Study For Kinematic Performance Of Spatial 6-DOF Position And Orientation Adjusting Platform

To accurately complete the adjustment for the optical modules in 6-DOF space, a spatial 6-DOF position and orientation adjusting platform is introduced in this paper. This platform is designed based on the precise assembling and calibrating procedure of optical modules. Regarding the characteristics of serial and parallel mechanism, a combination of 3-SPS/PU parallel mechanism and 3-PPR parallel mechanism is proposed. According to qualifications in assembling and calibrating of optical modules, this study in kinematic performance of spatial 6-DOF position and orientation adjusting platform is launched. The main contents of this paper are as follows:According to qualifications in precise assembling and calibrating, six functions of the mechanism are decomposed. The platform is serial with 3-SPS/PU parallel mechanism on the top and 3-PPR parallel mechanism on the bottom. This mechanism is illustrated with geometrograph, showing both of their working modes. The degree of freedom is calculated with screw theory, for the purpose of kinematic analysis.Based on the coordinate transformation theory, inverse position solution of 3-SPS/PU parallel mechanism could be obtained by analytical method and forward position solution of 3-SPS/PU parallel mechanism could be obtained by Newton iterative method. The precision of results calculated by Newton iterative method satisfies the requirements of the accuracy in assembling and calibrating. According to 3-PPR parallel mechanism, the forward and inverse position solutions are both obtained by analytical method. The simulating results by ADAMS and calculating results by MATLAB are compared in order to testify the correctness of kinematics mathematical models.The constrained conditions in workspace of 3-SPS/PU parallel mechanism and 3-PPR parallel mechanism are analyzed. Based on the numerical integrating method, workspace performance atlas is plotted with MATLAB. The pattern of the workspace as position and orientation parameters vary is obtained, then the extreme values of the motion in each DOF could be known. The study in the influence of mechanisms' structural dimensions onto the workspace is useful in the optimization of this mechanism.Based on the inverse position mathematical models of 3-SPS/PU parallel mechanism and 3-PPR parallel mechanism, Jacobian matrix could be derived by differential operations. In order to measure the dexterity of the mechanism from the whole picture, the global condition index is selected. The performance atlas is plotted with MATLAB, from which the variation of the global condition index with the change of structural dimensions could be obtained. This relationship is useful in the optimization in the structure of the mechanism.