Patent GB-1513016-A (GB)
Title: Multi-phase motor controller
IPC: H02P8/24
Filed: 1975-06-06
Abstract: 1513016 Automatic control of speed RICOH CO Ltd 6 June 1975 [6 June 1974] 24396/75 Heading G3R [ Also in Division H2] A multi-phase stepping motor 10 of the type having excitation means to sequentially excite the motor phases and a pulse generator 18, 22, 24 operatively connected with the motor shaft 14 to generate pulses each representing a predetermined magnitude of angular displacement whereby the pulse duration decreases with increasing motor shaft speed, has its motor shaft speed limited to a predetermined value by controlling the excitation means to excite the motor phases in such a manner as to reduce the accelerating force on the shaft when the pulse duration is below a predetermined duration for a time equal to the difference between the pulse duration and the predetermined duration so that the shaft speed is substantially limited to the predetermined value. As shown in Fig. 1a, the pulse generator comprises a disc 18 having circumferential slots 18a, a light source 22 and a receiver 24 which provides a pulse output to a controller 26 at a frequency proportional to shaft speed. As shown in Fig. 3, the controller includes a control unit 30 which provides a starting pulse A, a clockwise movement pulse CW and a counter-clockwise pulse CCW to a combination of AND and OR gates which control the states of flip-flops, F 1 , F 2  and F3 which in turn control the phases of the four-phase motor 10 over lines PH1-PH4 and drivers D1-D4. The pulses 13 from the receiver 24 are also applied to control the states of the flip-flops, and to a multi-vibrator 32 and the inverting input of an AND gate A11. The multi-vibrator produces constant duration pulses C (representing the predetermined duration) coincident with the pulses B and applied to an input of the gate A11. When the duration of a pulse B becomes smaller than that of a pulse C, the AND gate A11 provides a pulse for the duration that pulse C exists after pulse B terminates, this pulse being applied to alter the phase excitation sequence by one backward step which results in a reduction of torque applied to the motor. In an alternative arrangement, Fig. 4 (not shown), the gates A5, A6, A7, A8, A9, A10, 03 and 04 are omitted, the lines PH1-PH4 being connected to the "1" outputs of the flip-flops F2 and F 3 , and the pulses B are applied to one input of an OR gate (O15) and to the multi-vibrator whose output pulses C are applied to the other input of the OR gate, whose output is applied to OR gate 01 (011 in Fig. 4). In this embodiment, when a pulse B has a smaller duration than that of pulse C, the changing of the motor phases is delayed until the downclock of pulse C thereby reducing the accelerating force. In another arrangement, Fig. 6 (not shown), again the gates A5-A10, 03 and 04 are omitted, an AND gate is placed in each line PH1-PH4, and the pulses B and C are applied to the inverting and non- inverting inputs of a NAND gate whose output is applied to the other inputs of the AND gates in lines PH1-PH4. When a pulse B has a duration less than that of pulse C, a negative pulse is applied to one input of all the AND gates thereby disabling these gates and de-energizing the motor. In yet another arrangement, Fig. 8 (not shown), all phases of the motor are inverted when a pulse B has a duration less than that of pulses C which has the effect of taking two steps backward in the phase excitation sequence.