GB1398498A - Digital synchronizing and phasing system - Google Patents

Abstract

1398498 Automatic speed control; centrifugal governors WOODWARD GOVERNOR CO 23 March 1973 [14 June 1972] 14268/73 Headings G3B and G3R The speed of a prime mover is measured and represented as the frequency of an electrical signal which is compared with a reference frequency signal by feeding the two signals to respective inputs of a bi-stable device. The bi-stable output controls the energization of a magnetic biasing coil in a governor so as to adjust the prime mover speed to a value corresponding to the reference frequency. As shown in Fig. 1, a reference signal is provided by the shaft 23 of a master aircraft engine 21 connected to a transducer 61 supplying pulses through a Schmitt trigger circuit 75 to a differentiator 77 which supplies trigger pulses to the set input of flip-flop 79. The reset input receives similar pulses from a transducer 62 associated with a slave engine 22. The resulting rectangular signal at the set output of flip-flop 79 switches a transistor 59 into saturation for intervals whose duration determines the mean current in a winding 57a which magnetically controls the setting of a governor in the fuel supply system for the slave engine 22. In another arrangement, Fig. 5 (not shown), the winding 57a is connected across a transistor bridge and is energized alternately in opposite senses by the set and reset outputs of the flip-flop. Fig. 7 (not shown) illustrates an arrangement for manually setting a required phase relationship between the two engine shafts using an operational amplifier receiving an adjustable reference current to control the current in the magnetic winding. The phase setting may be automatically regulated by including a further operational amplifier with an integrating characteristic, Fig. 8 (not shown). A further arrangement Fig. 10 (not shown), concerns the synchronization of two engines each controlled by a governor with a magnetic biasing winding. The windings are energized by complementary signals derived respectively from the set and reset outputs of a flip-flop. The construction of the magnetic speed governor is shown in Fig. 2. Flyweights 43, 44 may be permanent magnets or magnetic material such as soft iron, and their rotation about pivots 52, 53 is controlled by a spring 49 and by the energization of a winding 57a. The position taken up by the weights determines the relative positions of a valve plunger 47 and sleeve 46 which hydraulically control a fuel servosystem for the prime mover.