Articles de revista
http://hdl.handle.net/2117/7010
2016-05-06T19:24:51ZPilot study for use of a virtual model for analyse paretic upper limb functional outcome evolution in acute stroke patients
http://hdl.handle.net/2117/28565
Pilot study for use of a virtual model for analyse paretic upper limb functional outcome evolution in acute stroke patients
Ticó Falguera, Neus; Peña Pitarch, Esteve; Romero Cullerés, Georgia; Sirvent Batalla, G.; Abenoza Guardiola, Montserrat
E-poster presentat a ISPRM – June 19–23, 2015, Berlin (Germany)
2015-07-13T07:44:31ZTicó Falguera, NeusPeña Pitarch, EsteveRomero Cullerés, GeorgiaSirvent Batalla, G.Abenoza Guardiola, MontserratHow common is immobilization hypercalcaemia on a brain injury rehabilitation unit? : a review of 337 patients
http://hdl.handle.net/2117/28564
How common is immobilization hypercalcaemia on a brain injury rehabilitation unit? : a review of 337 patients
Ticó Falguera, Neus; Peña Pitarch, Esteve; Romero Cullerés, Georgia; Sirvent-Batalla, G.; Abenoza Guardiola, Montserrat
E-poster presentat a ISPRM – June 19–23, 2015, Berlin (Germany)
2015-07-13T07:14:03ZTicó Falguera, NeusPeña Pitarch, EsteveRomero Cullerés, GeorgiaSirvent-Batalla, G.Abenoza Guardiola, MontserratGrasp quality measures: review and performance
http://hdl.handle.net/2117/26723
Grasp quality measures: review and performance
Roa Garzón, Máximo; Suárez Feijóo, Raúl
The correct grasp of objects is a key aspect for the right fulfillment of a given task. Obtaining a good grasp requires algorithms to automatically determine proper contact points on the object as well as proper hand configurations, especially when dexterous manipulation is desired, and the quantification of a good grasp requires the definition of suitable grasp quality measures. This article reviews the quality measures proposed in the literature to evaluate grasp quality. The quality measures are classified into two groups according to the main aspect they evaluate: location of contact points on the object and hand configuration. The approaches that combine different measures from the two previous groups to obtain a global quality measure are also reviewed, as well as some measures related to human hand studies and grasp performance. Several examples are presented to illustrate and compare the performance of the reviewed measures.
2015-03-16T12:12:56ZRoa Garzón, MáximoSuárez Feijóo, RaúlThe correct grasp of objects is a key aspect for the right fulfillment of a given task. Obtaining a good grasp requires algorithms to automatically determine proper contact points on the object as well as proper hand configurations, especially when dexterous manipulation is desired, and the quantification of a good grasp requires the definition of suitable grasp quality measures. This article reviews the quality measures proposed in the literature to evaluate grasp quality. The quality measures are classified into two groups according to the main aspect they evaluate: location of contact points on the object and hand configuration. The approaches that combine different measures from the two previous groups to obtain a global quality measure are also reviewed, as well as some measures related to human hand studies and grasp performance. Several examples are presented to illustrate and compare the performance of the reviewed measures.Grasp analysis and synthesis of 2D articulated objects with n links
http://hdl.handle.net/2117/26694
Grasp analysis and synthesis of 2D articulated objects with n links
Alvarado Tovar, Noé; Suárez Feijóo, Raúl
This paper proposes a solution to the problem of grasp analysis and synthesis of 2D articulated objects with n links considering frictionless contacts. The boundary of each link of the object is represented by a finite set of boundary points allowing links of any shape to be considered. Grasp analysis is carried out to verify whether a set of contact points on the object boundary allows a force-closure grasp, while the goal of grasp synthesis is to determine a set of contact points that allows a force-closure grasp. The paper describes the process of finding the elements of the generalized wrench vector generated by a force applied to any link of the articulated object and a procedure to search for a force-closure grasp based on these generalized wrenches. The approach has been implemented and some examples are included in the paper. (C) 2014 Elsevier Ltd. All rights reserved.
