Aldana, C.; Romero, E.; Nuño, E.; Basañez, L. International journal of robust and nonlinear control Vol. 25, num. 14, p. 2279-2298 DOI: 10.1002/rnc.3200 Data de publicació: 2015-09-25 Article en revista
This paper proposes a novel pose (position and orientation) consensus controller for networks of heterogeneous robots modeled in the operational space. The proposed controller is a distributed proportional plus damping scheme that, with a slight modification, solves both the leader-follower and leaderless consensus problems. A singularity-free representation, unit quaternion, is used to describe the robots orientation, and the network is represented by an undirected and connected interconnection graph. Furthermore, it is shown that the controller is robust to interconnection variable time delays. Experiments with a network of two 6-degrees-of-freedom robots are presented to illustrate the performance of the proposed scheme. Copyright (c) 2014 John Wiley & Sons, Ltd.
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.
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.
The paper deals with the problem of planning movements of two hand-arm robotic systems, considering the possibility of using the robot hands to remove potential obstacles in order to obtain a free access to grasp a desired object. The approach is based on a variation of a Probabilistic Road Map that does not rule out the samples implying collisions with removable objects but instead classifies them according to the collided obstacle(s), and allows the search of free paths with the indication of which objects must be removed from the work-space to make the path actually valid; we call it Probabilistic Road Map with Obstacles (PRMwO). The proposed system includes a task assignment system that distributes the task among the robots, using for that purpose a precedence graph built from the results of the PRMwO. The approach has been implemented for a real dual-arm robotic system, and some simulated and real running examples are presented in the paper. (C) 2014 Elsevier B.V. All rights reserved.
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.
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. (C) 2014 European Control Association. Published by Elsevier Ltd. All rights reserved.
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.
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.
Nuño, E.; Basañez, L.; Lopez-Franco, C.; Arana-Daniel, N. Journal of the Franklin Institute Vol. 351, num. 1, p. 241-258 DOI: 10.1016/j.jfranklin.2013.08.022 Data de publicació: 2014-01 Article en revista
This paper presents two Proportional-Derivative (PD) like controllers for nonlinear bilateral teleoperation systems. Compared to previous controllers of this kind, these schemes do not make use of velocity measurements. Under the assumptions that the human operator and the environment define passive maps from velocity to force, both controllers can ensure boundedness of velocities and position error. Moreover, in the case that the human and environment forces are zero, the controllers ensure velocity and position synchronization. Furthermore, the paper also presents a generalization to the case of teleoperation of networks of multiple robots. Simulations and real experiments, comparing the performance on free motion and interacting with a stiff wall, support the performance of the reported schemes. The experiments have been performed using two 3-degree-of-freedom nonlinear manipulators.
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.
The planning of collision-free paths for a handarm
robotic system is a difficult issue due to the large number
of degrees of freedom involved and the cluttered environment
usually encountered near grasping configurations. To cope
with this problem, this paper presents a novel importance
sampling method based on the use of principal component
analysis (PCA) to enlarge the probability of finding collisionfree
samples in these difficult regions of the configuration
space with low clearance. By using collision-free samples
near the goal, PCA is periodically applied in order to obtain
a sampling volume near the goal that better covers the free
space, improving the efficiency of sampling-based path planning
methods. The approach has been tested with success on
a hand-arm robotic system composed of a four-finger anthropomorphic
mechanical hand (17 joints with 13 independent
degrees of freedom) and an industrial robot (6 independent
degrees of freedom).
The present paper proposes two controllers for solving a consensus problem to a given desired position of networks composed of a class of under actuated mechanical systems: flexible joints robots. One of the controllers makes use of joint (motor) velocity signals while the other only uses joint positions. The only assumption on the directed and weighted interconnection graph is that it is connected. Further, the interconnection may induce variable time-delays. The paper presents some experiments, using three 3-Degrees of Freedom manipulators, which show the performance of the proposed approaches.