254 research outputs found

    The Shape of Damping: Optimizing Damping Coefficients to Improve Transparency on Bilateral Telemanipulation

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    This thesis presents a novel optimization-based passivity control algorithm for hapticenabled bilateral teleoperation systems involving multiple degrees of freedom. In particular, in the context of energy-bounding control, the contribution focuses on the implementation of a passivity layer for an existing time-domain scheme, ensuring optimal transparency of the interaction along subsets of the environment space which are preponderant for the given task, while preserving the energy bounds required for passivity. The involved optimization problem is convex and amenable to real-time implementation. The effectiveness of the proposed design is validated via an experiment performed on a virtual teleoperated environment. The interplay between transparency and stability is a critical aspect in haptic-enabled bilateral teleoperation control. While it is important to present the user with the true impedance of the environment, destabilizing factors such as time delays, stiff environments, and a relaxed grasp on the master device may compromise the stability and safety of the system. Passivity has been exploited as one of the the main tools for providing sufficient conditions for stable teleoperation in several controller design approaches, such as the scattering algorithm, timedomain passivity control, energy bounding algorithm, and passive set position modulation. In this work it is presented an innovative energy-based approach, which builds upon existing time-domain passivity controllers, improving and extending their effectiveness and functionality. The set of damping coefficients are prioritized in each degree of freedom, the resulting transparency presents a realistic force feedback in comparison to the other directions. Thus, the prioritization takes effect using a quadratic programming algorithm to find the optimal values for the damping. Finally, the energy tanks approach on passivity control is a solution used to ensure stability in a system for robotics bilateral manipulation. The bilateral telemanipulation must maintain the principle of passivity in all moments to preserve the system\u2019s stability. This work presents a brief introduction to haptic devices as a master component on the telemanipulation chain; the end effector in the slave side is a representation of an interactive object within an environment having a force sensor as feedback signal. The whole interface is designed into a cross-platform framework named ROS, where the user interacts with the system. Experimental results are presented

    Analyse de performances des actionneurs à fluide magnétorhéologique pour les interfaces haptiques

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    Les interfaces haptiques sont des dispositifs permettant un retour en force, qui est généralement fait par l’entremise de moteurs électriques. Les interfaces haptiques peuvent être utilisées en formation pour simuler des environnements virtuels, par exemple, des organes virtuels pour la formation de chirurgien. Cependant, les moteurs électriques font face à un dilemme technique entre la densité de couple et une réponse dynamique, limitant ainsi les performances des interfaces haptiques. Les actionneurs magnétorhéologiques, composé d’une source de puissance et d’embrayages à fluide magnétorhéologique, ont démontré leur potentiel face à ce dilemme technique. En effet, une multitude d’embrayages magnétorhéologique peuvent se partager une seule source de puissance. Les actionneurs magnétorhéologiques ont donc une excellente densité de couple tout en ayant de bonnes performances dynamiques. Ce projet de recherche présente une analyse de performances des actionneurs magnétorhéologique pour les interfaces haptique. Les performances des actionneurs magnétorhéologique ont été comparées avec les moteurs électriques présentement utilisés dans la plupart des interfaces haptiques. Des critères de performances ont été établis à l’aide de la littérature scientifique. Un modèle dynamique d’une interface haptique a été développé et utilisé pour faire une analyse sur les performances des actionneurs magnétorhéologiques et des moteurs électriques. Un banc de test a été développé pour valider le modèle et les résultats obtenus en simulation. Les résultats démontrent que les actionneurs magnétorhéologiques permettent une meilleure génération d’environnement virtuel. L’amortissement des actionneurs magnétorhéologiques doit être adressé pour augmenter la variété d’environnements virtuels pouvant être générés

    On the passivity of interaction control with series elastic actuation

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    Regulating the mechanical interaction between robot and environment is a fundamentally important problem in robotics. Many applications such as manipulation and assembly tasks necessitate interaction control. Applications in which the robots are expected to collaborate and share the workspace with humans also require interaction control. Therefore, interaction controllers are quintessential to physical human-robot interaction (pHRI) applications. Passivity paradigm provides powerful design tools to ensure the safety of interaction. It relies on the idea that passive systems do not generate energy that can potentially destabilize the system. Thus, coupled stability is guaranteed if the controller and the environment are passive. Fortunately, passive environments constitute an extensive and useful set, including all combinations of linear or nonlinear masses, springs, and dampers. Moreover, a human operator may also be treated as a passive network element. Passivity paradigm is appealing for pHRI applications as it ensures stability robustness and provides ease-of-control design. However, passivity is a conservative framework which imposes stringent limits on control gains that deteriorate the performance. Therefore, it is of paramount importance to obtain the most relaxed passivity bounds for the control design problem. Series Elastic Actuation (SEA) has become prevalent in pHRI applications as it provides considerable advantages over traditional sti actuators in terms of stability robustness and delity of force control, thanks to deliberately introduced compliance between the actuator and the load. Several impedance control architectures have been proposed for SEA. Among the alternatives, the cascaded controller with an inner-most velocity loop, an intermediate torque loop and an outer-most impedance loop is particularly favoured for its simplicity, robustness, and performance. In this thesis, we derive the necessary and su cient conditions to ensure the passivity of the cascade-controller architecture for rendering two classical linear impedance models of null impedance and pure spring. Based on the newly established passivity conditions, we provide non-conservative design guidelines to haptically display free-space and virtual spring while ensuring coupled stability, thus the safety of interaction. We demonstrate the validity of these conditions through simulation studies as well as physical experiments. We demonstrate the importance of including physical damping in the actuator model during derivation of passivity conditions, when integral controllers are utilized. We note the unintuitive adversary e ect of actuator damping on system passivity. More precisely, we establish that the damping term imposes an extra bound on controller gains to preserve passivity. We further study an extension to the cascaded SEA control architecture and discover that series elastic damping actuation (SEDA) can passively render impedances that are out of the range of SEA. In particular, we demonstrate that SEDA can passively render Voigt model and impedances higher than the physical spring-damper pair in SEDA. The mathematical analyses of SEDA are veri ed through simulations

