| 摘要 |
1,203,295. Control of stepping motors. PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd. 12 Sept., 1967 [15 Sept., 1966], No. 41515/67. Heading H2J. A stepping motor is decelerated with reduced oscillation and stopped in a desired position by interrupting a train of driving pulses before the position is reached, and then applying a clamping pulse when the rotor has moved at least one step beyond the point of interruption and starts to reverse. If the rotor moves beyond the point of interruption by more than 1¢ steps, clamping pulses are applied to the motor equal in number to the number of further steps and at a frequency equal to twice the natural frequency of damped oscillations of the rotor. The motor A is supplied through an electronic switch P controlled by a multivibrator comprising transistors 1, 2, the frequency of the pulses derived from the multivibrator being determined by the time-dependent voltage developed acros the emitter resistance 23 of transistor 24. A control circuit for the transistor 24 comprises switch S which is opened to render transistor 30 non-conductive whereby transistors 31, 38 conduct and diode 37 is blocked so that the multivibrator starts to oscillate. Capacitor 40 begins to charge and transistor 24 is driven to clamp the voltage applied to capacitors 3, 4, this voltage decreasing linearly with time to increase the frequency of the motor-driving pulses. When the switch S is closed, the multivibrator 1, 2 is cut-off and transistor 51 passes the last pulse to a monostable multivibrator OSA which, after a delay period, changes-over a flip-flop FF and drives multivibrator OSB into the astable state. Multivibrator 55, 56 now oscillates freely, with a delay equal to the time constant of the multivibrator OSA, and supplies a first clamping pulse to the switch P which differentiates the pulse for application to the motor. The voltage developed across the resistor 23 is transferred through diode 71 to the circuit OSA whose time constant is reduced as the motor speed increases. The multivibrator 55, 56 is adapted to produce a train of clamping pulses whose repetition rate is adjusted by oscillation of the rotor. When this train is interrupted, the multivibrator OSB drives the flip-flop FF back to its initial state in which it cuts-off the multivibrator 55, 56. |
