Patent GB-1000278-A (GB)
Title: Displacement measuring device
Filed: 1962-02-20
Abstract: 1,000,278. Measuring linear and angular displacement electrically. S. G. DEHN. (Telecomputing Corporation). Feb. 20,1962,No. 6563/62. Heading G1N. Relates to a transducer or resolver, having a phase modulated electrical output, responsive to relative angular or linear displacement of its two co-operating electrically coupled members, the mechanical displacement being proportional to electrical phase shift between a high frequency reference signal and a second high frequency output signal therefrom- Resolver construction Figs 1, 2, 3. A resolver to measure angular displacement comprises a stator 21 of glass or plastics secured to a standard 26, and a rotor 22 of similar material rotatable with a shaft 29. Conductive patterns 33, 31 eg. copper are formed respectively on the stator and rotor adjacent faces. Concentric rows of openings 42, 43, 45, 47 in the rotor pattern define concentric rows of rotor bars 40, 41, 44, 46 joined by concentric rings 35 to 39. There are 200 conductor bars in each of the radially outer two rows and 198 bars in each of the inner two rows. The stator pattern (Fig. 3) has five concentric conductor rings 48 to 52 each insulated from the rest of the pattern by annular spaces 53, 54 (detailed in Fig. 4). Located between the rings 48, 49 are conductive elements 55, 56 insulated from one another by a sinusoidally shaped spacer 57. Likewise a sinusoidal shaped space 60, 90 electrical degrees out of phase with those of space 57, define conductive elements 58, 59. The elements 55, 56, 58, 59 form one part of the stator pattern wherein there are 200 sinusoids (one sinusoid per 360 electrical degrees). The other part of the stator pattern including elements 61, 62, 64, 65 is similarly formed but has 198 sinusoids. Operation. In operation the conductive elements of the one part of the stator are connected to a 30 Kc source while those of the other part are connected to a 20 Kc source and the signal outputs are taken from the rings 48 to 52, the rotor bars electrostatically coupling the stator elements to the rings. Rotation of the rotor shaft varies the amount of overlap of the rotor bars with each stator element (Fig. 6 not shown) such that the output from each varies, and the resultant output vector rotates accordingly (Figs. 7 to 10 not shown) from an initial reference point. Due to the difference in the number of sinusoids and rotor bars on each said part, the resultant output vector of the said other part becomes increasingly out of phase with the resultant vector of the one part, (100 revolutions to 98 revolutions of the vector of the other part for each 180 mechanical degrees of the shaft), and the phase shift is taken as a measure of the angular displacement of the shaft (illustrated graphically Fig. 11 not shown). The stator outputs are combined and the composite signal I (Fig. 4) is fed to a filter (Fig. 12 not shown) which separates the 30 Kc component from the 20 Kc component. The 30 Kc component is fed to a mixer hetrodyned by a 50 Kc source and the output therefrom together with the original 20 Kc reference component is fed to a phase detector. In a second embodiment (Figs. 13 to 16 not shown) particularly for linear displacements the conductive patterns of the resolver are linearly disposed and are electromagnetically coupled. Coarse and fine signal outputs can be obtained from the resolver.