Design tool for small off road unmanned wheeled ground vehicles

Abstract

Small unmanned ground vehicles (SUGVs) are used more than ever before in fields ranging from planetary exploration to combat. The success of these vehi-cles depends largely on their energy system performance. In order to maximize the effectiveness of SUGVs and their mission success rate, energy system per-formance must be considered in the original design of the vehicle. For this rea-son an early-stage design tool for off-road skid-steering wheeled SUGVs was developed. The tool provides the user immediate feedback regarding the effect of vehicle and mission parameters on the system’s feasibility and efficiency. The design tool uses the fundamentals of energy conservation, component scal-ing laws, and the theory of terramechanics to determine system feasibility over a variety of operating conditions. This step can eliminate designs which would fail due to insufficient tractive force or energy supply, for example. Further analysis examines the tradeoff between any two vehicle parameters on system performance. In particular, this step is useful for analyzing the interdependence of motor size and transmission ratio on system feasibility and efficiency. Final-ly, the tool can quickly optimize both design and control for a predetermined mission (distance, elevation profile, soil type). Given a range of vehicle pa-rameter values, all design combinations are compared to find the optimal solu-tion using a predefined velocity profile. Then, using the optimal vehicle design, the velocity profile is treated as a control parameter and optimized for the mis-sion while maintaining total travel time. This process iterates until the solution converges. The design tool can help eliminate poor vehicle designs early in the process, lead to more robust designs capable of performing in a variety of oper-ating conditions, and provide insight into the benefits of autonomous operation through flexibility in vehicle speed.