JPH02189775A - Head positioning control circuit - Google Patents

Abstract

PURPOSE:To shorten the seek time by switching the speed control mode into the position control mode so as to optimize the transient response to the seek operation by a optimum timer time for each number of moving cylinder. CONSTITUTION:An optimum timer time with respect to each seek operation is stored in an arithmetic circuit 2 for each number of a cylinder subject to seeking. The arithmetic circuit 2 calculates a moving cylinder number by the seek operation depending on the content of an object cylinder register 3 and of a present cylinder register 4 and the timer time of a timer circuit 1 is set by the moving cylinder number. The timer circuit 1 starts counting when the magnetic head is moved up to a cylinder just before the object cylinder and outputs a switching signal 6 when the count is finished to switch the control mode of the head positioning control from the speed control mode into the position control mode. Thus, the seek time is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to head positioning control of a magnetic disk device, and particularly to switching control from speed control mode to position control mode.

[Conventional technology]

In general, head positioning @ control mode in the operation of moving the magnetic head of a magnetic disk drive from the currently positioned cylinder (current cylinder) to the target cylinder (target cylinder) has two control modes: speed control mode and position control mode. There is. The speed control mode is such that the movement speed of the magnetic head from the current cylinder to the target cylinder is controlled to a predetermined speed, and the movement of the magnetic head is controlled in this control mode until just before the target cylinder. Furthermore, the position control mode is a control mode in which the magnetic head moves to just before the target cylinder in the speed control mode, then positions it to the target cylinder and performs a seek operation.Furthermore, after the seek operation is completed, the magnetic head is positioned in the target cylinder. The position control mode is a control mode that is performed even when the position error signal is at zero level.

Here, the position error signal will be explained in detail.

Figure 2 is a diagram showing the relationship between the position error signal and the servo track.The position error signal is a signal obtained by demodulating the servo signal read by the servo head from the servo disk, which is the reference for positioning. As shown in FIG. 2, the position error signal 23 changes as the servo head 21 traverses the servo track 22. As shown in FIG. In the case of FIG. 2, the interval from the zero-crossing point 24a of the position error signal 23 to the next zero-crossing point 24b is one cylinder (one track). Servo track 22 and servo track 22
The position error signal 23 becomes zero level when the servo head 2I is located at the boundary between the servo head 2I and
1 is said to be 'on cylinder'°.

Furthermore, the signal level of the position error signal 23 is
1 is proportional to the distance from the on-cylinder.

FIG. 3 is a diagram showing the waveform of the position error signal 23 when seeking from the current cylinder to the target cylinder length.

The positioning of the magnetic head is controlled in the position control mode up to the start point of the seek operation, in the speed control mode from the start point A to point B immediately before the target cylinder, and in the position control mode from point B. A certain amount of time is required from point B, where the speed control mode is switched to position control mode, to point 0, where the seek operation ends. This is the time required for the position error signal 23 to stabilize before read/write operations are possible.The behavior of the position error signal 23 after entering the position control mode is called ``transient response of the position error signal''. , as shown in FIG. 3, there are cases of transient response 31 showing a response without overshoot, cases of transient response 32 showing a response with overshoot, etc. In the case of transient response 31 showing a response without overshoot, etc. The end point of the seek operation is point D, but the end point of the seek operation in the case of transient response 32 indicating an overshoot response is point E. If the transient response is large as described above, the above-mentioned settling time becomes longer, The time it takes to complete the seek operation also becomes longer.

Since it is efficient that the time spent on the seek operation is short, it is desirable that the transient response be as small as possible.

A switching control circuit for switching from a speed control mode to a position control mode in a head positioning control circuit of a conventional magnetic disk device has one timer circuit.
A timer circuit is activated at the cylinder immediately before the target cylinder, for example, 1/2 cylinder or 1/4 cylinder from the target cylinder, and the speed control mode is switched to the position control mode when the timer circuit does not time up. The timer time of this timer circuit is selected to minimize the transient response of the position error signal after entering the position control mode.

