In July 2012 during the Workshop on the theme: Innovative solution to help people to overcome disability limits – a challenge for International and Italian scientists organized in Pisa by the Andrea Bocelli Foundation, the SIRSLab of the Department of Information Engineering of the University of Siena showed a demo of the Wearable Haptic Device (F. Chinello, M. Malvezzi, C. Pacchierotti, D. Prattichizzo. A three DoFs wearable tactile display for exploration and manipulation of virtual objects. Proc. IEEE Haptics Symposium, Pages 71-76, Vancouver, Canada, 2012.) to Andrea Bocelli. Interacting and talking with Andrea Bocelli has been a very inspiring experience. We got new ideas for our research on wearable haptics and for new applications to help impaired people with the target of designing a world without barriers.
A great thank to Andrea Bocelli Foundation for inviting us to show our demo.
Domenico Prattichizzo, Francesco Chinello and Leonardo Meli
This post summarizes the research at SIRSLab on grasping with underactuated compliant robotic hands in the recent years. These studies have been realized SIRSLab also in collaboration with other Universities and research centres, e.g. University of Pisa and DLR.
The complexity of robotic hands is needed to adapt themselves to the many kinds of tasks, but the large number of motors needed to fully actuate the DoFs comes at the cost of size, complexity and weight of devices. A possible approach to solve this problem consists of reducing the number of actuators thus resulting more efficient, simpler and reliable than their fully actuated alternatives. Reducing control inputs seems to inspire also biological systems and in particular motor control of human hands, which share with robotic hands the large number of DoFs.
Reducing the number of control inputs, from fully actuated joints to few synergies, might reduce the dimension of the force and motion controllability subspaces thus compromising the dexterity of the grasp. In [PrMaBi11] and later in [GaBiPrMa11] we introduced the compliance in the quasi-static model at the contact points, at the joints and at the synergy actuation synergies. In particular, the introduction of compliance at the synergy level was referred to as soft synergies.
The solution of the quasi-static grasp problem when only a few actuators are present in the hand is possible if compliance is introduced in the model. In
We investigated the main structural properties of grasping with underactuated hands and in particular to what extent a hand with many DoFs can exploit postural synergies to control force and motion of the grasped object.
The analysis of grasp in terms of possible motions of the manipulated object and reachable internal forces has been investigated for robotic hands with underactuation in [PrMaBi11] using explicit manipulation of input and output variables and in [PrMaGaBi11] an using implicit analysis based on the study of the kernel of a system of equations. Both approaches explicit and implicit lead to the same results but the explicit one is more easy to read in terms of control actions.
In [GaBiPrMa11] the authors investigated the role of synergies in the optimal choice of contact forces in grasping.
In [MaPr13] we described some preliminary evaluations on grasping properties with underactuated hands and in particular we evaluated grasp stiffness in hands with passive joints.
In [MaPr11, PrMaAgWi12] the authors studied an interesting problem: when the robotic hand has not enough degrees of freedom and present compliance, it is possible that if you change the internal force the grasped object moves, due to the different deformation of the equivalent contact springs. These papers implicitly consider the underactuated hands as those hands with fewer DoFs with respect to those needed to control internal forces without moving the object. The results of this study have been applied to a real robotic hand, the experimental tests are described in [PrMaAgWi13].
Main publications on this topic:
[PrMaBi11] D. Prattichizzo, M. Malvezzi, A. Bicchi. On motion and force controllability of grasping hands with postural synergies. In Robotics: Science and Systems VI, pp. 49-56, The MIT Press, Zaragoza, Spain, June 2011. [pdf]
[PrMaGaBi11] D. Prattichizzo, M. Malvezzi, M. Gabiccini, A. Bicchi. On the Manipulability Ellipsoids of Underactuated Robotic Hands with Compliance. Robotics and Autonomous Systems, Elsevier, 2012. [pdf]
[GaBiPrMa11] M. Gabiccini, A. Bicchi, D. Prattichizzo, M. Malvezzi. On the role of hand synergies in the optimal choice of grasping forces. Autonomous Robots, Springer, 31:235-252, 2011. [pdf]
[MaPr11] M. Malvezzi, D. Prattichizzo. Internal force control with no object motion in compliant robotic grasps. In Intelligent Robots and Systems (IROS), 2011 IEEE/RSJ International Conference on, Pages 1008-1014, September 2011. [pdf]
[PrMaAgWi12] D. Prattichizzo, M. Malvezzi, M. Aggravi, T. Wimboeck. Object motion-decoupled internal force control for a compliant multifingered hand. In Proc. IEEE Int. Conf. on Robotics and Automation, 2012. [pdf]
[MaPr13] M. Malvezzi, D. Prattichizzo, Evaluation of Grasp Stiffness in Underactuated Compliant Hands, Accepted at IEEE Int. Conf. on Robotics and Automation, 2013. [pdf-draft]
[PrMaAgWi13] D. Prattichizzo, M. Malvezzi, M. Aggravi, T. Wimböck Compliant robotic hands with a low number of actuators: controlling grasping forces without affecting the object motion, submitted to the International Journal of Robotics Research, 2013.
