BILATERAL SERVOSYSTEM

1358580 Electric correspondence control GENERAL ELECTRIC CO 29 Sept 1971 [29 Sept 1970] 45299/71 Heading G1N A servo system comprises a master member 10; an electro-mechanical transducer 20 mechanically coupled to the member to produce an electrical output signal in accordance with angular displacement of axis 12 of the member from a predetermined orientation 13; a slave member 15; another e.m. transducer 21 mechanically coupled to the slave to produce an electrical output signal in accordance with displacement of slave axis 17 from another predetermined orientation 18, the output signal from the slave transducer being matched to the output signal from the master transducer so that an output signal from the master transducer corresponding to a predetermined displacement of the axis of the master member from said predetermined orientation is substantially equal to the output signal corresponding to the same predetermined displacement of the axis of the slave from orientation 18; a slave servo loop 18 including an electrical amplifier 41; a servo flow control valve 40 and a slave actuator 23 responsive to a difference in output signals from the transducers to tend to maintain said slave member axis in alignment with the master member axis; a master servo loop including the amplifier, the valve and a master actuator 22 connected between output ports 42, 43 of the valve and the master member so as to oppose the movement of the master member which causes the movement of the slave member, the inertia of the slave member being substantially greater than the inertia of the master member, the phase margin of the slave servo loop being positive at the frequency at which its open loop gain is unity, the open loop gain of the master servo loop being substantially higher than the open loop gain of the slave servo loop, means for stabilizing the master loop including an electrical network 50 which introduces phase lag in the signal from the transducer 20 over a low frequency range and phase lead in the signal over a higher frequency range whereby the phase margins at unity gain of the gain versus frequency characteristic of the master loop with stabiliization is positive, and means for reducing slew error of the system including an electrical network 51 in the slave loop which introduces phase lag and phase lead into the signal from the slave transducer over different frequency ranges thereof, the phase lag time constant being greater than the phase lead time constant o