Path tracking control with slip compensation of a global navigation satellite system based tractor-scraper land levelling system

Abstract

To provide accurate path tracking and satisfactory soil loading and unloading for a global navigation satellite system (GNSS) based tractor-scraper land levelling system, a novel model-based control method with slip compensation was developed. A sideslip estimator was developed and adapted into a tractor-scraper kinematic model. The steering angle control law was calculated based on the kinematic model, and its stability was verified using Lyapunov functions. The method was validated via field experiments in which a GNSS-based tractor-scraper land levelling system was controlled to track planned paths in a wet field to complete an autonomous land levelling operation. The experimental results showed that compared with path tracking performance of a pure pursuit control (PPC) method, the root mean square errors (RMSEs) of the total lateral deviations of the tractor and the scraper under the proposed method were reduced by 0.433 and 0.169 m respectively in headland turning. Moreover, the elevation distribution (i.e. evenness) of the field increased by 33.314% after the autonomous land levelling operation driven by the proposed method. The results showed that the proposed method could realise accurate path tracking and satisfactory land evenness. It can also be integrated into current GNSS-based tractor-scraper land levelling systems to realise autonomous land levelling with improved performance.