Controller Design for AGVs and Kalman Filter-Based Compensation of Disturbance Forces and Torques

Abstract

Controller design for autonomous 4-wheeled ground vehicles is performed with differential flatness theory. Using a 3-DOF nonlinear model of the vehicle's dynamics and through the application of differential flatness theory an equivalent model in linear canonical (Brunovksy) form is obtained. For the latter model a state feedback controller is developed that enables accurate tracking of velocity setpoints. Moreover, it is shown that with the use of Kalman Filtering it is possible to dynamically estimate the disturbances due to unknown forces and torques exerted on the vehicle. The processing of velocity measurements (provided by a small number of on-board sensors) through a Kalman Filter which has been redesigned in the form of a disturbance observer results in accurate identification of external disturbances affecting the vehicle's dynamic model. By including in the vehicle's controller an additional term that compensates for the estimated disturbance forces, the vehicle's motion characteristics remain unchanged. Numerical simulation confirms the efficiency of both the proposed controller and of the disturbance forces estimator.