a control circuit for a brushless dc motor providing positive control in all four quadrants of motor operation . the circuit provides control of motor current , thereby controlling motor torque , in response to an applied current command signal , relying solely on feedback signals of motor current and rotor angle . the heart of the system is a level dependent logic stage which selectively controls the states of the switches applying power to the motor windings in accordance with a current error signal developed by reference to the feedback current signal . the control circuit causes the motor current to correspond to any applied current command and works at any motor speed and torque for rotation in either direction . in a preferred embodiment , the basic control system is combined with additional feedback loops developing servo information regarding rate and actuator position to provide a overall position control system , such as is particularly useful in place of the hydraulic actuator systems now employed in aircraft .