A novel amplitude-to-phase converter for sine/cosine position transducers

Resolvers and various other types of sine/cosine encoders are used for both angular and linear position sensing. These devices provide analogue signals in the form of the sine and the cosine of an angle theta related to the position of the moving part of the transducer. A novel converter is described for the linearization of the sensor signals. The scheme converts the co-sinusoids into a nearly perfect triangular signal from which theta is determined using simple linear equation. The proposed converter makes use of the alternating pseudo-linear segments of the sensor signals, together with a dedicated and simple linearization technique to further improve the linearity of these segments. This enables unambiguous determination of theta over the full 360 degree range, with an absolute error of non-linearity of 0.041 degree. The conversion technique may be implemented numerically or electronically. The proposed converter was built using basic analogue electronic circuitry, and was successfully tested using both an electronic transducer model and a commercial resolver. The principle and theory of operation, computer simulation, and experimental results are given.