Research On Planar Tracking Technologies For Supported Gravity Compensation

Astronaut’s ground low-gravity training is an essential part of manned space missions.In order to solve the problems caused by the limitations of the suspended lowgravity system in multi-astronaut co-training,a supportive gravity compensation scheme is proposed.The key to achieving supported gravity compensation is the design of a low interference force for a supported planar position servo system.Firstly,this paper analyzes the requirements and principles of the support plane servo system,and proposes a plan-supported planar position servo system based on planar free two-bar linkage,which is designed and developed.Based on the Simulink Real-time module,the electrical system and program of the control system are designed,and a supporting plane follow-up platform is built to verify the feasibility of the scheme and tracking control strategy.Secondly,the dynamic model of the planar servo system is established based on the Lagrangian method.The dynamic model is split equally by disassembly of the target’s movement,reducing the difficulty of subsequent analysis.Through the numerical calculation method,the factors that influence the interference force are analyzed.The influence of rod length,target motion direction and connecting rod configuration on interference force is obtained.The initial configuration that the same length of the bar and the initial angle of 90° has the smallest interference force is determined.And the direction of target and the initial configuration between 0° and 45° has lower interference force.Then,based on the kinematics and dynamics model,the closed-loop control of the planar position servo system is designed.Two kinds of tracking strategies are proposed and analyzed,and a trcking controller with speed feedforward is designed with the motor speed loop as the inner loop.Through the co-simulation of Adams and Matlab,the verification of two tracking strategies is completed and the perspective of interference force are compared and analyzed.Finally,a functional verification experiment of planar tracking is completed.The feasibility of two tracking strategies is verified.According to the stationary problem of the target in the experiment,the control dead zone is designed and the PID controller has been further improved.Through two different motivation experiments,it is verified that both tracking strategies can perform planar position tracking.And the dual-freedom tracking strategy has better tracking performance and less interference.