Research on Rehabilitation Robotics

We are currently evaluating the usage of robotic and virtual reality technologies in the context of upper limb rehabilitation with chronic post-stroke patients, with a particular focus on exoskeleton technologies.

Neurorehabilitation aim is the recovery of the lost capabilities. The impairment of upper limb function is one of the most common and challenging sequelae following stroke, that limits the patient’s autonomy in daily living and may lead to permanent disability. The deficits are characterized:

  • Weakness of specific muscles
  • Abnormal muscle tone
  • Abnormal postural adjustment
  • Abnormal movement synergies
  • Incorrect timing of components within a movement pattern

Two factors that play a relevant role in the process of motor recovery, movement training associated with a task and volitional effort. So this means that functional recovery implies active movement & Task oriented training.

Robotic technologies in combination with Virtual Reality can provide high intensity of training together with an ecological and motivating representation of the task to be performed. Moroever it is possible to get feedback on both results and performance and provide facilitations to the patient for the execution of the exercises.

Patient using the LExos

Rootic exoskeeltons present several significant advantages, such as the possiiblity of providing a force feedback at the level of each joint, guiding the full kinematic chaing of the arm, full tracking of arm posture, possibililty of performing exercies in large workspaces.

Several exoskeleton devices have been developed at PERCRO laboratory and currently being used for neurorehabilitation. The L-exos has been already successfully employed in the neurorehabilitation of stroke patients .For further details please refer to Antonio Frisoli, Alberto Montagner, Luigi Borelli, Fabio Salsedo, Massimo Bergamasco, "A force-feedback exoskeleton for upper limb rehabilitation in Virtual Reality", Applied Bionics and Biomechanics", 6(2) , 2009, p. 115-126 [pdf]

In the picture below you can see a typical VR scenario used for proposing movement task to the patient,

For further details refer to:

Caterina Procopio, Fabio Salsedo, Massimo Bergamasco, Maria Chiara Carboncini, Bruno Rossi, Robot-Mediated Arm Rehabilitation in Virtual Environments for Chronic Stroke Patients: A Clinical Study , Proceedings of IEEE International Conference on Robotics & Automation ICRA 2008 [pdf].

A pilot clinical study on robotic assisted rehabilitation in VR with an arm exoskeleton device, A Montagner, A Frisoli, L Borelli, C Procopio, M Bergamasco, MC Carboncini, B Rossi, , Virtual Rehabilitation 2007, Venezia [pdf]

Frisoli, L. Borelli, A. Montagner, et al, “Arm rehabilitation with a robotic exoskeleleton in Virtual Reality”, Proceedings of IEEE ICORR 2007, Intern. Conf. on Rehabilitation Robotics [pdf]

Recent advances in this framework that curently being developed at PERCRO in the context of the project BRAVO (BRain computer interfaces for Robotic enhanced Action in Visuo-motOr tasks, Seed Project funded by IIT), such as the integration of new gaze tracking technologies for rehabiltiation and

For further information refert to C. Loconsole, R. Bartalucci, A. Frisoli, M. Bergamasco, “A new gaze-tracking guidance mode for upper limb robot-aided neurorehabilitation”, in IEEE - World Haptics Conference, WHC 2011, June 22-24 2011, Istanbul (Turkey)..

Decision in motion

In the context of the EU project Decisions in Motion, we have recently built an innovative robotic head to study the neural mechanisms used to guide behaviour in complex visual scenes, in which the observer is in motion and navigates to avoid moving objects. The robot is capable of using optical flow information to navigate through obstacles in order to reach a target.

Robot Moving

See the video of our robot features on the on NewScientist webpage



Interaction in Virtual Environments

The Integrated Project Presenccia is undertaking a research programme that has as its major goal the understanding and exploitation of brain mechanisms for the enhancement of presence and interaction in mixed and virtual reality. The project is highly interdisciplinary, combining neuroscience, computer science, psychiatry, psychology, psychophysics, mechanical engineering, philosophy and drama.

The main contribution of PERCRO has been the development of two innovative devices: a fingertip haptic interface for the display of local contact geometry; a vibro-tactile dataglove for virtual social environment.

A light dataglove for human-to-human or human-to-object mediated interaction, fulfilling the requirements of portability and integration with high immersive systems for their application in simulated virtual persistent communities and states of correlational presence. The use of vibrotactile pads applied on different parts of the hand, such as palm and fingerpads, allows testing the role of sensorial substitution or haptic illusions in the social use of haptics and virtual manipulation of objects.

DataGloveVirtual Manipulation

Innovative haptic interfaces: can local cutaneous cues improve haptic perception?

A novel device capable of providing simultaneously both kinesthetic and local haptic cues at the level of the fingerpad has been designed. It is composed of a supporting haptic interface and a fingertip haptic display. The augmentation of locally displayed haptic information improves the performance in tasks such as shape recognition by haptic exploration. Experimental investigation has been carried out on the role of kinesthetic and tactile modalities in virtual experiences mediated by touch, such as interpersonal interaction and active manipulation of objects.

