Patent GB-842340-A (GB)
Title: Synchronisation of rotating elements
IPC: G01S7/12
Filed: 1957-07-05
Abstract: 842,340. Electric synchronous movements. STANDARD TELEPHONES & CABLES Ltd. July 5, 1957 [July 9, 1956], No. 21377/57. Class 40(3). An arrangement for synchronizing two electric motors and two rotating elements respectively driven thereby comprises means controlled by each motor for generating a corresponding position pulse marking a particular angular position of the motor shaft, fine synchronizing adjustment means operating in response to a partial coincidence of the two position pulses and effective to cause a relative rotation of the stator and motor of one of the motors in such direction as to bring the two position pulses into closer coincidence, a normally inoperative coarse synchronizing adjustment means arranged to be brought into operation in response to a complete lack of coincidence of the position pulses and to cause a retardation of one of the motors in such manner as to bring the two position pulses into at least partial coincidence, and means for rendering the coarse synchronizing adjustment means again inoperative when partial coincidence of the two position pulses has been attained. A generator 3 produces at a predetermined position of the shaft of the motor 2 a narrow negative pulse 4 passed as a positive pulse 6 to a first clamp circuit 7 and to a second clamp circuit 34. A generator 30 produces at the corresponding position of the shaft of the distant or second motor 21 a pulse which passes from amplifier 31 to a clamp circuit 7<SP>1</SP> and also to the input of a clamp circuit 28. A positive pulse 8 from the circuit 7 triggers a flip-flop 9 to pass a relatively wide negative pulse 27 to the clamp 28, whilst the positive pulse from clamp 7<SP>1</SP> triggers flip-flop 9<SP>1</SP> to pass a relatively wide negative pulse 33 to the clamp 34. The flip-flops 9, 9<SP>1</SP> also pass positive pulses 10, 13 to a clamp circuit 11 which passes a pulse 14 having an amplitude twice that of pulse 10 or pulse 13 when these pulses coincide or overlap. A flip-flop 15 which is triggered by an impulse of the amplitude of the pulse 14, i.e. partial or complete coincidence of the pulses 10, 13, passes a pulse through a clamp 17 and control circuit 18 to a relay 19 operating contacts 20, 20A so that the coincidence or overlap of the pulses 10, 13 during coarse adjustment cuts out the resistance circuit 22 from the motor and the contacts 20A permit relay 40 to be operated by a control circuit 39. The pulses from clamp 11 also pass to a check circuit 23 controlled by a pulse 14, or by two pulses received within a predetermined time interval, in such a way that a relay 24 is not energized so that at contacts 25, 26 the voltage source B+ is applied to the control circuits 18, 39 for the coarse adjustment and fine adjustment relays 19, 40 respectively. If within a predetermined time interval the check circuit does not receive a pulse 14, or two pulses derived from the pulses 10, 13 consequent, for example, from the failure of one of the motors 2, 21 the relay 24 energizes and at contacts 25, 26 removes the voltage source B+ from the control circuits 18, 39. The positive pulse 29 and negative pulse 27 are applied to a circuit 28, whilst the positive pulse 6 and negative pulse 33 are applied to a circuit 34, the circuits 28, 34 passing a positive pulse to the gate 36, 36<SP>1</SP> in response to the occurrence of positive voltage at their respective inputs. The commencement of the negative pulse 27 and of the positive pulse 6 will coincide as will the beginnings of the negative pulse 33 and of the positive pulse 29. If the pulses 6, 29 are approximately in coincidence the positive pulses are neutralized by the negative pulses, and no output passes to the gate 36 or 36<SP>1</SP>, flip-flop 37 or 37<SP>1</SP> and circuit 38 or 38<SP>1</SP> to the fine adjustment relay control circuit 39. If, however, the pulse 29 lags behind the pulse 6, a positive pulse portion in the combined waveform will produce a positive pulse 35 passing through clamp 38 and the control circuit 39 to operate polarized relay 40 so that a voltage is applied to a servo motor 44 to rotate the stator of motor 21 in one direction towards the synchronized condition. If, however, pulse 29 leads the pulse 6, a positive pulse portion will occur in the waveform applied to the clamp 34 so that the gate 36<SP>1</SP> will pass a pulse to clamp 38<SP>1</SP> and relay control circuit 39 to energize the relay 40 in the opposite direction so that at contact 40A the motor 44 is operated to rotate the stator of motor 21 in the opposite direction towards the coincident condition of pulses 6, 29. When coincidence has been established, the circuit 39 is held in readiness to apply the necessary fine adjustment in response to any deviation from synchronism producing phase displacement of the pulses 6, 29.