Adaptive tracking control of a flexible link manipulator using a discrete-time nonlinear model

The aim of the paper is to develop a nonlinear adaptive control scheme for a discrete-time model of a single-link flexible manipulator. The discrete-time model of the system is derived using the forward difference method (Euler approximation). The state transformation and the internal and the zero dynamics are derived subsequently. The output re-definition method is used so that the resulting zero dynamics is guaranteed to be exponentially stable. Finally, the proposed indirect adaptive feedback linearization and tracking controller is applied to the manipulator where it is assumed that the "payload mass" is unknown but its upper bound is known a priori. The performance of the adaptively controlled closed-loop system is examined through numerical simulations to demonstrate the main features of the proposed strategy.