Abstract: In a system equipped with a plurality of magnetic disk devices, one magnetic disk device is used as a device (master unit) for generating reference signals for rotating other plurality of devices in synchronism. Other one or more magnetic disk devices (slave units) are rotated in synchronism following the reference signals generated from the master unit. In order to maintain the synchronism of revolution between the master unit and the slave units, the conditions of revolution of the two spindle motors are compared to maintain the synchronism of revolution. Index pulses recorded on the magentic disks of the master unit and the slave units are used as reference signals for maintaining synchronism of revolutions. Index pulses from the master unit and the slave units are compared to find a phase difference signal and a period difference signal, and the rotational speed of the slave units is compensated by using these two signals.

Abstract: A magnetic disc head positioning system using a stepper motor eliminates positioning errors due to different approach directions and distances to a target track position through a drive control of temporarily stopping the head at a position immediately preceding or following the target track depending on the approach direction and, thereafter, moving the head from this position to the target track with a constant transient response. The head is brought to the temporary stop position by utilizing the overshooting response of the stepper motor so as to minimize the positioning time.

Abstract: A positioning method and apparatus for precisely positioning a magnetic head on a desired track of a magnetic disc includes stepping motor having a plurality of stationary pole windings adapted to be rotated stepwise, and a mechanism for moving the magnetic head by a rotational movement of the stepping motor. By rotating the stepping motor stepwise by an integral multiple of the number of stationary pole windings of the stepping motor, the magnetic head is moved by one track width of the magnetic disc. By driving the stepping motor by the integral multiple of the number of stationary windings, the magnetic head is positioned by the same stationary pole windings without being affected by an assembling tolerance of the stationary pole windings. The stepping motor may also be driven so as to overrun a desired track by at least one step and then rotated in a reverse direction by the same number of steps so that a positioning error due to forward and reverse rotations of the stepping motor is eliminated.