1,721,233 research outputs found
Robotic Interaction Through Compliant Interfaces: Modelling and Identification
No full textIn this work, a new model, able to emulate theinteraction of a robot with the environment when viscoelasticphenomena occur, is presented. The starting point of thisresearch activity has been the study of soft pads for dexterousmanipulation but the results obtained are applicable to allsituations which foresee the interaction of a robotic manipulatorthrough/with a viscoelastic medium (e.g. robotic surgery).Based on the so called quasi-linear model, adopted to describethe behavior of human hand pads and, more generally, ofbiological tissues, this model allows to overcome the problemstied to classical (linear) models, often used in the robotic field.A procedure aiming to obtain the parameters of this nonlinearmodel is developed on the basis of classical identificationmethods and of physical insights. Finally, through experimentaltests on some viscoelastic materials (a polyurethane gel and asilicon rubber) the model is validated
Feedback linearization and simultaneous stiffness-position control of robots with antagonistic actuated joints.
No full textIn this paper, the dynamic model of a robot with antagonistic actuated joints is presented, and the problem of full linearization via static state feedback is analyzed. The use of transmission elements with nonlinear relation between the displacement and the actuated force allows to control both the position and the stiffness of each joint. The main advantage of this actuation modality is that the achieved stiffness becomes same mechanical characteristic of the system and it is not the result of an immediate control action as in the classical impedance control scheme. Different examples of implementation of this kind of devices are known in literature, even if limited to one single joint and the application of antagonistic actuated kinematic chains in the field of robotic hand design is under investigation. After a brief review of the dependence of the properties of antagonistic actuation on the transmission elements characteristics, a scheme for simultaneous stiffness-position control of the linearized system is presented. Finally, simulation results of a two-link antagonistic actuated arm are reported and discussed
On the Control of Redundant Robots with Variable Stiffness Actuation
No full textIn this paper, the control of a redundant robotic manipulator with variable stiffness actuation is addressed. The problem of controlling simultaneously the end-effector position and stiffness exploiting the robot redundancy for the optimization of the robot configuration is considered, and the relation between the manipulator redundancy and the selection of both the joint and end-effector stiffness is discussed. The controller is configured as a cascade system that allows the decoupling of the actuators dynamics from the arm dynamics and the consequent reduction of the order of the manipulator dynamic model. Only the actuator and joint positions are needed by the controller, introducing in this way a significant simplification with respect to previously proposed state feedback techniques. The effectiveness of the proposed approach is verified by simulations of a 3-DOF planar manipulator
Modelling and control of robotic joints based on sliding pairs
No full textIn this paper, the investigation on the friction phenomena acting at joint level in the robotic hand developed within the DEXMART project is reported. This side effect is given by the adoption of joints based on sliding pairs to reduce the complexity of the mechanism and to ease the assembly procedure. The joint friction has been modelled by means of a specialised version of the LuGre friction model in which the friction coefficients vary with the normal force. The estimated friction has been used in the joint position control loop as a feed-forward term for reducing the position error, as shown by experimental results. The developed friction model has been also used in the experiment to reconstruct the effects of the contact force applied to the joint by the external environment by means of a suitable observer. © 2013 IEEE
Bilateral Energy Transfer for high fidelity haptic telemanipulation
No full textAmong the methods to grant the stability of a telemanipulation system, the bilateral time domain passivity framework has the appealing characteristic to consider both, force and velocity signals exchanged between master and slave systems, and the power introduced or dissipated by the elements that compose the telemanipulation system. In previous works, [2, 3], it has been shown how the bilateral passivity controller
(BiPC) can preserve stability when the communication channel that conveys data between master and slave is affected by delay. In this work the authors intend to further explore the possibilities offered by the Bilateral Energy Transfer concept as design guideline, and to refine the control schemes already discussed in [3]. The underlying idea of the Bilateral Energy Transfer is to achieve a transport of energy between the two sides of the real system as faithful to an “ideal” (not delayed) system as allowed by the energy leaks. As energy leak is meant the behavior introduced by the not ideality of some components, such as the communication channel. At the same time, in order to obtain easy-to-use system, the control system must preserve, in some extend, the force, velocity, and position correspondences between master and slave. In order to achieve this goal, a modified version of passivity controller is presented. Its main characteristic is that its correction action aimed at dissipating energy, regarded as generated by energy leaks, is limited and deferred in time. Moreover, a drift compensator is introduced whose role is to solve a drift in position introduced by the operation of the same BiPC; in order to maintain the whole system passive, the action of this controller is bounded to the amount of energy that has been dissipated in excess by the BiPC
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Progetto e realizzazione di un attuatore a rigidezza variabile per applicazioni robotiche
No full textLo sviluppo di robot sicuri ed affidabili per l'interazione fisica uomo-macchina sta cambiando il modo in cui i robot stessi sono progettati, introducendo nuove problematiche tecnologiche. Esempi rilevanti sono l'adozione di ricoprimenti soffici e trasmissioni cedevoli (compliant) o la definizione di leggi di controllo del moto che garantiscono elevata cedevolezza in caso di possibili urti preservando, allo stesso tempo, elevate prestazioni e precisione durante l’esecuzione di compiti. In questo contesto, un interesse crescente è stato dedicato allo studio di giunti a rigidezza variabile. Questa memoria propone un giunto di tale tipologia basato sull'uso di meccanismi compliant, con l'obiettivo di migliorare la compattezza e la flessibilità delle soluzioni meccaniche esistenti. Si introduce una procedura sistematica per la sintesi di un quadrilatero articolato compliant che permette l'implementazione di un profilo di rigidezza desiderato. Infine, si mostra un prototipo del giunto complessivo
Progetto e realizzazione di un attuatore a rigidezza variabile per applicazioni robotiche
No full textLo sviluppo di robot sicuri ed affidabili per l'interazione fisica uomo-macchina sta cambiando il modo in cui i robot stessi sono progettati, introducendo nuove problematiche tecnologiche. Esempi rilevanti sono l'adozione di ricoprimenti soffici e trasmissioni cedevoli (compliant) o la definizione di leggi di controllo del moto che garantiscono elevata cedevolezza in caso di possibili urti preservando, allo stesso tempo, elevate prestazioni e precisione durante l’esecuzione di compiti. In questo contesto, un interesse crescente è stato dedicato allo studio di giunti a rigidezza variabile. Questa memoria propone un giunto di tale tipologia basato sull'uso di meccanismi compliant, con l'obiettivo di migliorare la compattezza e la flessibilità delle soluzioni meccaniche esistenti. Si introduce una procedura sistematica per la sintesi di un quadrilatero articolato compliant che permette l'implementazione di un profilo di rigidezza desiderato. Infine, si mostra un prototipo del giunto complessivo
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