Abstract: Compensation for friction affecting motion of moveable machine members is effected in servo control of the member actuators. An estimate of velocity is used in evaluation of a model of frictional force to produce compensation values. Alternative embodiments provide continuous models of estimated velocity and frictional forces and state models of estimated velocity and frictional forces. Compensation values determined according to either embodiment may be produced for application to servo control commands such as position or torque. The compensation accounts for step changes of friction upon reversal of direction of travel.

Abstract: Torque ripple in brushless DC motors is reduced by compensation of signals controlling energization of motor stator windings. Motor current magnitude is compensated in response to compensation factor values correlated to the ratio of actual torque to ideal torque at constant current at various relative positions of a motor rotor and stator. A motor current command component associated with a commanded torque is compensated for cogging torque associated with motor magnetization. Measured relative position values are compensated to account for torque profile distortions associated with motor current magnitude.

Abstract: A method and apparatus for limiting current through a switching device supplying current to a load. A control evaluates a model representing the switching device temperature as a nonlinear function of current and time. The model compares the temperature of the switching device to a maximum allowable temperature. The current limit is defaulted to peak current; and in response to the model detecting a temperature in excess of the maximum allowable temperature, a nominal current limit is set. The current limit reset to peak current after the model detects a switching device temperature a predetermined magnitude below the maximum allowable temperature.

Abstract: An apparatus and method for controlling brushless DC motors are provided. Velocity loop control is performed digitally to produce current commands at a high frequency loop closure interval. Commutation of field coil current is controlled in response to current commutation pattern control signals produced in response to measured relative position of the motor rotor and motor stator and a velocity average over a number of loop closure intervals. Switch control signals to control transistor switches providing current from a DC power source to the motor terminals are produced in response to the current commands, measured motor current and the commutation pattern control signals. The velocity loop control implements a selected transfer function relating velocity, the motor torque constant, and the moment of inertia of the motor and associated load. Facilities are provided for periodically adjusting velocity loop transfer function gain factors and the effective moment of inertia in response to input signals.