Coherent detection circuit for high precision encoders

Abstract

Robots and industrial machines today requires high precision of 0.1 /spl mu/m, high speed of 30-60 m/min, and durability for position sensing. Moreover, being compact in size and low in price is indispensable for practical applications. Inductosyn scale is one of the most widely used position sensors. It can attain either required precision or speed, however, not both of them at the same time. We propose, in this paper, a new coherent detection circuit, which enables them. The coherent detection circuit senses the amplitude of the induced carrier signals by digitizing and integrating them. It enables fast and high precision detection. In addition, the circuit can be implemented in a single chip ASIC, which guarantees compact size and low price. We prototyped a test system and executed necessary experiments, and made sure that our proposed technique worked as was designed and achieved our goals, 0.1 /spl mu/m precision, sensing speed of 41 m/min, on a robustly structured system.