Experimental comparison of adaptive controllers for trajectory tracking in agricultural robotics

This paper describes the development of several controllers to handle a trajectory tracking problem for a differentially wheeled robot. Both simulations and tests on a real robot were performed. A simple kinematic controller has been implemented to calculate desired velocities based on current position and trajectory. In order to also consider the current velocities, i.e. the dynamics of the system, the output of this controller was used as input to a dynamic controller derived from a nonlinear model. The dynamic controller was made adaptive by using an on-line parameter estimation scheme to estimate the unknown parameters of the nonlinear model. Lastly, a direct model reference adaptive controller (MRAC) based on a linear model was derived and implemented as an alternative to the adaptive dynamic controller.