Spatial integration for a nonlinear path tracking control law

A nonlinear spatial path tracking control law, called the ε-controller (C_ε), was developed for autonomous ground vehicles (AGVs) such as the USU T-series and ODIS (omni-directional inspection system) wheeled mobile robots (WMRs). It is essentially a SISO regulator operating on the normal spatial deviation, ε, of the robot from the desired path. As our performance expectation of C_ε is entirely spatial a logical choice of the regulator should avoid any reference to time. We present a spatial integrator PI (SI-PI) regulator for C_ε which is devoid of any time references while its structure includes some of the robot dynamics. It is also shown that the control action taken by this regulator represents the work done in moving the robot through an error vector field. The regulator gains are designed using a validated nonlinear Simulink™/StateFlow model. The experimental results presented show the effectiveness of the proposed SI-PI regulation scheme in the path tracking control of the ODIS WMR.