Input assignability of nonlinear system and its applications in robust/tracking control

It´s well known that measured or estimated uncertainty information is absolutely beneficial to design robust controller. However, few researches have been conducted on that due to the difficulties of obtaining uncertainty information. Most recently, development of observation/estimation and measurement techniques (especially for nonlinear systems) make it possible to get full or partial uncertainty information. Thus, in this paper, a new concept of input assignability is introduced and used to design robust controller for nonlinear systems. The main idea of this new control scheme is firstly presented with respect to two typical nonlinear systems; subsequently, it is generalized and combined with the input-output finite gain L₂ stable control to attenuate disturbances without deteriorating closed loop performance greatly; finally, experiments on a inverted pendulum testbed are carried out and the results verify feasibility and validity of the proposed scheme.