Cincinnati Milacron Inc.

Robert M Crovella

R William Kneifel, Ii

Stephen T Walsh

Thomas W Minnich

A Harold Morser

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 for efficiently interpolating sub-span position commands for control of a machine member. The method includes storing a set of coefficients defined by a parametric function relating member position and time, calculating the distance between a target coordinate axis position command and a current coordinate axis position command, generating first and second command modifiers from the stored coefficients, the calculated distance, and a current coordinate axis position command, and summing the current coordinate axis position command and the first and second command modifiers to generate a subspan position command.

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Rockford, IL, United States of America

Robert M Crovella