A new 4 DOF parallel mechanism with serial input limb is presented ——2UPS-RPU parallel mechanism, the limb with serial input is a less contrained active branched-chain,the number of its DOF is less than six,that is to say,the limbs not only transmitting driving force but also constraint force at the same time.Compared with traditional parallel mechanisms,the mechanism with serial input has greater number of DOF than the number of limbs and don’t lose the property of parallel mechanism. The inverse solutions to positions of the mechanism are modeled by inverse kinematic analysis in this paper, then the constraint conditions are established according to factors influencing the workspace of parallel mechanism,such as the limits of the hinge angle and the parallel link length.The workspace of 2UPS-RPU parallel mechanism can be obtained by using exetreme-boundary numerical algorithm in Matlab,the volume of workspace can be quantified by means of computation,and analyzing the impact of rod length ,circumradius of moving and fixed platform and motion pair rotation angle on the workspace.
Inverse dynamic equations of the 2UPS-2RPS mechanism are formulated by utilizing the virtual work principle. Kinematic analysis of the mechanism is presented, on the basis of which the Jacobian matrices of the limbs and the mechanism are deduced. By combining the dynamics of the limbs and the moving-platform, the inverse dynamic model of the mechanism is obtained. Finally a computer simulation is carried out to demonstrate the dynamic analysis of the moving platform.
The forward kinematics of manipulator was studied to analyze the positive position of the novel 2UPS-RPU parallel mechanism with series connection inputs. With the restrict condition of the lengths of three actuated limbs as constraint conditions, the constrained equations were established, and the four nonlinear equations were obtained to solve forward positional problems of the mechanism. Based on the elimination method, a two-dimensional equation is obtained by eliminating the four-dimensional equation. The search method based on the least square method of the MATLAB software was utilized to analyze forward position of 2UPS-RPU parallel mechanism. The results of numerical verification showed that through this method all forward solutions can be found which are basically coincident with the inverse ones, and the little error was caused by the accumulating calculation error. An error model was established based on differential theory and kinematics equations .This model simplified the installation error as the manufacturing error. Finally the error value was obtained by MATLAB ,which proved the error model was correct.
A new parallel kinematic machine UPS-2RPS with serial input limb is presented, the topological structure characteristics are described. The mathematic model of inverse position solution is derived. The workspace of the mechanism is analyzed and researched by results of MATLAB and Pro/E simulation, The research will be of great significance to promote its novation, application and spread .
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