How extending the kinematic model affects path following in off-road terrain for differential drive UGVs

Abstract

Traversal in off-road conditions for Unmanned Ground Vehicles is highly relevant for defence applications, with an increasing amount of research being put into the field. A central part of the autonomous traversal is path following, where there currently exist many stable controllers. However, conventional path following controllers often relies on ideal vehicle models that make assumptions about the terrain that are no longer valid in off-road conditions. Therefore, research is needed into how conventional controllers are affected by off-road terrain and if extending the vehicle model with relevant parameters can improve the performance. In this paper, a controller based on Active Disturbance Rejection Control and a controller based on Instantaneous Centre of Rotation are tested against a conventional controller in off-road conditions. Results from simulations illustrate how the conventional controller is affected by variations in the vehicle’s rotation centre while the proposed controllers have improved performance when simulating rough terrain conditions. Real world experiments were conducted in uneven sandy terrain, where all of the controllers showed decent performance, but the proposed controllers had the lowest cross-track error. Future Unmanned Ground Vehicle operations can improve performance by using the proposed controllers when the vehicle is experiencing rough terrain where the Instantaneous Centre of Rotation is considerably shifted from its ideal location. On the other hand, the conventional controller should produce decent performance in moderate conditions. Further research is needed to understand what types of real world conditions make the performance of the conventional controller significantly decrease, thus justifying the use of one of the proposed controllers.