Study and stability evaluation of a non-conventional Articulated Robotic System for Side-Slope Activities

At today, small tractors or (semi)-autonomous robotic systems able to move nimbly between wine rows on hills and/or in side-slope working activities are surely not common and still an exception. Indeed, the design of such a kind of versatile robotic platforms is still a challenge. One of the main problems is the stability of the overall vehicle [1] and the availability of real-time anti-overturning systems able to predict and avoid dangerous configurations. Conventional architectures, wheeled or tracked, have been usually exploited for such kind of attempts but, recently, new attention has been given to articulated-frame configurations [2, 3]. Wheeled articulated vehicles are made of two parts, each one made of an axle with two wheels, linked together through a 2 Degree of Freedom (DoF) universal “articulation joint”. The yaw DoF actively modifies the system steering angle, while the roll DoF is passive allowing the adaptation of the system to uneven terrains. Despite safety concerns and rapid evolution of both tractors and mobile robotic systems, little research has been made on the different stability and steering behaviours of the articulated platforms with respect to the conventional fixed-chassis ones [4]. This work wants to resume our current research stage on the study and development of a non-conventional (semi)-autonomous articulated robotic system suitable for side-slope activities. In particular, a numerical implementation and validation of an effective quasi-static model for the stability analysis of non-conventional articulated platforms has been done. Once the model is available, the analysis of the most critical configurations that can lead to a rollover have been highlighted, a stability index defined, and the locking effect, in terms of increment of the stability margin, of the 2nd DoF of the articulated joint investigated. Finally, a simple and cheap real-time anti-overturning mechatronic device based on a Microchip microcontroller and Inertial Measurement Units (IMUs), able to both predict critical configurations and to either alert the user in case of a driven vehicle or to actively react to avoid the possible overturning in case of an autonomous system, has been designed and developed.