Position error recovery and motor control system
AssigneeExxon Research & Engineering Co.
InventorHerman Itzkowitz
Life of this patent
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Abstract
A motor control system for driving a stepper motor and a typewriter or the like is provided, the control including reliable means for tracking incremental movements of the stepper and the element being driven by the stepper. Phase combinations of the stepper motor are energized as a function of tracked position, in a manner which optimizes movement from a present position to a target position. Present position is tracked by generating a pair of sensor signals and converting same to digital signals, which digital signals are constrained to change in accordance with the predetermined pattern on a step by step or increment by increment basis. If the pattern is not followed precisely the error is detected and a correction in position information can be made.
Claims22
A stepper motor system with improved tracking means, comprising:
- a stepper motor and an element coupled to and driven by said stepper motor;
- sensor means for generating a plural state sensor signal representative of movement of said element through a plurality of positions, said signal normally being cyclical with said movement and changing a predetermined number of states at a time;
- means continuously operable as said sensor signal goes through a plurality of cycles for determining when other than said predetermined number of states of said signal change at a time, whereby the sensor signal is continuously detected to be legal or in error as said stepper motor drives said element through a controlled number of positions.
Linear drive apparatus for use in a typewriter and the like, comprising:
- a. A linear stepper motor having a linearly driven slider element;
- b. Carriage means for carrying a printing mechanism, said carriage means mounted on said slider elment;
- c. Means for driving said stepper motor sequentially one step at a time;
- d. Sensor means connected to said carriage or said slider for generating two sensor signals 90.degree. out of phase, said sensor signals being periodic as said carriage moves and having a predetermined relationship to said motor steps;
- e. Means for converting said sensor signals to a 2 bit signal having a sequence such that normally only 1 of said 2 bits changes at a time and said signal repeats itself with each cycle of said sensor signals;
- and
- f. Means for periodically comparing each bit of said 2 bit signal with the corresponding prior bit and determining if other than 1 of said 2 bits has changed.
Rotary drive apparatus for a typewriter or the like, comprising:
- a. a rotary stepper motor;
- b. a print wheel, connected to be driven by said rotary stepper motor;
- c. means for driving said rotary motor sequentially a predetermined portion of a revolution at a time;
- d. sensor means operatively mounted relative to said print wheel for generating two sensor signals 90.degree. out of phase, said sensor signals being periodic as said print wheel rotates and having a predetermined relationship to print wheel rotation;
- e. means for converting said sensor signals to a cyclically changing 2 bit signal having a sequence such that normally only 1 of said 2 bits changes at a time, and comparison means for comparing each bit of each changed 2 bit signal with the corresponding bit of the prior 2 bit signal and determining if other than 1 bit of said 2 bit signal has changed.
In a typewriter device having a stepper motor for driving an element, and having sensor means for generating sensor signals carrying information concerning the position of said element, the improvement characterized by analog to digital means for converting said sensor signals to a plural bit digital signal, said digital signal changing periodically as said element is moved in a manner such that normally only one of said plural bits changes at a time, means for storing the just prior digital signal, means for comparing each bit of a new digital signal with the corresponding bit of the stored just prior signal and determining whether more than 1 bit of the plural bits of said signal has changed, and means for generating an error signal when said comparison is not valid.
A device having at least one element adapted to be moved through a plurality of positions, a controllable motor operatively connected to said element for moving said element to a selected position, said motor having a plurality of windings and energizing means for selectively energizing windings of said motor, characterized by said energizing means comprising tracking means for tracking the position of said element, said tracking means comprising means for generating a cyclically changing plural bit sensor signal which provides information concerning position changes of said element, means for comparing each bit of said sensor signal with the corresponding bit of the prior sensor signal and correcting said sensor signal as a function of said comparing, and means for selecting and energizing said windings as a function of the position of said element.
Dependencies are inferred from the claim text.