A torque motor for a low friction single axis turntable

A single axis turntable motor for a virtually frictionless turntable used for testing satellite attitude control systems is described. The torque motor simulates pulse jets for attitude control, low torques acting on the satellite, and compensates disturbance torques acting on the table. The torques are applied by forcing a current in the ironless rotor fixed to the ground, while the permanent magnet stator transfers the torques to the turntable, to which the stator is attached. The rotor is mounted on a servocontrolled subtable so that the angular position of the stator and rotor is maintained, in order to keep the torque transfer independent of the turntable position. The torquer can accept pulses as short as 3 msec and has a gain accuracy better than 0.5% within its range of 50 times 10 to the power -3 nanometers. The torquer is used to compensate the position dependent disturbance torques on the turntable, so that the friction of the table is lowered towards 3 times 10 to the power -6 nanometers.