Patent GB-785612-A (GB)
Title: Improvements in or relating to electrical integrating systems
IPC: G06G7/188
Filed: 1954-07-09
Abstract: 785,612. Analogue electric calculating systems. SOC. D'ELECTRONIQUE ET D'AUTOMATISME. July 9, 1954 [July 10, 1953], No. 20181/54. Class 37. Apparatus integrating an input signal comprises a servomotor-amplifier arrangement driving an output shaft, whose angular position represents the required integrand, in response to the input signal and a corrective signal fed back to the amplifier input, which is obtained from the algebraic sum of an output signal electrically derived from the position of the motor shaft and an output signal from an electronic circuit which also integrates the input signal over a limited range. Fig. 1 shows an integrating system wherein a unidirectional time variable voltage signal analogous to the input function energizes over resistance 2 an amplifier 3 controlling the excitation and sense of rotation of a bi-directional servomotor 4, which drives an output shaft 7 together with a tachometer generator 5 supplying a retro-active velocity voltage to the amplifier input. Shaft 7 drives the sliders of potentiometers 14, 15 having annular resistive stators whose terminal gaps are mutually displaced 180 degrees; the moving contacts of rotary switches 27, 28 each comprising a single narrow segmental contact angularly coincidental with each respective potentiometer gap; and also the moving contacts of rotary switches each comprising a segmental contact having a gap angularly coincidental with each respective potentiometer gap. The input signal also energizes a pair of electronic integrating circuits comprising high gain amplifiers 9, 12 with series input resistances 8, 11 and degenerative feedback capacitances 10, 13, short-circuitable respectively by switches 27, 28; the outputs being combined at the inputs of degenerative amplifiers 18, 22 to produce difference signals which are connected over switches 24, 25, common channel 37, and resistance 26 to the servo-amplifier input. The difference signals are also applied to energize threshold relays 29, 32 (which may respectively comprise double wound relays with holding contacts whose windings are energizable through oppositely poled and biased unidirectional conduting elements to operate at an input voltage +E and return to normal at an input voltage - E). Initially, the relays are inoperative and their contacts connect potentiometers 14, 15 to voltages (- E, O) and (O, - E) respectively, while the input signal is assumed to be positive and the servo-system at rest. The shaft 7 is rotated anticlockwise (35), the output voltages from integrating amplifiers 9, 10 vary from O towards - E, and the slider voltage of potentiometers 14, 15 vary from - E towards O. Switch 28 closes to short-circuit and restart integrating amplifier 12 and during its closure the slider of potentiometer 15 crosses its gap to develop a voltage - E. Relay 32 then receives a voltage +E from amplifier 22, operates and holds over contacts (not shown), and reverses the energization of potentiometer 15 so that its slider voltage varies from O to + E with shaft rotation. Switch 27 closes after 180 degrees further rotation to short-circuit and restart integrating amplifier 9, while the slider of potentiometer 14 crosses its gap to develop a voltage - E. Relay 29 then receives a voltage +E from amplifier 18 and reverses the energization of potentiometer 14. The outputs of amplifiers 18, 22 are connected to a common channel 37 over switches 24, 25 (which are continuously closed except when corresponding switches 27, 28 are closed and the sliders of potentiometers 14, 15 are traversing the stator gaps) to develop a signal fed back to the servo-amplifier input to compensate for errors due to the operative threshold and limited frequency response of the servosystem, so that the angular rotation of shaft 7 represents the integrated value of the input function, and integration proceeds until the sign of the input signal changes. On arrival of an initial negative input signal, shaft 7 is rotated clockwise (36) so that the voltage of potentiometer slider 14 varies from O towards - E and the output of integrating amplifier 9 varies from O towards +E. As the slider crosses the potentiometer gap to a point of zero voltage, switch 27 short-circuits and restarts integrating amplifier 9, while subsequently the voltage of potentiometer slider 14 and the output of integrating amplifier 12 also varies from O to - E and as the slider crosses the potentiometer gap to assume zero voltage, switch 28 similarly short-circuits and restarts integrating amplifier 12. Relays 29, 32 remain inoperative in their initial positions, so that integration proceeds as before. Change of input sign during the progress of integration initiates reversal of the rotation of shaft 7 and reversal of relays 29, 32 to energize the potentiometers in appropriate senses, so that the total angular rotation of the output shaft 7 over a period of time is proportional to the integral with respect to time of the input function. Rotary switches 27, 28, 24, 25 are replaceable by cam-operated micro-switches and the correction signal on channel 37 may be applied to the servo-amplifier input through a capacitance (Fig. 2, not shown).