Optimal control of uncertain nonlinear systems: an application to a two-link robotic arm

The authors present an adaptive optimal control algorithm for uncertain nonlinear systems. A variational technique based on Pontryagin´s maximum principle is used to track the system´s unknown terms and to calculate the optimal control. The reformulation of the variational technique as an initial value problem allows this microprocessor-based algorithm to perform as a closed-loop controller by updating the model and controlling the system online. To validate the algorithm a system representing a two-link mechanical manipulator is simulated. In the control model, the coupling and friction terms are unknown. The robot´s task is to follow a prescribed trajectory and to pick up an unknown mass