Research On Dynamic Analysis And Control Of 4-SPS/CS Parallel Mechanism

Compared with traditional serial robots,the parallel mechanism has a series of advantages such as strong bearing capacity,high motion accuracy,no accumulated error,and superior dynamic performance.The current research hotspot is especially focused on lower-mobility parallel mechanism,which are characterized by simple structure and low cost.The research object of this paper is 4-SPS/CS 4-DOF parallel mechanism.The mechanism can be rotated three-dimensionally along the space and moved longitudinally.The kinematics,dynamics and control model of the mechanism are studied in this paper.Firstly,the kinematic state model of the driving branch of 4-SPS/CS parallel mechanism is established,and the kinematics inverse kinematics and forward kinematics analysis are carried out.On this basis,the working space of the mechanism is analyzed.Given the position of the moving platform of the mechanism,the influence factors such as joint rotation angle constraint,rod length constraint,and radial dimension interference between connecting rods were taken into consideration.The posture working space of the t4-SPS/CS parallel mechanism is received at different heights.Based on the analysis of kinematics,the entire mechanism is divided into three parts:the dynamic platform,the restrained driven branch and the driving branch.The dynamic modeling are performed by the Lagrange method.The overall dynamic equation of the system is established by add the equations of all the components together.The driving forces of mechanism driving branches are obtained by combining with the principle of virtual displacement.The establishment of the system’s overall dynamic equations provides a theoretical basis for the design of the following control laws.At the same time,the dynamic modeling of 4-SPS/CS parallel mechanism is carried out based on the Newton-Euler method,and the balance equation is established for each component by the force analysis of the components of the mechanism,and the dynamic model of the mechanism is established through integrating all the equilibrium equations.In order to improve the efficiency of the solution,the invalid equation in the mechanism is omitted.According to the established dynamic model of the mechanism,the binding force and constraint reaction force of each joint of the mechanism are obtained.The trajectory tracking control of the space 4-SPS/CS parallel mechanism was studied by using sliding mode control.Firstly,the sliding mode control rate was established on the basis of the mechanism dynamics model established by Lagrange method,and the equivalent driving force of the system was obtained.the sliding mode control is used for forces caused by uncertain disturbances.The stability of the sliding mode control system is analyzed based on the Lyapunov function.