GB892216A - Improvements in or relating to control systems - Google Patents

Abstract

892,216. Electric selective signalling systems. BRITISH IRON & STEEL RESEARCH ASSOCIATION. July 17, 1959 [April 17, 1958], No. 12217/58. Class 40 (1). [Also in Group XXII] A control system for positionally controlling a forging manipulator comprises a device actuated by the manipulator and set according to its position, a datum device settable according to the desired manipulator position, a control circuit operated by these devices to change the manipulator position until it achieves the position to which the datum device is set, and setting means which when operated change the setting of the datum device by a prescribed value or by fixed multiples of a prescribed value. The manipulator, Fig. 1, comprises a carriage 12 driven through a rack- and-pinion arrangement 15, 16, by a stationary motor 14 which also drives an output potentiometer 22, Fig. 4, and a tacho-generator 24, Fig. 2 (not shown). The peel 17 of the manipulator may be moved vertically through links 21 and may be rotated within bearings 20. Longitudinal control.-The voltage from reference potentiometer 22, Fig. 4, is opposed by that from an input potentiometer 23, selectively set up as described below. Both potentiometers 22, 23 and the tacho-generator 24 (not shown) are supplied with the same A.C. and the difference voltage from the potentiometers (on line 28) is combined with the tacho-generator output (applied to terminals 26) after passing through the bridge circuit 27. The combined signal is amplified by valves 29, 30 and the resulting signal, biased by an A.C. reference voltage on line 31, applied to a cathode-follower 32, rectified by a diode 33, smoothed and applied to the control grids of two pentodes 34, 35. The bias voltage on line 31 is also applied to a cathode-follower 36, rectified by diode 37 and smoothed, the output appearing across two potentiometers 38, 40, in series, with their wipers connected to the control grids of two further pentodes 41, 42 respectively. Pentodes 34, 41 are each connected in series with one winding of a differentially-wound relay 43 controlling the forward motion of the manipulator. Similarly, a differentially-wound relay 44 controls the rearward movement. If the manipulator is at the position selected by potentiometer 23, the voltages applied to the control grids 34, 35 lies between that on the wipers of the potentiometers 38, 40, the current passed by pentode 41 exceeds that passed by pentode 34 and relay 43 remains in its off position. Similarly, relay 44 remains " off." If the manipulator is rearward of the required position, current in pentode 34 exceeds that in pentode 41 and relay 43 is switched to " on "; relay 44 remains " off " (as above) and the manipulator moves forward. Rearward motion is similarly effected. Vertical control.-Vertical movement of the peel 17, Fig. 1, is controlled by an hydraulic cylinder 72 with ram movement proportional to pilot valve movement, a direct connection between ram and pilot valve providing feedback. The pilot valve is coupled to an electric motor 73 which is controlled in a manner similar to that providing longitudinal motion. The input setting is upon a manual rotary potential divider and the position is indicated by a potential divider 75 rotated by rack-and-pinion drive from the ram. Rotational control.-The peel 17 is rotated by an hydraulic motor 76, Fig. 1, which also drives a selsyn 81 and a tacho-generator 79. The motor 76 is controlled by solenoid-operated valves which in turn are controlled by relays similar to 43, 44, Fig. 4. Relay control is effected by a setting selsyn 82, Fig. 5, opposed by selsyn 81, the difference voltage being applied to terminal 28 of a circuit similar to Fig. 4. The tacho-generator output is applied to terminal 26 as before and the peel 17 is driven until the difference is minimized. The selsyns 81, 82 are wired with a differential selsyn 90 as shown in Fig. 6. The initial setting of the peel is adjusted by the operation of a dial 91. A further control circuit, Fig. 5, enables the setting synchro 82, and hence the peel 17, to turn in one direction through one of a number of predetermined angles. The angular movement is selected by a four-position multipole switch SW1, SW2, SW3 and SW4. If the arm is placed at 15 degrees, and a button PB depressed, relay P is energized and, after a short delay, opens contacts P1. During the delay a circuit is completed from terminal 85, via button PB, contacts P1, SW1, SW2 a uniselector coil Z, interrupter contacts IC to a terminal 86. This causes stepping of the uniselector whereby the wipers in levels Z 1 , Z 2 complete a holding circuit to coil Z and contacts IC. Also, a solenoid Y receives four pulses and a ratchetwheel 83 is rotated through four teeth, setting the selsyn 82. After the uniselector has rotated through four steps wipers in levels Z 1 , Z 2 reach an unmarked contact and the stepping circuit is broken. Stepping occurs in a similar manner when other angles of rotation are selected through switches SW1-SW4. The foregoing movements may be initiated by cam-controlled switches or by the operation of relays by one movement to initiate a further movement. Specifications 874,908 and 874,909 are referred to.