Progettazione di una piattaforma robotica mobile sovra-attuata per compiti di assistenza = Design of a novel over-actuated mobile robotic platform for assistive tasks

This Thesis work discusses the functional design, the kinematic and dynamic performance of a novel over-actuated mobile platform for assistive robotics tasks. In the last decades, an unprecedented decrease in fertility and mortality rates in industrialized countries yielded the general aging of the population. Such a phenomenon affected the everyday life of individuals as well as organizations, either government or private, to the point that they are nowadays seeking the solution to the increasing demand for health care, housing, care-giving, and social security. In this scenario, this robotic platform aims to fulfill a design task, specifically oriented towards the field of assistance machines. Its main peculiarity is that of owning an innovative architecture expressly conceived to enhance the dynamics performance offered by the present-day solutions for omnidirectional planar motions. The machine, named Paquitop 01, is aimed at living and working in a domestic, non-structured, and variously populated environment, but can also be employed in other spaces, such as sanitary environment or even business or office scenarios. Such a premise is a crucial point within the design process, from either the mechanical or the control point of view, for it arises a set of uncharted challenges under many aspects. Which go from the ability to avoid or overpass small obstacles, passing through the capability to achieve specific person tracking tasks, and arriving at the need of operating with an as-high-as-possible dynamic performance. To achieve such a wide variety of issues a preliminary accurate analysis has been developed adopting a modular design. The first conceptual design consists of a mobile platform provided with a telescopic device on which exteroceptive sensors (like cameras or proximity devices) and a low-dexterity manipulation arm are installed. The mobile platform is suspended on four wheels: two standard off-centered passive castor wheels and two driven wheels which are also provided with a steering degree of freedom. Later, an accurate trajectory planning has been developed to minimize the dynamic loads generated by the motion assigned. This work proposes the use of Bézier's Polynomials to perform the definition of the path in the space. To impose the continuity of the path, the algorithm described implements an inner method to calculate the necessary points of control for the curve. On this "smooth" path, an appropriate time-dependency law is applied. To guarantee a steady floor contact and stability in every using condition, a proper mechanical design of the wheel's suspensions must also be foreseen. For this reason, the dynamics of the robot have been analyzed to define a designing method for the suspensions of the platform. The last part of this Work aims to propose some architectures for the robotic platform. In particular, some designs are drawn for the swerve-drive-wheel module, for the telescopic device, and for the chassis.