Harnessing steering singularities in passive path following for robotic walkers
This paper derives a new type of control law to steer the dynamic model of a wheeled robot of unicycle type along a desired spatial path. The methodology adopted for path following control deals explicitly with vehicle dynamics and plant parameter uncertainty. Furthermore, it overcomes stringent initial condition constraints that are present in a number of path following control strategies described in the literature. This is done by controlling explicitly the rate of progression of a ”virtual target” to be tracked along the path, thus bypassing the problems that arise when the position of the virtual target is simply defined by the projection of the actual vehicle on that path. The nonlinear adaptive control law proposed yields convergence of the (closed loop system) path following error trajectories to zero. Controller design relies on Lyapunov theory and backstepping techniques. Simulation results illustrate the performance of the control system proposed.