GB1057708A - Improvements in servo control systems - Google Patents

Abstract

1,057,708. Control of two D.C. motors. CANADIAN WESTINGHOUSE CO. Ltd. April 15, 1964 [April 19, 1963 (3)], No. 15600/64. Heading H2J. [Also in Divisions B3 and G3] A steering motor and a travel motor of a template follower are controlled by the outputs of a pair of photo-cells which are electromagnetically oscillated across a line on a template. Steering of the template follower.-The output of a steering photo-cell, Fig. 6 (not shown) is applied to a transistor amplifier and the natural frequency component filtered out in # el T network the fundamental frequency signal being applied to a push-pull pair of transistors having an output which is applied to a steering motor Figs. 1-3 (not shown), to rotate it in a direction and at a speed dependent on the phase and amplitude of the fundemental frequency signal. Velocity feedback is applied from a tachogenerator. Velocity control of the template follower.-The signal from a velocity controlling photo-cell, Fig. 7 (not shown), is amplified, rectified, filtered and applied as bias to a transistor which is rendered conductive by the photo-cell signal to actuate a relay through a transistor. The desired velocity signal is derived from a manually set potentiometer and is applied to a sine-cosine potentiometer of circuit 47 of Fig. 5B. During cornering the signal from the photo-cell falls and the velocity signal is limited by a Zener diode. On completion of a corner a capacitor prohibits the immediate resumption of conduction by the biased transistor so that rapid speed change is prevented. Positioning control.-The apparatus in dotted area 52, Fig. 5B, is arranged to produce timing pulses at supply frequency which are modified into ramp pulses by the charging of a capacitor 255 through a transistor 254 controlled by Zener diode 263. The outputs of area 52 are opposite phased pulses on lines 156, 182 and opposite phased ramp pulses on conductors 180, 157. The apparatus in area 47, Fig. 5B, derives X and Y co-ordinate signals on line 153, 274 from a sine-cosine potentiometer 145 supplied on line 356, 357 with a velocity dependent signal from velocity control system. Figs. 6, 7 (not shown). Fig. 5A shows apparatus for controlling the direction and velocity of an X co-ordinate motor 31. The arrangement is symmetrical and siliconcontrolled rectifiers 206, 209 are triggered by unijunction transistors 176, 201 responsive to transistors 173, 178. The ramp signal 157 is summated with the timing pulses 156 and velocity signal 153 through a tunnel diode in the base circuit of a transistor 165 connected through a transistor 170 and capacitor 170 to control the bias to the transistor 176. The summation of signals is such that the points in a cycle at which the silicon controlled rectifier 206 is triggered are dependent on the velocity signal 153, being earlier with an increase in signal level. Velocity feedback is derived from a tachogenerator and applied to the tunnel diodes 155, 158 through variable resistors 261, 262.