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Study of a measurement system and a method for determining the distance between the grooves of a hydraulic valve

Hydraulic valves are critical control components of hydraulic systems. To ensure hydraulic control systems are accurate, the distance between the grooves of hydraulic valves should be measured. This distance critically impacts how much oil is fed. In previous measurements, a coordinate-measuring machine or a universal tool microscope were applied. However, these two methods exhibited low measuring precision in terms of center eccentricity, incorrect initial position, boresight error, etc. In the present study, a high-precision non-contact automatic instrument is developed that solves chord length and uses a machine-vision technique to determine distance. Besides, an angle-compensation method is proposed to remedy the boresight error attributed to motion control in a closed-loop system. Moreover, an eccentricity-correction method is put forward to correct the angular error attributed to the eccentricity of the measurement system, enhancing measurement precision. As revealed by the experimental results, the maximum limit error of a single measurement is less than 3.3 μ m , verifying the feasibility of the novel instrument.