TY - CONF T1 - Nonlinear Decoupled Motion-Stiffness Control and Collision Detection/Reaction for the VSA-II Variable Stiffness Device T2 - Proc. IEEE/RSJ International Conference on Intelligent RObots and Systems Y1 - 2009 A1 - A. De Luca A1 - F. Flacco A1 - R. Schiavi A1 - A. Bicchi KW - Embedded Control KW - Physical Human-Robot Interaction (pHRI) KW - Robotics AB -

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.

JF - Proc. IEEE/RSJ International Conference on Intelligent RObots and Systems CY - St. Louis MO USA ER - TY - CONF T1 - Physical Human-Robot Interaction: Dependability, Safety, and Performance T2 - Proc. 10th Intl. Workshop Advanced Motion Control Y1 - 2008 A1 - A. Bicchi A1 - M. Bavaro A1 - G. Boccadamo A1 - D. De Carli A1 - R. Filippini A1 - G. Grioli A1 - M. Piccigallo A1 - A. Rosi A1 - R. Schiavi A1 - S. Sen A1 - G. Tonietti KW - Embedded Control KW - Physical Human-Robot Interaction (pHRI) KW - Robotics AB -

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.

JF - Proc. 10th Intl. Workshop Advanced Motion Control ER - TY - JOUR T1 - An atlas of physical human-robot interaction JF - Mechanism and Machine Theory Y1 - 2007 A1 - De Santis, A A1 - B. Siciliano A1 - A.De Luca A1 - A. Bicchi KW - Physical Human-Robot Interaction (pHRI) KW - Robotics AB -

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 ``cognitive

VL - 43 ER - TY - JOUR T1 - Robust sliding mode control of a robot manipulator based on variable structure-model reference adaptive control approach JF - IET Control Theory Appl. Y1 - 2007 A1 - S. Huh A1 - Z. Bien KW - Physical Human-Robot Interaction (pHRI) KW - Robotics AB -

A model reference adaptive-sliding mode control is presented and applied for a variable stiffness actuated (VSA) system. The VSA is a flexible stiffness machine with two coupled actuators in each link, and its safety during the movement can be guaranteed by varying both stiffness and the angular variables. Realisation of precise control of two coupled actuators poses a considerable challenge, however, because of uncertain time-varying parameters and unknown variation bounds. In this paper a neuro-sliding mode approach based on model reference adaptive control (MRAC) is proposed. The proposed MRAC control structure induces the VSA to follow its nominal dynamics with help of sliding mode control efforts. The sliding gain, implemented by a simple neural network (NN), is adaptively updated based on the Lyapunov criterion. A control law and adaptive laws for the sliding mode control as well as the weights in the NN are established so that the closed-loop system is stable in the sense of Lyapunov. The tracking errors of both the angular variables and stiffness are managed to guarantee the system to be asymptotically stable rather than uniformly ultimately bounded. And, the feasibility of the proposed control approach is demonstrated by means of experimental results as well as computer simulations.

VL - 1 ER - TY - CHAP T1 - Optimal Mechanical/Control Design for Safe and Fast Robotics T2 - Experimental Robotics IX: The 9th International Symposium on Experimental Robotics Y1 - 2006 A1 - G. Tonietti A1 - R. Schiavi A1 - A. Bicchi ED - Marcelo H. Ang, Oussama Khatib KW - Physical Human-Robot Interaction (pHRI) KW - Robotics AB -

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.

JF - Experimental Robotics IX: The 9th International Symposium on Experimental Robotics T3 - Springer Tracts in Advanced Robotics PB - Springer Berlin / Heidelberg VL - 21 ER - TY - CHAP T1 - Optimization and Fail-Safety Analysis of Antagonistic Actuation for pHRI T2 - European Robotics Symposium 2006 Y1 - 2006 A1 - G. Boccadamo A1 - R. Schiavi A1 - S. Sen A1 - G. Tonietti A1 - A. Bicchi ED - H. Christensen KW - Physical Human-Robot Interaction (pHRI) KW - Robotics AB -

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.

JF - European Robotics Symposium 2006 T3 - Springer Tracts in Advanced Robotics PB - Springer Berlin / Heidelberg VL - 22 ER - TY - CONF T1 - Compliant design for intrinsic safety: general issues and preliminary design T2 - Proc. IEEE Int. Symp. Intelligent Robots and Systems Y1 - 2001 A1 - A. Bicchi A1 - S. Lodi Rizzini A1 - G. Tonietti KW - Physical Human-Robot Interaction (pHRI) KW - Robot Arms AB -

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.

JF - Proc. IEEE Int. Symp. Intelligent Robots and Systems CY - Maui, Hawaii ER - TY - CONF T1 - Compliant robot arm design for intrinsic safety T2 - Proc. IARP/RAS Workshop on Technical Challenges for Dependable Robots in Human Environments Y1 - 2001 A1 - A. Bicchi A1 - S. Lodi Rizzini A1 - G. Tonietti ED - G. Giralt ED - P. Corke KW - Physical Human-Robot Interaction (pHRI) KW - Robot Arms AB - 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. JF - Proc. IARP/RAS Workshop on Technical Challenges for Dependable Robots in Human Environments ER - TY - JOUR T1 - Analysis and Optimization of Tendinous Actuation for Biomorphically Designed Robotic Systems JF - Robotica Y1 - 2000 A1 - A. Bicchi A1 - D Prattichizzo KW - Haptics KW - Physical Human-Robot Interaction (pHRI) KW - Robot Arms KW - Robot Hands VL - 18 ER - TY - CONF T1 - Advanced Rehabilitative Robots T2 - Proc. ISIR Int. Symposium and Exposition on Robots Y1 - 1988 A1 - P. Dario A1 - M. Bergamasco A1 - A. Sabatini A1 - A. Bicchi A1 - G. Buttazzo KW - Physical Human-Robot Interaction (pHRI) KW - Robot Arms JF - Proc. ISIR Int. Symposium and Exposition on Robots CY - Sydney, Australia ER -