Patent GB-777634-A (GB)
Title: Improvements in or relating to electrical control apparatus
Inventor: JR HENRY RICHARDS WALCOTT
IPC: H02P5/50
Filed: 1955-02-22
Abstract: 777,634. Electric indicating systems. BENDIX AVIATION CORPORATION. Feb. 22, 1955, No. 5308/55. Class 40 (1). [Also in Group XXXV] In a system for indicating the integral of a measured quantity a signal proportional to the measured quantity is translated into the relative speed of two motors for driving an output member at a speed proportional to the measured quantity, the member driving an integrator for indicating the net displacement of the member, and hence the integral of the measured quantity. As applied to indicating the distance travelled by an aircraft, the output of an indicator 100, Fig. 3, representing the air speed, is remotely applied over a synchro transmitter-receiver 102, 106 to energize a " follow-up " motor 110. The latter continually drives the rotor 107 of receiver 106 towards a null position and repositions a tap 112 on an A.C. potentiometer 114 in accordance with the air speed. The output of a wind indicator 121 is applied through a similar system (not shown) to re-position a tap 122 on a second A.C. potentiometer 123. The signals from tappings 112, 124 are algebraically added in a transformer 119, and the resulting signal, of phase and magnitude representing the corrected airspeed or ground speed, is applied over a transformer 26, Figs. 1, 3, and a changeover switch 78 to the input of an amplifier 23. The output of the latter controls the speed of a motor 29 relative to a constant speed motor 16, the two motors normally running in synchronism. The motors 16, 29 drive the rotors of a synchro transmitter 47 and a synchro differential 54 respectively, so that the output from the differential rotor 56 to a synchro receiver 62 is proportional to the relative motor speed and hence to the ground speed of the aircraft. The output of receiver 60 in its rotor 63 controls a reversible follow-up motor 67 which continually drives the rotor 63 towards its null position and rotates an output member 69 at a speed proportional to the ground speed of the aircraft. An integrator 70 coupled to member 69 indicates the net displacement of the member and hence the distance travelled by the aircraft. In the absence of a ground speed signal applied to transformer 26, motors 16, 29 are synchronized by opposing speed signals from generators 33, 18 driven by the motors in the input to amplifier 23, and in order to compensate for inherent differences in the generator outputs in spite of speed synchronism the amplifier input from generator 33 may be modified by the manual or automatic adjustment of a tapping 72 on a resistor 71 in series with the generator output winding. The automatic adjustment is effected through linkage 74 by movement of output member 69 which responds to lack of synchronism between the motors as already described. A coupler 75 disconnects the linkage 74 when synchronism is attained, and operates change-over switch 78 to permit a ground speed signal to be applied to amplifier 23. The servo operation of member 69 prevents fluctuations in the loading of member 69 being repeated in the control circuits. A network, Fig. 2 (not shown), is described for compensating for out-of-phase component in the input to amplifier 23. A mechanical differential may replace the synchro system described.