Analysis of the Effects of Path Properties on Autonomous Motion Control of a Hydraulic Tracked Vehicle

Mobile working machines have recently been developed towards field robotics systems that are more self-aware, intelligent, autonomous and energy-efficient. Such autonomy can offer advantages in, for example, construction sites, where a number of tasks involve accurate path following. From the robotic viewpoint, a mobile robot is supposed to follow the desired values perfectly to remain on a certain path as long as its localization provides the necessary pose feedback. In field robotics, especially in the cases of hydraulic working machines, there are nonlinear system dynamics affecting the mobile platform, which makes accurate motion control challenging. The sources of these nonlinearities can be the internal system dynamics or environmental effects. Due to the use of generic autonomous motion planning and control methods in the existing literature, there are certain effects of hydrostatic driveline on the system that have been overlooked. To fill such a gap, this paper first analyzes and points out the effects of geometrical path properties on the performance of hydraulic actuators in path-following control. Then, using a closed-loop model of a skid-steered vehicle with hydraulic propulsion, we show simulation results with the machine following paths with different curvatures around an obstacle. Analysis of the results show the significant role of the system dynamics in shifting the optimal path when the dynamics of the driveline and terrain contact are included.