A Sinusoidal Encoder-to-Digital Converter Based on an Improved Tangent Method
Mohieddine Amor Benammar, Asem Khattab, Sharief Saleh, Fayçal Bensaali, Farid Touati · IEEE Sensors Journal · 2017
Sinusoidal encoders are used for the measurement of angular position and linear displacement. These provide electrical signals dependent on the sine and cosine of the position θ of their moving part relative to the stationary one. Conventional tangent/cotangent converters for determining θ from the encoder signals produce alternating highly non-linear segments of tangent and cotangent. Lookup tables are used for determining θ. This paper presents a novel converter for estimating θ without the lookup table. The method is based on dividing the circle angular interval into N sections. A crude or coarse measure θCof the unknown angle θ is first determined by identifying the section in which θ is located. This is followed by the determination of a fine measure θF. These measures are combined to yield a precise measure of θ; the maximum error of the method depends on N. The converter has been implemented on a dSPACE set and has been successfully tested both with a sensor emulator and a real Hall-Effect sinusoidal encoder. This paper describes full details of the theory, simulation, and experimental results. The experimental results demonstrate excellent agreement with theory and simulation.