Path Planning For Target Capturing And System Implemention Of The Space Robot

In recent years,the research for on-orbit service using space robot system has been highly focused in aerospace field.Based on 863 aerospace research projects,this dissertation made a research in the problems of path planning and dynamic parameter identification in the course of target capturing.Dynamics simulator and software system of the central controller have been designed in order to demonstrate the tasks and algorithm for path planning and parameter identification,.The study includes the following aspects:Under the disturbance of the gravity,the ground experiment of space robot can hardly reflect the dynamic characteristic in micro-gravity environment.However,the embarrassment can be overcome by mathematics modeling.Integrating with the needs for the validation on the earth,a set of strong migrative and efficient scheme for modeling and simulation of space robot is proposed.According to the Lagrange equation and Newton-Euler equation,the dynamic equtions are developed and its nonliear term is derived with a special numerical method.Futhermore,the dynamic impact of gravity gradient on the robotic system is minimized after series of analysis.In order to validate target capturing capability,mathematics simulator and hard-in-loop simulator are established based on on-orbit mission scenario.On-orbit services using space robot can generally be divided into four stages: target approaching,target capturing,system stabilization and target maintenance.Approaching is the most important phase,the base attitude is disturbed because of the motion of manipulator and collision at the time of capturing,and it is very important for the energy and communication.A coordinated path planning algorithm is proposed to solve these problems.The trajectory of manipulator joint and the angular momentum of reaction wheel are planed,they are coordinated each other.After the capture operation is performed,the payload increment will induce a change on the equivalent dynamic parameters of the end body,naturally the dynamic parameter identification is required before space robot controller design.A kind of dynamic parameter identification method based on inertia re-distribution is proposed,the different manipulator configuration will generate different inertia distribution on known parts,then the dynamics parameters of unknown parts can be identified.As the remarkable advantage of this method,only velocity and position level measurement is necessary for the identification,more over,the calculation for identification results can be simplified by adopting least square method.In order to provide a reference for the parameter identification applications,the influence of measurement error on the identification accuracy is also analyzed.Since the angle velocity remaining on the post capture manipulator and platform,the base attitude should be regulated with captured target docked in a given location.Based on the Particle Swarm Optimization algorithm,a kind of nonholonomic path planning method for the target docking and platform attitude regulation is proposed.Firstly the non-zero momentum system kinematics of free-floating space robot is developed,and then the joint function is parameterized,by using the Particle Swarm Optimization algorithm,the manipulator trajectory can be obtained,the planning trajectory acquired by the above method is smooth enough,which satisfies the constraints about joint's position,velocity and acceleration,furthermore during the manipulator movement,the disturbance of angular momentum on the base also can be assigned before the trajectory planning.In order to fully verify the on-orbit operation functions,the corresponding on-orbit missions are programmed for the space robot system,and the mission supporting software are also designed based on space level micro-processor.By configuration optimization and task decomposition,the coupling relations between tasks and the switching relations between task models are distinguished clearly,which enable the software system a highly efficiency data and command management function for the complex on orbit operations.Application function module is an emphases and the algorithms are given.Two extended missions are design base on the algorithms which are proposed in this thesis,and they are demonstated with the software.