Stefano Mintchev

A novel autonomous, bioinspired swimming robot developed by neuroscientists and bioengineers

This paper describes the development of a new biorobotic platform inspired by the lamprey. Design, fabrication and implemented control are all based on biomechanical and neuroscientific findings on this eel-like fish. The lamprey model has been extensively studied and characterized in recent years because it possesses all basic functions and control mechanisms of higher vertebrates, while at the same time having fewer neurons and simplified neural structures. The untethered robot has a flexible body driven by compliant actuators with proprioceptive feedback. It also has binocular vision for vision-based navigation. The platform has been successfully and extensively experimentally tested in aquatic environments, has high energy efficiency and is ready to be used as investigation tool for high level motor tasks.

The green leafhopper, Cicadella viridis (Hemiptera, Auchenorrhyncha, Cicadellidae), jumps with near-constant acceleration

SUMMARY Jumping insects develop accelerations that can greatly exceed gravitational acceleration. Although several species have been analysed using different tools, ranging from a purely physical to a morpho-physiological approach, instantaneous dynamic and kinematic data concerning the jumping motion are lacking. This is mainly due to the difficulty in observing in detail events that occur in a few milliseconds. In this study, the behaviour of the green leafhopper, Cicadella viridis, was investigated during the take-off phase of the jump, through high-speed video recordings (8000 frames s−1). We demonstrate that C. viridis is able to maintain fairly constant acceleration during overall leg elongation. The force exerted at the foot–ground interface is nearly constant and differs from the force expected from other typical motion models. A biomechanical model was used to highlight that this ability relies on the morphology of C. viridis hind legs, which act as a motion converter with a variable transmission ratio and use the time-dependent musculo-elastic force to generate a nearly constant thrust at the body–ground interface. This modulation mechanism minimizes the risk of breaking the substrate thanks to the absence of force peaks. The results of this study are of broad relevance in different research fields ranging from biomechanics to robotics.

Variable Stiffness Fiber with Self-Healing Capability

A variable stiffness fiber made of silicone and low melting point alloys quickly becomes >700 times softer and >400 times more deformable when heated above 62 °C. It shows remarkable self-healing properties and can be clamped, knitted, and bonded, as shown in a foldable multi-purpose drone, a wearable cast for bone injuries, and a soft multi-directional actuator.

Underwater navigation based on passive electric sense

In underwater robotics, several homing and docking techniques are currently being investigated. They aim to facilitate the recovery of underwater vehicles, as well as their connection to underwater stations for battery charging and data exchange. Developing reliable underwater docking strategies is a critical issue especially in murky water and/or in confined and cluttered environments. Commonly used underwater sensors such as sonar and camera can fail under these conditions. We show how a bio-inspired sensor could be used to help guide an underwater robot during a docking phase. The sensor is inspired by the passive electro-location ability of electric fish. Exploiting the electric interactions and the morphology of the vehicle, a sensor-based reactive control law is proposed. It allows the guidance of the robot toward the docking station by following an exogenous electric field generated by a set of electrodes fixed to the environment. This is achieved while avoiding insulating perturbative objects. This control strategy is theoretically analysed and validated with experiments carried out on a setup dedicated to the study of electric sense. Though promising, these results are but a first step towards the implementation of an approach to docking in more realistic conditions, such as in turbid salt water or in the presence of conductive perturbative objects.

Mechatronic design of a miniature underwater robot for swarm operations

Due to extreme and unpredictable conditions, oceanic missions are still a persistent challenge in robotics. With the aim of improving decision autonomy and robustness against unforeseen circumstances, the EU-funded CoCoRo project is developing a cognitive swarm of underwater robots. Swarm and cognition algorithms will be studied and validated with a large number of miniaturized and affordable AUVs, named Jeff, whose custom mechanical design is described in this paper. Jeff is conceived for high-mobility in 3D cluttered environments and has distributed sensors for multi-directional perception and communication. The propulsion and the buoyancy systems are designed with watertight and energetically efficient solutions to improve system reliability and energetic autonomy. The manuscript also describes the design of a docking system that allows Jeff to passively align and connect to a submerged docking station for battery charging.

