| This thesis deals with the kinematic analysis, error modeling, parameter identification, source error analysis, error compensation and computer simulation of a novel reconfigurable hybrid robot—Tricept-IV. The following creative work has been completed.1) The inverse and forward position analysis of Tricept-IV is carried out using vector based method with the consideration of the redundant translational degree of freedom. The corresponding algorithm is programmed using numerical iterative method and proportional distribution principle.2) The orientation error vector of any passive joints in Tricept-IV robot can be decomposed to two parts—constant structural error vector and variable movable error vector. Using the above assumption, the linear mapping between the variable movable error vectors and all of the constant geometrical error parameters has been derived through the closed-loop constraint equations. Applying the linear mapping to one of kinematic chains of the robot, the full geometric error mapping model of the hybrid robot has been obtained.3) The laser tracker is employed to the error measurement and the corresponding parameter identification model is also formulated. According to the size of the source errors, the procedure of the parameter identification and compensation are divided into three steps to identify measurement coordinate system errors, the home position error of the robot and the geometric errors respectively. By analyzing the reduced row echelon form of parameter identification matrix, the source errors are separated to independent, relevant and zero ones. The strategy of the error compensation is carried out by modifying the system input.4) The locations and number of the measurement points is optimized using the condition number of the identification matrix as the evaluation index in order to achieve proper efficiency and robustness. The feasibility and effectiveness of the proposed kinematic calibration method is verified by simulation results. |
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