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European Control Conference (ECC)

作者： S. Brás J. F. Vasconcelos C. Silvestre P. Oliveira Institute for Systems and Robotics (ISR) Instituto Superior Técnico Lisbon Portugal

This paper addresses the design and discrete time implementation of nonlinear observers for the estimation of position and attitude with application to Unmanned Air Vehicles. A continuous time nonlinear observer on SE(3) is derived, that uses inertial and ranges measurements. The estimation errors are shown to converge exponentially fast to the desired equilibrium points in the presence of bias in the rate gyros. An observer discrete time implementation is proposed that resorts to recent geometric numeric integration results suitable for solving ODEs on SO(3). Simulation results are presented to assess the performance of the continuous time observer and of the discrete time implementation. The estimation results in the presence of noise in the inertial and range measurements are also analyzed.

关键词： Observers Angular velocity Estimation error Vehicles Acoustics Receivers Position measurement

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A Nonlinear GPS/IMU based observer for rigid body attitude and position estimation

A Nonlinear GPS/IMU based observer for rigid body attitude a...

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IEEE Conference on Decision and Control

作者： J.F. Vasconcelos C. Silvestre P. Oliveira Institute for Systems and Robotics (ISR) Instituto Superior Técnico Lisboa Portugal

ISBN: (纸本)9781424431236

This work proposes a position and attitude nonlinear observer based on inertial measurements and GPS pseudorange readings. The observation problem is formulated on SE(3), and the solution yields exponential convergence of the attitude and position estimates. The GPS pseudorange measurements and inertial sensor readings are exploited directly in the observer, and the integration of vector readings in the observer is discussed. The proposed observer dynamics compensate for the bias in the angular velocity sensor and the clock offset in GPS pseudorange measurements. The stability of the position and velocity estimates in the presence of bounded accelerometer noise is also analyzed. The properties of the GPS/IMU based observer are illustrated in simulation for a rigid body describing a challenging trajectory.

关键词： Global Positioning System Position measurement Convergence Sensor phenomena and characterization Estimation error Stability Accelerometers Vehicles Satellites Filtering

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Influence of slot geometry on air gap magnetic flux density of rotating machines 16

Influence of slot geometry on air gap magnetic flux density ...

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16th International Conference on Environment and Electrical Engineering, EEEIC 2016

作者： De Lima, Rodrigo Alves Coimbra, A. C. Paulo Almeida, Tony Gomes, Viviane Margarida Pereira, Thiago Martins Alves, Aylton Jose Calixto, Wesley Pacheco Program in Electronic Systems and Automation PGEA Department of Electrical Engineering ENE University of Brasilia UnB Brazil Institute of Systems and Robotics ISR University of Coimbra UC Portugal Experimental and Technological Research and Study Group NExT Federal Institute of Goias IFG Brazil

ISBN: (纸本)9781509023196

The objective of this work is to investigate the influence of slotted air gap constructive parameters on magnetic flux density of rotating machines. For this purpose, different approaches were used to solve the air gap field diagram using finite element method and the magnetic field distribution uniformity was evaluated by Carter's factor calculation. Sensitivity analysis of slot constructive parameters was performed and results show that slot geometry modifies the magnetic flux on air gap and shifts the air gap magnetic equipotential midline of double slotted machines. © 2016 IEEE.

关键词： Finite element method

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Multiple Model Adaptive Estimation and model identification usign a Minimum Energy criterion

Multiple Model Adaptive Estimation and model identification ...

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American Control Conference (ACC)

作者： Vahid Hassani A. Pedro Aguiar Michael Athans Antonio M. Pascoal Institute for Systems and Robotics (ISR) Instituto Superior Técnico Lisboa Portugal

This paper addresses the problem of Multiple Model Adaptive Estimation (MMAE) for discrete-time, linear, time-invariant MIMO plants with parameter uncertainty and unmodeled dynamics. Model identification is analyzed in a deterministic setting by adopting a Minimum Energy selection criterion. The MMAE system relies on a finite number of local observers, each designed using a selected model (SM) from the original set of possibly infinite plant models. Results akin to those previously obtained in a stochastic setting are derived in a far simpler manner, in a deterministic framework. We show, under suitable distinguishability conditions, that the SM identified is the one that corresponds to the observer with smallest output prediction error energy. We also develop a procedure to analyze the behavior of MMAE when the true plant is not one of the SMs. This leads to an algorithm that computes, for each SM, the set of equivalently identified plants, that is, the set of plants that will be identified as that particular SM. The impact of unmodeled dynamics on model identification is discussed. Simulation results with a model of a motor coupled to a load via an elastic shaft illustrate the performance of the methodology derived.