2015-03-13T12:45:23ZAlvarado Tovar, NoéSuárez Feijóo, RaúlThis paper proposes a solution to the problem of grasp analysis and synthesis of 2D articulated objects with n links considering frictionless contacts. The boundary of each link of the object is represented by a finite set of boundary points allowing links of any shape to be considered. Grasp analysis is carried out to verify whether a set of contact points on the object boundary allows a force-closure grasp, while the goal of grasp synthesis is to determine a set of contact points that allows a force-closure grasp. The paper describes the process of finding the elements of the generalized wrench vector generated by a force applied to any link of the articulated object and a procedure to search for a force-closure grasp based on these generalized wrenches. The approach has been implemented and some examples are included in the paper. (C) 2014 Elsevier Ltd. All rights reserved.Control of teleoperators with joint flexibility, uncertain parameters and time-delays
http://hdl.handle.net/2117/24836
Control of teleoperators with joint flexibility, uncertain parameters and time-delays
Nuño, Emmanuel; Sarras, Ioannis; Basañez Villaluenga, Luis; Kinnaert, Michel
The problem of controlling a rigid bilateral teleoperator has been the subject of study since the late 1980s and several control approaches have been reported to deal with time-delays, position tracking and transparency. However, the general flexible case is still an open problem. The present paper reports an adaptive and damping injection controller and a proportional plus damping injection (P +d) controller which are capable of globally stabilizing a nonlinear bilateral teleoperator with joint flexibility and time-delays. More precisely, the adaptive scheme is able to cope with uncertainty in the parameters and constant timedelays, while the P + d scheme is shown to treat variable time-delays. In both cases, the teleoperator is composed of a rigid local manipulator and a flexible joint remote manipulator. The extension to the case where the local and remote manipulators exhibit joint flexibility is also reported using the P +d scheme. Under the common assumption that the human operator and the environment are passive it is proven, for the P +d schemes, that the joint and actuator velocities as well as the local and remote position errors are bounded. Moreover, if the human operator and remote environment forces are zero then, for both controllers, position tracking is established and local and remote velocities asymptotically converge to zero. Simulations and experiments are presented to depict the performance of the proposed schemes.
2014-11-25T11:51:55ZNuño, EmmanuelSarras, IoannisBasañez Villaluenga, LuisKinnaert, MichelThe problem of controlling a rigid bilateral teleoperator has been the subject of study since the late 1980s and several control approaches have been reported to deal with time-delays, position tracking and transparency. However, the general flexible case is still an open problem. The present paper reports an adaptive and damping injection controller and a proportional plus damping injection (P +d) controller which are capable of globally stabilizing a nonlinear bilateral teleoperator with joint flexibility and time-delays. More precisely, the adaptive scheme is able to cope with uncertainty in the parameters and constant timedelays, while the P + d scheme is shown to treat variable time-delays. In both cases, the teleoperator is composed of a rigid local manipulator and a flexible joint remote manipulator. The extension to the case where the local and remote manipulators exhibit joint flexibility is also reported using the P +d scheme. Under the common assumption that the human operator and the environment are passive it is proven, for the P +d schemes, that the joint and actuator velocities as well as the local and remote position errors are bounded. Moreover, if the human operator and remote environment forces are zero then, for both controllers, position tracking is established and local and remote velocities asymptotically converge to zero. Simulations and experiments are presented to depict the performance of the proposed schemes.An adaptive controller for nonlinear teleoperators with variable time-delays
http://hdl.handle.net/2117/24712
An adaptive controller for nonlinear teleoperators with variable time-delays
Sarras, Ioannis; Nuño, Emmanuel; Basañez Villaluenga, Luis
In most real-life bilateral teleoperators the available physical parameters are uncertain and the communications exhibit variable time-delays. In order to confront these situations and only assuming that a bound of the time-delays is known, the present work reports an adaptive controller which ensures asymptotic convergence of both position errors and velocities to zero, provided that a sufficient condition on the control gains is met. Compared to previous related works that only treated constant time-delays, the stability analysis does not rely on the cascade interconnection structure of the local and remote nonlinear dynamics and the linear interconnection map. Instead, the paper employs a different Lyapunov candidate function that incorporates a strictly positive term, the local and remote position error. Some simulations, in free space and interacting with a rigid wall, and experiments, using two nonlinear manipulators, illustrate the performance of the proposed control scheme in the presence of uncertain parameters and variable time-delays. (C) 2014 The Franklin Institute. Published by Elsevier Ltd. All rights reserved.
