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US 4,489,259 AGranted
Method and apparatus for controlling a stepper motor
AssigneeRodime PLC
InventorsJames N. J. White, David S. Ruxton, Alec D. Stewart
Life of this patent
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AssigneeRodime PLC
InventorsJames N. J. White, David S. Ruxton, Alec D. Stewart
Estimating the term…
A method and apparatus for controlling a stepper motor and a disk drive is described for minimization of stepper motor oscillations for a single step, minimizing the time taken for the stepper motor to move between tracks for multi-track seeks, and reduction of angular hysteresis due to the mechanical and magnetic properties of the stepper motor construction. This control is achieved using a microprocessor-based circuit adapted to drive the stepper motor in accordance with predetermined programs. Oscillations of the stepper motor are damped by controlling, using one program, the current applied to the stepper motor during the last step of its motion by switching this current on and off within small predetermined time intervals. The time taken to move between tracks is controlled by another program in which the non-linear torque speed characteristics of a particular stepper motor are matched by a non-linear pulse rate which is determined by data held in the memory of the microprocessor circuit. This data can be modified to suit the requirements of the stepper motor and load. Another program controls minimization of hysteresis by ensuring that each track on the disk is approached from the same direction and from the same previously energized set of windings. The microprocessor controls the direction of motion of the stepper motor and hence decides whether or not the read/write head should cross the desired track and return it to ensure uniformity of approach.
A method of minimising the tracking overshoots in an open loop disk device having a signal processing means, programmable memory means connected to the signal processing means, said signal processing means having an output connected to the stepper motor, and an input connected to a controller for use with the disk drive, the programmable memory means including a program for controlling the movement of the stepper motor from one track to another,
A method of minimising the time taken to move a stepper motor between two angular positions, corresponding to tracks on a disk surface, comprising,
A method for compensating for variable magnetic and mechanical hysteresis when moving between tracks comprising the steps of:
Apparatus for minimising the tracking errors and oscillations in a single step in an open-loop disk drive, said apparatus comprising, signal processing means, programmable memory means connected to the signal processing means, said signal processing means having an output connected to the stepper motor, and an input connectable to a controller for use with a disk-drive, said programmable memory means including a program for controlling the movement of the stepper motor, whereby in use said signal processing means divides the last pulse into a predetermined number of pulse elements in accordance with the program and the ambient position of the stepper motor, and applies a finite amount of current to a winding of the stepper motor in at least one pulse element duration, so that the magnitude of the current pulse is spread over the entire duration of the pulse and the stepper motor is moved between tracks in accordance with the finite amounts of current applied thereto.
A drive circuit for controlling the movement of a stepper motor comprising a signal processing means, a programmable memory means connected to the signal processing means, said signal processing means having an input connected to the output of a controller, and an output connected to the stepper motor, said programmable memory means having a program corresponding to the torque/speed characteristics of the stepper motor stored therein, said signal processing means executing said program in response to instructions from the controller and instructing said signal processing means to match the rate of pulses applied to the stepper motor to the disk speed characteristics during the movement of the stepper motor whereby the stepper motor is moved between two angular positions in a minimum time for the particular disk speed characteristic.
Dependencies are inferred from the claim text.