GB883737A - Digital control system for positioning shafts - Google Patents

Abstract

883,737. Programmed electric control systems. SOC. D'ELECTRONIQUE ET D'AUTOMATISME S.A. Dec. 14, 1959 [Dec. 19, 1958], No. 42389/59. Class 38 (6). The angular position of a shaft is controlled from a binary coded record by first positioning an auxiliary shaft which carries a coding disc until the outputs of the disc and the record coincide; and then rotating the main shaft until it coincides with the auxiliary shaft. The desired sequence of shaft positions is recorded on a punched tape 12, as follows. In the first row of 5 bits, a signal in the 5th column indicates the direction of rotation, the remaining 4 columns remaining blank. The second row contains the " tens " of a decimal number using a 4-bit binary code. The third row similarly contains the " units." The arrangement then repeats as desired. The shaft thus has 100 possible angular settings. The " excess 3 " code is used, i.e. zero is expressed as conventional binary 3, one as conventional 4, &c. The direction of rotation signal amplified at 16 is stored at 17 and also controls a reversing relay 29 controlling a motor 4 which drives the auxiliary shaft 3. Auxiliary shaft 3 carries a coding disc 9, which is rotatable past eight photo-electric readers 11. The disc, Fig. 2 (not shown), is divided in 100 sectors numbered in the reflected binary code. The four inner code rings defining the " tens " and the outer four rings the " units." The outputs of the " tens " readers are passed by gates 22 to a coincidence comparator 20 for comparison with the " tens " output of the tape reader. This output is first converted from the excess 3 binary code to the reflected binary code at 19. Any output from comparator 20 causes motor 4 to rotate the disc 9 into coincidence. The tape 12 is then moved and the " units " read, and gates 23 are closed so that the " units " from the disc are read, and the motor 4 is again energized until the disc 9 is in coincidence. The tape 12 is again moved on and the next direction of rotation sign read and stored. The original direction of rotation sign moves on to an auxiliary store 33 to control a reversing relay 35 for the motor 2 driving the main shaft 1. A gate 38 is now rendered conductive and the motor 2 drives shaft 1 until light from a source 7 falls on a photo-diode 8 through an index slot in a further disc 5 also on shaft 3 so that shafts 1 and 3 are in coincidence. The diode 8 then renders gate 38 non-conducting and also applies a transfer pulse to a gate 18 so that the tape 12 steps forward to the next "tens " instruction and the cycle repeats.