关键词： Adaptive estimation Samarium State estimation Stochastic processes Uncertain systems Information analysis Uncertainty Observers MIMO Computational modeling

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Iterative multi-step explicit camera calibration

Iterative multi-step explicit camera calibration

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International Conference on Computer Vision (ICCV)

作者： J. Batista H. Araujo A.T. De Almeida ISR-Institute of Systems and Robotics DEE-FCTUC University of Coimbra Coimbra Portugal

Perspective camera calibration has been in the last decades a research subject for a large group of researchers and as a result several camera calibration methodologies can be found in the literature. However only a small number of those methods base their approaches on the use of monoplane calibration points. This paper describes one of those methodologies that uses monoplane calibration points to realize an explicit 3D camera calibration. To avoid the singularity obtained with the calibration equations when monoplane calibration points are used, this method computes the calibration parameters in a multi-step procedure and requires a first-guess solution for the intrinsic parameters. These parameters are updated and their accuracy increased through an iterative procedure. A stability analysis as a function of the pose of the camera is presented. Camera pose view strategies for accurate camera orientation computation can be extracted from the pose view stability analysis.

关键词： Cameras Calibration Robot vision systems Equations Stability analysis Nonlinear distortion Iterative methods Matrix decomposition Transmission line matrix methods Physics computing

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Real-time gesture recognition system based on contour signatures

Proceedings - International Conference on Pattern Recognitio...

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Proceedings - International Conference on Pattern Recognition 2002年第1期16卷 447-450页

作者： Peixoto, P. Gonçalves, J. Araújo, H. ISR - Institute of Systems and Robotics Dept. of Electrical Engineering University of Coimbra 3030 Coimbra Portugal

In this paper we describe a real-time gesture recognition algorithm based on contour signature images, generated by collecting a set of contour signatures over time. 'Each contour signature is generated in each frame by computing the polar coordinates of each point of the contour in relation to the center of mass of that contour. The gesture recognition is reduced to the problem of finding the correspondent contour signature image from a set of previously learned image contour signatures. This is achieved using a Karhunen-Loeve (KL) transform that reduces the set of trained images to a low-dimensional eigenspace, making recognition easier. This method is particularly suitable for the recognition of gestures that can be perfectly described by silhouettes. Since no shape or 3D model is required the proposed method can easily be adapted to recognize several other types of gestures not necessarily performed by humans. The proposed algorithm is able to extract target gesture motions and classify them at the same time. Preliminary experimental results demonstrate robustness and real-time performance of the proposed algorithm. © 2002 IEEE.

关键词： Gesture recognition

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3D laser-based sensor for robotics

3D laser-based sensor for robotics

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Mediterranean Electrotechnical Conference (MELECON)

作者： L. Marques F. Moita U. Nunes A.T. de Almeida ISR-Institute of Systems and Robotics Electrical Engineering Department University of Coimbra Coimbra Portugal

The paper presents the analysis and design of a distance and orientation sensor based on the triangulation principle, using three laser diodes and a position sensitive detector (PSD). A 16-bit microcontroller controls the acquisition and the lasers, processes the data and integrates the sensor in a distributed sensor network (DSN). A DSP based processing system gathers the multisensor data, for real-time control of a PUMA 560 robot manipulator through the DSN network. A sensor model based on theoretical and experimental results is emphasized.< >

关键词： Robot sensing systems Optical design Diode lasers Position sensitive particle detectors Microcontrollers Optical control Laser modes Laser theory Digital signal processing Real time systems

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Intelligent traffic management at intersections: Legacy mode for vehicles not equipped with V2V and V2I communications

Intelligent traffic management at intersections: Legacy mode...

