@conference {DLFSB-IROS09, title = {Nonlinear Decoupled Motion-Stiffness Control and Collision Detection/Reaction for the VSA-II Variable Stiffness Device}, booktitle = {Proc. IEEE/RSJ International Conference on Intelligent RObots and Systems}, year = {2009}, month = {October, 11 - 15}, pages = {5487-5494}, address = {St. Louis MO USA}, abstract = {

Variable Stiffness Actuation (VSA) devices are being used to jointly address the issues of safety and performance in physical human-robot interaction. With reference to the VSA-II prototype, we present a feedback linearization approach that allows the simultaneous decoupling and accurate tracking of motion and stiffness reference profiles. The operative condition that avoids control singularities is characterized. Moreover, a momentum-based collision detection scheme is introduced, which does not require joint torque sensing nor information on the time-varying stiffness of the device. Based on the residual signal, a collision reaction strategy is proposed that takes advantage of the proposed nonlinear control to rapidly let the arm bounce away after detecting the impact, while limiting contact forces through a sudden reduction of the stiffness. Simulations results are presented to illustrate the performance of the overall approach. Extensions to the multi-dof case of robot manipulators equipped with VSA-II devices are also considered.

}, keywords = {Embedded Control, Physical Human-Robot Interaction (pHRI), Robotics}, author = {A. De Luca and F. Flacco and R. Schiavi and A. Bicchi} } @conference {AMC08, title = {Physical Human-Robot Interaction: Dependability, Safety, and Performance}, booktitle = {Proc. 10th Intl. Workshop Advanced Motion Control}, year = {2008}, pages = {9-14}, abstract = {

In this paper we discuss the problem of achieving good performance in accuracy and promptness by a robot manipulator under the condition that safety is guaranteed throughout task execution. Intuitively, while a rigid and powerful structure of the arm would favor its performance, lightweight compliant structures are more suitable for safe operation. The quantitative analysis of the resulting design trade-off between safety and performance has a strong impact on how robot mechanisms and controllers should be designed for human-interactive applications. We discuss few different possible concepts for safely actuating joints, and focus on aspects related to the implementation of the mechanics and control of this new class of robots.

}, keywords = {Embedded Control, Physical Human-Robot Interaction (pHRI), Robotics}, author = {A. Bicchi and M. Bavaro and G. Boccadamo and D. De Carli and R. Filippini and G. Grioli and M. Piccigallo and A. Rosi and R. Schiavi and S. Sen and G. Tonietti} } @article {DSSDLB07, title = {An atlas of physical human-robot interaction}, journal = {Mechanism and Machine Theory}, volume = {43}, number = {3}, year = {2007}, pages = {253-270}, abstract = {

A broad spectrum of issues have to be addressed in order to tackle the problem of a safe and dependable physical Human-Robot Interaction (pHRI). In the immediate future, metrics related to safety and dependability have to be found in order to successfully introduce robots in everyday enviornments. While there are certainly also {\textquoteleft}{\textquoteleft}cognitive

}, keywords = {Physical Human-Robot Interaction (pHRI), Robotics}, author = {De Santis, A and B. Siciliano and A.De Luca and A. Bicchi} } @inbook {ISER04, title = {Optimal Mechanical/Control Design for Safe and Fast Robotics}, booktitle = {Experimental Robotics IX: The 9th International Symposium on Experimental Robotics}, series = {Springer Tracts in Advanced Robotics}, volume = {21}, year = {2006}, pages = {311 - 320}, publisher = {Springer Berlin / Heidelberg}, organization = {Springer Berlin / Heidelberg}, abstract = {

The problem to ensure safety of performant robot arms during task execution was previously investigated by authors. The problem can be approached by studying an optimal control policy, the "Safe Brachistocrone", whose solutions are joint impedance trajectories coordinated with desired joint velocities. Transmission stiffness is chosen so as to achieve minimum-time task execution for the robot, while guaranteeing an intrinsic safety level in case of an unexpected collision between a link of the arm and a human operator. In this paper we extend this approach to more general classes of robot actuation systems, whereby other impedance parameters beside stiffness (such as e.g. joint damping and/or plasticity) can vary. We report on a rather extensive experimental campaign validating the proposed approach.

