Speed and Position Measurement of Rotating Machinery With a Triangular Pattern Vision Encoder

The measurement of the position and speed of rotating machinery is essential in the manufacturing industry in order to effectively control a process. Traditional measurement methods such as encoders, resolvers, and tachometers are limited to a single rotating element, require precise (mechanical) installation, and measure on the motor shaft rather than the load. This article proposes a novel methodology to overcome the shortcomings of conventional sensors with a triangular pattern vision encoder. The approach uses single pixellines in combination with a triangular pattern applied to a roller to capture the position and speed of one or more axes simultaneously. First, a preprocessing step detects the position of a roller in the frame. Second, the width of the triangle is detected and mapped to accurately measure the position of the roller. The main contributions are improved robustness compared to state-of-the-art techniques, straightforward multitarget velocity analysis, and the integration of FDZP as a subpixel technique. The proposed design is validated on an industrial web processing machine (WPM) and achieves an accuracy of $480~\mu $ rad, an improvement of approximately 38% over the benchmark incremental optical encoder, which achieves an accuracy of $770~\mu $ rad.