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A Configurable Architecture for Two Degree-of-Freedom Variable Stiffness Actuators to Match the Compliant Behavior of Human Joints

TitleA Configurable Architecture for Two Degree-of-Freedom Variable Stiffness Actuators to Match the Compliant Behavior of Human Joints
Publication TypeJournal Article
Year of Publication2021
AuthorsLemerle, S, Catalano, MG, Bicchi, A, Grioli, G
JournalFrontiers in Robotics and AI
Volume8
Date Published03/2021
ISSN2296-9144
Keywordsarticulated soft robotics, artificial joints, humanoids, prostheses, variable stiffness
Abstract

Living beings modulate the impedance of their joints to interact proficiently, robustly, and safely with the environment. These observations inspired the design of soft articulated robots with the development of Variable Impedance and Variable Stiffness Actuators. However, designing them remains a challenging task due to their mechanical complexity, encumbrance, and weight, but also due to the different specifications that the wide range of applications requires. For instance, as prostheses or parts of humanoid systems, there is currently a need for multi-degree-of-freedom joints that have abilities similar to those of human articulations. Toward this goal, we propose a new compact and configurable design for a two-degree-of-freedom variable stiffness joint that can match the passive behavior of a human wrist and ankle. Using only three motors, this joint can control its equilibrium orientation around two perpendicular axes and its overall stiffness as a one-dimensional parameter, like the co-contraction of human muscles. The kinematic architecture builds upon a state-of-the-art rigid parallel mechanism with the addition of nonlinear elastic elements to allow the control of the stiffness. The mechanical parameters of the proposed system can be optimized to match desired passive compliant behaviors and to fit various applications (e.g., prosthetic wrists or ankles, artificial wrists, etc.). After describing the joint structure, we detail the kinetostatic analysis to derive the compliant behavior as a function of the design parameters and to prove the variable stiffness ability of the system. Besides, we provide sets of design parameters to match the passive compliance of either a human wrist or ankle. Moreover, to show the versatility of the proposed joint architecture and as guidelines for the future designer, we describe the influence of the main design parameters on the system stiffness characteristic and show the potential of the design for more complex applications

URLhttps://www.frontiersin.org/article/10.3389/frobt.2021.614145
DOI10.3389/frobt.2021.614145

Wearable Integrated Soft Haptics in a prosthetic socket

TitleWearable Integrated Soft Haptics in a prosthetic socket
Publication TypeJournal Article
Year of Publication2021
AuthorsBarontini, F, Catalano, MGiuseppe, Grioli, G, Bianchi, M, Bicchi, A
JournalIEEE Robotics and Automation Letters
Start Page1785
KeywordsHaptics and Haptic Interfaces; Prosthetics and Exoskeletons; Soft Robot Applications
Abstract

Modern active prostheses can be used to recover part of the motor function associated with the loss of a hand. Nevertheless, most sensory abilities are lost, and the person has to manage interaction by relying mostly on visual feedback. Despite intensive research devoted to convey touch related cues, very few solutions have been integrated in a real prosthesis worn by a user. This letter describes a soft pneumatic feedback system designed with integrability and wearability among its main concerns. At the system core, two soft pneumatic actuators are placed in contact with the subject's skin and inflated to provide pressure stimuli, which can be used to represent force exerted by the hand grasping. We report on the design and the characterization of the system, including behavioural experiments with able-bodied participants and one prosthesis user. Results from psychophysical, dexterity and usability tests show that the system has the potential to restore sensory feedback in hand amputees, and can be a useful tool for enabling a correct modulation of the force during grasping and manipulation tasks.

