@article {3717, title = {Analysis of series elasticity in locomotion of a planar bipedal robot}, journal = { INTERNATIONAL JOURNAL OF MECHANICS AND CONTROL}, year = {2019}, author = {S. Manara and G M Gasparri and M. Garabini and D. Caporale and M Gabiccini and A. Bicchi} } @article {3326, title = {Decentralized Trajectory Tracking Control for Soft Robots Interacting with the Environment}, journal = {IEEE Transactions on Robotics (T-RO).}, volume = {Early Access}, year = {2018}, month = {06/2018}, abstract = {

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.

}, keywords = {Robotics}, author = {F. Angelini and C. Della Santina and M. Garabini and M. Bianchi and G M Gasparri and G. Grioli and M. G. Catalano and A. Bicchi} } @article {3364, title = {Efficient Walking Gait Generation via Principal Component Representation of Optimal Trajectories: Application to a Planar Biped Robot With Elastic Joints}, journal = {IEEE Robotics and Automation Letters}, volume = {3}, year = {2018}, pages = {2299{\textendash}2306}, abstract = {

Recently, the method of choice to exploit robot dynamics for efficient walking is numerical optimization (NO). The main drawback in NO is the computational complexity, which strongly affects the time demand of the solution. Several strategies can be used to make the optimization more treatable and to efficiently describe the solution set. In this letter, we present an algorithm to encode effective walking references, generated offline via numerical optimization, extracting a limited number of principal components and using them as a basis of optimal motions. By combining these components, a good approximation of the optimal gaits can be generated at run time. The advantages of the presented approach are discussed, and an extensive experimental validation is carried out on a planar legged robot with elastic joints. The biped thus controlled is able to start and stop walking on a treadmill, and to control its speed dynamically as the treadmill speed changes.

}, author = {G M Gasparri and S. Manara and D. Caporale and G. Averta and M. Bonilla and H. Marino and M. G. Catalano and G. Grioli and M. Bianchi and A. Bicchi and M. Garabini} } @conference {3390, title = {Parametric Trajectory Libraries for Online Motion Planning with Application to Soft Robots}, booktitle = {18th International Symposium on Robotics Research}, year = {2017}, abstract = {

In this paper we propose a method for online motion planning of constrained nonlinear systems. The method consists of three steps: the offline generation of a library of parametric trajectories via direct trajectory optimization, the online search in the library for the best candidate solution to the optimal control problem we aim to solve, and the online refinement of this trajectory. The last phase of this process takes advantage of a sensitivity-like analysis and guarantees to comply with the first-order approximation of the constraints even in case of active set changes. Efficiency of the trajectory generation process is discussed and a valid strategy to minimize online computations is proposed; together with this, an effective procedure for searching the candidate trajectory is also presented. As a case study, we examine optimal control of a planar soft manipulator performing a pick-and-place task: through simulations and experiments, we show how crucial online computation times are to achieve considerable energy savings in the presence of variability of the task to perform.

}, author = {T. Marcucci and M. Garabini and Gasparri, G. M. and Alessio Artoni and M Gabiccini and A. Bicchi} } @article {2875, title = {The Quest for Natural Machine Motion: An Open Platform to Fast-Prototyping Articulated Soft Robots}, journal = {IEEE Robotics and Automation Magazine }, volume = {24}, year = {2017}, note = {

Open access

e wish to thank Samuele Batazzi, Fabio Bonomo, Alberto
Brando, Andrea Di Basco, Tommaso Pardi, Riccardo Persichi-
ni, and Alessandro Raugi for their valuable support in the
development of the hardware prototype. This work was sup-
ported by SOFTPRO (grant 688857) and SOMA (grant
645599){\textemdash}projects of the European Commission{\textquoteright}s Horizon
2020 research program{\textemdash}and by Walk-Man grant 611832.
Support also came from the European Research Council
under an Advanced Grant for {\textquotedblleft}SoftHands: A Theory of Soft
Synergies for a New Generation of Artificial Hands{\textquotedblright} (grant
ERC-291166).
}, pages = {48 - 56}, abstract = {
Soft robots are one of the most significant recent evolutions in robotics. They rely on compliant physical structures purposefully designed to embody desired characteristics. Since their introduction, they have shown remarkable applicability in overcoming their rigid counterparts in such areas as interaction with humans, adaptability, energy efficiency, and maximization of peak performance. Nonetheless, we believe
that research on novel soft robot applications is still slowed by the difficulty in obtaining or developing a working soft robot structure to explore novel applications.
In this article, we present the Natural Machine Motion Initiative (NMMI), a modular open platform that aims to provide the scientific community with tools for fast and easy prototyping of articulated soft robots. Such a platform is composed of three main open hardware modules: the Qbmoves variable-stiffness actuators (VSAs) to build the main robotic structure, soft end effectors (EEs) to interact with the world, and a pool of application-specific add-ons. We also discuss many novel uses of the platform to rapidly prototype (RP) and test new robotic structures with original soft capabilities, and we propose NMMI- based experiments.
}, keywords = {Robotics}, issn = {1070-9932 }, doi = {10.1109/MRA.2016.2636366}, url = {http://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=7857692}, author = {C. Della Santina and C. Piazza and Gasparri, G. M. and M. Bonilla and M. G. Catalano and G. Grioli and M. Garabini and A. Bicchi} } @conference {2889, title = {Robust Optimization of System Compliance for Physical Interaction in Uncertain Scenarios}, booktitle = {IEEE International Conference on Humanoid Robots (HUMANOIDS2016)}, year = {2016}, note = {
This work was supported by the European Commission projects (FP7 framework) Walk-Man and the European Commission Grant no. H2020- ICT-645599 {\textquotedblleft}SOMA{\textquotedblright}: SOft MAnipulation
}, publisher = {IEEE}, organization = {IEEE}, address = {Cancun, Mexico, 15-17 Nov. 2016 }, abstract = {

