Articulated steering control design for autonomous tracked vehicles

The ongoing trend towards driving automation increases the interest of applying novel automated vehicle concepts also to tracked vehicles. The vehicle presented in this paper is an articulated tracked vehicle that is characterized by two units connected through a hydraulically actuated multi axial joint designed for steering operation. The paper provides a vehicle mathematical model and presents a methodology for controlling the hydraulic joint to enable an autonomous steering operation on a rigid and flat surface. The vehicle planar motion is analyzed through a non-linear model describing longitudinal, lateral and yaw dynamics of the units’ body which is completed by the rotational dynamics of the four tracks, the kinematic relations imposed by the steering joint and the hydraulic response of the actuation system. The steering operation is accomplished by imposing a relative angle (hitch angle) between the two units thus providing a desired vehicle cornering behavior. The first addressed issue is to correlate the vehicle trajectory curvature radius to the hitch angle by means of specific characteristics for the whole vehicle speed operative range. The second issue is to provide a well-defined procedure to design a directional controller characterized by a high-level logic designed for calculating the reference hitch angle and a low-level logic for controlling the hydraulic system and tracking the desired relative angle. The methodology is formulated to design the autonomous steering controller when the vehicle cornering characteristics is provided.