Physical Human-Robot Interaction: DepENDability and Safety



A Cognitive Systems and Robotics project
supported by the European Commission
under the 6th Framework Programme
 (STReP IST-045359)
— 30.09.2009

project website

Presentation  Documents  Papers  Videos

Last update: September 8, 2010


The contributions to the PHRIENDS project by members of our Robotics group at DIS, Università di Roma "La Sapienza", were mainly focused on WP3: Collision Detection, Reaction, and Safe Control. The objective of this workpackage is to develop efficient collision detection methods, using only robot proprioceptive sensors, and safe reaction strategies preventing additional damages in the post-impact phase. In addition, to design safety-oriented motion controllers for lightweight manipulators with compliance at the joints and for robotic devices with variable impedance actuation. Research work is organized around four tasks, in cooperation with the project partners DLR, KUKA, UNIPI, and UNINA.

T3.1: Collision detection with proprioceptive sensors

Development and test of methods for the detection and isolation of robot collisions based on physically relevant quantities, such as the total energy or the generalized momentum of the robot (with or without joint elasticity). Only on-board proprioceptive (joint position and, possibly, joint torque) sensors are used. An additional force/torque wrist sensor allows to distinguish between undesired collisions and intentional interaction with a human at the robot end-effector level.

T3.2: Reaction strategies

Directional (and intensity) information about collision forces embedded in a “residual” vector obtained at collision detection is used to generate reactive robot motion in the post-impact phase. Strategies range from safely removing the robot arm away from the collision area, to temporarily stop and then resuming motion, up to continuos Cartesian task execution (with a redundant
manipulator) by dynamically decoupling the joint-space reaction to collision.

T3.3: Control of existing lightweight robots with joint elasticity

Safety-oriented control solutions are discussed, including the use of impedance-based schemes and the combination of an inverse dynamics (model-based) feedforward action with a passive feedback law. Emphasis is given to control designs that use only partial measurements of the robot state (typically, the motor position and either the link position or a joint torque sensing). Full-state feedback is also considered.

T3.4: Control of variable impedance actuation devices

Design and test of
feedback control laws for single-dof and multiple-dof robot devices having innovative variable impedance actuation. For different passively safe mechanical designs, both control of motion with pre-specified time-varying transmission stiffness and simultaneous control of both motion and stiffness are considered.
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The list of deliverables produced under the coordination of our group during the three-year project, with project month due (M1=October 2006). 

T3.1/D3.1 Detection and Isolation of Robot Collisions (M12)
T3.1/D3.2 Combined Intentional and Undesired Contacts with Humans (M12)
T3.2/D3.3 Reflex Robot Reaction to Collisions (M12)
T3.2/D3.4 Preserving Task Completion under Collisions (M24)
T3.3/D3.5 Motion Control of Robots with Joint Elasticity (M18)
T3.3/D3.6 Interaction Control of Robots with Joint Elasticity (M24)
T3.4/D3.7 Modeling and Motion Control with Time-varying Stiffness (M24)
T3.4/D3.8 Simultaneous Control of Motion and Stiffness (M30)
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A. De Luca, F. Flacco, A. Bicchi, R. Schiavi, "Nonlinear decoupled motion-stiffness control and collision detection/reaction for the VSA-II variable stiffness device," 2009 IEEE/RSJ International Conference on Intelligent Robots and Systems, St. Louis, MO, pp. 5487-5494, 2009 (pdf).

A. De Luca, L. Ferrajoli, "A modified Newton-Euler method for dynamic computations in robot fault detection and control," 2009 IEEE International Conference on Robotics and Automation, Kobe, J, pp. 3359-3364, 2009 (pdf).

A. De Santis, B. Siciliano, A. De Luca, A. Bicchi, "An atlas of physical human-robot interaction," Mechanism and Machine Theory, vol. 43, no. 3, pp. 253–270, 2008 (pdf).

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’" issues involved, due to the human perception of the robot (and vice versa), and other objective metrics related to fault detection and isolation, our discussion focuses on the peculiar aspects of "physical" interaction with robots. In particular, safety and dependability are the underlying evaluation criteria for mechanical design, actuation, and control architectures. Mechanical and control issues are discussed with emphasis on techniques that provide safety in an intrinsic way or by means of control components. Attention is devoted to dependability, mainly related to sensors, control architectures, and fault handling and tolerance. Suggestions are provided to draft metrics for evaluating safety and dependability in pHRI, and references to the works of the scientific groups involved in the pHRI research complete the study. The present atlas is a result of the EURON perspective research project ‘‘Physical Human–Robot Interaction in anthropic DOMains (PHRIDOM)’’, aimed at charting the new territory of pHRI, and constitutes the scientific basis for the ongoing STReP project ‘‘Physical Human–Robot Interaction: depENDability and Safety (PHRIENDS)’’, aimed at developing key components for the next generation of robots, designed to share their environment with people. DOI:10.1016/j.mechmachtheory.2007.03.003

L. Le Tien, A. Albu-Schäffer, A. De Luca, G. Hirzinger, "Friction observer and compensation for control of robots with joint torque measurements," 2008 IEEE/RSJ International Conference on Intelligent Robots and Systems, Nice, F, pp. 3789-3795, 2008 (pdf).

S. Haddadin, A. Albu-Schäffer, A. De Luca, G. Hirzinger, "Collision detection and reaction: A contribution to safe physical human-robot interaction," 2008 IEEE/RSJ International Conference on Intelligent Robots and Systems, Nice, F, pp. 3356-3363, 2008 (pdf). IROS 2008 Best Application Paper Award

A. De Luca, L. Ferrajoli, "Exploiting robot redundancy in collision detection and reaction," 2008 IEEE/RSJ International Conference on Intelligent Robots and Systems, Nice, F, pp. 3299-3305, 2008 (pdf).

G. Palli, C. Melchiorri, A. De Luca, "On the feedback linearization of robots with variable joint stiffness," 2008 IEEE International Conference on Robotics and Automation, Pasadena, CA, pp. 1753-1759, 2008 (pdf).

S. Haddadin, A. Albu-Schäffer, A. De Luca, G. Hirzinger, "Evaluation of collision detection and reaction for a human-friendly robot on biological tissues," 6th IARP/IEEE/EURON Joint Workshop on Technical Challenges for Dependable Robots in Human Environments, Pasadena, CA, 2008 (pdf).

A. De Luca, A. Albu-Schäffer, S. Haddadin, G. Hirzinger, "Collision detection and safe reaction with the DLR-III lightweight manipulator arm," 2006 IEEE/RSJ International Conference on Intelligent Robots and Systems, Beijing, PRC, pp. 1623-1630, 2006 (pdf).
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Videos related to the IROS06 paper "Collision detection and safe reaction with the DLR-III lightweight manipulator arm" (see the paper for the reaction strategies)

    Impact with dummy: no reaction, at 20°/sec (strategy 0); with reaction, at 20°/sec (strategy 2)

    Impact with balloon: reaction strategy 4, at 90°/sec

    Impact and play with human: reaction strategy 4, at 60°/secreaction strategy 3, at 60°/secreaction strategy 3, at 90°/sec

Video accompanying the ICRA08 paper "Exploiting robot redundancy in collision detection and reaction"

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