Research Of A Novel Linear 3-DOF Parallel Robot

In view of the application demand of depth grasping for light industry,based on the analysis of the structural characteristics of the traditional three-degree-of-freedom parallel robot,a novel linear three-degree-of-freedom parallel robot is presented in this paper.The mechanism of robot uses two symmetrical moving branches and one rotating branch to replace three rotating branches of the traditional three-degree-of-freedom parallel robot,so as to reduce the difficulty of the analysis of robot structure and improve the workspace of the robot.And analysis and research of its kinematic characteristics,dynamic characteristics,trajectory planning and motion control are performed,completing the design and research of this novel configuration robot system.First of all,the structure of the novel linear three-degree-of-freedom parallel robot is designed,and the kinematic model is established.The forward and inverse kinematic position solutions of the robot are derived by space analytic geometry and vector method.Based on the inverse kinematic model,the search algorithm is adopted to achieve the reachable workspace of the robot.The result shows that the robot has a larger workspace.Then,according to the robot Jacobian matrix,the typical singular configuration of the mechanism is analyzed,which lays a theoretical foundation for the follow-up trajectory planning to avoid singular positions.Secondly,based on the kinematic model,the Lagrange equation method is applied to solve the kinetic energy and potential energy of the robot system,and the Lagrange function of the system is obtained to establish the dynamic model.The correctness of the dynamic model is verified by MATLAB software,and the relationship between the load and mechanism parameters and the joint drive torque and force characteristics is analyzed,which provides a theoretical basis for the optimization of the robot's design parameters and follow-up trajectory planning.Then,the rules of the trapezoidal velocity,the trapezoidal accelerated velocity and the modified trapezoidal accelerated velocity are used to study the trajectory planning of the robot,and the optimal rule of the modified trapezoid accelerated velocity is determined.Then,in the optimized gate-type path,the trajectory planning of the robot is performed with the modified trapezoidal accelerated velocity rule,and the displacement curves of the robot's joints are obtained,which provides a trajectory basis for the motion control of the robot.Finally,the motion control strategy of the linear three-degree-of-freedom parallel robot is studied to realize the high precision control of the robot.Based on the establishment of the servo system model,PID and fuzzy PID controllers are designed.And the tracking control of each motor angular of branches in the robot are simulated and compared.The simulation results show that making use of fuzzy PID control method has a faster dynamic performance and better adaptability to the nonlinear factors in the control system,and it also effectively reduces the trajectory tracking errors,improving control accuracy of the parallel robot control system.