2014-11-13T10:25:29ZSarras, IoannisNuño, EmmanuelBasañez Villaluenga, LuisIn most real-life bilateral teleoperators the available physical parameters are uncertain and the communications exhibit variable time-delays. In order to confront these situations and only assuming that a bound of the time-delays is known, the present work reports an adaptive controller which ensures asymptotic convergence of both position errors and velocities to zero, provided that a sufficient condition on the control gains is met. Compared to previous related works that only treated constant time-delays, the stability analysis does not rely on the cascade interconnection structure of the local and remote nonlinear dynamics and the linear interconnection map. Instead, the paper employs a different Lyapunov candidate function that incorporates a strictly positive term, the local and remote position error. Some simulations, in free space and interacting with a rigid wall, and experiments, using two nonlinear manipulators, illustrate the performance of the proposed control scheme in the presence of uncertain parameters and variable time-delays. (C) 2014 The Franklin Institute. Published by Elsevier Ltd. All rights reserved.Leader-follower and leaderless consensus in networks of flexible-joint manipulators
http://hdl.handle.net/2117/24462
Leader-follower and leaderless consensus in networks of flexible-joint manipulators
Nuño, Emmanuel; Valle, Daniela; Sarras, Ioannis; Basañez Villaluenga, Luis
This work presents some first results on the consensus for networks of nonlinear under-actuated mechanical systems without assuming that the gravity effects are negligible or locally pre-compensated. In particular, the study is focused on networks composed of nonidentical flexible-joint robot manipulators. Through a straightforward Lyapunov stability analysis, it is established that a simple control law provides a solution to the leader-follower consensus problem, provided that at least one follower has a direct access to the leader's position, and to the leaderless consensus problem. The network is modeled as an undirected graph and the network interconnection can have variable time-delays. The proposed controller consists of two different terms, one that dynamically compensates the robot gravity and another which ensures the desired consensus objective. This last term is a simple Proportional plus damping scheme. Simulations, using a network with ten manipulators, and experiments, with three 3 degrees-of-freedom manipulators, are provided to support the theoretical contributions of this work.
2014-10-24T07:47:12ZNuño, EmmanuelValle, DanielaSarras, IoannisBasañez Villaluenga, LuisThis work presents some first results on the consensus for networks of nonlinear under-actuated mechanical systems without assuming that the gravity effects are negligible or locally pre-compensated. In particular, the study is focused on networks composed of nonidentical flexible-joint robot manipulators. Through a straightforward Lyapunov stability analysis, it is established that a simple control law provides a solution to the leader-follower consensus problem, provided that at least one follower has a direct access to the leader's position, and to the leaderless consensus problem. The network is modeled as an undirected graph and the network interconnection can have variable time-delays. The proposed controller consists of two different terms, one that dynamically compensates the robot gravity and another which ensures the desired consensus objective. This last term is a simple Proportional plus damping scheme. Simulations, using a network with ten manipulators, and experiments, with three 3 degrees-of-freedom manipulators, are provided to support the theoretical contributions of this work.Operational space consensus of multiple heterogeneous robots without velocity measurements
http://hdl.handle.net/2117/22584
Operational space consensus of multiple heterogeneous robots without velocity measurements
Aldana López, Carlos Iván; Nuño, Emmanuel; Basañez Villaluenga, Luis; Romero, Eduardo
This paper proposes a control algorithm for networks of multiple heterogeneous robot manipulators, which solves the leader follower and the leaderless consensus problems in the operational space. In the leader-follower scenario, the controller ensures that all the robots in the network asymptotically reach a given leader pose (position and orientation), provided that, at least, one follower robot has access to the leader pose. Without a leader pose, in the leaderless problem, the robots asymptotically reach a pose of consensus. The controller is a simple distributed proportional plus clamping injection (P+d) scheme which does not require velocity measurements. A singularity-free representation, unit quaternions, is used to describe the orientation of each manipulator. The paper presents some simulations, with a network of six 6-Degrees-of-Freedom (DoF) manipulators, and experiments, with a network of three 6-DoF manipulators, to show the effectiveness of the proposed controller. (C) 2013 The Franklin Institute. Published by Elsevier Ltd. All rights reserved.
