Method and apparatus for detecting a stall condition in a stepping motor
AssigneeFreescale Semiconductor, Inc.
InventorsJohn M. Pigott, Thomas Jeffrey Reiter
Life of this patent
Estimating the term…
Abstract
Stepped rotary motion is imparted to the rotor of a stepping motor by alternately driving at least first and second coils which interact with a plurality of magnetic poles on the rotor. When each of the coils transitions from a driven to a non-driven state, the continued motion of the rotor causes a back electro-motive force to be generated in the coil. The electro-motive forces produced by the coils are rectified, integrated, and then compared with a threshold to determine if a motor stall condition exists.
Claims20
An apparatus for detecting a stall condition of a stepping motor of the type which includes at least first and second coils and a rotor having a plurality of magnetic poles therearound, said apparatus comprising;
- a current generator for alternately supplying drive currents to said first and second coils causing the rotor to step, each of said first and second coils generating signals when transitioning from a driven state to a non-driven state, said signals resulting from motion of said rotor;
- an integrator having an input coupled to receive said signals and for generating an integrated version thereof;
- and
- a comparator coupled to said integrator for comparing said integrated version with a predetermined threshold to detect the stall condition.
An apparatus for detecting a stall condition of a stepping motor of the type which includes at least first and second coils and a rotor having a plurality of magnetic poles therearound, said apparatus comprising;
- current generating means for alternately driving said first and second coils causing said rotor to perform a stepping rotation, each of said first and second coils generating a back emf voltage signal when transitioning from a driven to a non-driven state due to the rotation of said rotor;
- integrating means coupled to receive said back emf voltage signals to generate an integrated version thereof;
- and
- detecting means coupled to said integrating means for determining if said integrated version is representative of the stall condition.
An apparatus for displaying a measure of a variable, comprising;
- a stepping motor, comprising;
- at least first and second coils;
- and
- a rotor having a plurality of magnetic poles therearound;
- a display actuator coupled to said rotor for movement by said rotor to reflect a measure of said variable;
- a current generator for alternately supplying drive currents to said first and second coils causing said rotor to rotate by an amount indicative of the measure of said variable, each of said first and second coils generating signals when transitioning from a driven to a non-driven state, said signals resulting from the motion of said rotor;
- an integrator having an input coupled to receive said signals for generating an integrated version thereof;
- and
- a detector coupled to said integrator for determining if said integrated version is representative of a stall condition.
A method for detecting a stall condition of a stepping motor of the type which includes at least first and second coils and a rotor having a plurality of magnetic poles therearound, said apparatus comprising;
- alternately driving said first and second coils to with drive signals to cause said rotor to rotate, each of said first and second coils generating emf signals when transitioning from a driven to a non-driven state, said emf signals being caused by movement of said rotor;
- integrating the emf signals;
- and
- monitoring the integrated emf signals to detect a stall condition.
Dependencies are inferred from the claim text.