Error modeling and simulation of open-chain linkage using virtual joint method

With the wide application of agricultural robots, their motion accuracy draws more and more attention. Conventional error models of linkage mechanisms are based on homogeneous transformation matrix differential. The limitation is that modeling process is cumbersome, and the error transformation matrix is not homogeneous. For this reason, using screw theory, the D-H parameters errors of open-chain linkage were treated as the result of equivalent virtual joint screw motion, and the error model was established. Meanwhile, the position and orientation error of output link were represented as prismatic and revolute pair screw motion, respectively, and its calculation formula were also given. As an example, the error simulation of PUMA560 was performed via Matlab programming. Furthermore, Adams’s simulation were used in verifying the established model, the difference between two methods was only 0.001 mm. The results indicate that the simulation method is effective and correct,the modeling process is simple and intuitive.