}, keywords = {Physical Human-Robot Interaction (pHRI), Robotics}, author = {G. Tonietti and R. Schiavi and A. Bicchi}, editor = {Marcelo H. Ang, Oussama Khatib} } @inbook {BSSTB06, title = {Optimization and Fail-Safety Analysis of Antagonistic Actuation for pHRI}, booktitle = {European Robotics Symposium 2006}, series = {Springer Tracts in Advanced Robotics}, volume = {22}, year = {2006}, pages = {109 - 118}, publisher = {Springer Berlin / Heidelberg}, organization = {Springer Berlin / Heidelberg}, abstract = {

In this paper we consider some questions in the design of actuators for physical Human-Robot Interaction (pHRI) under strict safety requirements in all circumstances, including unexpected impacts and HW/SW failures. We present the design and optimization of agonistic-antagonistic actuation systems realizing the concept of variable impedance actuation (VIA). With respect to previous results in the literature, in this paper we consider a realistic physical model of antagonistic systems, and include the analysis of the effects of cross-coupling between actuators. We show that antagonistic systems compare well with other possible approaches in terms of the achievable performance while guaranteeing limited risks of impacts. Antagonistic actuation systems however are more complex in both hardware and software than other schemes. Issues are therefore raised, as to fault tolerance and fail safety of different actuation schemes. In this paper, we analyze these issues and show that the antagonistic implementation of the VIA concept fares very well under these regards also.

}, keywords = {Physical Human-Robot Interaction (pHRI), Robotics}, author = {G. Boccadamo and R. Schiavi and S. Sen and G. Tonietti and A. Bicchi}, editor = {H. Christensen} } @conference {BLT01, title = {Compliant design for intrinsic safety: general issues and preliminary design}, booktitle = {Proc. IEEE Int. Symp. Intelligent Robots and Systems}, year = {2001}, month = {October}, pages = {1864-1869}, address = {Maui, Hawaii}, abstract = {

In this paper, we describe some initial results of a project aiming at development of a programmable-compliance, inherently safe robot arm for applications in anthropic environmnets. In order to obtain safety in spite of worst-case situations (such as unexpected delays in teleoperation, or even controller failure), we will consider achieving compliance by mechanical rather than by control design. We first describe some of the control problems that the presence of large, possibly unknown mechanical compliance typically introduces, and present a result that shows the possibility to cope with these uncertainties in an adaptive way. In the second part of the paper we describe the initial development of a new prototype arm under construction in our laboratory. The arm is designed to achieve arbitrary position tracking in 3D with controlled effective compliance at the joints.

}, keywords = {Physical Human-Robot Interaction (pHRI), Robot Arms}, author = {A. Bicchi and S. Lodi Rizzini and G. Tonietti} } @conference {BLT01-iarp, title = {Compliant robot arm design for intrinsic safety}, booktitle = {Proc. IARP/RAS Workshop on Technical Challenges for Dependable Robots in Human Environments}, year = {2001}, pages = {100-106}, abstract = {In this paper, we describe some initial results of a project aiming at development of a programmable-compliance, inherently safe robot arm for applications in anthropic environmnets. In order to obtain safety in spite of worst-case situations (such as unexpected delays in teleoperation, or even controller failure), we will consider achieving compliance by mechanical rather than by control design. We first describe some of the control problems that the presence of large, possibly unknown mechanical compliance typically introduces, and present a result that shows the possibility to cope with these uncertainties in an adaptive way. In the second part of the paper we describe the initial development of a new prototype arm under construction in our laboratory. The arm is designed to achieve arbitrary position tracking in 3D with controlled effective compliance at the joints.}, keywords = {Physical Human-Robot Interaction (pHRI), Robot Arms}, author = {A. Bicchi and S. Lodi Rizzini and G. Tonietti}, editor = {G. Giralt and P. Corke} } @article {BP00-Robotica, title = {Analysis and Optimization of Tendinous Actuation for Biomorphically Designed Robotic Systems}, journal = {Robotica}, volume = {18}, year = {2000}, month = {January}, pages = {23-31}, keywords = {Haptics, Physical Human-Robot Interaction (pHRI), Robot Arms, Robot Hands}, author = {A. Bicchi and D Prattichizzo} } @conference {DBSBB88, title = {Advanced Rehabilitative Robots}, booktitle = {Proc. ISIR Int. Symposium and Exposition on Robots}, year = {1988}, address = {Sydney, Australia}, keywords = {Physical Human-Robot Interaction (pHRI), Robot Arms}, author = {P. Dario and M. Bergamasco and A. Sabatini and A. Bicchi and G. Buttazzo} }