Analysis And Control Of Movement Behavior Of Mechanism With Clearance Under Different Gravity Environments

With the continuous development of science and technology,the increasing demand for space resources development has also made space robot technology more widely concerned.However,due to the environment constraints,the existing space robots are applied to the space environment after completing dynamic analysis and modeling,system installation and debugging work on the ground.When the space robot is in the working state,due to the change of gravity condition,the motion characteristics of the clearance between the hinges of the mechanical arm and the dynamic characteristics of the mechanical arm will change,which causes the controller cannot track the desired trajectory,may result in serious consequences.Therefore,this paper analyzes the motion characteristics of the inter-hinge clearance in the microgravity environment,and proposes a space robot end trajectory tracking controller that adapts to different gravity conditions.The system modeling is completed and verified by simulation,and the end trajectory tracking tasks of ground and space are realized.The main contents are as follows:Firstly,the modeling principles of the clearance light bar model and the spring damping model are analyzed.The model of the two-degree-of-freedom with clearance manipulator is obtained according to different modeling methods,then the kinematics and dynamic equations of different models are given,laying the foundation for follow-up research.Secondly,construct a ground simulation experimental platform to study the effect of clearance on the motion characteristics of the mechanism.By analyzing and summarizing the structure of the mechanism with clearance,the two bar linkage mechanism with gap is established,which lays a theoretical foundation for the experimental platform.Compare the advantages and disadvantages of several clearance measurement methods,choose the appropriate method to apply to the experimental platform to complete the measurement of the clearance between the two linkages.In order to verify the influence of clearance on the end tracking behavior under different gravity orientations,the experimental platform was used to collect the data and compare with the simulation data to verify the validity of the mathematical model,and the motion characteristic of the clearance mechanism under different gravity environments were analyzed.Then,aiming at the problem of the end trajectory tracking of the manipulator with clearance,a model-free adaptive controller is designed after the dynamic linearization transformation of the two-degree-of-freedom manipulator with clearance,the stability of the controller is verified,and the simulation proves that the controller can adapt to the trajectory tracking task of the end of the manipulator in both ground and space environment,and the control strategy has high adaptability.Finally,in order to improve the accuracy and robustness of the control system,a model-free adaptive sliding mode control strategy is proposed,which is applied to the two-degree-of-freedom manipulator with clearance to complete the end trajectory tracking task,compared with the simulation results of pure model-free adaptive control,the results show that the model free adaptive sliding mode control has higher accuracy and robustness.