Position Measurement Using Sinusoidal Encoders and All-Analog PLL Converter with Improved Dynamic Performance

Abstract

This paper describes a phase-locked loop (PLL) converter with improved dynamic response for the determination of mechanical angle from sinusoidal encoders and resolvers. PLL converters are tracking-type converters that use the sine and cosine signals of the transducer in a closed-loop arrangement aiming to match an estimated output angle to the true angle encoded in the sine and cosine input signals. Such a scheme requires means to determine the sine and cosine of the estimated output angle; conventional converters achieve this by using voltage-controlled oscillators, digital-to-analog converter (DAC), counter, and lookup tables. The proposed converter simplifies implementation by making use of the estimated output angle signal to approximate its sine and cosine using analog triangle-sine conversion technique. A new method is also proposed to enhance the dynamic performance of the converter enabling near instantaneous response. This paper describes the proposed method, full details of its analog implementation, and experimental results. Results demonstrate agreement with theory and computer simulation.