Output feedback stabilization of hydraulic drives based on bilinear approximations and canonical observers

This paper deals with the control of hydrostatic drives on the basis of bilinear models. It is shown that by using bilinear models a considerably better approximation of the non-linear behaviour of hydraulic drives can be achieved compared with common linear models. The bilinear model approach gives rise to control results valid not only for fixed operating points but also for the complete operation range of the drives. In particular, an output feedback using a canonical observer and quadratic state feedback is proposed. A separation theorem for this non-linear control scheme similar to that for linear systems is proved, i.e. the dynamics of the observer and of the controlled plant are adjustable separately.