Study and Implementation of Algorithms Inspired by Movements and Control Strategies of Plant Roots

Aim of the present work is to implement innovative solutions for the movements and control of plant-inspired robots, by extracting fundamental behavioral rules from plant roots. Biological systems have been source of inspiration for engineers and roboticists since long time; especially animals, or even simpler organisms such as bacteria, have inspired morphology and behavior of robots and optimization algorithms. Plants have instead been taken as models in robotics only relatively recently. Being sessile organisms and devoid of a neural system, they have rarely sparked interest in robotics community. On the contrary, plants show a numerous series of movements and communication abilities that can offer new cues for designing innovative robots for exploration tasks. In particular, root apparatus and its apexes represent the organ delegates to anchor and forage the whole plant system and has to mediate among many stimuli and needs. These observations motivated the present dissertation which presents a series of data from literature and purposely performed experiments to extract specifications and design rules from plant roots for the development of innovative penetration strategies and control algorithms. Results of a deep study on a peculiar movement observed in plant roots, i.e., circumnutation, demonstrate its role in optimizing root soil penetration. Such strategy can indeed be considered relevant for both real plants and artificial penetration devices, helping to employ less forces and energy in digging tasks. Moreover, the same movement has been investigated as mechanism in plant roots for resources exploration and exploitation; by comparing it with the oscillatory movement actuated during chemical stimulation by a relatively similar simple organism, i.e., Drosophila larvae. Two different control strategies are also presented, which take inspiration from tropic responses and from the uptake-kinetic of nutrients by roots. In particular, the latter, because of a distributed knowledge achieved by internal communication channels, reveals an interesting emerging collaborative behavior among roots for the optimization of plant wellness. All the investigated strategies are implemented for the control of a plant-inspired robot, called Plantoid, which nicely validates the hypothesis on circumnutations’ role and collaborative behavior done on the biological counterpart. The expected impacts of present study are twofold: I) to demonstrate that plant roots are a valid model for the realization of innovative technological solutions, specifically control strategies, potentially useful to expand algorithms in the swarm intelligence field; II) to provide an effective approach for the validation of biological hypotheses formulated on plant movements and behavior.