A Bioinspired Fluid-Filled Soft Linear Actuator.

In bioinspired soft robotics, very few studies have focused on fluidic transmissions and there is an urgent need for translating fluidic concepts into realizable fluidic components to be applied in different fields. Nature has often offered an inspiring reference to design new efficient devices. Inspired by the working principle of a marine worm, the sipunculid species Phascolosoma stephensoni (Sipunculidae, Annelida), a soft linear fluidic actuator is here presented. The natural hydrostatic skeleton combined with muscle activity enables these organisms to protrude a part of their body to explore the surrounding. Looking at the hydrostatic skeleton and protrusion mechanism of sipunculids, our solution is based on a twofold fluidic component, exploiting the advantages of both pneumatic and hydraulic actuations and providing a novel fluidic transmission mechanism. The inflation of a soft pneumatic chamber is associated with the stretch of an inner hydraulic chamber due to the incompressibility of the liquid. Actuator stretch and forces have been characterized to determine system performance. In addition, an analytical model has been derived to relate the stretch ability to the inlet pressure. Three different sizes of prototypes were tested to evaluate the suitability of the proposed design for miniaturization. The proposed actuator features a strain equal to 40-50% of its initial length-depending on size-and output forces up to 18 N in the largest prototypes. The proposed bioinspired actuator expands the design of fluidic actuators and can pave the way for new approaches in soft robotics with potential application in the medical field.

Marine Robotics for Deep-Sea Specimen Collection: A Taxonomy of Underwater Manipulative Actions.

In order to develop a gripping system or control strategy that improves scientific sampling procedures, knowledge of the process and the consequent definition of requirements is fundamental. Nevertheless, factors influencing sampling procedures have not been extensively described, and selected strategies mostly depend on pilots' and researchers' experience. We interviewed 17 researchers and remotely operated vehicle (ROV) technical operators, through a formal questionnaire or in-person interviews, to collect evidence of sampling procedures based on their direct field experience. We methodologically analyzed sampling procedures to extract single basic actions (called atomic manipulations). Available equipment, environment and species-specific features strongly influenced the manipulative choices. We identified a list of functional and technical requirements for the development of novel end-effectors for marine sampling. Our results indicate that the unstructured and highly variable deep-sea environment requires a versatile system, capable of robust interactions with hard surfaces such as pushing or scraping, precise tuning of gripping force for tasks such as pulling delicate organisms away from hard and soft substrates, and rigid holding, as well as a mechanism for rapidly switching among external tools.

Marine Robotics for Deep-Sea Specimen Collection: A Systematic Review of Underwater Grippers.

The collection of delicate deep-sea specimens of biological interest with remotely operated vehicle (ROV) industrial grippers and tools is a long and expensive procedure. Industrial grippers were originally designed for heavy manipulation tasks, while sampling specimens requires dexterity and precision. We describe the grippers and tools commonly used in underwater sampling for scientific purposes, systematically review the state of the art of research in underwater gripping technologies, and identify design trends. We discuss the possibility of executing typical manipulations of sampling procedures with commonly used grippers and research prototypes. Our results indicate that commonly used grippers ensure that the basic actions either of gripping or caging are possible, and their functionality is extended by holding proper tools. Moreover, the approach of the research status seems to have changed its focus in recent years: from the demonstration of the validity of a specific technology (actuation, transmission, sensing) for marine applications, to the solution of specific needs of underwater manipulation. Finally, we summarize the environmental and operational requirements that should be considered in the design of an underwater gripper.

Research Trends and Future Perspectives in Marine Biomimicking Robotics.

Mechatronic and soft robotics are taking inspiration from the animal kingdom to create new high-performance robots. Here, we focused on marine biomimetic research and used innovative bibliographic statistics tools, to highlight established and emerging knowledge domains. A total of 6980 scientific publications retrieved from the Scopus database (1950-2020), evidencing a sharp research increase in 2003-2004. Clustering analysis of countries collaborations showed two major Asian-North America and European clusters. Three significant areas appeared: (i) energy provision, whose advancement mainly relies on microbial fuel cells, (ii) biomaterials for not yet fully operational soft-robotic solutions; and finally (iii), design and control, chiefly oriented to locomotor designs. In this scenario, marine biomimicking robotics still lacks solutions for the long-lasting energy provision, which presently hinders operation autonomy. In the research environment, identifying natural processes by which living organisms obtain energy is thus urgent to sustain energy-demanding tasks while, at the same time, the natural designs must increasingly inform to optimize energy consumption.

Protrusion mechanism study in sipunculid worms as model for developing bio-inspired linear actuators.

