Nonlinear structurally stable control of a two link flexible robot arm

Addresses the problem of end point trajectory control of a two link flexible arm in the presence of nonlinear plant perturbations. First, the regulator problem with internal stability is reviewed and its relationship with the exact tracking problem with internal bounded evolution pointed out. Next, in the framework of Lyapunov theory, it is shown that with the addition of some dynamics it may be possible to achieve the structural stability. This result can be seen as an extension to the nonlinear case of the internal model principle. The case of tracking a ramp in spite of plant uncertainties is fully developed and illustrated by means of some numerical simulations.<>