Indirect nonlinear robust control of robot manipulators

In this paper, a new robust control strategy to accomplish the precise control of robot manipulators under load uncertainty is proposed using a nonlinear optimal control formulation and solution. This approach is based on the underlying relation between the robust stability and performance optimality. A class of robust control problems can be transformed to an equivalent optimal control problem by incorporating the uncertainty bounds into the cost functional. The ε-D optimal control method is utilized to find an approximate closed-form feedback solution to the resultant nonlinear optimal control problem via a perturbation process. Numerical simulations show that the proposed robust controller is able to control the robot manipulator precisely under large load variations.