a magnetic disk drive, a compensation signal for compensating for a steady external force applied to the head carriage and for compensating for a DC offset of the driver circuit is input to the driver circuit in addition to the output signal of the servo circuit. , Compensate for the steady external force and the DC offset by sequentially changing the value of the compensation signal and comparing the output signal of the servo circuit with a reference level in addition to the output signal of the servo circuit using a comparator. 1. A magnetic disk drive having a self-calibration function that determines the value of a compensation signal. (2) The self-calibration function in claim 1 is executed on a plurality of tracks on a magnetic disk, and the value of the compensation signal is calculated by a CPU so that it can be set to a different value depending on the target track. 2. A magnetic disk device according to claim 1, wherein the magnetic disk device stores information.