Porta, J.M.; Ros, L.; Bohigas, O.; Manubens, M.; Rosales, C.; Jaillet, L.G. IEEE robotics and automation magazine Vol. 21, num. 3, p. 105-114 DOI: 10.1109/MRA.2013.2287462 Data de publicació: 2014 Article en revista
Many situations in robotics require the analysis of the motions of complex multibody systems. These are sets of articulated bodies arising in a variety of devices, including parallel manipulators, multifingered hands, or reconfigurable mechanisms, but they appear in other domains too as mechanical models of molecular compounds or nanostructures. Closed kinematic chains arise frequently in such systems, either due to their morphology or due to geometric or contact constraints to fulfill during operation, giving rise to configuration spaces of an intricate structure. Despite appearing very often in practice, there is a lack of general software tools to analyze and represent such configuration spaces. Existing packages are oriented either to open-chain systems or to specific robot types, which hinders the analysis and development of innovative manipulators. This article describes the CUIK suite, a software toolbox for the kinematic analysis of general multibody systems. The implemented tools can isolate the valid configurations, determine the motion range of the whole multibody system or of some of its parts, detect singular configurations leading to control or dexterity issues, or find collision- and singularity-free paths between configurations. The toolbox has applications in robot design and programming and is the result of several years of research and development within the Kinematics and Robot Design group at IRI, Barcelona. It is available under GPLv3 license from http://www.iri.upc.edu/cuik.
Supervision of long-lasting extensive botanic
experiments is a promising robotic application that some recent technological advances have made feasible. Plant modeling for this application has strong demands, particularly in what concerns three-dimensional (3-D) information gathering and speed.
This article presents the realization of a tensegrity-based robot composed of a three-bar symmetric prismlike minimal tensegrity configuration. Statics and kinematics are studied presenting the workspace for the designed robot. After a detailed implementation description of the physical robot, some trajectories within its workspace are analyzed. Although our long-term objective is to provide mobile tensegrity-based robots to the community, this work studies a case in which the robot is anchored to the ground. This provides us with a first insight of how these structures should be actuated and sensed to produce movement.
This article is centered on how we can accurately estimate the robot pose uncertainty and how this uncertainty is propagated to future states (the robot state, in this context, is its pose). Some attention has been paid to this issue in the past. The first approach considering the uncertainty of position estimation. A min/max error bound approach is proposed resulting in bigger and bigger circles in the x-y plane representing the possible positions for the robot. Those circles are computed as projections of cylinders in the configuration space. Basically, the same approach was independently derived using a scalar as an uncertainty measure in the plane position but without reference to the orientation error. The main contribution of this article is the proposal of a novel solution for the calculation of such cross-covariance terms. In this way, we are able to catch the highly nonlinear behavior of the pose uncertainty while accurately estimating it. The basic idea is to fit the covariance matrix for the previous pose using a set of equations obtained by eigen decomposition. The cross-covariance terms are then derived using these set of equations together with the already-known expressions for the vehicle pose increments