    HapBead: on-skin microfluidic haptic interface using tunable bead

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    On-skin haptic interfaces using soft elastomers which are thin and flexible have significantly improved in recent years. Many are focused on vibrotactile feedback that requires complicated parameter tuning. Another approach is based on mechanical forces created via piezoelectric devices and other methods for non-vibratory haptic sensations like stretching, twisting. These are often bulky with electronic components and associated drivers are complicated with limited control of timing and precision. This paper proposes HapBead, a new on-skin haptic interface that is capable of rendering vibration like tactile feedback using microfluidics. HapBead leverages a microfluidic channel to precisely and agilely oscillate a small bead via liquid flow, which then generates various motion patterns in channel that creates highly tunable haptic sensations on skin. We developed a proof-of-concept design to implement thin, flexible and easily affordable HapBead platform, and verified its haptic rendering capabilities via attaching it to users’ fingertips. A study was carried out and confirmed that participants could accurately tell six different haptic patterns rendered by HapBead. HapBead enables new wearable display applications with multiple integrated functionalities such as on-skin haptic doodles, mixed reality haptics and visual-haptic displays

    Fractional order control in haptics

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    Fractional order (FO) calculus—a generalization of the traditional calculus to arbitrary order differointegration-is an effective mathematical tool that broadens the modeling boundaries of the familiar integer order calculus. The effectiveness of this remarkable mathematical tool has been observed in many practical applications. For instance, FO models enable faithful representation of viscoelastic materials that exhibit frequency dependent stiffness and damping characteristics within a single mechanical element. In this dissertation, we propose and analyze the use of FO controllers in haptic systems and provide a systematic analysis of this new control method in the light of the fundamental trade-off between the stability robustness and the transparency performance. FO controllers provide a promising generalization that allows one to better shape the frequency response of a system to achieve more favorable robustness and performance characteristics. In particular, the use of FO calculus in systems and control applications provides the user with an extra design variable, the order of differointegration, which can be tuned to improve the desired behavior of the overall system. We introduce a generalized FO nondimensionalized sampled-data model for the haptic system and study its frequency dependent behaviour. Then, we analyze the stability of this system with and without a human operator in the loop. Moreover, we experimentally verify the stability analysis and demonstrate that the experiments capture the essence of the stability behaviour between different differentiation orders. The passivity analysis is conducted for two cases: the first approach takes the environment model into account and ensures the passivity of the haptic system together with the virtual environment, while the second approach assumes the presence of a passive environment model in the control loop and introduces a controller to the closed-loop system that acts like a buffer between the haptic display and the virtual environment. The second approach is more suitable for complex environments as it investigates the passivity properties of the two-port haptic system together with a virtual coupler. After characterizing the stability boundaries for the FO haptic system, we analyse the performance of the system by studying the transparency performance of the haptic rendering with such controllers. In particular, we employ effective impedance analysis to decompose the closed-loop impedance of a haptic system into its parts and study the contribution of FO elements on the stiffness and damping rendering characteristics of the system. Finally, we apply the theoretical results to a novel haptic rendering scenario: haptic rendering of viscoelastic materials. A fractional order mathematical model for the human prostate tissue with history depended stress and deflection behavior, is chosen as the viscoelastic physical system to be rendered. The stress relaxation of the haptic rendering is verified against the experimental data, indicating a high fidelity rendering

    Design and Analysis of Haptic Interface and Teleoperator Feedback Systems.

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    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 Guidance for Extended Range Telepresence

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    A novel navigation assistance for extended range telepresence is presented. The haptic information from the target environment is augmented with guidance commands to assist the user in reaching desired goals in the arbitrarily large target environment from the spatially restricted user environment. Furthermore, a semi-mobile haptic interface was developed, one whose lightweight design and setup configuration atop the user provide for an absolutely safe operation and high force display quality

    Haptics: Science, Technology, Applications

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    This open access book constitutes the proceedings of the 13th International Conference on Human Haptic Sensing and Touch Enabled Computer Applications, EuroHaptics 2022, held in Hamburg, Germany, in May 2022. The 36 regular papers included in this book were carefully reviewed and selected from 129 submissions. They were organized in topical sections as follows: haptic science; haptic technology; and haptic applications

    Musical Haptics

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    Haptic Musical Instruments; Haptic Psychophysics; Interface Design and Evaluation; User Experience; Musical Performanc
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