The invertebrates ability to adapt to the environment during motion represents an intriguing feature to inspire robotic systems. We analysed the sipunculid speciesPhascolosoma stephensoni(Sipunculidae, Annelida), and quantitatively studied the motion behaviour of this unsegmented worm. The hydrostatic skeleton and the muscle activity make the infaunalP.stephensoniable to extrude part of its body (the introvert) from its burrow to explore the environment by remaining hidden within the rocky substrate where it settled. The introvert protrusion is associated with changes in the body shape while keeping the overall volume constant. In this study, we employed a marker-less optical tracking strategy to quantitatively study introvert protrusion (i.e. kinematics, elongation percentage and forces exerted) in different navigation media. WhenP.stephensonispecimens were free in sea water (outside from the burrow), the worms reached lengths up to three times their initial ones after protrusion. Moreover, they were able to elongate their introvert inside a viscous medium such as agar-based hydrogel. In this case, the organisms were able to break the hydrogel material, exerting forces up to 3 N and then to navigate easily inside it, producing stresses of some tens of kPa. Our measurements can be used as guidelines and specifications to design and develop novel smart robotic systems.

Sensing pressure distribution on a lower-limb exoskeleton physical human-machine interface.

A sensory apparatus to monitor pressure distribution on the physical human-robot interface of lower-limb exoskeletons is presented. We propose a distributed measure of the interaction pressure over the whole contact area between the user and the machine as an alternative measurement method of human-robot interaction. To obtain this measure, an array of newly-developed soft silicone pressure sensors is inserted between the limb and the mechanical interface that connects the robot to the user, in direct contact with the wearer's skin. Compared to state-of-the-art measures, the advantage of this approach is that it allows for a distributed measure of the interaction pressure, which could be useful for the assessment of safety and comfort of human-robot interaction. This paper presents the new sensor and its characterization, and the development of an interaction measurement apparatus, which is applied to a lower-limb rehabilitation robot. The system is calibrated, and an example its use during a prototypical gait training task is presented.

The neuro-robotics paradigm: NEURARM, NEUROExos, HANDEXOS.

This work describes the neuro-robotics paradigm: the fusion of neuroscience and robotics. The fusion of neuroscience and robotics, called neuro-robotics, is fundamental to develop robotic systems to be used in functional support, personal assistance and neuro-rehabilitation. While usually the robotic device is considered as a "tool" for neuroscientific studies, a breakthrough is obtained if the two scientific competences and methodologies converge to develop innovative platforms to go beyond robotics by including novel models to design better robots. This paper describes three robotic platforms developed at the ARTS lab of Scuola Superiore Sant'Anna, implementing neuro-robotic design paradigm.

Humans can integrate force feedback to toes in their sensorimotor control of a robotic hand.

Tactile sensory feedback is essential for dexterous object manipulation. Users of hand myoelectric prostheses without tactile feedback must depend essentially on vision to control their device. Indeed, improved tactile feedback is one of their main priorities. Previous research has provided evidence that conveying tactile feedback can improve prostheses control, although additional effort is required to solve problems related to pattern recognition learning, unpleasant sensations, sensory adaptation, and low spatiotemporal resolution. Still, these studies have mainly focused on providing stimulation to hairy skin regions close to the amputation site, i.e., usually to the upper arm. Here, we explored the possibility to provide tactile feedback to the glabrous skin of toes, which have mechanical and neurophysiological properties similar to the fingertips. We explored this paradigm in a grasp-and-lift task, in which healthy participants controlled two opposing digits of a robotic hand by changing the spacing of their index finger and thumb. The normal forces applied by the robotic fingertips to a test object were fed back to the right big and second toe. We show that within a few lifting trials, all the participants incorporated the force feedback received by the foot in their sensorimotor control of the robotic hand.

A sensorized thumb for force closed-loop control of hand neuroprostheses.

In this paper, we presented a sensorized thumb based on a matrix of piezoresistive force sensors, with an acquisition unit and a special wearing support. The sensor was calibrated and then the device was tested during different tasks simulating activities of daily living performed by seven able-bodied subjects. By means of these experiments, we verified that the device proposed can be used to extract force information during grasp. In fact, the device was able to provide useful force information in the 98% of the trials with a good repeatability during all the different conditions. Moreover, we evaluated the patterns obtained during the different grasping tasks. The palmar grasps were performed in a similar manner, whereas the lateral pinch and the spherical volar grip were more different. This device can provide force information with good performance and acceptability and it can be used for force closed-loop control of hand neuroprostheses.