New interpolation method for quadrature encoder signals

Abstract

This paper presents a new interpolation method suitable for increasing the measurement resolution obtainable from quadrature encoder signals. Based on the existing sinusoidal signals, high-order sinusoids can be derived, from which binary pulses can be generated, which can be decoded using only standard servo controllers for position information. A look-up table, constructed off-line, serves as the inferencing engine for the proposed method. Imperfections in the encoder signals can be directly compensated for in the look-up table, including mean and phase offsets, amplitude difference, and waveform distortion. Simulation and experimental results are provided in this paper.