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International Conference on Intelligent Transportation

作者： Luís Conde Bento Ricardo Parafita Sérgio Santos Urbano Nunes ESTG Polytechnic Institute of Leiria Portugal ISR-Institute of Systems and Robotics University of Coimbra Portugal

This paper describes a legacy algorithm for an intelligent traffic management system applied to automatic regulation of traffic at intersections. The application of the legacy algorithm enables the intelligent intersection to accommodate vehicles, in a low percentage, not equipped or with faulty V2V and V2I communications. The developed intelligent traffic management techniques, which are based on a spatiotemporal reservation scheme, aim to minimize accidents, traffic congestion and consequently the environmental costs of road traffic. The performance of three intelligent traffic management algorithms applied to road intersections, roundabouts and crossroads, are analyzed. Compared with traditional traffic management techniques, simulation results using the developed intelligent traffic management techniques, show that the traffic output flux can be increased, traffic flow rate can be higher and the average time to cross intersections can be significantly reduced. This reduction is more pronounced when the traffic flow is heavy. The conducted studies show that the inclusion of a low percentage of vehicles, not equipped or with faulty V2V and V2I communications, in intelligent intersections using the legacy algorithm, have a low impact on the traffic flow.

关键词： Roads Artificial intelligence Algorithm design and analysis Space vehicles Simulation Sensors

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Terrain following controller for affine parameter-dependent systems: An application to model-scale helicopters

Terrain following controller for affine parameter-dependent ...

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AIAA Guidance, Navigation, and Control Conference 2005

作者： Paulino, Nuno Silvestre, Carlos Cunha, Rita Instituo Superior Técnico Institute for Systems and Robotics Lisbon Portugal Av. Rovisco Pais 1 1046-001 Lisboa Portugal DEEC ISR IST Portugal AIAA United States

ISBN: (纸本)1563477378

This paper presents a terrain following controller for model-scale helicopters that takes into account the terrain characteristics ahead of the vehicle as measured by a Laser Range Scanner. The methodology used to solve the terrain following control problem amounts to posing it as a discrete time path following control problem where a conveniently defined error state space model of the plant is augmented with terrain preview data. A piecewise affine parameter-dependent model representation is used to accurately describe the linearized error dynamics, for a pre-defined set of operating regions. For each region, the synthesis problem is stated as a state feedback H2 control problem for affine parameterdependent systems and solved using Linear Matrix Inequalities (LMIs). A sub-optimal technique to compute the feed-forward preview gain matrix is proposed that avoids solving LMIs involving a large number of unknowns. The resulting nonlinear controller is implemented under the scope of gain-scheduled control theory using the D-methodology. Simulation results obtained with the full nonlinear helicopter model are presented and discussed. Copyright © 2005 by the American institute of Aeronautics and Astronautics, Inc. All rights reserved.

关键词： Helicopters

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Joint Positioning and Navigation Aiding systems for Multiple Underwater Robots

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IFAC Proceedings Volumes 2009年第18期42卷 167-172页

作者： R. Sousa P. Oliveira T. Gaspar Instituto Superior Técnico (IST) and Institute for Systems and Robotics (ISR) Lisbon Portugal renato.lisboa pjcro

This paper proposes a new joint positioning and navigation aiding system for multiple underwater robots. In the scenario adopted, each submersed target carries a pinger that emits acoustic signals periodically, as determined by a low precision clock. The targets are tracked from the surface by a set of buoys equipped with acoustic hydrophones/projectors, GPS receivers, and electronic circuitry that measures the times of arrival of the acoustic signals emitted by the pinger. The buoys at surface, synchronized with the GPS timing, emit periodically distinctive signals that the underwater vehicles can use as aids to their onboard navigation systems. In the case where buoys drift away more than a pre-specified distance from their nominal positions, coded signals are emitted. The scheme proposed allows for the performance in the tracking and navigation systems to be independent from the number of targets present in the scenario of operation. Simulation results are presented to assess the performance of both the positioning tracker and a simplified onboard integrated navigation system.

关键词： Navigation systems Positioning systems Marine systems Extended Kalman filters

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