%0 Conference Paper %B IEEE International Conference of Robotics and Automation (ICRA2016) %D 2016 %T Reflex Control of the Pisa/IIT SoftHand during Object Slippage %A A. Ajoudani %A E. Hocaoglu %A Altobelli, A %A M. Rossi %A E. Battaglia %A N G Tsagarakis %A A. Bicchi %K Haptics %K Robotics %X
In this work, to guarantee the Pisa/IIT SoftHand’s
grasp robustness against slippage, three reflex control modes,
namely Current, Pose and Impedance, are implemented and
experimentally evaluated. Towards this objective, ThimbleSense
fingertip sensors are designed and integrated into the thumb
and middle fingers of the SoftHand for real-time detection and
control of the slippage. Current reflex regulates the restoring
grasp forces of the hand by modulating the motor’s current
profile according to an update law. Pose and Impedance reflex
modes instead replicate this behaviour by implementing an
impedance control scheme. The difference between the two
latter is that the stiffness gain in Impedance reflex mode is
being varied in addition to the hand pose, as a function of
the slippage on the fingertips. Experimental setup also includes
a seven degrees-of-freedom robotic arm to realize consistent
trajectories (e.g. lifting) among three control modes for the sake
of comparison. Different test objects are considered to evaluate
the efficacy of the proposed reflex modes in our experimental
setup. Results suggest that task-appropriate restoring forces
can be achieved using Impedance reflex due to its capability
in demonstrating instantaneous and rather smooth reflexive
behaviour during slippage. Preliminary experiments on five
healthy human subjects provide evidence on the similarity of the
control concepts exploited by the humans and the one realized
by the Impedance reflex, highlighting its potential in prosthetic
applications.
%B IEEE International Conference of Robotics and Automation (ICRA2016) %I IEEE %C Stockholm, Sweden %P 1972 - 1979 %G english %U http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=7487344 %R 10.1109/ICRA.2016.7487344 %0 Journal Article %J IEEE Transactions on Haptics %D 2016 %T ThimbleSense: a fingertip-wearable tactile sensor for grasp analysis %A E. Battaglia %A M. Bianchi %A Altobelli, A %A G. Grioli %A M. G. Catalano %A A. Serio %A M. Santello %A A. Bicchi %K Haptics %K Robotics %XAccurate measurement of contact forces between hand and grasped objects is crucial to study sensorimotor control during grasp and manipulation. In this work we introduce ThimbleSense, a prototype of individual-digit wearable force/torque sensor based on the principle of intrinsic tactile sensing. By exploiting the integration of this approach with an active marker-based motion capture system, the proposed device simultaneously measures absolute position and orientation of the fingertip, which in turn yields measurements of contacts and force components expressed in a global reference frame. The main advantage of this approach with respect to more conventional solutions is its versatility. Specifically, ThimbleSense can be used to study grasping and manipulation of a wide variety of objects, while still retaining complete force/torque measurements. Nevertheless, validation of the proposed device is a necessary step before it can be used for experimental purposes. In this work we present the results of a series of experiments designed to validate the accuracy of ThimbleSense measurements and evaluate the effects of distortion of tactile afferent inputs caused by the device’s rigid shells on grasp forces.
%B IEEE Transactions on Haptics %V 9 %P 121-133 %8 03/2016 %G eng %U http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=7294702 %N 1 %R 10.1109/TOH.2015.2482478 %0 Conference Paper %B 37th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC2015) %D 2015 %T Effect of Homogenous Object Stiffness on Tri-digit Grasp Properties %A S. B. Godfrey %A Altobelli, A %A M. Rossi %A A. Bicchi %K Haptics %K Robotics %XEffective execution of a manipulation task using prosthetic or robotic hands requires that the motion and the impedance profiles of the fingers be appropriately commanded. This, however, brings some design and control challenges regarding the individual planning and realization of the finger motion and stiffnesstrajectories. It appears that the central nervous system solves for this complexity in an effective and coordinated manner which has been well-recognized under the concept of hand synergies. While the exploitation of this concept in kinematic coordinates has lead to the development of several successful robotic designs and control strategies, its extension to dynamic coordinates, such as coordinated stiffening of the fingers, remains to be investigated. Indeed, in this study we provide preliminary evidence on the existence of such coordinated stiffening patterns in human fingers and establish initial steps towards a real-time and effective modelling of the finger stiffness in a tripod grasp. To achieve this goal, the endpoint stiffness of the thumb, index and middle fingers of five healthy subjects are experimentally identified and correlated with the electromyography (EMG) signals recorded from a dominant antagonistic pair of the forearm muscles. Our findings suggest that: i) the magnitude of thestiffness ellipses at the fingertips grows in a coordinated way, subsequent to the co-contraction of the forearm muscles; ii) the length of the ellipses' axes appears to have a nearly linear relationship with the co-contraction level of the antagonistic muscle pair.
%B International Conference on Rehabilitation Robotics (ICORR), 2015 %I IEEE %C Singapore, 11 – 14 August 2015 %P 181-186 %G english %U http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=7281196 %R 10.1109/ICORR.2015.7281196 %0 Conference Paper %B 14th IEEE/RAS-EMBS International Conference on Rehabilitation Robotics, ICORR 2015 %D 2015 %T An instrumented manipulandum for human grasping studies %A Altobelli, A %A M. Bianchi %A M. G. Catalano %A A. Serio %A Baud-Bovy, G %A A. Bicchi %B 14th IEEE/RAS-EMBS International Conference on Rehabilitation Robotics, ICORR 2015 %I IEEE %C Singapore, 11-14 Aug. 2015 %P 169-174 %G english %U http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=7281194 %R 10.1109/ICORR.2015.7281194 %0 Conference Paper %B 22nd Mediterranean Conference of Control and Automation (MED) 2014 %D 2014 %T Three-digit grasp haptic device with variable contact stiffness for rehabilitation and human grasping studies %A Altobelli, A %A M. Bianchi %A A. Serio %A Baud-Bovy, G %A M Gabiccini %A A. Bicchi %K Haptics %K Robotics %XThis paper describes an haptic system designed to vary the stiffness of three contact points in an independent and controllable fashion, by suitably regulating the inner pressure of three pneumatic tactile displays. At the same time, the contact forces exerted by the user are measured by six degree-of-freedom force sensors placed under each finger. This device might be profitably used in hand rehabilitation and human grasping studies. We report and discuss preliminary results on device validation as well as some illustrative measurement examples.
%B 22nd Mediterranean Conference of Control and Automation (MED) 2014 %I IEEE %C Palermo, Italy, 16-19 June 2014 %P 346 - 350 %U http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=6961395 %R 10.1109/MED.2014.6961395