Trajectory Deformations from Physical Human-Robot Interaction

Robots are finding new applications where physical interaction with a human is necessary: manufacturing, healthcare, and social tasks. Accordingly, the field of physical human-robot interaction (pHRI) has leveraged impedance control approaches, which support compliant interactions between human and robot. However, a limitation of traditional impedance control is that---despite provisions for the human to modify the robot's current trajectory---the human cannot affect the robot's future desired trajectory through pHRI. In this paper, we present an algorithm for physically interactive trajectory deformations which, when combined with impedance control, allows the human to modulate both the actual and desired trajectories of the robot. Unlike related works, our method explicitly deforms the future desired trajectory based on forces applied during pHRI, but does not require constant human guidance. We present our approach and verify that this method is compatible with traditional impedance control. Next, we use constrained optimization to derive the deformation shape. Finally, we describe an algorithm for real time implementation, and perform simulations to test the arbitration parameters. Experimental results demonstrate reduction in the human's effort and improvement in the movement quality when compared to pHRI with impedance control alone

Stability of Haptic Obstacle Avoidance and Force Interaction

Abstract-Stability problems associated with haptics and robot control with obstacle avoidance are analyzed. Obstacle avoidance algorithms are revised to accomplish stable redesign using absolute stability and passivity theory. A modification of potential functions for haptic rendering and obstacle avoidance allowing stable operation for high stiffness is proposed. The modification leads to velocity-dependent potential-like repulsive stable haptic force interaction with obstacles. Using strictly positive real re-design, stable force interaction can be provided also for high stiffness of manipulated objects or obstacles

Haptics in Robot-Assisted Surgery: Challenges and Benefits

Robotic surgery is transforming the current surgical practice, not only by improving the conventional surgical methods but also by introducing innovative robot-enhanced approaches that broaden the capabilities of clinicians. Being mainly of man-machine collaborative type, surgical robots are seen as media that transfer pre- and intra-operative information to the operator and reproduce his/her motion, with appropriate filtering, scaling, or limitation, to physically interact with the patient. The field, however, is far from maturity and, more critically, is still a subject of controversy in medical communities. Limited or absent haptic feedback is reputed to be among reasons that impede further spread of surgical robots. In this paper objectives and challenges of deploying haptic technologies in surgical robotics is discussed and a systematic review is performed on works that have studied the effects of providing haptic information to the users in major branches of robotic surgery. It has been tried to encompass both classical works and the state of the art approaches, aiming at delivering a comprehensive and balanced survey both for researchers starting their work in this field and for the experts

Conception et validation expérimentale d’un gant haptique alimenté par des actionneurs magnétorhéologiques pour la manipulation d’objets dans un environnement virtuel

En réalité virtuelle (VR), les systèmes haptiques sont en mesure de fournir un retour de force à l’utilisateur pour des applications de jeux et d’entrainement (simulation). Les interfaces haptiques pour la main sont limitées par les technologies d’actionnement d’aujourd’hui. En effet, la vaste majorité des systèmes robotiques est actionnée par des moteurs DC couplés à un ratio de démultiplication (« gearbox »). Ces systèmes font face à un compromis inévitable entre la densité de couple et la réponse dynamique. De récentes recherches ont démontrées que les embrayages magnétorhéologiques (MR) couplées à une source de puissance (ex : moteur DC) sont une alternative prometteuse pour l’obtention d’une haute réponse dynamique à un coût moindre. Jusqu’à présent, la technologie MR n’a pas été démontrée pour des systèmes robotiques ayant de multiple (6 et +) degrés-de-liberté (ddls). Ce mémoire a pour but d’étudier le potentiel de la technologie des embrayages MR pour des applications d’interfaces haptiques VR pour la main. D’abord, les requis de conception sont établis par la littérature. Ensuite, un système haptique complet permettant aux utilisateurs de manipuler des objets virtuels a été développé basé sur un actionnement à tendons alimentés par des embrayages MR (« tendon-driven manipulator powered by MR actuators », TDM-MR). Ce système haptique utilise un actionnent à configuration semi-distribuée qui permet à deux moteurs DC, couplés à un ratio de démultiplication, de fournir la puissance nécessaire pour alimenter 10 embrayages MR actionnant 7 ddls. Ce système haptique a d’ailleurs été testé expérimentalement. Les résultats démontrent d’excellentes réponses dynamiques, de hautes forces générées et une tolérance aux impacts. Pour finir, un jeu VR consistant à démonter la performance du prototype auprès de 10 utilisateurs a été développé et très bien reçu par ceux-ci

