Drive circuit and method for an electric actuator with spring return
AssigneeHoneywell International Inc.
InventorChristopher M. Lange
Life of this patent
Estimating the term…
Abstract
A spring return rotary actuator incorporating a DC brush commutated electric motor and a pulse width modulation drive circuit which reduces the voltage at which current is supplied to the motor once a rotation sensor senses that the actuator output shaft has stalled. The drive circuit also includes a temperature responsive feature which increases the voltage at which current is supplied to the motor in the event a sensed temperature exceeds a temperature limit.
Claims29
A drive circuit for an actuator having an output shaft, a spring coupled to the shaft operable to bias the shaft for rotation toward a rest position, and an electric motor coupled to the shaft and energizable by electric current at at least a predetermined average voltage to rotate the shaft against the bias of the spring away from the rest position, the spring being operable to return the shaft to the rest position when the motor is not energized, the drive circuit comprising:
- input means for providing current at at least the predetermined average voltage when it is desired to rotate the shaft away from the rest position;
- a rotation sensor operable to produce a first signal indicative of whether or not the actuator output shaft is rotating;
- and
- a modulation circuit operable in response to both current received from said input means and the first signal indicating rotation of the actuator output shaft to supply current at a first average voltage adequate to energize the electric motor to continue to rotate the output shaft away from the rest position against the bias of the spring, and operable in response to current received from said input means to supply current at a second average voltage less than the first average voltage, but sufficient to hold the actuator output shaft in position against the bias of the spring when the first signal indicates that the actuator output shaft has stalled.
A method of energizing an actuator system in which an output shaft is rotated away from a rest position by an electric motor and is returned to the rest by biasing means operable to rotate the shaft when the motor is not energized, the method comprising the steps of:
- supplying electric current to the motor when rotation of the output shaft away from its rest position is desired;
- sensing whether or not the shaft is rotating;
- controlling the average voltage at which current is supplied to the motor to a first level sufficient to sustain rotation of the shaft against the urging of the biasing means if the shaft is rotating;
- and
- controlling the average voltage at which current is supplied to the motor to a second level less than the first level, but sufficient to hold the shaft in position against the urging of the biasing means if the shaft has stalled.
An electrically energizable actuator system comprising:
- an output member mounted for rotation about an axis;
- a biasing element coupled to said output member operable to urge said output member to rotate in a first direction;
- an electric motor coupled to said output member operable to rotate said output member in a second direction opposite the first direction against the urging of said biasing element when energized with electric current at at least a first average voltage;
- conductors for supplying electric current from a source of electric current at at least the first average voltage;
- a rotation sensor operable to produce a first signal indicative of whether or not said output member is rotating;
- and
- a control circuit connected to receive current supplied by said conductors and the first signal from said rotation sensor and to supply energization current to said electric motor, said control circuit being operable to control the voltage at which current is supplied to said electric motor to at least the first average voltage when receiving both current from said conductors and the first signal from said rotation sensor indicates that said output member is rotating, said control circuit further being operable to control the voltage at which current is supplied to said electric motor to a second average voltage less than the first average voltage, but sufficient to hold said output member in position against the urging of said biasing element when receiving both current from said conductors and the first signal from said rotation sensor indicates that said output member has stalled.
In an actuator system of the type including an output shaft rotatable between a rest position and a limiting stop position, a spring biasing the output shaft toward the rest position, and a motor which, when energerized with electric current at at least a first average voltage, is operable to rotate the output shaft against the bias of the spring toward the limiting stop position, an improved circuit for supply energization to the motor, comprising:
- a supply circuit for selectively supplying electric current to energize the motor;
- a rotation sensor for producing a rotation signal indicative of whether the output shaft is rotating;
- and
- a modulation circuit operable to vary the average voltage at which electric current is supplied to the motor by said supply circuit in response to the rotation signal produced by said rotation sensor, the average voltage being sufficient to sustain rotation of the output shaft against the bias of the spring if the rotation signal indicates rotation of the shaft, the average voltage being reduced, but sufficient to hold the output shaft in position against the bias of the spring, if the rotation signal indicates that rotation of the output shaft has ceased.
Dependencies are inferred from the claim text.