The control of semi-autonomous two-wheeled robots undergoing large payload-variations

We report on the control of semi-autonomous two-wheeled mobile robots undergoing large variations of the payload. These robots being underactuated, their control poses some challenges when resorting to a simple controller. The latter being a linear controller, its robustness with respect to model uncertainty needs to be investigated. To do this, we conducted a time-domain analysis of robustness of the foregoing controller with respect to parametric and unmodeled dynamics uncertainty. The controller, which is designed by a dominant second-order pole technique, turns out to be fragile (as opposed to robust) with respect to unmodeled dynamics uncertainty. In order to cope with this problem, a linear-quadratic regulator is designed. By numerical simulation we show that the latter features robustness with respect to both types of uncertainty.