Patent GB-772089-A (GB)
Title: Improvements in apparatus for analog computation
IPC: G06G7/20
Filed: 1954-07-09
Abstract: 772,089. Electric analogue calculating systems. BENDIX AVIATION CORPORATION. July 9, 1954 [July 17, 1953; Sept. 24, 1953], No. 20183/54. Class 37. An electric analogue computer determining the proportional unknown z to three known quanwx tities w, x, y in the monomial expression z =  y comprises two rotationally variable coupling transformers having identical laws (which may be sinusoidal) each having a stator and a rotor wherein the first rotor is energized by an alternating voltage analogous to y, the second rotor ganged for common movement with the first is energized by an alternating voltage analogous to x, and the first stator is energized by an alternating voltage analogous to w so that, when the common rotors are adjusted to a position such that the analogue voltage of w is equal to and balanced by the voltage induced in the first stator from the first rotor, the voltage developed by the second stator winding is the analogue of the unknown z, which by assigning appropriate values to wand y may be made to represent #x or x<SP>2</SP>. In an extension according to the same principle, n variable transformers are provided with ganged rotors and the first stator is energized by analogue voltage u 1  to develop a first rotor analogue voltage u 2  energizing the second stator to develop a second rotor analogue voltage u 3  which energizes the third stator, and so on in sequence, until a rotor analogue voltage un of the (n - 1 )th transformer energizes the stator of the nth transformer to develop an nth rotor analogue voltage w; the common rotors being adjustable to a position such that w is equated to unity voltage, at, which it is shown that where u j , u k  are the voltages appearing across the rotors of any arbitrarily selected transformer numbered (j - 1) and (k - 1) so that multiple powers and roots of x may be computed. In Fig. 1, two identical rotationally variable transformers of sinusoidal law have stators 12, 13 and ganged rotors 14, 15 driven by a 2-phase induction motor 17 over shaft 16. The rotors are respectively energized by analogue voltages x and y derived from A.C. energized potentiometers 22, 23 over normally positioned 2-way switches 24, 25, and stator 12 is supplied with analogue voltage w from A.C. energized potentiometer 20 in series with the input of amplifier 19 energizing the control winding of motor 17 and in subtractive opposition to the voltage induced in the stator by the rotor excitation, whereby the motor runs to a position of the rotors at which w=y sin # and z=x sin #, where # is the angle between the stator axes and the normal to the rotor axis, and z is the output voltage developed by the stator 13, so that z = wx/y. Voltmeters 26, 27, 28, 29 measure the respective analogue voltages, while switches 24, 25 in their off-normal positions enable y to be made equal to z so that z = #wx and x to be made equal to w so that z = x<SP>2</SP>/y. The analogue voltages of w and y may be made equal to unity by potentiometers 20, 22 at which z = #x or x<SP>2</SP>, and in similar manner z = x/y, z = wx, and z =1/y may be computed. In a modification (Fig. 2) for 1 1 2 5 evaluating the powers -, -, -, -, 2 and 3 of a 3 2 3 2 variable, three identical rotationally variable transformers 30, 31, 32 of sinusoidal law have respective stators and rotors 33, 36; 34, 37; and 35, 38; the rotors being ganged for rotation by two-phase motor 42 into identical positions relative to their respective stators. Stator 35 is energized by the analogue voltage of variable x derived from A.C. energized potentiometer 39 indicated by voltmeter 43, and the corresponding'rotor 38 develops the analogue voltage of a variable y indicated by voltmeter 46 which also energizes stator 34. Corresponding rotor 37 develops the analogue voltage of a variable z indicated by voltmeter 45 which also energizes stator 33, and the corresponding rotor 36 develops a voltage which is balanced against the analogue voltage of a variable w, derived from A.C. energized rheostat 40 and indicated by voltmeter 44, at the input of amplifier 41 energizing the control winding of motor 42, which drives the ganged rotors to an angle # with the normals to the axes of the corresponding stators, at which balance is obtained and the motor stops. Then for transformers 30, 31, 32 respectively so that for adjustment of voltage w to the selected unitary value of the computation, and it follows that by adjustment of potentiometer 39 to give a required value of x on voltmeter 43 the values of 2/x<SP>3</SP>, 1/x<SP>3</SP> may be read off from voltmeters 46, 45; by adjustment of the potentiometer 39 to give a required value of y 1 3 on voltmeter 46 the values of y<SP>2</SP>, y<SP>2</SP> may be read off from voltmeters 45, 43; and by adjustment of the potentiometer 39 to give a required value of z on voltmeter 45, the values of z<SP>2</SP> and z<SP>3</SP> may be read off from voltmeters 46, 43. The apparatus may be structurally assembled with the voltmeters, input terminals, potentiometer, and rheostat mounted on a panel, and the motor and variable transformers mounted in vertical axial alignment on a base carrying the panel (Fig. 3, not shown). Input and output analogue voltages may be derived from and supplied to the elements of larger computing or control devices, and the variable transformers may follow any continuous law provided that they are identical.