Optimal Design And Trajectory Planning Of An Orthogonal Four-degree-of-freedom High-speed Parallel Manipulator

With the application and development of parallel manipulators,especially the four-degree-of-freedom high-speed parallel manipulators,due to their compact structure,high work efficiency and flexible working environment,they have received extensive attention.Based on this,an orthogonal four-degree-of-freedom high-speed parallel manipulator is taken as the research object,and its structural principle,kinematics,dimension optimization and trajectory planning are analyzed and studied.The prototype and experimental verification of the manipulator are completed.According to the structure characteristics of the mechanism,the degree of freedom of the mechanism is analyzed.By changing the arrangement of the driving motor and the connection form of the connecting rod,a variety of derivative mechanisms are put forward.Finally,the kinematics characteristics of the mechanism are verified by software simulation.By establishing the kinematic model of the mechanism,the positive and negative solutions of the mechanism are obtained,and the speed,acceleration and singularity of the mechanism are analyzed.In the dimension optimization analysis,the whole machine is divided into two parts to simplify the difficulty of analysis according to the structure characteristics of the whole machine.The relationship between the structural parameters of the mechanism and the two performance indicators of workspace and force transfer characteristics are established respectively.The optimal solution region is obtained and verified by an example.Finally,three different workspaces corresponding to the size series are given,their rotation ability is analyzed,and the limit boundary search method is used to obtain the rotation range of the driving joint in a given workspace,which is prepared for the following trajectory planning.In the trajectory planning research,two kinds of motion regular curves and two kinds of gate-shaped paths are used to form four trajectory planning schemes,An trajectory planning strategy is proposed.Given the motion period of the manipulator and taking the maximum angular acceleration of the driving joint as the objective function,the time of each path segment of the door-type is optimized.The rationality of the trajectory planning strategy is verified by software simulation.Finally,by comparing the optimization results of four schemes,choose the best one for later prototype experiment.The repetitive positioning accuracy of the manipulator is measured by the built motion control system,and the prototype experiment of the manipulator are completed under two different trajectory planning strategies.By comparing the experimental results,the practicability and feasibility of the trajectory planning strategy proposed in this paper are further verified.