A synchro torque receiver has its rotor wound with an additional winding at right-angles to its existing, continuously energized rotor-winding. The three-phase stator-windings of the receiver are energized conventionally from the corresponding windings of a synchro torque transmitter. A control unit detects signals induced in the additional rotor-winding of the receiver and energizes this to create torque aiding the normal reactive torque that drives the receiver-rotor to maintain rotational correspondence between the receiver- and transmitter-rotors. The induced signal is sampled alternately with energization of the additional winding, at a frequency lower than, or the same as, that of the receiver- and transmitter-energization. Alternatively detection and energization of the additional winding can take place concurrently using phase or frequency as the discriminant for detection of the induced signal. Large current-flow into the normal rotor-winding of the receiver, accompanying large deviation from correspondence, is detected to energize the additional winding independently of the induced signal.
An improved heliostat device for an electrooptical system in which a mirror is gimbaled in two axes for line-of-sight direction and stabilization. A half angle drive system is connected to the mirror for controlling azimuth rotation of the mirror relative to the stable body from which the mirror is mounted. The half angle drive system comprises a N-2N-speed synchro transmitter-receiver pair, with the N-speed synchro control transmitter mounted on the stable body axis, and the 2N-speed control receiver mounted on the mirror axis. This synchro transmitter-receiver pair is operable with a null error signal controlling mirror drive such that the angular rotation of the mirror is one-half that of the angular rotation of the stable body.
