Cii Honeywell Bull

Jean-Jacques Couette

Christian Maury

Daniel Carteau

Pham Dan Tam

Pham D Tam

A DC motor drives a magnetic disk memory transducer head between a position proximate the disk periphery to an area on the disk where data are located during which time the head is lowered from an idle to a hovering position. During this time the motor is supplied with a current impulse having a predetermined polarity, amplitude and duration. The polarity of the current impulse is opposite to that of current applied to the motor while the head is being driven between a position beyond the disk periphery to the position proximate the disk periphery. The duration and amplitude of the current impulse are such that the motor angular velocity has a zero value at the completion of the current pulse. Thereafter, a ramping voltage having an average linear waveform is applied to the motor to prevent overshoot of the motor speed and prevent oscillation of the head relative to a face of the disk. The linear ramp current decreases to a zero value, at which time the motor has a constant, non-zero angular velocity.

Method of and apparatus for controlling the displacement of a movable

A magnetic disk memory is moved between a first position beyond the disk periphery to a second position proximate the disk periphery while the head is at an idle height above the disk face. The head is moved between the disk periphery and a third position at the edge of an area on the disk where data are located while the head is lowered and raised between the idle height and a hovering height above a face of the disk. An assembly carrying the head includes a radially extending arm, turned by a rotary DC motor. A continuous step excitation waveform is supplied to the motor as the head is driven between the first and second positions until the head arrives at one of the two positions. Each of the steps has a constant amplitude that differs from the immediately preceding step by a predetermined incremental value. All of the steps, except the last step, has the same predetermined duration. The last step has a time duration no greater than that of the previous steps and determined by when the head arrives at the one position. To drive the head between the second and third positions a damping impulse having a predetermined constant amplitude and duration is applied to the motor to cause the motor to stop. The motor is stopped without overshoot and driven to a predetermined speed by then applying a decreasing ramp excitation waveform to it.

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Montigny le Bretoneux, France

Jean-Jacques Couette