A preliminary study of active stabilization for agricultural machines using a movable mass

Side overturning is a potentially dangerous phenomenon that can easily happen to agricultural machines because they typically have a high center-of-gravity (CoG) and a very narrow track-width (e.g., tractors operating in orchards). Overturning occurs when the direction of the resultant of the forces acting on the vehicle CoG intercepts the support plane outside of the “support polygon”, defined by taking the footprints of the vehicle wheels as its vertices. Here, we propose the use of a stabilization system that shifts the CoG position to ensure that the resultant force stays within the support polygon. This active stabilization is accomplished by equipping the vehicle with an additional mass that can be moved using an actuator. Using numerical simulations of a four-wheeled narrow-track tractor moving along a trajectory at constant speed, we characterize how the position of the movable mass affects vehicle stability under a quasi-static assumption. The path is a horizontal Euler spiral, having a continuously varying turning radius. The simulations are used to: (i) analyze the sensitivity of four metrics related to the vehicle stability with respect to the additional weight of the moveable mass and the position of the stabilization system, and (ii) find an optimal configuration of the stabilization system that will improve the operational limits of the vehicle.