Patent GB-696283-A (GB)
Title: Improvements in apparatus for electrical resolution of vectors
IPC: G06G7/22
Filed: 1949-10-31
Abstract: 696,283. Electric analogue calculating systems. LANGHAM, E. M., BELL, J., and BUCKINGHAM, J. Dec. 13, 1950 [Oct. 31, 1949], No. 27811/49. Class 37. Apparatus for electromechanical resolution of vectors comprises a relatively rotatable stator and rotor, both having biphase inductive windings which are sine distributed so that a current therein would produce a flux sinusoidally distributed with respect to the appropriate winding axis in a uniform magnetic circuit, and are applicable to the measurement of the magnitude and phase of the flux linking each winding; each such rotor or stator winding having a coaxial duplicate winding not necessarily sinusoidally distributed whereby errors in resolution due to, e.g. flux distribution irregularities are compensated by energization of the respective duplicate windings from high-gain amplifiers controlled by the differences between datum voltages and the appropriate outputs of the corresponding sinusoidally distributed windings. In an electro-mechanical resolver (Fig. 1) duplicated biphase windings 1, 1A; 2, 2A are wound on a cylindrical laminated stator and a similar rotor is wound with biphase windings 1R, 2R. The windings may be sinusoidally distributed so that currents therein produce a sinusoidally disposed flux circumferentially of the rotor and stator, and if winding 1 is excited by a voltage VI, a voltage VIA appears across winding 1A, and voltages appear across the rotor windings where # is the angle between the stator and rotor axes. A magnitude and phase error occurring between V1 and VIA due to the non-linear permeability of the magnetic circuit with variable excitation, and the temperature coefficient of the windings, is eliminated (Fig. 4) by exciting winding 1A from a datum voltage in series with a null indicator, and varying the amplitude and phase of the excitation of winding 1 until the null indicator shows zero, when the flux linking winding 1A accurately corresponds in magnitude and phase to the datum voltage. If windings 2, 2A are similarly excited, and if both sets of stator windings are excited together in this way In the latter case, a further error due to spurious high permeability axes arising in manufacture of the core material is removed (Fig. 6) by energizing the pairs of stator windings respectively from voltages VA, VB in series with windings 1A, 1B and the inputs of high gain amplifiers energizing windings 1, 2 in such senses that the voltages induced into windings 1A, 1B are degenerative of the input voltages VA, VB. Then VA is approximately equal to V1A and VB to V2A, and the phase error is accordingly eliminated. If VB is zero, and if windings 1R and 1A are interchanged it is shown that The resolver stator inputs may be energized in quadrature to produce a precisely-defined rotating field, so that if 6 is the angle between the axes of 1R and 1A, the voltage V1R is shifted in phase by #, referred to VIA. The rotor and stator windings may be interchanged, and the duplicate windings 1, 2 need not necessarily be sinusoidally distributed. Applications of the device to the transformation of polar and cartesian co-ordinates, and the transformation of cartesian co-ordinates to new axes displaced by 6 are described.