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Force/Torque-Sensorless Joint Stiffness Estimation in Articulated Soft Robots

TitleForce/Torque-Sensorless Joint Stiffness Estimation in Articulated Soft Robots
Publication TypeJournal Article
Year of Publication2022
AuthorsTrumic, M, Grioli, G, Jovanovic, K, Fagiolini, A
Date Published05/2022
KeywordsCalibration and Identification, Compliant Joints and Mechanisms, Flexible Robots, Safety in HRI

Currently, the access to the knowledge of stiffness values is typically constrained to a-priori identified models or datasheet information, which either do not usually take into account the full range of possible stiffness values or need extensive experiments. This work tackles the challenge of stiffness estimation in articulated soft manipulators, and it proposes an innovative solution adding value to the previous research by removing the necessity for force/torque sensors and generalizing to multi-degree-of-freedom robots. Built upon the theory of unknown input-state observers and recursive least-square algorithms, the solution is independent of the actuator model parameters and its internal control signals. The validity of the approach is proven analytically for single and multiple degree-offreedom robots. The obtained estimators are first evaluated via simulations on articulated soft robots with different actuations and then tested in experiments with real robotic setups using antagonistic variable stiffness actuators.

Comparison between rigid and soft poly-articulated prosthetic hands in non-expert myo-electric users shows advantages of soft robotics.

TitleComparison between rigid and soft poly-articulated prosthetic hands in non-expert myo-electric users shows advantages of soft robotics.
Publication TypeJournal Article
Year of Publication2021
AuthorsCapsi-Morales, P, Piazza, C, Catalano, MG, Grioli, G, Schiavon, L, Fiaschi, E, Bicchi, A
JournalScientific Reports
Start Page1
Date Published12/2021
ISBN NumberISSN 2045-2322

Notwithstanding the advancement of modern bionic hands and the large variety of prosthetic hands in the market, commercial devices still present limited acceptance and percentage of daily use. While commercial prostheses present rigid mechanical structures, emerging trends in the design of robotic hands are moving towards soft technologies. Although this approach is inspired by nature and could be promising for prosthetic applications, there is scant literature concerning its benefits for end-users and in real-life scenarios. In this work, we evaluate and assess the role and the benefits of soft robotic technologies in the field of prosthetics. We propose a thorough comparison between rigid and soft characteristics of two poly-articulated hands in 5 non-expert myo-electric prosthesis users in pre- and post-therapeutic training conditions. The protocol includes two standard functional assessments, three surveys for user-perception, and three customized tests to evaluate the sense of embodiment. Results highlight that rigid hands provide a more precise grasp, while soft properties show higher functionalities thanks to their adaptability to different requirements, intuitive use and more natural execution of activities of daily living. This comprehensive evaluation suggests that softness could also promote a quick integration of the system in non-expert users.


WRAPP-up: A Dual-Arm Robot for Intralogistics

TitleWRAPP-up: A Dual-Arm Robot for Intralogistics
Publication TypeJournal Article
Year of Publication2021
AuthorsGarabini, M, Caporale, D, Tincani, V, Palleschi, A, Gabellieri, C, Gugliotta, M, Settimi, A, Catalano, MGiuseppe, Grioli, G, Pallottino, L
JournalIEEE Robotics Automation Magazine

The diffusion of e-commerce has produced larger and larger volumes of varying items to be handled in warehouses, with the effect that the need for picking automation is increasing. Conventionally, automation has been achieved through a custom plant designed for large-scale production of items having well-established characteristics that are expected to change slowly and to only a small degree over time. However, today the challenge is to realize a solution that is flexible enough to handle goods with different shapes, sizes, and physical properties and that require different grasping modes. To solve this problem, we first analyzed how humans perform picking and then synthesized their behavior according to four main tactics. These were then used as guidelines for the design, planning, and control of WRAPP-up, a dual-arm robot composed of two anthropomorphic manipulators: a Pisa/IIT SoftHand and a velvet tray (Figure 1). The system has been validated and evaluated through extensive experimental tests.


Scaling of joint mass and metabolism fluctuations in in silico cell-laden spheroids

TitleScaling of joint mass and metabolism fluctuations in in silico cell-laden spheroids
Publication TypeJournal Article
Year of Publication2021
AuthorsBotte, E, Biagini, F, Magliaro, C, Rinaldo, A, Maritan, A, Ahluwalia, A
JournalProceedings of the National Academy of Sciences

Variations and fluctuations are characteristic features of biological systems and are also manifested in cell cultures. Here, we describe a computational pipeline for identifying the range of three-dimensional (3D) cell-aggregate sizes in which nonisometric scaling emerges in the presence of joint mass and metabolic rate fluctuations. The 3D cell-laden spheroids with size and single-cell metabolic rates described by probability density functions were randomly generated in silico. The distributions of the resulting metabolic rates of the spheroids were computed by modeling oxygen diffusion and reaction. Then, a method for estimating scaling exponents of correlated variables through statistically significant data collapse of joint probability distributions was developed. The method was used to identify a physiologically relevant range of spheroid sizes, where both nonisometric scaling and a minimum oxygen concentration (0.04 mol⋅m−3) is maintained. The in silico pipeline described enables the prediction of the number of experiments needed for an acceptable collapse and, thus, a consistent estimate of scaling parameters. Using the pipeline, we also show that scaling exponents may be significantly different in the presence of joint mass and metabolic-rate variations typically found in cells. Our study highlights the importance of incorporating fluctuations and variability in size and metabolic rates when estimating scaling exponents. It also suggests the need for taking into account their covariations for better understanding and interpreting experimental observations both in vitro and in vivo and brings insights for the design of more predictive and physiologically relevant in vitro models.


Breathing in vitro: Designs and applications of engineered lung models

TitleBreathing in vitro: Designs and applications of engineered lung models
Publication TypeJournal Article
Year of Publication2021
AuthorsNossa, R, Costa, J, Cacopardo, L, Ahluwalia, A
JournalJournal of Tissue Engineering
Keywordsaerosol exposure, fluidic systems, in vitro models, Lung models, stretching systems

The aim of this review is to provide a systematic design guideline to users, particularly engineers interested in developing and deploying lung models, and biologists seeking to identify a suitable platform for conducting in vitro experiments involving pulmonary cells or tissues. We first discuss the state of the art on lung in vitro models, describing the most simplistic and traditional ones. Then, we analyze in further detail the more complex dynamic engineered systems that either provide mechanical cues, or allow for more predictive exposure studies, or in some cases even both. This is followed by a dedicated section on microchips of the lung. Lastly, we present a critical discussion of the different characteristics of each type of system and the criteria which may help researchers select the most appropriate technology according to their specific requirements. Readers are encouraged to refer to the tables accompanying the different sections where comprehensive and quantitative information on the operating parameters and performance of the different systems reported in the literature is provided.