Patent GB-1385284-A (GB)
Title: Motor and control system
IPC: H02P8/00
Filed: 1973-05-30
Abstract: 1385284 Motor control systems INTERNATIONAL BUSINESS MACHINES CORP 30 May 1973 [6 June 1972] 25826/73 Heading H2J An apparatus comprising a control system and an electric motor having a rotor, includes an acceleration control means supplying energy to the motor so as to accelerate the motor until it reaches a first predetermined angular position and deceleration control means for supplying energy to the motor to decelerate the motor to standstill together with means for modifying the operation of the deceleration control means in accordance with the time taken by the motor to reach the first predetermined position so that the motor is brought to a standstill at a second predetermined position. A stepper motor 24 comprises a plurality of poles 30-44 on each of which poles a pair of windings A 1 , A 2 ; B 1 , B 2  are disposed, each pair of windings having a centre tap C all of which centre taps are connected together and the similarly designated windings connected in parallel with one another, the paralleled windings being connected to terminals 56, 58, 60 or 62 which can be connected across a battery 172 by transistors 262, 260, 258, 256 respectively. The motor 24 also comprises a permanently magnetized rotor 26 which drives a shaft 46 to rotate a toothed wheel 68 which cooperates with a magnetic transducer 70 so as to produce signals on a lead 72 to the basic controlling circuitry R shows in Fig. III, the part P of the circuitry shown in Fig. II being directly attached to the motor 24 and the part Q of Fig. II being designated the "smart stop" circuitry. Movement of the rotor 26 from a steady state position a, b as illustrated in Fig. I is initiated by momentarily closing a switch 74. The resulting pulse on line 100 produces a pulse on output line 78 from an OR circuit 80-by way of various logic elements-whereby triggers 250, 252 change state such that triggers 252, 254 render transistors 258, 262 conductive to energize windings A2, B1 causing the rotor 26 to move in a direction X towards the stator pole 30. When the rotor 26 is aligned with the pole 30 the transducer 70 emits a pulse on the lead 72. Emitter amplifier 114 then produces a pulse on lead 112 whereby a second pulse is produced on lead 78, by way of pulses on leads 108, 104, 82 whereby triggers 250, 254 change state whereby triggers 252, 254 now cause conduction of transistors 258, 260 to energize windings A2, B2 causing further rotation of the rotor 26. Rotation of the rotor 26 then continues under maximum acceleration until five pulses have appeared on line 78 at which point a "count 5" logic element 102 produces an output on line 118 to energize two delay circuits 124, 128, the circuit 124 delay being shorter than that of circuit 128. These two circuits cause two more pulses the 6th and 7th, in rapid succession to appear on line 78 which pulses are effective cause the effective torque on the rotor to change so as to produce maximum deceleration of the motor 26. The 8th pulse on line 78 is provided by way of the circuitry Q, and this pulse is produced a predetermined time after the 5th pulse by way of an output pulse from AND circuit 148 which turns on transistors 174, 184 so as to charge capacitor 186, the charging of which is proportional to the time the rotor 26 was accelerating. At the same time a capacitor 212 begins to charge, under control of line 146 and transistors 204, 208, to provide a pulse on lead 140 whereby an 8th pulse is produced on lead 78 at a time which varies in accordance with the period of time between the 1st and 5th pulses and the load on the shaft 46 of the rotor 26. The 9th pulse on line 78 is produced under control of a pulse from transducer 70 which cause a latch 136 to produce an output and thus an output on line 88 which energizes the required windings of the motor to bring the motor to standstill without hunting.