Sampled-data feedback control of uncertain nonholonomic systems in chained forms

It is imperative to find a sampled-data controller for nonholonomic systems due to the need to implement through the use of digital computers. Nonholonomic systems in chained form are sufficiently important to research to the numerous real world applications, mobile robots being one of the biggest. Moreover, due to the presence of uncertain nonlinearities, most of the existing design methods are inapplicable to these systems. It has been proven that under a lower-triangular growth condition, a class of uncertain nonlinear systems can be globally stabilized by a sampled-data output feedback controller whose observer and control laws are discrete-time and linear. In this thesis, using a change of coordinates and combining the recently developed sampled-data output feedback control method, we first design a sampled-data output feedback controller to stabilize the nonholonomic system with a single z-state. For nonholonomic systems with two-dimensional z-states, the output feedback control problem becomes much more challenging since the boundedness of the change of coordinates is not proved. To solve this problem, we design a controller for the z-system, which can guarantee the boundedness of the change of coordinates after a certain time. From this we can construct a globally stabilizing output feedback controller for the nonholonomic systems. Computer simulations are conducted to show the effectiveness of the proposed controllers.