Research On Space Robot Teleoperation System And Local Autonomous Technology

Space robot technology can effectively improve the safety of astronauts and reduce the cost of space maintenance and exploration.The space robot with local autonomous control ability and the space robot remote operating system which assists human to carry on the distance operation and decision are the mainstream research direction at present.Based on the design of space robot teleoperation system,this paper studies the structure and function design of teleoperation system,security control strategy,online and offline trajectory reconstruction algorithm,end gripper sliding detection algorithm and state observer.According to the tasks and functional requirements of the on-orbit self-maintenance space robot and its teleoperation system,the corresponding ground teleoperation system is established.The system has online and offline trajectory planning functions,trajectory planning function when a joint is damaged and locked,master-slave/bilateral teleoperation function,operation coordinate system conversion function,virtual reality function,realtime display and supervision of instructions.In addition,the system has the necessary security control strategy,including: collision detection,speed limiting and joint limit functions and avoiding singular functions.At the same time,a virtual simulation system and virtual delay are also established,and the function verification of the established remote operating system can be utilized.At the master end of the teleoperation system,force-reflective equipment,two kinds of master-side shared control strategies are proposed for the problem that the dynamic tracking accuracy of the arm end is reduced due to the operator's hand shake during teleoperation.Firstly,a single joint model is established for the problem of the dynamic tracking accuracy of the end of the robot arm caused by the operator's hand shake during teleoperation,and the relationship of the acceleration and jerk of planning trajectory and the tracking accuracy is analyzed.Then,this paper proposes online and offline trajectory reconstruction algorithms,in which the offline trajectory reconstruction algorithm utilizes the fixed interval smoother based on interior point method to achieve higher computational efficiency,and the online trajectory reconstruction algorithm adopts a self-tuning variance fixed-lag Kalman smoother proposed in this paper.Both of these algorithms can constrain the acceleration and jerk of the reconstructed trajectory to a specified range,so as to improve the accuracy of the end tracking.At the slave end of the teleoperation system,space robot,two kinds of slave-side supervisory control strategies are proposed for the sliding problem and motion state estimation of the end gripper during teleoperation.Firstly,a slipping process model is proposed that involves the nonlinear and noise characteristics for the slippage.Then,to improve the detection accuracy,the multi-threshold is determined by the method of partitioned statistics to reduce the influence of the loading force and nonlinearity of the system on the detection part.At the same time,to achieve the goal of minimizing the loading force increment after stabilization,a constant micro-increment controller is employed.Finally,considering that the noise of the sensor plays a decisive role in the detection accuracy,a moving average filter is used as the preset filter and the effect is compared with the low-pass filters.Aiming at the problem of motion state estimation from the end gripper finger,the noise characteristics of the potentiometer position sensor are analyzed,and a state observer based on adaptive fixed lag smoother is proposed.Finally,the space robot ground teleoperation system designed in this paper is used as the experimental system.The real-time teleprogramming function,trajectory reconstruction algorithm,end-side sliding suppression strategy and state observer are verified by experiments.The experimental results show that the real-time tele-programming function can effectively plan the linear and circular trajectories,and ensure that the planned trajectory meets the requirements of position and speed limit,anti-collision and avoiding singularity.And the planned trajectory guarantees the tracking accuracy requirements of the end space robot.The experimental results of trajectory reconstruction show that the acceleration and jerk of the reconstructed trajectory can be effectively constrained within the specified range.Compared with the unconstrained filter,the reconstructed trajectory has good dynamic tracking accuracy and small residual vibration,and the deformation of the end trajectory is small.In the slip prevention experiment,the parameters selection merely depends on the system characteristics and is basically irrelevant to the object being grasped.The experimental results show that the detection accuracy of the proposed algorithm is better than the single threshold detection algorithm,and the loading force increment is also comparatively small.The experimental results of the state observer show that this method can effectively improve the observation accuracy of the moving state compared with the direct difference of the original position data.Compared with the state observer based on standard Kalman filter and fixed-lag Kalman smoother,this method has better effect on dynamic response.