In the last decades, an unprecedented decrease of fertility and mortality rates in industrialized countries yielded a general ageing of the population. Such 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 of health care, housing, care-giving, and social security. In this scenario, this piece of research aims to fulfil a design task, specifically oriented towards the field of assistance machines. The functionalities which should be guaranteed are mainly two: to follow and monitor reduced mobility subjects, to maintain a constant view contact with its targets, and to accomplish such duties in a non-structured and possibly peopled environment. In particular, the paper analyses the dynamics of Paquitop, a novel over-actuated mobile platform. Its main peculiarity is that of owning an innovative architecture expressly conceived to enhance the performance offered by the present-day solutions for omni-directional planar motions. Given its purpose, the robot architecture was thought for guaranteeing an effective fulfilment of its primary tasks. This arises a set of uncharted challenges, under both mechanical and control points of view.

The platform which is the main objective of the manuscript is suspended on four wheels: two standard off centred passive castor wheels and two driven wheels which are also provided with a steering degree of freedom. Such configuration provides a redundant set of constraints, under both actuation and stability points of view. On the one hand, the structure yields several advantages related to a superior manoeuvrability and to an enhanced stability during high-dynamics motions. On the other, some cons are to be taken into proper consideration. Firstly, the presence of a redundant set of actuators implies the need of a careful motion planning strategy which must consider the redundancy and control the motors accordingly to the set of kinematics constraint which limits the mobility of the platform. Moreover, a proper mechanical design must be foreseen, in order to guarantee that the four wheels are always in contact with the ground at the same time even when the robot is passing over obstacles or is performing curved trajectories. To such aim, the wheels must be attached to the platform with many suspension systems, expressly designed on the robot purpose and physical properties, able to adjust the mutual pose of chassis and wheels to ensure a steady floor contact and the stability in every using condition.

The manuscript analyses the dynamics of the proposed solution, in order to characterize it with respect to the robot tasks. A set of possible steering configurations are investigated under different use conditions. The vertical dynamics of the suspensions is taken into consideration, together with the whole robot stability while approaching different trajectories. The main objective is that of providing a set of guidelines for the succeeding design and prototyping steps of the project for both passive mechanical components and actuation systems.


Dynamics Characterization of Paquitop: A Novel Platform for Robotized Domestic Applications

Division / Sponsors: 
Aerospace, Bioengineering, Applied Mechanics, Design Engineering Division, Advanced Energy Systems, Manufacturing Engineering Division, Noise Control and Acoustics, Nondestructive Evaluation, Diagnosis, and Prognosis (NDPD), Nuclear Engineering Division, Process Industries Division, Fluids Engineering, Heat Transfer, Materials, Microelectromechanical Systems, Safety Engineering and Risk Analysis, Computers & Information in Engineering


Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2020/volume/84478

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