| With the launch of Chang’e-5 at the Wenchang Space Launch Site in Hainan on November 24,2020,and took back soil samples from the moon successfully,it marks that the manned lunar landing project of China has taken another big step forward.Because the environment on the moonscape is different from the earth’s surface extremely,to ensure the safety of astronauts and complete operations on the moon successfully,sufficient simulation training must be done on the earth to adapt to the lunar environment before astronauts set foot on the surface of the moon,and the low-gravity simulation plays an important part in the simulation training.The purpose of this subject is to design a low-gravity simulation system that uses a rope parallel mechanism to follow the trainer actively and uses a constant tension sling to provide a compensating force to achieve the purpose of low gravity simulation that has a significant meaning for low-gravity training of astronauts.The specific research contents of the dissertation are as follows:The force characteristics of the human body on the earth ground have been analyzed to simulate the low gravity environment on the moonscape,and the required compensating force and the compensating moment have been calculated to simulate the moon’s gravity environment based on the previous force analysis model data.The feasibility of providing gravity compensation with one rope has been demonstrated by analyzing the compensating moment.The structural plan and overall control plan of the simulation system have been determined according to technical requirements,and the detailed communication solution of the control system has been determined according to actual requirements.The kinematics analysis of the system is carried out,and the relationship between the rope length of the follow-up system and the midpoint space coordinates of the follow-up plane is solved.The Jacobian matrix of the system has been analyzed and combined with the movement acceleration changes of the trainer the working space of the follow-up plane has been analyzed and acquired,and the best follow-up plane movement height has been got according to the size of the working space of the follow-up plane at different heights.The system can be divided into two spatial states according to the trainer’s contact state with the ground.The established module is verified in the Simulink module by the dynamic models of the system in the two spatial states which are established by the second type of Lagrangian method.The force control model of the rope unit is established which is driven by the DC motor.The controller of the constant tension subsystem is designed and the parameters of the controller are adjusted.The control law of the follow-up mechanism is determined according to the conditions that the deflection angle,deflection angle differential,and deflection angle integral(interference force impulse)are zero,and combine the transposed inverse Jacobian control method to design the follow-up mechanism controller with an outer loop which is a position loop and an inner loop which is a speed loop.Simulink simulation analysis is performed on the control system of the constant force mechanism and the follow-up mechanism,and the system control method is verified through the output curve.The experimental prototype is established which is composed of a motion control card,DC servo drive,data acquisition card,tension sensor,angle sensor,industrial computer,etc.The stability of the DC servo motor drive unit is analyzed by the host computer,and the performance of the drive unit is corrected by adjusting the parameters of the drive control unit.The constant force control of the constant tension mechanism and the single motor position control of the follower mechanism are verified by performing the rope drive unit constant force control experiment and the rope drive unit angle tracking experiment on the prototype. |
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