Cincinnati Milacron Inc.

Thomas W Minnich

Alfred H Morser

Stephen T Walsh

R William Kneifel, Ii

Robert M Crovella

A Harold Morser

Stanley L Myers

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.

Method and apparatus for torque ripple compensation

A method and apparatus for machine member motion control are provided which reduce position path errors in sampled data motion control systems. Position commands defining locations of a moveable machine member are periodically produced at a predetermined interval as is conventional in sampled data motion control. Intermediate position commands are produced at a predetermined sub-interval less than the predetermined interval in response to a parametric function relating member position and time, the parametric function being continuous through positions defined by the position commands. The intermediate position coordinates are computed as the sum of products of coefficients and coordinates of selected member position commands. To reduce processing time, the coefficients are computed and stored in advance of execution of motion for recall as motion progresses. Where a parabolic function is used to produce intermediate position commands, the sum of products of coefficients and, respectively, past, present and target coordinates are used to compute intermediate positions between the present and target positions.

Method and apparatus for sub-span interpolation

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. Additionally, current loop amplification gain factors and time constants are made selectable by input signals.

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Franklin, OH, United States of America

Thomas W Minnich