Analysis And Control Scheme Of Microgravity Simulation Platform Based On Hybrid Pneumatic-Electric Actuators

With the development and progress of space technology,space exploration has become one of the important directions for the future development of aerospace industry.In order to ensure the aerospace devices with good dynamic performance and high control accuracy,it is necessary to implement microgravity simulation experiment on the ground.Therefore,the research and exploration of related experimental systems is important.Based on the microgravity platform scale synthesis and mechanical performance analysis,the symmetry of the workspace and the Jacobian matrix,the modeling and control strategy of the single-axis hybrid pneumatic-electric actuator is studied in this paper.The research content is divided into four parts.The first part analyzes the Stewart mechanism.“Symmetrical Stewart mechanism possesses symmetrical workspace and Jacobian matrix” is proposed.To prove it,the inverse kinematics and Jacobian matrix of the mechanism are deduced.The modified Euler angles are introduced to represent the orientation of the end effector,not only can directly express the rotation ability of the platform,but also benefit definition of symmetrical poses making the workspace and Jacobian symmetry appear.Then that permutation relationship is existed in joint variables of each symmetrical pose and that singular values of Jacobian matrix in symmetrical pose are the same are proved by mathematical deduction and a numerical example.This paper provides a theoretical basis for the use of symmetry in the analysis and optimization calculation for this mechanism and other similar mechanism.The third part is pressure control research.Integral linear active disturbance rejection control applied to valve-based air pressure control system.This algorithm can increase the convergence speed of the system and reduce the steady-state error by adding an integral part on the linear active disturbance rejection control.Controller and pneumatic system model is built in the MATLAB/SIMULINK for air pressure control algorithm simulation.And experiments are implemented in the actual system.The results of them are consistent,which show that the integral linear active disturbance rejection control can achieve better constant pressure control.At the same time,it shows that the low cost pneumatic control system based on fast on\off valves can achieve high control precision.The fourth part is the microgravity simulation experiment of the single-axis motor actuator and hybrid pneumatic-electric actuator.The payload uniformly accelerates under constant force in a simulated microgravity environment.The system performs well in the simulation and the results of experiments show that the hybrid actuator can achieve about 90% of the ideal acceleration under the constant load in microgravity situation.Besides,the results show that the hybrid actuator improves the load capacity of the system and eliminates the influence of the load on the maximum speed of the motor.So,the feasibility and effectiveness of the joint drive scheme are verified.