Compliance in robot design and control is often introduced to improve the robot performance in tasks where interaction with environment or human is required. However a rigorous method to choose the correct level of compliance is still not available. In this work we use robust optimization as a tool to select the optimal compliance value in a robotenvironment interaction scenario under uncertainties. We propose an approach that can be profitably applied on a variety of tasks, e.g.manipulation tasks or locomotion tasks. The aim is to minimize the forces of interaction considering model constraints and uncertainties. Numerical results show that: i) in case of perfect knowledge of the environment stiff robots behave better in terms of force minimization, ii) in case of uncertainties the optimal stiffness of the robot is lower than the previous case and optimal solutions provide a faster task accomplishment, iii) the optimal stiffness decreases as a function of the uncertainty measure. Experiments are carried out in a realistic set-up in case of bi-manual object handover.

}, keywords = {Robotics}, isbn = {978-1-5090-4718-5 }, doi = { 10.1109/HUMANOIDS.2016.7803381}, url = {http://ieeexplore.ieee.org/document/7803381/}, author = {Gasparri, G. M. and F. Fabiani and M. Garabini and L. Pallottino and M. G. Catalano and G. Grioli and R. Persichini and A. Bicchi} } @conference {2881, title = {Toward an Adaptive Foot for Natural Walking}, booktitle = {International Conference on Humanoid Robots (HUMANOIDS2016)}, year = {2016}, address = {Cancun, Mexico, November 15-17, 2016}, abstract = {

Many walking robot presented in literature stand
on rigid flat feet, with a few notable exceptions that embed
flexibility in their feet to optimize the energetic cost of walking.
This paper proposes a novel adaptive robot foot design, whose
main goal is to ease the task of standing and walking on uneven
terrains. After explaining the rationale behind our design
approach, we present the design of the SoftFoot, a foot able
to comply with uneven terrains and to absorb shocks thanks to
its intrinsic adaptivity, while still being able to rigidly support
the stance, maintaining a rather extended contact surface,
and effectively enlarging the equivalent support polygon. The
paper introduces the robot design and prototype and presents
preliminary validation and comparison versus a rigid flat foot
with comparable footprint and sole.

}, keywords = {Robotics}, doi = {10.1109/HUMANOIDS.2016.7803423}, url = {http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=\&arnumber=7803423}, author = {C. Piazza and C. Della Santina and Gasparri, G. M. and M. G. Catalano and G. Grioli and M. Garabini and A. Bicchi} } @conference {2450, title = {Variable Stiffness Control for Oscillation Damping}, booktitle = {IEEE International Conference of Intelligent Robots and Systems (IROS2015)}, year = {2015}, note = {
This work is supported by the EC under the grant agreements no.611832 Walk-Man and ICT-287513 {\textquotedblleft}SAPHARI{\textquotedblright}
}, pages = {6543 - 6550}, publisher = {IEEE}, organization = {IEEE}, address = {Hamburg, Germany, September 28 - October 02, 2015}, keywords = {Robotics}, doi = {10.1109/IROS.2015.7354312}, url = {http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=\&arnumber=7354312}, author = {G M Gasparri and M. Garabini and L. Pallottino and L. Malagia and M. G. Catalano and G. Grioli and A. Bicchi} } @conference {1987, title = {Soft-Actuators in Cyclic Motion: Analytical Optimization of Stiffness and Pre-Load}, booktitle = {IEEE-RAS International Conference on Humanoid Robots}, year = {2013}, address = {Atlanta, Georgia, USA}, keywords = {Robotics}, author = {A. Velasco and G M Gasparri and M. Garabini and L. Malagia and P Salaris and A. Bicchi} }