Cincinnati Milacron Inc.

Stanley L Myers

Alfred H Morser

Stephen T Walsh

Thomas W Minnich

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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Cincinnati, OH, United States of America

Stanley L Myers