Study On Coordinated Compliance Control Technology Of Robonaut

Human astronauts cannot stay long in the outer space to execute tasks for their disability to adapting to the severe space environment,while common space robots are unable to be capable well of.complicated and various space missions for its weakness such as poor flexibility,weak operational capability,and so on.Hence,the study of the alternative of human astronaut,i.e.,robonaut,has been more and more urgent.Compared with other space robots,robonauts' most obvious advantage is its outstanding coordinated operation ability.In order to meet the requirements of precise operation,the necessary operating force in tasks must be controlled and the harmful force for task systems must be limited,i.e.,force compliance must be achieved.This paper studies on the control problems of the object trajectory tracking,object force compliance,contact force between links and environment and so on in the process of the robonaut's coordinated operations and then verifies the effectiveness of the related control algorithms by simulations and experiments of typical coordinated tasks.For the problems of position tracking and force control of robots in constraint environment,this paper studies robot compliance control methods.Based on robot dynamic model,position control method and force control method are studied and then hybrid force/position control strategy is applied to combine position and force control to deduce the compliance control model of robot.For the circumstance of existing dynamic parameter error,parameter adaptive law is introduced to robot compliance control model and adaptive compliance control model of robot is obtained.These compliance control methods achieve stable force and position tracking and satisfy the accuracy requirements of most compliance control tasks.For the problems of object position tracking and force compliance control during the robonaut coordinated operation,this paper designs the compliance control system of the robonaut coordinated operation.First the dynamic model of robonaut including the coupled torso and two manipulators is established based on Lagrange method.Then for loose and tight coordination tasks,coordinated compliance control algorithms of robonaut are designed respectively,achieving stable force and position tracking of objects under precise dynamic model.Besides,for the case of existing dynamic parameter error,robust control term to compensate the force and position tracking accused by dynamic parameter error is introduced to the coordinated compliance control model,achieving the stable force and position tracking of objects under uncertain dynamic model.For the case that robonaut performs tasks in complicated environment and its links contact with environment,this paper proposes the torque in null space be utilized to control the contact force between the links of robonaut and the environment without influence on the operation tasks.Compared with common obstacle avoidance control algorithm,the algorithm in this paper avoids sacrificing the operating space around the obstacles,increasing the number and types of the executable tasks of robonaut.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 effectiveness of the control algorithms proposed in this paper.