Study Of Robonaut Force/position Control Technology Based On Uncertain Environment

With the continuous deepening of the aerospace exploration mission,as a kind of high flexibility space agency, space robot is playing a more important role. Among them, robonaut is undertaking more and more complex space operations due to the high flexibility and strong coordination operation ability. In order to meet the requirements of precise operation, it is necessary to precisely control the operating position while controlling the necessary operating force during the coordinated operation task, i.e., the hybrid force/position control in the task is required. However, the space environment is complex and uncertain, and the environment precision parameters are often unknown.This requires that robonaut has the ability to perform the hybrid force/position control under uncertain environment. Therefore, this paper studies on the control problems of the object trajectory tracking, object force compliance and so on in the process of robonaut's coordinated operations under uncertain environment and then and then verifies the effectiveness of the related control algorithms by simulations and experiments of typical coordinated tasks. The research content has important theoretical significance and engineering value to the development of national space robot technology. The main work of this paper is as follows:Firstly, the study of force position control method in the contact transition process is carried out. Aiming at the problem of large oscillations and long settling time during the transition from the non-contact to the contact of the end of the robot with the environment,based on the energy analysis method, a method of providing damping for the control of space force by means of acceleration feedback is proposed.This method can quickly achieve stability during the transition. Taking into account the characteristics of large stiffness with high bounce velocity, the end of the robot would lose contact with the surface of the environment. Based on the force control strategy of introducing the feedback of acceleration, the switching strategy is proposed, which makes the new control method has a certain robustness to different stiffness environment.Secondly, the research on the force position control method is carried out when the stiffness of the environment is uncertain. For the problems of operating tasks when the stiffness of constraint environment is uncertain, the force control algorithm for coordinated operations of robonaut is studied. Based on the analysis of the stability of PID force control method, by using the capability of approximating any nonlinear function of BP neural network, the incremental PID control based on BP neural network is used in the force control loop. Then, the object of the study is extended from the single arm robot to robonaut, on the basis of the dynamic model of robonaut, the constraint relation of the dual arm coordinated operation along the surface of the environment is analysed synthetically, and the flexible control system of robonaut under uncertain environment is designed. So as to improve the self-adaptability to the uncertainty of the environmental stiffness while controlling the internal force of the operator.Then, the research on the force position control method is carried out when the geometry of the environment is uncertain. For the problems of operating tasks when the geometry of constraint environment is uncertain,the force control algorithm for coordinated operations of robonaut is studied. The adjustment algorithm of end pose and force is designed by the establishing of environmental surface tracking motion model. The pose and position of the end of the manipulator is adjusted by feedback information detected by six axis force sensor; then, the object of the study is extended from the single arm robot to robonaut, in order to realize the coordinated movement with a fixed position and the desired contact force along the unknown environment of robonaut, the pose and position of the end of the dual-arm is adjusted according to the pose and the contact force of the operator.Finally, the experimental study on coordinated operation force control of robonaut is carried out. To verify the validity and feasibility of the control algorithms put forward in this paper, experiments of typical coordinated tasks are carried out and experimental results in line with expectations are obtained, verifying the correctness and effectiveness of the control algorithms proposed in this paper.