Adaptive controller for a motor vehicle engine throttle operator
AssigneeGeneral Motors Corporation
InventorsCarl A. Nehmer, Lary R. Hocken
Life of this patent
Estimating the term…
Abstract
The phase winding energization frequency of a stepper motor throttle operator is adjusted in relation to a comparison between the actual neutral voltage crossing of back-EMF in the phase windings and a previously determined optimum point of crossing. The energization frequency is increased to increase motor speed when the actual crossing occurs prior to the optimum point, and decreased to decrease motor speed when the actual crossing occurs after the optimum point.
Claims10
An electrical servo system for positioning a mechanical load, the system including a stepper motor having a plurality of stator windings adapted to be energized in predetermined sequence to develop a rotating stator magnetic field, a permanent magnet rotor drivingly connected to the load and having a magnetic field which tends to rotate in synchronism with the stator magnetic field, and a controller for sequentially energizing the motor stator windings at a rate determined in accordance with a motor speed command to rotatably drive the rotor for positioning the load in accordance with a position command, a method of operation comprising the steps of:
- initializing the motor speed command to a predetermined starting rate at the initiation of motor operation;
- and thereafter during the energization of each phase winding,
- detecting a crossing of the back-EMF voltage in the stepper motor phase winding about to be energized, the point at which such crossing occurs being related to the degree of misalignment between the magnetic fields of the rotor and stator;
- determining a motor speed correction in relation to the amount by which the detected crossing deviates from a desired crossing corresponding to an empirically derived amount of misalignment which permits the motor to withstand a predetermined level of variation in the torque which opposes motor rotation without substantial loss of synchronism between the rotor and stator magnetic fields;
- and
- adjusting the motor speed command in relation to said motor speed correction so as to drive the actual crossing into correspondence with the desired crossing, whereby the motor speed is adaptively controlled in accordance with the torque it must overcome, and the motor speed is maximized for reliable operation under all load conditions.
An electrical servo system for positioning a mechanical load, the system including a stepper motor having a plurality of stator windings adapted to be energized in predetermined sequence to develop a stator magnetic field which rotates step-by-step, a permanent magnet rotor drivingly connected to the load and having a magnetic field which tends to rotate in synchronism with the stator magnetic field, and a controller for sequentially energizing the motor stator windings to rotatably drive the rotor for positioning the load in accordance with a position command, apparatus comprising:
- back-EMF detection means for detecting the crossing of the back-EMF voltages in the various stepper motor phase windings, the point at which such crossing occurs being related to the degree of misalignment between the magnetic fields of the rotor and stator;
- and
- means including controller means activated a predetermined number of times in each motor step, such means being effective when activated to determine whether a back-EMF neutral voltage crossing has been detected by said back-EMF detection means, and to adjust the motor speed command in accordance with the result of said determination so that following the adjustment, the back-EMF neutral voltage crossing of a stator winding about to be energized will tend to occur at a desired point in the the motor step defined by the preceding stator winding energization, said desired point corresponding to an empirically derived amount of misalignment which permits the motor to withstand a predetermined level of variation in the torque which opposes motor rotation without substantial loss of synchronism between the rotor and stator magnetic fields, whereby the motor speed is adaptively controlled in accordance with the torque it must overcome, and the motor is maximized for reliable operation under all load conditions.
Dependencies are inferred from the claim text.