Research On Dynamic Modeling And Singularly Perturbed Controlling Of Flexible-base Flexible-joint Space Robot

In the 21st century,the earth's resources and space are becoming scarce,and the outer space has become a battleground for the future survival and development of human beings.However,the harsh outer space environment is not suitable for human beings to do some long-time extravehicular operations,and it is more likely to pose a potential threat to the safety of their lives.To solve the above problems,space robots with the operational characteristics of the human arm have stepped into the stage of history and begin to play their expected application advantages.In recent years,in order to reduce costs and improve efficiency,the mass of space robots has become lighter and the structure of them has become more flexible.As a result,the flexibilities of the base and joints have attracted much attention.To guarantee the control performance of the system,this paper intends to study the dynamic modeling and motion control of space robot with the flexible base and flexible joints.Firstly,based on the reasonable assumptions and simplified descriptions of the flexible deformation of the base and joints,the whole dynamic model of a planar two-link flexible-base flexible-joint space robot with an attitude-controlled base is established by using of the momentum conservation of the system and Lagrange equation.Secondly,to realize the independent design of controllers for rigid trajectory tracking motion and the flexible motion of the base and joints,the singular perturbation technique based on the flexible compensation is applied to decouple the rigid and flexible motions from the whole dynamic equation of flexible-base flexible-joint space robot.Then,the rigid slow subsystem and the flexible fast subsystem are obtained.Furthermore,based on the above fast and slow subsystems,a series of reasonable control schemes are designed for a flexible-base flexible-joint space robot to achieve the rigid trajectory tracking and flexible vibration suppression control under different working conditions.Under the condition that the model parameters of the system are known,two control schemes are proposed for the slow subsystem to accomplish the trajectory tracking:computed torque control scheme and fuzzy control scheme.Under the condition that the model parameters of the system is uncertain,an adaptive control scheme in which the inertial parameters can be adjusted online in real time and a robust fuzzy sliding mode control scheme that can actively compensate for system uncertainties are proposed for the slow subsystem.Under the complex condition that the system suffers from the influences of the uncertain parameters and external disturbances,two kinds of compound control schemes are designed for the slow subsystem:a robust adaptive terminal sliding mode control scheme and a robust adaptive neural network finite-time control scheme.To simplify the control design,the uncertain parts of the system is ignored,and the linear quadratic optimal control scheme is adopted for the fast subsystem,which presents the flexible vibration of the base and joints,to suppress the vibration of the system.Combining each slow control scheme with the fast optimal control scheme,the whole hybrid control scheme for the flexible-base flexible-joint space robot under different working conditions can be obtained.Finally,the proposed control schemes are simulated and verified in a flexible-base flexible-joint space robot system.The simulation results confirm the effectiveness of the proposed control schemes.