Research On Six Degrees Of Freedom Motion Platform For A Special Vehicle

The six degree of freedom motion platform is a kind of equipment integrating mechanical transmission and precision servo control.It has the characteristics of strong bearing capacity,fast response speed,high control accuracy and good stability.Therefore,it is widely used in simulation driving,high-precision machine tools and medical robots.As a typical parallel robot,the six degree of freedom motion platform is prone to reduce the overall dynamic performance in engineering applications due to the large number of mechanical joint components and the strong coupling of each joint component,which will affect its bearing capacity and control accuracy.This kind of problem is more and more obvious especially in the high load working environment.In order to solve these problems,this paper designs a six degree of freedom motion platform with excellent dynamic output performance under high load(payload 2000kg)working environment based on the specific application field of simulated driving.Based on the inverse kinematics theory,the homogeneous coordinate transformation matrix is given according to the structural parameters,and the mathematical model is established.Taking the trapezoidal motion mode as the standard working condition,the solution of the extension and movement speed of the actuator cylinder under six postures is carried out in MATLAB software.The force analysis of the upper platform and the actuating cylinder is carried out.According to the force and moment balance equations in three spatial directions,the load calculation of the actuating cylinder along the axis direction under statics is completed for the 12 limit positions of the upper platform under six postures.According to the principal vector and the principal moment of the upper platform,the inertia matrix and the dynamic equation are established.The mechanical solutions of the six attitude motion processes are completed in MATLAB software,and the load curves of each actuator cylinder are obtained.So as to determine the design indexes of the maximum load,the maximum expansion and contraction amount and the maximum movement speed of the actuator cylinder.Based on the design index,the structural design part completes the selection and verification of the main parts of the actuator cylinder,such as the ball screw pair and the servo motor,and the strength and stiffness verification and static simulation of the push rod and cylinder barrel.Based on the characteristics of fast response rate and high control accuracy of the six freedom motion platform,the fuzzy PID control algorithm is selected as the control algorithm of the motion system.According to the composition and control principle of the control system,the selection of the control system hardware and the design of the electrical circuit are completed.Through the performance test of the expansion and contraction amount and movement speed of the actuator cylinder completed by the PC end of the upper computer in the trapezoidal movement mode,the test data are less than the theoretical calculation index,which verifies the rationality of the mechanism.