Lorenzo Masia



CARAPACE: Compliant Advanced Robotic Actuation Powering Assistive Composite Exoskeleton

This project aims to propose an unconventional and bio-inspired approach to robotic assistive/augmenting design, able to provide a superior wearability, to deliver assistance as needed or to enhance physical performance, continuously monitoring subject’s interaction due to its extraordinary ergonomics. The principal aim is the development of a new generation of adaptive/multifunctional structures working in nonlinear regimes taking inspiration from nature. The purpose is to study compliant exoskeleton architectures in order to overcome the joint misalignment problem, allowing a gentle interaction between humans and robotic devices by lightweight and human friendly solutions. The main idea is studying flexible structures and developing Shape-Morphing Compliant Mechanisms with embedded actuators which can be integrated in the exoskeleton at the level of joint or even providing motion and torque by a tendon driven transmission or Novel Multistable Composite Structures . A distributed compliant architecture will allow to overcome the problem of joint misalignment providing a more comfortable lightweight and human friendly structure. The benefits of this approach are twofold:
•    It would allow removing unnecessary stiffness thus realizing substantial weight reduction.
•   It would allow structures to deform in a well-behaved manner by incorporating a functional  kinematics that so far have been distinctive of mechanical devices.

The revolutionary idea is to introduce flexible structures able to deform in a well-behaved manner by incorporating a functional kinematics which can be integrated in the rehabilitation devices at the level of joint and providing motion and torque by novel transmission elements based on Multistable Composite Carbon Fiber Structures. Exploitation of nonlinear behaviors in such kind of mechanisms will lead to design novel generation of multifunctional compliant devices based on a continuous and variable mechanical impedance modulation at the end effector mimicking to the biological systems where the muscles have the inherent ability to regulate stiffness (and impedance) over a wide range of loads and motions, enabling control of acceleration and force in a highly efficient manner.
The possibility to finely modulate and predict the mechanical impedance and the strain energy offered by Multistable Composite Structures is achieved by using fibre-reinforced plastic in combination with of residual stresses induced during the cure cycle and the lamination (lay-up). The use of this solution may provide several advantages in robotics regard the implementation of a robust and biologically inspired approach to human machine interaction: my initial design consisted in a novel type of muscle-like actuator employing classical electric motor and Multistable Composite Structure (MCS) to transmit motion, capable of large rotary-linear deformations, by using pre-stressed carbon fiber flanges joined to introduce multiple stable configurations (see figure).

multistable composite trasmission and different configurations of equilibrium

  Figure: strain energy of the Mulsistable Composite Transmission (MCT) and configurations of equilibrium (CLICK HERE FOR YOUTUBE VIDEO)


The foundational hypothesis for the CARAPACE system (see title for the acronym meaning) can be summarized as follows. Structural components in robotic systems are generally designed to be stiff and respond linearly to the stimuli arising from different operating regimes. However, allowing controlled, well-behaved, nonlinear deformations could enable stiffness tailoring, to adapt deformations and work constructively as an integrating part of the wider mechanism.

Figure: Exoskeleton concept: a simple way of using the discrete configurations of equilibrium for providing assistance or harvesting energy.

DSC 3487

  Figure: assembled test bench for studying agonist-antagonist configuration.


Masia L., Lachenal X., Pirrera A., Cappello L., Mattioni F., Morasso P. and Waver P. “CARAPACE: a novel Composite Advanced Robotic Actuator Powering Assistive Compliant Exoskeleton: Preliminary Design” Submitted to IEEE ICORR 2013

X. Lachenal, P. M. Weaver, S. Daynes. Multistable composite twisting structure for morphing applications. Proceedings of the Royal Society A: Mathematical, Physical and Engineering Science 2012; 468: 21. DOI: 10.1098/rspa.2011.0631.

A. Pirrera ‘Bistable Structures for Morphing Applications Using Anisotropic Shells’, 2011. Thesis University of Bristol

New Journal on Rehabilitation Technology

Journal of Rehabilitation and Assistive Technologies Engineering (click here)

Lorenzo MASIA (Associate Editor)



Journal Topics

Research Topic (click here)





International Conference on Rehabilitation Robotics

Singapore 11th-14th August 2015 Hosted by NTU

General Chair: Wei Tech ANG

Program Chair: Lorenzo MASIA



IEEE BIOROB 2016 (clickhere)



  • L. Masia, Nanyang Tech. University
  • S. Kukreja, National University of Singapore





Lorenzo MASIA Editor of Biorob 2014



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