Dynamic Modeling And Trajectory Tracking Control Of Flexible Joint Space Manipulators

In order to solve the problems of flexible joint space manipulators in dynamics modeling and simulation,a model with three-dimensional four-link flexible-joint manipulators is taken into account.Considering the nonlinear stiffness coefficient of the torsion-spring,and inertia coupling,the dynamics model of flexible-joint manipulators with revolute joints are established by the Lagrange method.The correctness of the model is tested and verified by a PD controller with continuous linear feedback loops.Meanwhile,the influence of different values of the flexible joints stiffness coefficient for system stability is taken into analysis and comparison.When the stiffness coefficient is small,and flexible variable of the joints is big,which is very adverse to the stability of the system.On the contrary,when the stiffness coefficient is bigger,flexible variable of the joints is smaller which is more conducive to control the system.The vibration suppression is a difficulty in the controlling problem of flexible-joint space manipulators,which is settled by solving the energy optimal nonlinear control problem based on the research above.With using Legendre pseudo-spectrum method,the complex two-point boundary value nonlinear optimal control problem is converted to the corresponding nonlinear programming problem and then solved by SNOPT solver.Compared with the traditional controller,the simulation results show that the joint trajectory accommodates the joint flexibility so well that the manipulator moves smoothly and the vibration associated with the flexibility is suppressed.Since the residual vibration is cancelled,the control precision of end-effector is improved.