An underwater reconfigurable robot with bioinspired electric sense

Morphology, perception and locomotion are three key features highly inter-dependent in robotics. This paper gives an overview of an underwater modular robotic platform equipped with a bio-inspired electric sense. The platform is reconfigurable in the sense that it can split into independent rigid modules and vice-versa. Composed of 9 modules, the longer entity can swim like an eel over long distances, while once detached, each of its modules is efficient for small displacements with a high accuracy. Challenges are to mechanically ensure the morphology changes and to do it automatically. Electric sense is used to guide the modules during docking phases and to navigate in unknown scenes. Several aspects of the design of the robot are described and a particular attention is paid to the inter-module docking system. The feasibility of the design is assessed through experiments.

A bioinspired autonomous swimming robot as a tool for studying goal-directed locomotion

The bioinspired approach has been key in combining the disciplines of robotics with neuroscience in an effective and promising fashion. Indeed, certain aspects in the field of neuroscience, such as goal-directed locomotion and behaviour selection, can be validated through robotic artefacts. In particular, swimming is a functionally important behaviour where neuromuscular structures, neural control architecture and operation can be replicated artificially following models from biology and neuroscience. In this article, we present a biomimetic system inspired by the lamprey, an early vertebrate that locomotes using anguilliform swimming. The artefact possesses extra- and proprioceptive sensory receptors, muscle-like actuation, distributed embedded control and a vision system. Experiments on optimised swimming and on goal-directed locomotion are reported, as well as the assessment of the performance of the system, which shows high energy efficiency and adaptive behaviour. While the focus is on providing a robotic platform for testing biological models, the reported system can also be of major relevance for the development of engineering system applications.

Investigation of Collective Behaviour and Electrocommunication in the Weakly Electric Fish, Mormyrus rume, through a biomimetic Robotic Dummy Fish

A robotic fish has been developed to create a mixed bio-hybrid system made up of weakly electric fish and a mobile dummy fish. Weakly electric fish are capable of interacting with each other via sequences of self-generated electric signals during electrocommunication. Here we present the design of an artificial dummy fish, which is subsequently tested in behavioural experiments. The robot consists of two parts: a flexible tail that can move at different frequencies and amplitudes, performing a carangiform oscillation, and a rigid head containing the motor for the tail oscillation. The dummy fish mimics the weakly electric fish Mormyrus rume in morphology, size and electric signal generation. In order to study electrical interactions, the dummy fish is equipped with ten electrodes that record electric signals of nearby real fish and generate electric dipole fields around itself that are similar to those produced by real fish in both waveform and sequence. Behavioural experiments demonstrate that the dummy fish is able to recruit both single individuals and groups of M. rume from a shelter into an exposed area. The development of an artificial dummy fish may help to understand fundamental aspects of collective behaviour in weakly electric fish and the properties necessary to initiate and sustain it in closed-loop feedback experiments based on electrocommunication.

Foldable and self-deployable pocket sized quadrotor

Aerial robots provide valuable support in several high-risk scenarios thanks to their capability to quickly fly to locations dangerous or even inaccessible to humans. In order to fully benefit from these features, aerial robots should be easy to transport and rapid to deploy. With this aim, this paper focuses on the development of a novel pocket sized quadrotor with foldable arms. The quadrotor can be packaged for transportation by folding its arms around the main frame. Before flight, the quadrotors arms self-deploy in 0.3 seconds thanks to the torque generated by the propellers. The paper describes the design strategies used for developing lightweight, stiff and self-deployable foldable arms for miniature quadrotors. The arms are manufactured according to an origami technique with a foldable multi-layer material. A prototype of the quadrotor is presented as a proof of concept and performance of the system is assessed.

Towards docking for small scale underwater robots

This article presents a novel docking system developed for miniature underwater robots. Recent years have seen an increased diffusion of robots for ocean monitoring, exploration and maintenance of underwater infrastructures. The versatility of those vehicles is extremely affected and limited by energetic constraints and difficulties in updating their mission parameters. Submerged docking stations are a promising solution for providing energy sources and data exchange, thus extending autonomy and mission duration of underwater robots. Furthermore, the docking capability is a novel, but promising approach to enable modularity and reconfigurability in underwater robotics. The authors here propose a hybrid docking system composed of a magnetic alignment unit and a mechanical connection. The former passively aligns and guides the underwater vehicle facilitating a subsequent mechanical connection. The reliability of the system is both analytically investigated and experimentally validated. Finally, the mechanical design of the docking system of two miniature underwater robots is described in detail.