Error modeling of a novel flexible lunar sampler

A lunar sampler plays the critical role and is of great importance in lunar explorations. In this paper, an error model was established for a novel flexible lunar sampler which has low weight, small volume, large workspace, and low power consumption. Based on its specific configuration, the forward and inverse kinematic models and the kinetostatic model are developed to formulate the volumetric error model of the mechanism. The error model is built by considering three classes of error sources: flexibility-induced errors, structural parameter-induced errors, and joint clearance errors. The flexible errors are compensated according to the experimental data; the second class of errors are modeled based on complete differential-coefficient theory, while the third class of errors are modeled based on the deterministic method. For the third class in error modeling, contact modes are introduced to build a joint clearance-induced error model. The relationship between different error sources and the output pose error of the sampling head is obtained. Finally, the error distribution in the workspace is evaluated.