Smith predictor based generalized PI control for a class of input delayed nonlinear mechanical systems

This article addresses the problem of Linear Active Disturbance Rejection Control for a class of nonlinear mechanical input time delayed systems. To solve the problem, it is necessary to obtain a set of predictive lumped disturbance estimations, which is carried out by a purely linear high gain observer of Extended Luenberger type, denoted as a Generalized Proportional Integral (GPI) Observer. This task is performed using an approximation of the predictive disturbance using a truncated Taylor series expansion, where the set of necessary values for the estimation are provided by the observer. Once the (approximate) disturbance canceling is made, the control task is reduced to a simple linear Smith Predictor PD control, using the simplified model of the mechanical system. Some experimental results show the effectiveness of the strategy in a trajectory tracking task for a perturbed flywheel.