hand and object configuration, the right ones the final.
This short post summarizes the research on wearable haptics and sensory subtraction in the recent years. The wearable cutaneous devices we have developed are presented in . We have used them in several applications but the most relevant work employing them, which aims at comparing the performance of kinesthetic and cutaneous feedback, is . In [2,3] we analyzed the performance of cutaneous and kinesthetic feedback in a simple teleoperation task (needle insertion in 1 DoF) pointing out how cutaneous feedback can improve the overall safety of the system. After that, we have developed other types of cutaneous devices. For instance the one presented in  can be attached to the end-effector of commercial kinesthetic devices (such as the Omegas) in order to be able to easily switch between cutaneous + kinesthetic and cutaneous only.
To get wearability in haptics it is very important to deal with the skin. Devices we are developing are able to apply cutaneous forces without kinesthetic force feedback. This is of course an issue but it is mandatory if we want to have wearable device. It is a requirement for the design of the devices. Which are the errors we get in using cutaneous only stimulation instead of kinesthetic feedback? To which extent we can avoid kinesthetic feedback ? An answer to this questions has been provided in  in cooperation with K. Minamizawa, who developed the gravity grabber which inspired our research on wearable haptics.
Publications/Videos/pdf also available on our website (sirslab.dii.unisi.it)
 F. Chinello, M. Malvezzi, C. Pacchierotti, D. Prattichizzo. A three DoFs wearable tactile display for exploration and manipulation of virtual objects. In Proc. IEEE Haptics Symposium (HAPTICS), Volume, Pages 71-76, Vancouver, Canada, 2012. [pdf]
 D. Prattichizzo, C. Pacchierotti, G. Rosati. Cutaneous force feedback as a sensory subtraction technique in haptics. IEEE Transactions on Haptics, PrePrint available on IEEEXplore, 2012. [pdf]
 C. Pacchierotti, F. Chinello, D. Prattichizzo. Cutaneous device for teleoperated needle insertion. In Proc. 4th IEEE RAS EMBS Int. Conf. on Biomedical Robotics and Biomechatronics (BioRob), Pages 32-37, Rome, Italy, 2012. [pdf]
 C. Pacchierotti, F. Chinello, M. Malvezzi, L. Meli, D. Prattichizzo. Two finger grasping simulation with cutaneous and kinesthetic force feedback. In Haptics: Perception, Devices, Mobility, and Communication. Eurohaptics 2012, Lecture Notes in Computer Science, Pages 373-382, Tampere, Finland, 2012. [video] [pdf]
 K. Minamizawa, D. Prattichizzo, S. Tachi. Simplified Design of Haptic Display by Extending One-point Kinesthetic Feedback to Multipoint Tactile Feedback. In IEEE Haptic Symposium, Pages 257-260, Waltham, Massachusetts, USA, 2010. [video] [pdf]
In the European Project ROBOCAST, leaded by Politecnico di Milano, the research unit at Dipartimento di Ingegneria dell’Informazione at the University of Siena designed and developed the haptic loop. As reported in the time.com article:
“Needles and catheters inserted through the skull can then be moved by a probe operated by a surgeon, who can feel the resistance of the brain thanks to an advanced haptic device which gives tactile feedback to the operator of the machine. In the future, the probe will be used to perform surgical procedures not possible today, such as allowing surgeons to take a curved path from an entry point in the skull to a targeted lesion.”
D. De Lorenzo, E. De Momi, R. Manganelli, I. Dyagilev, A. Formaglio, D. Prattichizzo, M. Shoham, G. Ferrigno. Force feedback in a piezoelectric linear actuator for neurosurgery. The International Journal of Medical Robotics and Computer Assisted Surgery, 2011