2014-04-09T13:49:43ZAldana López, Carlos IvánNuño, EmmanuelBasañez Villaluenga, LuisRomero, EduardoThis paper proposes a control algorithm for networks of multiple heterogeneous robot manipulators, which solves the leader follower and the leaderless consensus problems in the operational space. In the leader-follower scenario, the controller ensures that all the robots in the network asymptotically reach a given leader pose (position and orientation), provided that, at least, one follower robot has access to the leader pose. Without a leader pose, in the leaderless problem, the robots asymptotically reach a pose of consensus. The controller is a simple distributed proportional plus clamping injection (P+d) scheme which does not require velocity measurements. A singularity-free representation, unit quaternions, is used to describe the orientation of each manipulator. The paper presents some simulations, with a network of six 6-Degrees-of-Freedom (DoF) manipulators, and experiments, with a network of three 6-DoF manipulators, to show the effectiveness of the proposed controller. (C) 2013 The Franklin Institute. Published by Elsevier Ltd. All rights reserved.Coordination of multi-agent Euler-Lagrange systems via energy-shaping: Networking improves robustness
http://hdl.handle.net/2117/22313
Coordination of multi-agent Euler-Lagrange systems via energy-shaping: Networking improves robustness
Nuño, Emmanuel; Ortega, Romeo; Jayawardhana, Bayu; Basañez Villaluenga, Luis
In this paper, the robust coordination of multi-agent systems via energy-shaping is studied. The agents are nonidentical, Euler–Lagrange systems with uncertain parameters which are regulated (with and without exchange of information between the agents) by the classical energy-based controller where the potential energy function is shaped such that, if the parameters are known, all agents converge globally to the same desired constant equilibrium. Under parameter uncertainty, the globally asymptotically stable (GAS) equilibrium point is shifted away from its desired value and this paper shows that adding information
exchange between the agents to the decentralized control policy improves the steady-state performance.
More precisely, it proves that if the undirected communication graph is connected, the equilibrium of the networked controller isalways closer (in a suitable metric) to the desired one than that of the decentralized
controller. The result holds for all interconnection gains if the potential energy functions are quadratic, else, it is true for sufficiently large gains. An additional advantage of networking is that the asymptotic stabilization objective can be achieved by using lower gains into the loop. Some experimental results (using two nonlinear manipulators) given support to the main results of the paper
2014-03-20T13:22:47ZNuño, EmmanuelOrtega, RomeoJayawardhana, BayuBasañez Villaluenga, LuisIn this paper, the robust coordination of multi-agent systems via energy-shaping is studied. The agents are nonidentical, Euler–Lagrange systems with uncertain parameters which are regulated (with and without exchange of information between the agents) by the classical energy-based controller where the potential energy function is shaped such that, if the parameters are known, all agents converge globally to the same desired constant equilibrium. Under parameter uncertainty, the globally asymptotically stable (GAS) equilibrium point is shifted away from its desired value and this paper shows that adding information
exchange between the agents to the decentralized control policy improves the steady-state performance.
More precisely, it proves that if the undirected communication graph is connected, the equilibrium of the networked controller isalways closer (in a suitable metric) to the desired one than that of the decentralized
controller. The result holds for all interconnection gains if the potential energy functions are quadratic, else, it is true for sufficiently large gains. An additional advantage of networking is that the asymptotic stabilization objective can be achieved by using lower gains into the loop. Some experimental results (using two nonlinear manipulators) given support to the main results of the paperConsensus in networks of nonidentical Euler-Lagrange systems using P plus d controllers
http://hdl.handle.net/2117/22306
Consensus in networks of nonidentical Euler-Lagrange systems using P plus d controllers
Nuño, Emmanuel; Sarras, Ioannis; Basañez Villaluenga, Luis
This paper presents a proportional plus damping controller that can asymptotically drive a network composed of N nonidentical Euler-Lagrange (EL) systems toward a consensus point. The agents can be fully actuated or can belong to a class of underactuated EL-systems. The network is modeled as a weighted and undirected static interconnection graph that can exhibit asymmetric variable time delays. Simulations, using a network with ten EL-systems, are reported to support the theoretical contributions of this study.
2014-03-20T08:07:08ZNuño, EmmanuelSarras, IoannisBasañez Villaluenga, LuisThis paper presents a proportional plus damping controller that can asymptotically drive a network composed of N nonidentical Euler-Lagrange (EL) systems toward a consensus point. The agents can be fully actuated or can belong to a class of underactuated EL-systems. The network is modeled as a weighted and undirected static interconnection graph that can exhibit asymmetric variable time delays. Simulations, using a network with ten EL-systems, are reported to support the theoretical contributions of this study.