Precise method for linearizing sine and cosine signals in resolvers and quadrature encoders applications

Resolvers and quadrature encoders provide electrical signal related to the sine and cosine of the mechanical shaft angle over the full 360 degree range. A converter is described for the linearization of these signals, enabling the angle to be determined using simple linear equations. The converter is based upon the difference between the absolute values of the transducer signals, together with a dedicated linearization technique. The converter provides a nearly perfect triangular signal from which the angle is determined unambiguously over the full range. The theoretical error of non-linearity may be cut down to 7/spl times/10/sup -4/degree. The principle and theory of operation, and computer simulation are given. The converter, full details of which are given, has been implemented using analogue electronic circuitry. The practical performance of the converter has been evaluated using a PC-based test rig. The converter was successfully tested with a commercial resolver. The experimental results obtained are in excellent agreement with theory and simulation.