Analysis And Motion Control Of 6-DOF Position And Pose Mechanism

With the development of economy and society,the national defense industry has put forward higher requirements for motion simulation equipment with large movement range,quick adjustment,high control accuracy and strong carrying capacity.This paper studies the kinematics analysis,dynamics analysis,control strategy,and precision detection methods of the 6-DOF parallel platform,based on the research and development task of the vehicle-mounted posture platform undertaken by Beijing institute of aerospace control devices.In the kinematics analysis,firstly,according to the constraint relationship between the upper platform and actuator,the mathematical model of the inverse solution of the 6-DOF platform is established,and the corresponding simulation research is carried out in Matlab to verify the accuracy of the kinematics inverse solution model.Then,aiming at the defects of low precision and difficulty in initial value selection in the kinematics forward solution,a method of Newton iterative initial value compensation based on SOA search algorithm is proposed,and the simulation model is built and the calculation example is given.Finally,through experiments on the developed 6-DOF platform prototype,it is found that the new forward solution algorithm has high convergence accuracy and stability.In dynamic analysis,firstly,this paper sets up a virtual prototype of 6-DOF platform in the Simulink software,and defines structure parameters of platform and six actuators.Then,this paper studies the electric actuators,and establishes the mathematical models of the electric cylinder and the PMSM motor.Finally,a dual PI controller and a sliding mode speed loop controller are designed for the motor model.Through simulation,it is found that the sliding mode speed loop controller can effectively reduce the motor adjustment torque and adjustment time.In the research of motion control strategy,firstly,this paper separately designs two strategies of hinge point space feedforward decoupling PD control and workspace adaptive sliding mode control.The simulation experiment shows that the workspace control has good robustness but relatively poor control accuracy,and the hinge point space feedforward control has high accuracy but is sensitive to external interference.In order to solve this problem,this paper proposes a two-layer control strategy,namely the inner layer uses feed-forward decoupling PD control to ensure the control accuracy,and the outer layer uses adaptive sliding mode control on the workspace to offset the external interference.It is found through experiments that the two-layer control can significantly improve the tracking accuracy of the pose platform.In the precision detection and analysis of pose platform,this paper first introduces the commonly used functional modules and software and hardware components of the 6-DOF platform control system.Then,this paper uses the inclinometer and dualfrequency laser interferometer combined with special tooling to detect the linear displacement and angular displacement accuracy of the position and attitude platform respectively,and it is found that under the two-layer control strategy,the angular position accuracy reach 0.018°,and the line displacement accuracy reach 1.2mm.Then,this paper measures the dynamic accuracy of the platform,and finds that during 5 ° 1Hz roll motion,the amplitude only attenuated by 3.6%,meeting the dynamic requirements of the system.