Patent GB-1157328-A (GB)
Title: Electronic Analog Resolver
IPC: G06G7/22
Filed: 1966-07-12
Abstract: 1,157,328. Electronic resolvers. GENERAL ELECTRIC CO. 12 July, 1966 [12 July, 1965], No. 31354/66. Heading G4G. In an electronic analogue resolver (Fig. 2) input signals V x , V Y  proportional to co-ordinate variables x, y of initial conditions are set into integrators 10, 20 over switches 11, 21. A timing generator 34 responsive to a clock frequency fc synchronizes a logic circuit 19 comprising input controls 16, 26; rotation controls 17, 27 and output controls 18, 28 for operation over successive time periods T 1 , T 2 , T 3  and over T 1  switches 11, 21 are closed by the input controls so that the integrators are set to receive input signals V X , Y Y  y. (Fig. 3). Over T 2 , switches 12, 22 are closed by the rotation controls while 11, 21 are opened, and the integrators are thus connected as harmonic oscillator elements in a closed loop over inverter 30, and the loop oscillates from the initial conditions set by integrator outputs V X 1, Y Y <SP>1</SP> in accordance with differential equation X = KX. It is shown that where R, C are integrator resistances and capacitances, so that frequency is determined by integrator time constants, amplitude and phase are determined by initial signals V X , Y Y , and the outputs of integrators 10, 20 determine the orthogonal components of vector R, which rotates due to their sinusoidal variations. Vectorial rotation through an angle A is obtained by closing the loop for time interval t A  proportional thereto, determined by a pulse signal applied to rotation controls 17, 27. During rotation the integrators generate signals representing V X <SP>1</SP>, Y Y <SP>1</SP> and by the initial insertion thereof a vector and an angle are introduced. By rotation until V X <SP>1</SP> = 0, #|R| = V Y <SP>1</SP> and # = #t, so that the time of rotation during the interval T 2  for V X <SP>1</SP> to change from the initial value to zero, represents the polar co-ordinate #. Zero detector 14 responsive to the output of integrator 10 at V X <SP>1</SP> = 0, terminates rotational oscillation and develops a pulse width signal t X  by switching a reference voltage V R  to the output. During interval T 3 , output control 28 closes switch 23 to derive a pulse width signal t 1  of duration proportional to polar co-ordinate #|R| = V Y <SP>1</SP>, and also switches a reference voltage V R  to discharge integrator 20 at the beginning of the interval. Zero detector 24 senses the discharged condition, at which V Y <SP>1</SP> = 0 and terminates the output pulse. Thus intervals t 1  and t 2  represent the components of the rotating vector, in R and #. For co-ordinate rotation, input signals V X , V Y  are connected to the input of integrators 10, 20 over T, and the integrated voltages V X <SP>1</SP>, V Y <SP>1</SP> increase at gradients proportionally to V X , V Y  until the end of the period, when and during T 2  the integrators and the inverter oscillate to generate sine and cosine waveforms for a time established by a pulse width input signal tA representing the angle of rotation. V X <SP>1</SP>, V Y <SP>1</SP> remain constant from the end of t A  to the end of T 2 , since the loop is then opened and no inputs are connected. Reference voltages V R  are connected to the integrators by closure of 13, 23 at the beginning of T 3  to reduce V X 1, V Y <SP>2</SP> to zero, as detected at 14, 26, so that time durations from beginning of T 3  to the zero instant for V X <SP>1</SP>, V Y <SP>1</SP> are given by which show range and angle of the rotated co-ordinates; V X <SP>1</SP> and V Y <SP>1</SP> being values of V X 1 2 2 and V Y <SP>1</SP> at end of period T 2 . Switching may be effected by transistors controlled by NOR gating circuits, and the zero detectors comprise conventional differential amplifiers with feedback over parallel oppositely poled diodes, whose output signals are inverted and applied to a set reset flip-flop over a NOR gate. Signals R, V control operation for vectorial rotation and for rectangular to polar co-ordinate conversion. Hyperbolic functions are generable by by-passing invertor 30, so that the rotating vector is given by R = (X<SP>2</SP> - Y<SP>2</SP>)¢ and angle A by For sine and cosine generation one integrator is supplied with a reference voltage, the other with zero voltage, and the rotational time defined by pulse width t A  represents the angle, so that the final condition readout represents the required sine and cosine.