Error compensation strategy with high installation tolerance for angle encoders

Radial error (comprising eccentricity error and runout error) and graduation error of circular scales are the primary sources of error for angle encoders. This paper presents a compensation strategy for radial error and graduation error with a high installation tolerance, achieved through the utilization of three measurement heads and one calibration head. Three reading heads, evenly distributed, are employed to compensate for radial error and non-3k order graduation error, while one reading head, positioned in a specific arrangement, serves to identify 3k order errors for compensation purposes. To mitigate the installation tolerance requirements of reading heads, this study employs two methods. Firstly, it investigates the impact of reading head position deviation on compensating radial error and proposes a method for compensating residual radial error. Secondly, it utilizes the Monte Carlo method to assess the effect of reading head position deviation on identifying graduation error when the maximum deviation is ±1°. The simulation and experimental results confirm that the proposed method effectively compensates for radial error and the first 10-order graduation error within a position deviation range of ±1°. Based on the experimental results, this method demonstrates superior compensation accuracy, achieving an error of 0.44″, compared to evenly distributing three reading heads (0.53″) and four reading heads (0.85″). Additionally, when compared to the combination method of evenly distributing three and four reading heads (0.47″), it provides similar compensation accuracy while utilizing fewer reading heads.