Patent GB-1507720-A (GB)
Title: Motor drive system including a feedback loop
IPC: G05B19/40
Filed: 1975-08-20
Abstract: 1507720 Control of stepping motors BURROUGHS CORP 20 Aug 1975 [30 Dec 1974] 34552/75 Heading H2J A motor drive system for driving a motor incrementally in accordance with the generation of motion-command pulses COMO comprises motor rotation sensing means 12, 16 for generating a feedback pulse FB for each predetermined incremental movement of the motor 6, timing means for setting out a predetermined time interval, and means effective upon the generation of each feedback pulse or the run-out of the predetermined time interval, which ever occurs last, for generating a motion-command pulse and for restarting the timing means, whereby the motor rotates one increment for each feedback pulse but its speed is limited to a predetermined regulated speed in which the time of each increment of movement is not less than said predetermined time interval. As shown in Fig. 2, the system consists of a main start and speed control unit 20 having four inputs to receive a START signal, a HIGH SPEED signal, a DECELERATION signal and the feedback pulses FB and an output 28 connected to a motion-command pulse generator 30, and a stop-sequence control unit 32 which has two inputs to receive a STOP signal and the pulses FB and an output 38 connected to generator 30, the feedback pulses being derived from a magnetic sensor 16 for sensing teeth on a disc 12 connected to the motor shaft. The various operations will now be described: Starting.-As shown in Fig. 2a, when a START signal is received, a command pulse is generated immediately via an OR gate G1 and generator 30 to step the motor 6. A feedback pulse is thus generated which is applied to generate a second command pulse via an AND gate G2, OR gate G3, OR gate G1 and generator 30. The motor thus speeds up until it reaches the predetermined regulated speed. Speed-regulation.-The duration between each pulse FB is compared at SO with the duration of a timer TS1, which is reset either by a feedback pulse or a command pulse, and as soon as the pulse duration becomes less than that of timer TS1, gate G2 is inhibited and the commandpulse is generated at the end of the timer duration via inverter 12, AND gate G4, OR gate G3, OR gate G1 and generator 30. High speed running.-When high speed is desired, a signal is applied on input 24 which immediately causes generation of a command pulse so that the command pulses are in onephase -advanced relation with the feed back pulses which accelerates the motor, the operation of timer TS1 being inhibited. Deceleration.-When it is desired to decelerate the motor after high speed running signal is applied on input 26, which causes the next two feedback pulses to skip the generation of command pulses whereby the command pulses are thereafter in one-phase-delayed relation with the feed back pulses thereby decelerating the motor until the regulated speed is reached. Stopping.-When a stop command is applied, see Fig. 2b, the next feedback pulse FB 0  is caused to skip the generation of a command pulse thereby causing deceleration of the motor, the motor then being brought to a complete stop at the end of the next three pulses FB 1 -FB 3  (which generate command pulses). The duration between the pulses FB 2  and FB 3  is compared with the duration of a timer TS 2 , set by the FB 2  pulse, and the third and last command pulse is generated either by the FB 3  pulse or the run-out of timer TS 2 , whichever occurs first. With the generation of the last pulse, a timer TS 3  is operated to inhibit a gate G 12  to prevent further operation of the motor to preventing re-starting of the motor due to hunting. The description with reference to Figs. 5-9 (not shown), relates to a system driving a synchronous-sequential machine, the provision of the command pulses to a phase-sequencer and of a limited current signal, which is applied when the motor is at rest, to the phase windings of the motor being under the control of a motor state machine (60) which is a MOS LSI circuit which can take sixteen states depending upon the presence or absence of inputs relating to HIGH SPEED and DECELERATIONSTART, STOP, FB, and timer signals.