BRUSHLESS DC TORQUE MOTOR DEVELOPMENT

Three high-performance 7 ft-lb brushless dc torquers were designed, fabricated and tested under this contract. The torquer characteristics were specifically optimized for use as CMG gimbal actuators. The brushless dc torquers employ Hall generators to resolve rotor-position and control the currents in the two motor phases. The associated electronic controller incorporates a redundant standby channel for reliability and uses pulse width modulated power amplifiers to achieve high efficiency. To provide a rate signal for closed loop operation a brushless dc tachometer integral with the motor was fabricated and tested. The brushless dc torquer developed on this contract results in the following improvements when compared to a high performance brush-type torquer: infinite life, 10/1 reliability improvement, 4/1 lower friction, 3/1 lower rotor inertia, fewer ripple torque cycles per revolution, and improved heat removal from the windings. These are achieved with approximately the same weight and power characteristics. The brushless dc torquer was thoroughly evaluated in a series of functional and environmental tests. These tests showed that the torquer is suitable for long life space missions. (Author)