"A Fingertip Haptic Display for Improving Curvature Discrimination A. Frisoli, M. Solazzi, F. Salsedo, M. Bergamasco Presence: Teleoperators & Virtual Environments December 2008, Vol. 17, No. 6: 550–561 [PDF]

Fingertip Haptics

On the cross-modal integration of cutaneous and kinesthetic studies

In our recent article publshed in Brain Bulletin Research we demonstrate that the discrimination perceptual threshold in a task consisting in the discrimination of the angle among two parallel planes, both cutaneous and kinesthetic cues are combined to

  1. Antonio Frisoli, Massimiliano Solazzi, Miriam Reiner, Massimo Bergamasco,The contribution of cutaneous and proprioceptive sensory modalities in haptic perception of orientation, on-line available Brain Researc Bulletinh 85(5), 2011 [pdf]



Screw theory and Lie algebra methods for theoretical and applied kinematics

Lie algebra and screw theory represent a fascinating framework in which studying and representing geometrical and dynamic properties of complex mechanisms. In our recent paper we analyze how clerances in parallel manipulators can affect position accuracy.

Antonio Frisoli, Massimiliano Solazzi, Dario Pellegrinetti, Massimo Bergamasco, A new screw theory method for the estimation of position accuracy in spatial parallel manipulators with joint clearances, Mechanisms and Machine Theory 46 (2011) 1929–1949 [pdf]

There is growing interest on Low DOFs parallel manipulator, for their potentiality of being employed in manufacturing, assemblying and CNC centers. In this seminal paper below, there is a systematic synthesis of parallel manipulators which can allow only translational motions of the coupler, All the study is performed by using only an algebraic representation of instantaneous motion by means of screws.

A.Frisoli, D. Checcaci, F.Salsedo, M.Bergamasco,Synthesis by screw algebra of translating in-parallel actuated mechanisms in Advances in Robot Kinematics ed. by J. Lenarcic and M.M. Stanisic, 2000 Kluwer Academics Publ.


If you are interested on how screw theory methods can be extended to analyze dynamic properties of mechanisms, we have analyzed this aspect for the case of parallel manipulators. By introducing the notion of the accelerator, it is possible to extend the geometrical analysis to the study of acceleration.

J. Gallardo, J. M. Rico, A. Frisoli, D. Checcacci and M. Bergamasco, Dynamics of parallel manipulators by means of screw theory, Pages 1113-1131 , Mechanisms and Machine Theory (2003), Volume 38, Issue 11 [pdf]



Research on Haptic Interfaces


Haptic Interfaces are electro-mechanical devices that are used to return force feedback to an operator, immersed in a VE. HI allow the feeling of objects, during the computer interaction. With respect to GUI, the man-computer interaction is enhanced and a more realistic feeling is achieved during simulations.



The PureForm Haptic Interface system

Here it is a picture of the Haptic Interface system that we are currently using in the PureForm system (see link at The system in a force-feedback arm exoskeleton for the arm. It is made of carbon fiber and can achieve the value of weight/payload ration ~ 1:1. The arm-exoskeleton is integrated with an haptic interface for the fingertips which can apply two independent forces on the two fingertips. The mobility off the all system can cover 80% of arm workspace together will full mobility of wrist and index/thumb fingers.




The 6 DOF Haptic Interface

This is the CAD model of a 6 dof joystick, based on an innovative tendon drive system. The HI has been designed for simulation in VE of tasks of dextrous manipulation.

More information related to the joystick system is available following the link 6DOFJOY.


The 2 DOF Highly Isotropic Haptic Interface

This is the CAD model of a 2 dof HI, based on an closed-loop tendon drive system, which enhances the quality of force feedback.  The system is based on a closed-loop 5-bar linkage and allows the user to perceive 2D force inside a planar rectangular workspace.

More information related to 5-bar system is available following the link 2DOFJOY.

Download an AVI file



The 3 DOF Haptic Interface

The 3 DOF system is a parallel mechanism system that allows only a three dimensional translational motion of the upper platform. The kinematics has been selected among all the possible symmetric parallel arrangements of legs which constraint the possible rotational motions of the platform. The kinematic optimazion and the mechanical design has been performed by Damaso Checcacci, in his degree thesis in mechanical engineering.

In the picture above version #1 and verison #2 of the 3DOF haptic interface.

See the following reference for the development of force control on this system.

Force-based impedance control of a haptic master system for teleoperation Frisoli A.; Sotgiu E.; Avizzano C.A.; Checcacci D.; Bergamasco M. Sensor Review, 6 February 2004, vol. 24, iss. 1, pp. 42-50(9) MCBUniversity Press [pdf]




The first PERCRO arm-exoskeleton for force-feedback in VEs

Here there is an image of the 5 DOF arm exoskeleton developed at PERCRO in 1993. The system was realized under the GLAD-in-ART project.

I and Luc Mo Costabella of EPFL (Lausanne, Switzerland) developed an application for a virtual interaction with deformable objects. This is the scheme of the exoskeleton control system that we used for this application. 

The exoskeleton control system is based on a transputer control network, which computes the kinematics and gravity compensation forces with a maximum frequency of 1000 Hz. The control system has been implemented by the control engineer Carlo Albero Avizzano, leader of the PERCRO control group. We used the force feedback library, developed by him, to test an algorithm for the collision detection with deformable objects. All the work was supervised by eng. Avizzano, whose help was  indispensable and greatly appreciated.

Download the avi file


Here you can see the wrist-exos interface, designed by eng. Fabio Salsedo, head of unit of the PERCRO group of mechanics. The device allows the force feedback on the flexion-extension and abduction-adduction movements of the wrist.



The wrist and the 5 dof exo-skeleton can be assembled together for implementing a whole arm interaction. Recently we have changed the motors of the 5dof exo-skeleton to improve the back-drivability of the system. We are going to develop new applications on the exo-wrist system.