URLhttps://ieeexplore.ieee.org/document/9359346

A Bioinspired In Vitro Lung Model to Study Particokinetics of Nano-/Microparticles under Cyclic Stretch and Air-Liquid Interface Conditions

TitleA Bioinspired In Vitro Lung Model to Study Particokinetics of Nano-/Microparticles under Cyclic Stretch and Air-Liquid Interface Conditions
Publication TypeJournal Article
Year of Publication2021
AuthorsDoryab, A, Taskin, MBerat, Stahlhut, P, Schröppel, A, Orak, S, Voss, C, Ahluwalia, A, Rehberg, M, Hilgendorff, A, Stöger, T, others,
JournalFrontiers in Bioengineering and Biotechnology
Volume9
Pagination42
Abstract

Evolution has endowed the lung with exceptional design providing a large surface area for gas exchange area (ca. 100 m2) in a relatively small tissue volume (ca. 6 L). This is possible due to a complex tissue architecture that has resulted in one of the most challenging organs to be recreated in the lab. The need for realistic and robust in vitro lung models becomes even more evident as causal therapies, especially for chronic respiratory diseases, are lacking. Here, we describe the Cyclic I n VI tro Cell-stretch (CIVIC) “breathing” lung bioreactor for pulmonary epithelial cells at the air-liquid interface (ALI) experiencing cyclic stretch while monitoring stretch-related parameters (amplitude, frequency, and membrane elastic modulus) under real-time conditions. The previously described biomimetic copolymeric BETA membrane (5 μm thick, bioactive, porous, and elastic) was attempted to be improved for even more biomimetic permeability, elasticity (elastic modulus and stretchability), and bioactivity by changing its chemical composition. This biphasic membrane supports both the initial formation of a tight monolayer of pulmonary epithelial cells (A549 and 16HBE14o−) under submerged conditions and the subsequent cell-stretch experiments at the ALI without preconditioning of the membrane. The newly manufactured versions of the BETA membrane did not improve the characteristics of the previously determined optimum BETA membrane (9.35% PCL and 6.34% gelatin [w/v solvent]). Hence, the optimum BETA membrane was used to investigate quantitatively the role of physiologic cyclic mechanical stretch (10% linear stretch; 0.33 Hz: light exercise conditions) on size-dependent cellular uptake and transepithelial transport of nanoparticles (100 nm) and microparticles (1,000 nm) for alveolar epithelial cells (A549) under ALI conditions. Our results show that physiologic stretch enhances cellular uptake of 100 nm nanoparticles across the epithelial cell barrier, but the barrier becomes permeable for both nano- and micron-sized particles (100 and 1,000 nm). This suggests that currently used static in vitro assays may underestimate cellular uptake and transbarrier transport of nanoparticles in the lung.

URLhttps://www.scilit.net/article/5248244598cddff1c98a95dbb333fa77?action=show-references

Development of a dynamic in vitro stretch model of the alveolar interface with aerosol delivery

TitleDevelopment of a dynamic in vitro stretch model of the alveolar interface with aerosol delivery
Publication TypeJournal Article
Year of Publication2021
AuthorsCei, D, Doryab, A, Lenz, A-G, Schröppel, A, Mayer, P, Burgstaller, G, Nossa, R, Ahluwalia, A, Schmid, O
JournalBiotechnology and Bioengineering
Volume118
Pagination690–702
Abstract

We describe the engineering design, computational modeling, and empirical performance of a moving air–liquid interface (MALI) bioreactor for the study of aerosol deposition on cells cultured on an elastic, porous membrane which mimics both air–liquid interface exposure conditions and mechanoelastic motion of lung tissue during breathing. The device consists of two chambers separated by a cell layer cultured on a porous, flexible membrane. The lower (basolateral) chamber is perfused with cell culture medium simulating blood circulation. The upper (apical) chamber representing the air compartment of the lung is interfaced to an aerosol generator and a pressure actuation system. By cycling the pressure in the apical chamber between 0 and 7 kPa, the membrane can mimic the periodic mechanical strain of the alveolar wall. Focusing on the engineering aspects of the system, we show that membrane strain can be monitored by measuring changes in pressure resulting from the movement of media in the basolateral chamber. Moreover, liquid aerosol deposition at a high dose delivery rate (>1 µl cm−2 min−1) is highly efficient (ca. 51.5%) and can be accurately modeled using finite element methods. Finally, we show that lung epithelial cells can be mechanically stimulated under air–liquid interface and stretch‐conditions without loss of viability. The MALI bioreactor could be used to study the effects of aerosol on alveolar cells cultured at the air–liquid interface in a biodynamic environment or for toxicological or therapeutic applications.

