Method of and apparatus for controlling the displacement of a movable system driven by an electric motor

Apparatus for driving a transducer head of a magnetic disk memory between a position proximate the periphery of a disk of the memory and an area on the disk where data are located while lowering the head between an idle position and a hovering position above a plane defining a face of the disk, the head arriving at the position proximate the disk periphery from a position beyond the disk periphery with a velocity in a predetermined velocity range, the apparatus comprising an assembly for carrying the head, the assembly including a radially extending arm, a rotary DC motor for turning the arm, the assembly including mechanical structure synchronized with the turning of the assembly so that as the head is driven between the position proximate the disk periphery and the position where data are located on the disk the head moves between the idle and hovering positions, means for driving the motor so the head is moved between the positions proximate the disk periphery and an edge of the area on the disk where data are located, said driving means supplying an excitation waveform to the motor as the motor drives the head between the positions proximate the disk periphery and the edge of the data, the waveform including an initial constant value having a predetermined interval to cause the motor to have a predetermined angular velocity at the completion of the interval even though the velocities of the head and motor are indeterminate as the head initially leaves the position proximate the disk periphery toward the edge of the data, the initial constant value of the waveform being followed by a ramp having a decreasing amplitude, the ramp having a shape so that the motor angular velocity is maintained constant, without overshoot, at the predetermined angular velocity for a substantial interval after the completion of the predetermined interval and causing the motor angular velocity to be constant as the head approaches and arrives at the edge of the data at the completion of the ramp, when the ramp has a value of zero.

Apparatus for driving a member from a first predetermined location to a second predetermined location, the member being driven to the first predetermined location on its way to the second predetermined location, with an indeterminate velocity in a predetermined velocity range, the apparatus comprising a DC motor for driving the member, means for activating the motor so the member is driven from the first location to the second location, said activating means supplying an excitation waveform to the motor, the excitation waveform including an initial constant value having a predetermined interval to cause the motor to have a predetermined angular velocity at the completion of the interval so the initial speed of the element is in a predetermined range between maximum and minimum predetermined values, the element being subjected to a sudden acceleration less than a maximum predetermined value causing the speed of the element to be unstable and undetermined, applying a damping current to the motor to cause the motor shaft to have an angular velocity reduced to a reference angular velocity such that the element has a reference speed, the waveform including a ramping portion having a decreasing amplitude following the completion of the predetermined interval, the ramping portion of the waveform having a shape causing the motor angular velocity to be maintained at the predetermined velocity for a substantial interval after completion of the predetermined interval and causing the motor angular velocity to have a constant value as the member approaches and arrives at the second location.

A method of loading a transducer head of a magnetic disk, the method comprising the steps of:

• mechanically driving said head with a DC motor having an output shaft coupled to the head via a mechanism including a cam follower driven by the shaft along a cam surface having first, second and third segments, the second and third segments being separated by a break point, the mechanism being subjected to constant resistive forces for the duration of each particular cycle, the resistive forces having a tendency to vary substantially from one cycle to another cycle, the mechanism including structure synchronized with turning of the shaft to cause the head to be moved from an idle position when the cam follower is at the break point to a hovering position when the cam follower is driven to a destination point on the third segment, activating the mechanism to drive the head from a position outside of the disk periphery to a position adjacent the disk periphery, the head moving from the disk periphery to a position at an edge of data tracks on the disk in response to the shaft driving the mechanism so that the cam moves to follower a second break point,
• applying a control excitation impulse to the motor when the cam follower reaches the break point from the second segment, the control excitation impulse having a predetermined value and duration to cause the shaft to have a predetermined reference angular velocity at the completion of the duration of the control excitation impulse so that the mechanism has a predetermined velocity to overcome the inertia of the mechanism when it reaches the break point from the second segment.

Apparatus for driving a transducer head of a magnetic disk memory between a second position proximate the periphery of a disk of the memory and a third position inside of the periphery of the disk at the edge of data tracks on the disk, the apparatus comprising an assembly for carrying the head, the assembly including a radially extending arm, a rotary DC motor for turning the arm, the assembly including mechanical structure synchronized with turning of the arm so that as the head is moved between the second and third positions the head moves between an idle position in a plane above a face of the disk and a hovering position where the head is located to operatively transduce magnetic data on the disk, means for detecting when the head arrives at the second position, and means responsive to said detecting means for driving the motor so the head is moved between said second and third positions, said driving means:

• supplying a excitation waveform having a predetermined polarity to the motor while the head is at the second position and is being driven toward the third position, the excitation waveform including an initial constant value having a predetermined interval causing the motor to have a predetermined angular velocity at the completion of the interval, the waveform including a ramp following the initial constant value thereof, the ramp causing the motor angular velocity to remain at the predetermined angular velocity it had at the completion of the predetermined interval for a substantial time period so that the motor shaft and head do not overshoot and oscillate, the ramp decreasing toward zero from the initial constant value to cause the motor shaft angular velocity to have a constant predetermined value at the time the head approaches and arrives at the third position.