High precision of 0.1μm, high speed of 30-60m/min, and durability are all required in position sensing for machine tools and robots, today. In addition, compact size and low price are necessary for practical use. Inductosyn scale is one of the most widely used position sensors; however, it does not attain both the precision and speed at the same time. In this paper, we propose new techniques, which achieve them.
Firstly, we propose a new coherent detection circuit, which detects the amplitude of the induced carrier signals by digitizing and integrating them. It enables fast and high precision detection. Secondly, to optimize the precision of the above detection, we proposed an automatic phase adjustment circuit, which adjusts the phase of the carrier signal so that the integration can obtain maximum dynamic range. Those circuits can be implemented in a single chip ASIC, which ensures compact size and low price.
We prototyped a test system, and confirmed, through several experiments that our new technique worked as was anticipated and accomplished our goals, sub-micron precision, sensing speed of 41m/min, on a solidly structured system.
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