Moiré Fringe Signal Subdivision System of a Stained Code Disc of a Grating Displacement Sensor

When a code disk of a displacement sensor is exposed to dust or other impurities, it causes distortion of the grating moiré fringe signal, and thereby provides wrong displacement information from the sensor. Therefore, it is necessary to analyze the distortion in the reading due to the stains. In this paper, multiple reading heads were used to collect the moiré fringe signal of the sensor and were evenly distributed on the fine code channel. Each reading head was used to subdivide the moiré fringe signal collected by it, calculate the signal amplitude value corresponding to each sampling point, and analyze the stains of the code disk corresponding to the reading head according to the signal amplitude value. According to the stains of the code disk, the subdivision value of each reading head was considered to have a certain weight. It was found that when the reading head is stained, the weight decreases, whereas when it is clean, the weight increases. Finally, the weighted average value of the two reading heads was taken as the final subdivision value of the sensor. The experimental results showed that the system provides output with high-precision displacement values even when the moiré fringe signal was abnormal due to the local stains of the sensor’s code disk, therefore it significantly increases the anti-stain ability of the sensor.