Design of a 2 D.O.F. Haptic Device

Master'sMASTER OF ENGINEERIN

Design and Analysis of Haptic Interface and Teleoperator Feedback Systems.

This dissertation analyzes feedback design within haptic interface and teleoperator systems to reveal fundamental tradeoffs between design objectives, uncover intrinsic limitations imposed by hardware, and improve existing design practice. The challenge of haptic rendering and teleoperation is to synthesize a realistic mechanical sensation through feedback control while achieving other satisfactory feedback properties including robustness to hardware, noise attenuation, and stability. Special performance requirements and human-in-the-loop stability issues inherent to haptic rendering and teleoperation mean that certain conventional tools for servo-control design are not applicable. This dissertation addresses the gap in applicable theory by applying linear systems analysis to reveal previously unrecognized algebraic and analytic design relationships within haptic rendering and teleoperation. The introduction of distortion as a new performance metric for haptic rendering and teleoperation is a key contribution of this work and leads to a suite of new design relationships and tools. Important feedback design goals including performance, stability robustness, insensitivity to hardware parameter variations, and noise attenuation present a multi-objective synthesis problem with intrinsic tradeoffs. Furthermore, properties of the hardware including actuator bandwidth limitations, sensor and actuator noise, hardware nonlinearities and lightly damped structural modes constrain the feedback design and achievable goals. The analyses of haptic rendering and teleoperation presented in this dissertation yield relationships that distinguish feasible from infeasible specifications and predict performance as well as other feedback properties that may be expected from a well-tuned controller. Hardware dynamics play a key role in feedback design tradeoffs and limitations. If desired feedback properties are not feasible with given hardware, interpretation of tradeoff relationships and limitations provides direction for hardware re-design.Ph.D.Mechanical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/60859/1/paulgrif_1.pd

Haptic communication between partner dancers and swing as a finite state machine

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2005.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Vita.Includes bibliographical references (p. 129-138).To see two expert partners, one leading and the other following, swing dance together is to watch a remarkable two-agent communication and control system in action. Even blindfolded, the follower can decode the leader's moves from haptic cues. The leader composes the dance from the vocabulary of known moves so as to complement the music he is dancing to. Systematically addressing questions about partner dance communication is of scientific interest and could improve human-robotic interaction, and imitating the leader's choreographic skill is an engineering problem with applications beyond the dance domain. Swing dance choreography is a finite state machine, with moves that transition between a small number of poses. Two automated choreographers are presented. One uses an optimization and randomization scheme to compose dances by a sequence of shortest path problems, with edge lengths measuring the dissimilarity of dance moves to each bar of music. The other solves a two-player zero-sum game between the choreographer and a judge. Choosing moves at random from among moves that are good enough is rational under the game model.(cont.) Further, experiments presenting conflicting musical environments to two partners demonstrate that although musical expression clearly guides the leader's choice of moves, the follower need not hear the same music to properly decode the leader's signals. Dancers embody gentle interaction, in which each participant extends the capabilities of the other, and their cooperation is facilitated by a shared understanding of the motions to be performed. To demonstrate that followers use their understanding of the move vocabulary to interact better with their leaders, an experiment paired a haptic robot leader with human followers in a haptically cued dance to a swing music soundtrack. The subjects' performance differed significantly between instances when the subjects could determine which move was being led and instances when the subjects could not determine what the next move would be. Also, two-person teams that cooperated haptically to perform cyclical aiming tasks showed improvements in the Fitts' law or Schmidt's law speed-accuracy tradeoff consistent with a novel endpoint compromise hypothesis about haptic collaboration.by Sommer Elizabeth Gentry.Ph.D