[Problem to be solved by the invention]

In the head positioning control circuit of the conventional magnetic disk drive described above, the position is adjusted from the speed control mode so that the transient response is small on average for all seek operations consisting of the combination of the current cylinder and the target cylinder in the seek operation. Although a switching point for switching to control mode is set, the transient response of the position error signal may vary greatly depending on the distance the magnetic head seeks, that is, the difference between the target cylinder and the current cylinder, or it may become excessive during a certain seek operation. Even if the timer time is selected to minimize the response, other seek operations may result in a response that is larger than the excessive response, so it is not necessarily optimal for each seek operation, and the seek The disadvantage is that it takes a long time.

[Means to solve the problem]

The present invention provides a head positioning control circuit for a magnetic disk device, in which when the magnetic head moves to the cylinder immediately before the target cylinder in a seek operation, the movement is performed within one of a plurality of preset timer times. It is comprised of a timer circuit that counts according to the number of cylinders to be used and outputs a signal for switching the control mode in the seek operation from the speed control mode to the position control mode when the count is completed.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 shows a block diagram of a head positioning control circuit according to the present invention. In FIG. 1, the current cylinder register 4 records the cylinder number one where the magnetic head is currently positioned, and the target cylinder register 3 records the cylinder number one of the target cylinder instructed by the host device of the magnetic disk drive. Ru. The contents of the long purpose cylinder register 3 are transferred to the current cylinder register 4 after the seek operation is completed. Calculation time F! @2 calculates the number of cylinders to be moved by this seek operation from the contents of the target cylinder register 3 and the current cylinder register 4, and sets the timer time of the timer circuit 1 based on this number of cylinders to be moved. Timer circuit 1
is a signal indicating that the magnetic head has moved to the cylinder immediately before the target cylinder, and in this embodiment, a 1/2 cylinder signal 5 indicating that the magnetic head has moved to one 1/2 cylinder before the target cylinder is input. and the timer circuit 1 starts counting. The timer circuit 1 outputs a switching signal 6 when counting is completed. This switching signal 6
The control mode of the head positioning control is switched from the speed control mode to the position control mode.

Here, the timer time that the arithmetic circuit 2 sets in the timer circuit 1 is the timer time that minimizes the magnitude of the transient response of the position error signal after switching the speed control mode to the position control mode. 2, the optimum timer time for each seek operation is recorded in advance for each number of cylinders to be sought.

〔Effect of the invention〕

As explained in detail above, according to the head positioning control circuit of the present invention, the speed control mode is changed to the position control mode so that the transient response to the seek operation is optimized by the optimum timer time for each number of cylinders to be moved. Since the switching point is determined, the transient response of the position error signal is small, and the variation due to cylinders in the distance the magnetic head seeks, that is, the difference between the target cylinder and the current cylinder, is small, making it optimal for individual seek operations. This has the effect of increasing head positioning control, shortening seek time, and increasing efficiency.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a head positioning control circuit according to the present invention, FIG. 2 is a diagram showing the relationship between a position error signal and a servo track, and FIG. 3 is a waveform diagram of a position error signal during a seek operation. 1... Timer circuit, 2... Arithmetic circuit, 3... Target cylinder register, 4... Current cylinder register, 5... 1/2 cylinder one signal, 6... Switching signal, 21. ... Servo head, 22... Servo track, 23... Position error signal, 24a, 24b
...Zero crossing point, 31...Transient response indicating a response without overshoot, 32...Transient response indicating a response with overshoot.

Claims (1)

[Claims] In the head positioning control circuit of a magnetic disk drive, when the magnetic head moves to the cylinder immediately before the target cylinder during a seek operation, one of multiple preset timer times is set to the given number of cylinders to be moved. 1. A head positioning control circuit comprising: a timer circuit that counts the number of times in accordance with the time and outputs a signal for switching the control mode in the seek operation from a speed control mode to a position control mode when the counting is completed.