Path planning,modeling and simulation of an autonomous articulated heavy construction machine performing a loading cycle

This research presents path planning and tracking for an articulated large wheel loader during the travel portion of a loading cycle. The study proposes a methodology for path planning, modeling, simulation and control of such vehicles; the analysis focuses on all of these components together and explains the relation among them. The developed methodology for path planning takes into account the dynamics and the performance characteristics of the heavy construction articulated vehicles, it also takes into account the construction working site constraints. The path optimization criterion is based on distance and cusp minimization without neglecting the constraints imposed by the size of the vehicle and its stable turning radius. The proposed path planning methodology is an extension and an improvement for Reeds and Shepp algorithm for a point shortest path calculation. The optimal path is consisted of circular arcs and straight segments, the radius is constant and identical for each arc in the desired path, the radius assumed to be similar to the minimum turning radius of the machine. When optimizing articulated machine path; to best account for machine size and articulation; more than one approach are discussed and compared. The machine is modeled and simulated during tracing the pre-defined planned path. The machine model includes the main frames, tires and a steering controller. The developed PID controller is used to keep machine lateral position within the pre-defined path while traveling with constant speed. The results showed an acceptable optimized path which the machine is able to track closely.