Design and implementation of a state observer for a flexible robot

The design and the realization of an observer for a two-link flexible arm characterized by a nonlinear model are described. The presence of several detectable modes of vibration and of noisy deflection measures requires the observer to perform a well-defined filtering action. In order to comply both with the nonlinearity of the model and with these requirements, the subset of equations describing the flexible dynamics is extracted from the whole robot model. The nonlinear interactions between the rigid variables and the flexible ones must be compensated. This procedure yields an observer with linear dynamics, suitable for imposing the prescribed filtering behavior. The proposed observer has been implemented on a 386-based computer, interfaced with a flexible arm and tested using a control approach derived from singular perturbation theory. Experimental tests are reported