Rigid-flexible Coupling Dynamics And Control Of Flexible Space Manipulator

With the rapid development of aerospace technology and the the depth of spaceexploration, a space manipulator will become an important tool for the human beings’space activities. Since its workspace is required to be as large as possible, and the massas light as possible, the structure flexiblility of most space manipulators can not beignored. During on-orbit missions, inappropriate movement will excite the vibration ofa flexible manipulator, causing the task failure. This thesis will deal with therigid-flexible coupling dynamics modeling and vibration suppression control strategies.The main contents are as follows:The rigid-flexible coupling dynamic model of a flexible space manipulator isderived based on the analytical method. The analytical model is taken as the basis fortrajectory planning and control methods. A space manipulator is composed ofconnecting links and joints, performing different flexible behaviors according todifferent application conditions. Therefore, the modes of two rigid links, two flexiblelinks, and one rigid and one flexible link maniopulator are respectively establishedusing the Lagrangian methods, in which the deformation of flexible links is describedbased on the assumed mode method.The modal of a flexible space manipulator is analyzed using the Ansys software.The modes of the flexible manipulator corresponding to different typical configurationsand different loads are respctively analyzed, obtaining the relationships between thenatural frequencies and manipulator configuretion, and manipulated load. Based on theanalyzing results, the corresponding rigid-flexible coupled dynamics model is created inthe Adams environment. Then the derived analytical model is verified using the Adamsmodel.Then, the motion planning method for vibration reducing is studied and theproposed aporoach is verified using the rigid-flexible coupling dynamics model createdin Adams. According to the theoretical analysis, the joint acceleration is the main factorof exiciting the vibration, so the joint acceleration is the goal of motion planning. In theplanning, the "sine trapezoidal" function is taken as the base function, the accelerationtrajectory is obtained using the superposition of a number of basis functions. Theascension and decrease stages of the " sine trapezoidal" basis function are sine functions.Therefore, different acceleration curves are abtained by adjusting the acceleration,deceleration, the uniform percentage of time, as well as function amplitude.Finally, a control stratege of vibration suppression is proposed combiningfeedforward and feedback control methods. Vibration suppression methods include twomajor categories: passive control and active control. For passive control methods, the vibration is reduced by isolating vibration sources, increasing the structural damping,and so on. Their drawbacks are increasing the weight and size of the system, andreducing the dexterity of the manipulator. Hence, an active control method composed offeedforward and feedback control is proposed. The key of this method is the desiredtrajectory (joint angle, angular velocity and angular acceleration) is used to estimatedthe inertial torques based on the anaylitical dynamic model and used as the feedforwardtorque. At last, the vibration is reduced under the feedforward and feedback torques.The simulation results verify the proposed method.The rigid-flexible coupled dynamics modeling, trajectory planning and control forvibration suppression are studied in this thesis. The research results have the importanttheory and application values for the space manipulator application.