Flexible Space Manipulator Control Strategy Study

In the 21st century, with the rapid development of aerospace industry and the deepening of space exploration, more and more future space missions, such as the construction of the space station, space equipment maintenance, and other scientific experiments need to be finished, but it is still hard to be completed all by astronaut. Space manipulator has the capability of adapting space environment, so it is significant to complete some tasks using space manipulator, and it has become an important research direction in space technology field. This paper come from the Ministry of Research Science and Technology major projects "space flexible robot dynamics/control coupling system research", Based on this project, this paper mainly focus on the large flexible space manipulator dynamics modeling theory and control strategy research, the paper's main work are as follows:Firstly, a six freedom, large space manipulator is designed, and raises the needed tasks target, distributes the accuracy of flexible manipulator aimed at the specific task target on the basis of the space flexible manipulator accuracy analysis; The dynamics modeling is build on the flexible links and flexible joints manipulator, and verify the effect of dynamic model; An air space simulation test table on the ground is build and aimed at the configuration features of space manipulator on test table, a simplified flat two-link manipulator is set up; The flexibility-damping boundary conditions of flexible manipulator is analyzed, and the dynamic characteristics are researched under this restrictive conditions.Secondly, the manipulator joint nonlinearities are analyzed, and the nonlinear dynamics model of flexible joints is set up; To overcome the influences of such nonlinear factors, a kind of two-position closed-loop servo control system, an anti-saturation output feedback high-precision PID control and the adaptive friction compensation strategy based on LuGre friction model are proposed; Experiment on the designed manipulator single joint test table verify that the control strategy not only improved the nonlinear position control precision and stability, but also the global stability of space manipulator system can be realized under the influence of saturation, and control algorithms structure is simple, control parameter setting rules are clear.Thirdly, flexible-joint manipulator cascade dynamic equation is established under the influence of uncertainty; Based on the backstepping methods, a virtual control variable is designed to achieve cascade equation's control, an integration function is synthesized to elimination of tracking steady-state errors furthermore, and the adaptive sliding controller is designed to eliminate the influence of uncertainties, and improve the whole system's stability and the convergence to errors by Lyapunov theory; In order to avoid the complexity for the repeated derivation of virtual control, combine the dynamic sliding-control and Neural networks, a space flexible-joint manipulator adaptive dynamic sliding-control strategy is proposed. Then, the stability analysis, simulation and test verification are finished.Fourthly, aimed at the flexible-joints and flexible-link space manipulator, for the positioning control of flexible manipulator, simplify the nonlinear dynamics of flexible manipulator through the input and output linearization, a recursive learning the output feedback control strategy is proposed for the vibration suppression in position control; In the trajectory control tasks, flexible space manipulator will be simplified to two separate subsystems based on the singular perturbation method, and then using composite control strategy to achieve precision tracking and achieve effective vibration suppression at the same time, and simulation research are studied; Finally, verify the control strategy in the space manipulator ground simulation test table.Finally, aimed at the set-point control and tracking control tasks of space manipulator, the indicators task targets are verified on the six freedom flexible space manipulator experiment platform.