URLhttps://onlinelibrary.wiley.com/doi/epdf/10.1002/bit.27600

Overcoming the Torque/Stiffness Range Tradeoff in Antagonistic Variable Stiffness Actuators

TitleOvercoming the Torque/Stiffness Range Tradeoff in Antagonistic Variable Stiffness Actuators
Publication TypeJournal Article
Year of Publication2021
AuthorsMengacci, R, Garabini, M, Grioli, G, Catalano, M, Bicchi, A
JournalIEEE/ASME Transactions on Mechatronics
Pagination1-1
KeywordsAntagonisticVSAs, Modular Robots, Soft robotics, Variable Stiffness Actuation
Abstract

To face the demand for applications in which robots have to safely interact with humans and the environment, the research community developed new types of actuators with compliant characteristics. To embody compliance into the actuator, elastic elements with fixed or variable compliance can be used. Among the variable stiffness mechanisms, a popular approach is based on the agonistic-antagonistic (A-A) layout, where two prime movers are elastically connected to the output shaft of the actuator. Notwithstanding the conceptually simple realization of the A-A layout, one limitation is that, due to the nonlinear torque/deflection characteristic of the elastic transmissions and to the limited spring elongation, the stiffness range achievable at the output shaft reduces as the external torque increases. In this work, a novel layout, based on the A-A principle, is proposed to increase the torque/stiffness capability of the actuator. To achieve this result, we combine elastic transmissions with linear and nonlinear torque/deflection characteristics. The mathematical model of the new layout and a possible implementation are analyzed. Then, the design of a novel variable stiffness actuator is presented and experimental validations are shown to compare the new device with the benchmark.

URLhttps://ieeexplore.ieee.org/document/9339937
DOI10.1109/TMECH.2021.3055364

Elastic Structure Preserving Control for Compliant Robots Driven by Agonistic-Antagonistic Actuators (ESPaa)

TitleElastic Structure Preserving Control for Compliant Robots Driven by Agonistic-Antagonistic Actuators (ESPaa)
Publication TypeJournal Article
Year of Publication2021
AuthorsMengacci, R, Keppler, M, Pfanne, M, Bicchi, A, Ott, C
JournalIEEE Robotics and Automation Letters
Pagination1-1
KeywordsCompliance and Impedance Control, Compliant Joints and Mechanisms
Abstract

The regulation of the link positions of compliant robots, damping out undesired link oscillations while preserving the system's inherent elasticity is still a challenging task in practical applications. This task becomes even harder to be tackled in the case of compliant robots driven by agonistic-antagonistic variable stiffness actuators in which there are two motors associated with each joint of the system. In this work, leveraging on the physical realization of the elastic mechanism of such actuators, we propose a novel control law able to simultaneously achieve a good regulation performance and a desired damped behavior at the link, while preserving the elastic structure of the system as well as the possibility of adjusting the passive stiffness at the joints. Simulations on the agonistic-antagonistic actuators of the forearm and wrist joints of the Hand Arm System from the German Aerospace Center (DLR) and experiments on a planar platform with an analogous actuation unit, namely qbMove Advanced, validate the proposed method.

URLhttps://ieeexplore.ieee.org/document/9327475
DOI10.1109/LRA.2021.3052434

Integrating Wearable Haptics and Obstacle Avoidance for the Visually Impaired in Indoor Navigation: A User-Centered Approach

TitleIntegrating Wearable Haptics and Obstacle Avoidance for the Visually Impaired in Indoor Navigation: A User-Centered Approach
Publication TypeJournal Article
Year of Publication2021
AuthorsBarontini, F, Catalano, MG, Pallottino, L, Leporini, B, Bianchi, M
JournalIEEE Transactions on Haptics
Volume14
Start Page109
Issue1
Pagination1-1
URLhttps://ieeexplore.ieee.org/document/9099604
DOI10.1109/TOH.2020.2996748