| Due to the microgravity environment in space,the astronauts' tasks in space are quite different from those in the ground where gravity acts.The microgravity environment in space will affect the ability of the astronaut to work.In this paper,a rope-driven robot is studied to simulate the motion of an object in microgravity environment,and to study the motion characteristics and control strategies of the robot.The research status of microgravity simulation technology and cable-driven parallel robot at home and abroad is analyzed.According to the functional requirements of the robot,combined with the structure and motion characteristics of the human arm,the configuration scheme of the robot is designed.The structure of the robot is determined by the workspace and static analysis of the robot,and the dimensions of the moving platform and the fixed platform are determined by the stiffness analysis.The overall control scheme is designed according to the characteristics of the mechanism.The model of the human arm mechanism is simplified.The forward and inverse position solutions of the end of the arm are obtained by the closed-loop vector method.The kinematics simulation of the human arm mechanism is carried out by Simulink,and the rotation curves of the shoulder joint and the elbow joint are obtained.The kinematics analysis and simulation of the robot are carried out to obtain the relationship between the position of the moving platform and the length of the four cables.The kinematics analysis and Simulation of man-machine system are also carried out.The dynamic analysis and simulation of the human arm are carried out to study the relationship between the motion state of the object and the moment of action of each joint of the arm.The dynamic analysis of the robot is performed to obtain the relationship between the acceleration of the moving platform and the force of the cable.The tension of the cable is optimized.Compare the minimum variance optimization algorithm with the minimum norm optimization algorithm.Then the dynamic simulation of the human-machine system is carried out.The model of the driving unit is established,and the position control strategy is studied and simulated by using the double closed-loop control method of speed and position.Then the force control method is analyzed and simulated in two aspects: forward channel force control strategy and redundant force control strategy.In the forward channel control strategy,the control effect of the single closed-loop control mode of comparative force and the double closed-loop control mode of speed and force are compared.The redundant force controllers are designed based on the single closed-loop control mode of force and the double closed-loop control mode of speed and force respectively.Feedforward controller is designed based on force single closed-loop control mode,and local feedback controller is designed based on speed and force double closed-loop control mode to compensate the disturbance caused by speed at the end of the cable.The Matlab/Simulink is used to analyze the excess force curves and the force following curves at different loading frequencies,and the control effects of the two redundant force control strategies are compared.The force control strategy of the robot system is simulated and analyzed.The influence of non-linear factors and driving unit parameters on the system is also analyzed.The control strategy of active loading of the single cable drive unit is verified by experiment,and the following ability of the two control strategies is compared.The control strategy of passive loading of two cable driving units is verified by experiments,and the feasibility of the control strategy is verified. |
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