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Decentralized Trajectory Tracking Control for Soft Robots Interacting with the Environment

TitleDecentralized Trajectory Tracking Control for Soft Robots Interacting with the Environment
Publication TypeJournal Article
Year of PublicationIn Press
AuthorsAngelini, F, C. Della Santina,, Garabini, M, Bianchi, M, Gasparri, GM, Grioli, G, Catalano, MG, Bicchi, A
JournalIEEE Transactions on Robotics (T-RO).

Despite the classic nature of the problem, trajectory

tracking for soft robots, i.e. robots with compliant elements

deliberately introduced in their design, still presents several

challenges. One of these is to design controllers which can

obtain sufficiently high performance while preserving the physical

characteristics intrinsic to soft robots. Indeed, classic control

schemes using high gain feedback actions fundamentally alter the

natural compliance of soft robots effectively stiffening them, thus

de facto defeating their main design purpose. As an alternative

approach, we consider here to use a low-gain feedback, while

exploiting feedforward components. In order to cope with the

complexity and uncertainty of the dynamics, we adopt a decentralized,

iteratively learned feedforward action, combined with

a locally optimal feedback control. The relative authority of the

feedback and feedforward control actions adapts with the degree

of uncertainty of the learned component. The effectiveness of the

method is experimentally verified on several robotic structures

and working conditions, including unexpected interactions with

the environment, where preservation of softness is critical for

safety and robustness.

Refereed DesignationRefereed

Dynamic Control of Soft Robots Interacting with the Environment

TitleDynamic Control of Soft Robots Interacting with the Environment
Publication TypeConference Paper
Year of PublicationIn Press
Conference NameIEEE International Conference on Soft Robotics
AuthorsC. Della Santina,, Katzschmann, RK, Bicchi, A, Rus, D
Conference Location24 - 28 April 2018, Livorno, Italy

Despite the emergence of many soft-bodied robotic

systems, model-based feedback control has remained an open

challenge. This is largely due to the intrinsic difficulties in

designing controllers for systems with infinite dimensions. In

this paper we propose an alternative formulation of the soft

robot dynamics which connects the robot’s behavior with the

one of a rigid bodied robot with elasticity in the joints. The

matching between the two system is exact under the common

hypothesis of Piecewise Constant Curvature. Based on this

connection we introduce two control architectures, with the

aim of achieving accurate curvature control and Cartesian

regulation of the robot’s impedance, respectively. The curvature

controller accounts for the natural softness of the system,

while the Cartesian controller adapts the impedance of the

end effector for interactions with an unstructured environment.

This work proposes the first closed loop dynamic controller

for a continuous soft robot. The controllers are validated

and evaluated on a physical soft robot capable of planar


Refereed DesignationRefereed

W-FYD: a Wearable Fabric-based Display for Haptic Multi-Cue Delivery and Tactile Augmented Reality

TitleW-FYD: a Wearable Fabric-based Display for Haptic Multi-Cue Delivery and Tactile Augmented Reality
Publication TypeJournal Article
Year of PublicationIn Press
AuthorsFani, S, Ciotti, S, Battaglia, E, Moscatelli, A, Bianchi, M
JournalIEEE Transactions on Haptics
KeywordsHaptics, Robotics

Despite the importance of softness, there is no evidence of wearable haptic systems able to deliver controllable softness cues. Here, we present the Wearable Fabric Yielding Display (W-FYD), a fabric-based display for multi-cue delivery that can be worn on user's finger and enables, for the first time, both active and passive softness exploration. It can also induce a sliding effect under the finger-pad. A given stiffness profile can be obtained by modulating the stretching state of the fabric through two motors. Furthermore, a lifting mechanism allows to put the fabric in contact with the user's finger-pad, to enable passive softness rendering. In this paper, we describe the architecture of W-FYD, and a thorough characterization of its stiffness workspace, frequency response and softness rendering capabilities. We also computed device Just Noticeable Difference in both active and passive exploratory conditions, for linear and non-linear stiffness rendering as well as for sliding direction perception. The effect of device weight was also considered. Furthermore, performance of participants and their subjective quantitative evaluation in detecting sliding direction and softness discrimination tasks are reported. Finally, applications of W-FYD in tactile augmented reality for open palpation are discussed, opening interesting perspectives in many fields of human-machine interaction.

