Lorenzo Masia

Assistive Exosuit for Elbow Flexion/Extension


 Robotic exoskeletons have been developed for a large number of applications and now represent an appealing frontier for human assistance or augmentation. They have been largely used in rehabilitation of people who suffer from neurological impairments (such as stroke or tetraplegia) or spinal cord injuries. Whilst a large number of devices have been engineered for the lower limbs, considerably fewer solutions exist for the upper limbs.

 The reason can be found in the complexity of the actions that a human arm/hand must perform, ranging from a simple flexion of the elbow to the complex act of manipulating an object. That's why at present the technology for rehabilitation of upper limbs involves the use of complex rigid systems deployed in hospitals for constrained induced motion therapy, consisting in repetitive movements to partially recover voluntary control. Unfortunately the degree of recovery is seldom enough to allow the patient to be fully independent.

This makes the case for an asssitive device that is portable, low-profile and lightweight enough to be used on a daily basis in "real-world" scenarios. Our approach is to design clothing-like devices that constrain as little as possible natural movements and provide assistance when needed.  The working principle consists of actuating, using a motor attached to a backpack or around the waist, a set of artificial tendons routed in the "exosuit" along specific loadpaths. Retracting or releasing the tendons results in the application of a torque on the user's joints in a fashion that closely resembles the way natural muscles work. Following this rationale, we are designing and testing a soft exosuit to assist elbow flexion/extension movements while minimizing  power consumption, weight and overall size of the system.

ElbowExoSketchFigure: First concept sketch of the textile-based exoskeleton for assistance of elbow flexion/extension. The sleeve is composed of an elastic substratum to adapt to the user's morphology and inextensible fabric that supports the loads applied by the tendons. 

Soft Arm Compliant Exoskeleton - Alpha prototype

A video showing the design concept and an animated explode view of the actuation unit, responsible for flexion/extension of the elbow via a pair of tendons, can be viewed  here. Tendons are wrapped around an array of two spool on the same shaft, so that the elbow is moved in an agonist/antagonist fashion. An electromechanical clutch allows to couple the spools with the frame, locking the system and unloading the motor. This results in the possibility of keeping a static posture with minimum power consumption.

The mechanism is completely backdrivable, which makes it transparent to the wearer, allowing free movement when both the clutch and motor are turned off. This whole mechanism is enclosed in a 3D printed case and designed to be carried as a backpack.


Figure: side adn rear view of the soft rame for tendon routing on the elbow joint. Tendons are attached on both sides of the joints to a pair of anchor points that allow to apply a torque on the joint. Inextensible fabric minimises displacement of the suit along the load paths.


Figure: actuation mechanism of the soft arm compliant exoskeleton. The two tendons are wrapped around a spool driven by an electrical DC motor. An epyciclic gear train connects the motor, the spool and an electromechanical clutch. This allows to amplify the maximum holding torque of the clutch. A feeder mechanism prevents slack in the cables. 

A special thanks to This email address is being protected from spambots. You need JavaScript enabled to view it. and This email address is being protected from spambots. You need JavaScript enabled to view it. for contributing to the design and manufacturing the Soft Arm Compliant Exoskeleton.

Beta prototype - Work in progress


 Further information about the soft exo can be found on Michele's website


Related works

  1. Khanh D. B, Cappello L.,Masia L. "Localized Extreme Learning Machines for Online Inverse Dynamic Estimation in Soft Wearable Exoskeleton", International Conference on Biomedical Robotics and Biomechatronics (BIOROB), Singapore, June 2016.
  2. Xiloyannis M., Cappello L., Khanh D. B., Antuvan C. W., Masia L. "Preliminary design and control of a soft exosuit for assisting elbow movements and hand grasping in activities of daily living", Journal of Rehabilitation and Assistive Technologies Engineering (RATE), October 2016.
  3.  Xiloyannis M., Cappello L., Khanh D. B., Antuvan C.W., Masia L. "Design and preliminary testing of a soft exosuit for assisting elbow movements and hand grasping". International Conference on Neurorehabilitation (ICNR), Segovia, Spain, October 2016.
  4.   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” , IEEE ICORR 2013, Seattle, USA, June 24-26, 2013 
  5.   Cappello L, Lachenal L, Pirrera A, Mattioni F, Weaver P and Masia L. "Design, characterization and stability test of a Multistable Composite Actuator for Exoskeletons" . Submitted to IEEE Biorob 2014.
  6.   Chris Wilson Antuvan, Federica Bisio, Erik Cambria, Lorenzo Masia. "Discrete Classification of Upper Limb Motions Using Myoelectric Interface". IEEE International Conference on Robotic Rehabilitation 2015, 11-14 August 2015, Singapore.
  7.  Leonardo Cappello, Alberto Pirrera, Paul Weaver, Lorenzo Masia. "A Series Elastic Composite Actuator for Soft Arm Exosuits: Design and Preliminary Test." IEEE ICORR2015, 11-14 August Singapore
  8.  Binh Khanh Dinh, Leonardo Cappello, Lorenzo Masia. "Control Implementation of Compliant Composite Material Actuators for Wearable Robotic Exoskeletons", IEEE International Conference on Robotic Rehabilitation 2015, 11-14 August 2015, Singapore
  9. S. El-Khoury, I. Batzianoulis, C. W. Antuvan, S. Contu, L. Masia, S. Micera and A. Billard. "EMG-based learning approach for estimating wrist motion". 37th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC 2015) 

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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