Evaluation and stability comparison of different vehicle configurations for robotic agricultural operations on side-slopes

Progress in sensors, controllers and mechatronics devices and the development of (semi-) autonomous systems that can travel safely on uneven terrain and perform many operations has encouraged research interest in the use of robotics for agriculture and forestry in hilly and mountainous terrains. Here, the main mobile configurations that are likely to be used for robotic platforms as implement-carriers (3-wheeled, conventional/articulated 4- wheeled, tracked) were reviewed and discussed in terms of their suitability for agricultural operations and their stability. A numerical index accounting for the lateral stability of a vehicle, the roll stability index, was used to indicate the in-field working capacity of these platforms during side-slope operations. Assuming the same overall dimensions for all the configurations, the 3-wheel configuration, although very simple and agile, was seen as being the least stable, while a tracked vehicle was the most stable, although it had some important drawbacks when used in an agricultural context. This drawbacks included increased soil erosion and landslides caused by its tracks especially in the areas involving turning manoeuvres. The articulated system was found to be the most suitable for uneven and side-slope terrains because of its optimal steering capacity, agility and good stability. It was found to reach a critical stability angle close to the 4-wheel vehicle.