Refereed DesignationRefereed

Towards Minimum-Information Adaptive Controllers for Robot Manipulators

TitleTowards Minimum-Information Adaptive Controllers for Robot Manipulators
Publication TypeConference Proceedings
Year of PublicationIn Press
AuthorsMarcucci, T, C. Della Santina,, Gabiccini, M, Bicchi, A
Conference NameAmerican Control Conference, AMC2017
Conference LocationMay 24–26 2017, Seattle USA

The aim of this paper is to move a step in the direction of determining the minimum amount of information needed to control a robot manipulator within the framework of adaptive control. Recent innovations in the state of the art show how global asymptotic trajectory tracking can be achieved despite the presence of uncertainties in the kinematic and dynamic models of the robot. However, a clear distinction between
which parameters can be included among the uncertainties, and which parameters can not, has not been drawn yet. Since most of the adaptive control algorithms are built on linearly parameterized models, we propose to reformulate the problem as finding a procedure to determine whether and how a given dynamical system can be linearly parameterized with respect to a specific set of parameters.
Within this framework, we show how the trajectory tracking problem of a manipulator can be accomplished with the only knowledge of the number of joints of the manipulator. As an illustrative example, we present the end-effector trajectory tracking control of a robot initialized with the kinematic model of a different robot.

Refereed DesignationRefereed

Polymeric microporous nanofilms as smart platforms for in vitro assessment of nanoparticle translocation and Caco-2 cell culture

TitlePolymeric microporous nanofilms as smart platforms for in vitro assessment of nanoparticle translocation and Caco-2 cell culture
Publication TypeJournal Article
Year of PublicationIn Press
AuthorsRicotti, L, Gori, G, Cei, D, Costa, J, Signore, G, Ahluwalia, A
Journal IEEE Transactions on NanoBioscience

The study of nanomaterial translocation across epithelial barriers is often hindered by the low permeability of transwell membranes to nanoparticles. To address this issue ultra-thin poly(L-lactic acid) nanofilms with zero tortuosity micropores were developed for use in nanoparticle passage tests. In this study we demonstrate that microporous polymeric nanofilms allow a significantly higher passage of silver nanoparticles in comparison with commercial membranes normally used in Transwell inserts. A robust procedure for collecting free-standing nanofilms which enables their manipulation and use in lab-on-chip systems is described. We also demonstrate the cytocompatibility of porous nanofilms and their ability to sustain the adhesion and proliferation of Caco-2 cells. Ultra-thin microporous membranes show promise as low-cost nanomaterial screening tools and may be used as matrices for the development of bioengineered systems for mimicking the intestinal epithelium.

Refereed DesignationRefereed

Sample, testing and analysis variables affecting liver mechanical properties: A review

TitleSample, testing and analysis variables affecting liver mechanical properties: A review
Publication TypeJournal Article
Year of PublicationIn Press
AuthorsAhluwalia, A, Mattei, G
JournalActa Biomaterialia

Given the critical role of liver mechanics in regulating cell response and directing the development of tissue fibrosis, accurately characterising its mechanical behaviour is of relevance for both diagnostic purposes as well as for tissue engineering and for the development of in-vitro models. Determining and quantifying the mechanical behaviour of soft biological tissues is, however, highly challenging due to their intrinsic labile nature. Indeed, a unique set of values of liver mechanical properties is still lacking to date; testing conditions can significantly affect sample status and hence the measured behaviour and reported results are strongly dependent on the adopted testing method and configuration as well as sample type and status. This review aims at summarising the bulk mechanical properties of liver described in the literature, discussing the possible sources of variation and their implications on the reported results. We distinguish between the intrinsic mechanical behaviour of hepatic tissue, which depends on sample variables, and the measured mechanical properties which also depend on the testing and analysis methods. Finally, the review provides guidelines on tissue preparation and testing conditions for generating reproducible data which can be meaningfully compared across laboratories.

Refereed DesignationRefereed

No More Heavy Lifting: Robotic Solutions to the Container Unloading Problem

TitleNo More Heavy Lifting: Robotic Solutions to the Container Unloading Problem
Publication TypeJournal Article
Year of PublicationIn Press
AuthorsStoyanov, T, Vaskeviciusz, N, Mueller, CA, Fromm, T, Krug, R, Tincani, V, Mojtahedzadeh, R, Kunaschk, S, Ernits, RM, Canelhas, DR, Bonilla, M, Schwertfeger, S, Bonini, M, Halfar, H, Pathak, K, Rohde, M, Fantoni, G, Bicchi, A, Birk, A, Lilienthal, A, Echelmeyer, W
JournalIEEE Robotics and Automation Magazine
Refereed DesignationRefereed