Research On Trajectory Planning And Control Of Space Robot After Autonomously Taking Over A Noncooperative Target

It is one of the most important means to ratio nally use the orbital resources,restore the faulty spacecraft's functions,improve the spacecraft's economic benefits,reduce the cost of space industry and ensure the safety of space assets by using space robot to maintain and protect the high-value spacecraft,which has obviously political,economic and positive significence.After the space robot takes over a noncooperative target,the compound system is formed.The compound system is nonlinear and has strong coupling,and its initial momentum is unkno wn,the attitude of the base has many constraints,so the configuration design,parameter identification,trajectory planning,stabilization control are challenging problems.In order to deeply understand the dynamic properties of the compound system formed by the space robot and target,the dynamic equations of the compound system are deduced and the coupling between target and base with different mass and inertia is analyzed for typical trajectories.Based on this,the control strategy of space robot is proposed.Furthermore,the workspace and manipulability of the single-arm and multi-arm space robot are analyzed.Using the manipulability index,the configuration of the multi-arm space robot is optimized.Aiming at the problem that large attitude disturba nce to the base is occured during the real-time process for parameter identification of noncooperative target when the initial momentum of compound system is unknown.A parameter identification method based on null reaction space adaptive trajectory planning with multiple constraints is proposed.With constrains by the gradient of the joint potential function and using the space manipulator's null space characteristic,the recursive least squares adaptive method with forgetting factor is used to realize the minimum disturbance to the base,the momentum increment equation of the compound system is established to solve the dynamic parameters of the target preciselyIn order to solve the problem that the base attitude is unstable when a noncooperative target is manipulated by the space robot,a coordinated stabilization between the base and manipulators based on adaptive sliding mode control is proposed.The method uses delay parameter estimation to reduce the dependency on the exact dynamics model,and the derivatives of the adaptive gains are proportional to the sliding variables,which is used to achieve good control performance with small chattering effect during the target manipulation.By the coordinated motion o f the base and manipulators,the attitude disturbance to the base is greatly reduced in the process of the target manipulation,the stabilization control of compound system is realized.To validate and evaluate the method proposed in thesis,a semi-physical experiment verification system is developed,which is consisted of a mathematical model of the space robot and a modular reconfigurable robot,its main idea is to combine the dynamic model with the physical object.Using this system,the experiment of null reaction space adaptive trajectory planning is carried out,which verifies the validity of the algorithm.It also shows that the semi-physical experiment system has the capability to carry out and verify other methods.The semi-physical experiment system has a good scalability,which is able to play a role in the follow-up study.From the view of on-orbit services and space security,stabilization and control of space robot after capturing a target are a future research and hot spots.The results of this thesis provide a reference for the pract ical application of space robot technology.