The Kinematics Of A Nevol 4-DOF 3-RRUR Parallel Robot

Compared with the general 6-DOF (degrees of freedom) parallel mechanism, lower-mobility parallel mechanisms have advantages of less components, larger workspace, simpler controlling and lower cost in design and manufacturing so that it has been a hot subject and has great potentials in practical application. However, compared with the 2 or 3-DOF parallel mechanisms, 4 or 5-DOF parallel mechanisms have been just begin, which limit the development and application of this kind of parallel mechanism to some extent. 4 or 5-DOF parallel mechanisms, especially symmetric ones, with identical branch, symmetric construction, isotropy have great applicable potentiality. This paper focuses on the kinematic analyze of a novel symmetric 4-DOF 3-RRUR parallel robot.First, the restrict equations of this mechanism based on analyzing the mechanism model were be set up, then the accuracy of choosing input is considered based on Screw Theory. The forward and inverse kinematics of this mechanism are solved according to the restrict equation.Based on the mechanism model, we considered the interference between the limbs and the base platform. In this paper, we presented five conditions for searching 3-RRUR parallel robot's workspace. A flow chart about the condition of the interference between the limbs and base platform for searching the workspace was given, the corresponding profile chart and graphic model are showed. To meet the project application, the concept of thorough workspace was presented, then analyzed the thoroughness of this mechanism and it is confirmed。Then the Jacobian matrix and quadratic matrix of 3-RRUR parallel mechanism are established by using the method called imaginary mechanism, then establish the velocity equation, and find the input velocity change rule under the condition of uniform motion of the motion platform. The numerical examples of velocity and acceleration are given, and the corresponding curves typical input was shown, they illustrate the kinematics characteristics. Finally, this kinematics of the 4-DOF parallel mechanism is simulated by using dymamic simulative software.The research work of this thesis establishes theoretical basis for the further research of the four-DOF parallel mechanism practically and give the theoretical support for the future application.