Kinematic Modeling, Analysis and Control of Highly Reconfigurable Articulated Wheeled Vehicles

The Articulated Wheeled Vehicle (AWV) paradigm examines a class of wheeled vehicles where the chassis is connected via articulated chains to a set of ground-contact wheels. Activelyor passivelycontrolled articulations can help alter wheel placement with respect to chassis during locomotion, endowing the vehicle with significant reconfigurability and redundancy. The ensuing ‘leg-wheeled’ systems exploit these capabilities to realize significant advantages (improved stability, obstacle surmounting capability, enhanced robustness) over both traditional wheeledand/or legged-systems in a range of uneven-terrain locomotion applications. In our previous work, we exploited the reconfiguration capabilities of a planar AWR to achieve internal shape regulation, secondary to a trajectory-following task. In this work, we extend these capabilities to the full 3D case – in order to utilize the full potential of kinematicand actuationredundancy to enhance rough-terrain locomotion. INTRODUCTION Articulated Wheeled Vehicles (AWVs) consist of a principal vehicle-chassis connected to a set of wheels with ground contact via activelyor passively-articulated chains. The presence of the so-called ‘articulated leg-wheel’ chain endows reconfigurability, by allowing relocation of the wheel with respect to the chassis. The AWV paradigm offers immense possibilities for enhanced locomotion-performance of autonomous mobile robots while assuring the reliability of the system. For instance, the articulated-suspensions permit the vehicle to change the location of center of mass by adjusting the linkages/joints, so as to avoid the rollover when passing the uneven terrain [1, 2]. Similarly, the vehicle can reduce its footprint to pass narrow doorways or expand the wheelbase when stability is required. The resulting class of Leg-Wheel Vehicles (as the AWVs are also called) have many potential applications (ranging from planetary exploration [3, 4], agriculture [5, 6] to military and rescue operations) due to their advantages over traditional wheeled systems. Figure 1: Schematic of Leg-Wheel Vehicles. In most applications, the wheels of an AWR are considered to be rigid discs with a single point-of-contact with the terrain. The wheel velocities are governed by a set of non-holonomic constraints, which permit rolling along the disk-plane without allowing lateral side-slip. However, potentially, these velocitylevel constraints can be violated, but results in slipping and skidding. Minimization of slipping and skidding is usually desired (both from the perspective of reducing the energy dissipation and improving measurement uncertainty) and can be Aliakbar Alamdari Mechanical and Aerospace Engineering, SUNY at Buffalo Buffalo, NY, 14260 [email protected] Xiaobo Zhou Mechanical and Aerospace Engineering, SUNY at Buffalo Buffalo, NY, 14260 [email protected] Venkat N. Krovi Mechanical and Aerospace Engineering, SUNY at Buffalo Buffalo, NY, 14260 [email protected]