Path accuracy analysis of industrial robot based on continuous dynamic time warping algorithm

Path accuracy is the key index for measuring the motion performance of industrial robots. The relevant standards are formulated for the detection and evaluation of industrial robots locally and abroad. Owing to deviation in robot movement, the sampling frequency of the measurement system and the measurement error during the detection process, mapping errors between the theoretical and the actual trajectory may arise. In this paper, we analyze in detail the methods for evaluation of path accuracy in domestic and foreign standards, propose the application of the dynamic time warping (DTW) method to the path analysis of industrial robots, present how we realize the continuity of the DTW method by developing an interpolation model to improve the accuracy of the algorithm, and analyze the effect of the robot movement speed and sampling frequency of the measurement system on the path mapping method. The experimental results showed that, when compared with the path accuracy of the ISO standard method, that of the continuous DTW (CDTW) algorithm improved by 73%, the standard deviation decreased by 86%, and the overall error fluctuation decreased significantly. The ISO standard method and the DTW algorithm can be well applied to the accuracy evaluation of a linear path. For the corner path, the ISO method has obvious mapping errors, whereas the DTW algorithm solves the mapping error. However, owing to the effect of the robot motion speed and to the sampling frequency of the measurement system, there is a multi-point mapping problem. The CDTW algorithm effectively solves this problem and improves the path accuracy.