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Nonlinear Path Following Control of Autonomous Underwater Vehicles *

IFAC Proceedings Volumes 2003年第4期36卷 25-30页

作者： L. Lapierre D. Soetanto A. Pascoal Institute for Systems and Robotics and Department of Electrical Engineering and Computers Instituto Superior Tecnico Av. Rovisco Pais 1 1049-001 Lisboa Portugal

A new type of control law is derived to steer an autonomous underwater vehicle (AUV) along a desired path. The methodology adopted for path following deals explicitly with vehicle dynamics. Furthermore, it overcomes stringent initial condition constraints that are present in a number of path following control strategies described in the literature. Controller design builds on Lypaunov theory and backstepping techniques. The resulting nonlinear feedback control law yields convergence of the path following error trajectories to zero. Simulation results illustrate the performance of the control system proposed.

关键词： Non Linear Control Path Following Autonomous Underwater Vehicles

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Coordinated motion control of marine robots *

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IFAC Proceedings Volumes 2003年第21期36卷 217-222页

作者： L. Lapierre D. Soetanto A. Pascoal Institute for Systems and Robotics and Department of Electrical Engineering and Computers Instituto Superior Técnico Av. Rovisco Pais 1 1049-001 Lisboa Portugal

This paper addresses the problem of coordinated motion control of marine robots. A nonlinear control law is derived to steer two underwater vehicles along identical parallel paths, while ensuring that the lateral distance between them remains constant. The key idea explored in the paper is to elect one of the vehicles as leader and the other as follower. Both the leader and follower execute the same path following algorithm, the leader traveling along its assigned path at a desired speed profile. The velocity of the follower is then adapted based on the measure of a "generalized along-path distance" between the two vehicles. The amount of information to be exchanged between the two vehicles is thus kept at a minumum. Controller design builds on Lyapunov theory and backstepping techniques. Simulation results illustrate the performance of the coordinated motion control system proposed.

关键词： Coordinated motion control Control of marine vehicles Path following control

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Real-time gesture recognition system based on contour signatures

Real-time gesture recognition system based on contour signat...

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International Conference on Pattern Recognition

作者： P. Peixoto J. Goncalves H. Araujo ISR-Institute of Systems and Robotics Department of Electrical Engineering University of Coimbra Coimbra Portugal

ISBN: (纸本)076951695X

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.

关键词： Real time systems Image recognition Humans Surveillance Image generation Karhunen-Loeve transforms Space technology Robot kinematics Shape Cameras

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Learning variable-resolution maps for navigation in dynamic worlds

Learning variable-resolution maps for navigation in dynamic ...

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Annual Conference of Industrial Electronics Society

作者： R. Araujo G. Gouveia A.T. de Almeida Institute for Systems and Robotics (ISR) and Department of Electrical and Computer Engineering University of Coimbra Coimbra Portugal

Map building is an important component to enable autonomous mobile robots to navigate in complex unfamiliar environments. This paper introduces a new method for learning multiresolution maps for navigation in unknown and dynamic worlds. It extends our navigation architecture that integrates a multiresolution grid world model and fuzzy ART based world model. The fuzzy ART world model is composed of a set of rectangular geometric primitives, or features. In a companion paper we introduce a new method for updating the fuzzy ART model in dynamic worlds. In this paper we describe our new navigation architecture that, by integrating the new proposed map building method for dynamic worlds, is able to dynamically not only increase but also decrease local resolution according to variations in the local clutter and complexity of the world. With the new overall navigation architecture the mobile robot is able to cope with, and navigate, in changing worlds. The paper presents experimental results obtained with a Nomad 200 mobile robot that demonstrates the effectiveness of the proposed methods.

关键词： Navigation Mobile robots Spatial resolution Solid modeling Subspace constraints Buildings Extraterrestrial measurements Fuzzy sets Motion-planning Orbital robotics

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Data fusion for compliant motion tasks based on human skills

Data fusion for compliant motion tasks based on human skills

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IEEE International Workshop on Intelligent Robots and systems (IROS)

作者： R. Cortesao R. Koeppe U. Nunes G. Hirzinger Electrical and Computer Engineering Department Institute of Systems and Robotics (ISR) University of Coimbra Coimbra Portugal Institute of Robotics and Mechatronics German Aerospace Center Germany

The paper discusses new developments of the data fusion paradigm due to Cortesao and Koeppe (1999, 2000). A bank of Kalman filters is analyzed in the fusion process. Experiments for a robotic compliant motion task (peg-in-hole) emerged from human skills are reported. Stereo vision and pose sense are fused to execute the task. Feedforward artificial neural networks (ANNs) are trained to transfer human skills to robotic manipulators.

关键词： Humans Sensor phenomena and characterization Stochastic resonance Robot sensing systems State estimation Information filtering Information filters Aerospace engineering Mechatronics Stereo vision

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Integrating laser and infrared sensors for learning dynamic self-organizing world maps

Integrating laser and infrared sensors for learning dynamic ...

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International Conference on Multisensor Fusion and Integration for Intelligent systems (MFI)

作者： R. Araujo D. Lourenco G. Ferreira Institute for Systems and Robotics (ISR) and Electrical Engineering Department University of Coimbra Coimbra Portugal

Mobile robots require the ability to build their own maps to operate in unknown environments. This article introduces a new online method for learning world maps in non-static worlds. The new approach expands the previously proposed method by Araujo et al. (1998, 1999), based on the fuzzy ART neural architecture (FARTNA) towards the application in non-static worlds. For this purpose we introduce the prune-able fuzzy ART neural architecture (PAFARTNA) which extends the FARTNA self-organizing neural network to include the ability to selectively remove recognition categories. A method is proposed for the perception of object removals, and integrated with the PAFARTNA. To study and experimentally validate the proposed methods we integrated sensor information from a laser range finder sensor and a ring of infrared range sensors. Results of experiments with a Nomad 200 mobile robot are presented, demonstrating the effectiveness of the proposed methods.

关键词： Infrared sensors Subspace constraints Solid modeling Mobile robots Robot sensing systems Sonar navigation Computational efficiency Buildings Sensor phenomena and characterization Gas insulated transmission lines

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A focusing-by-vergence system controlled by retinal motion disparity

A focusing-by-vergence system controlled by retinal motion d...

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IEEE International Conference on robotics and Automation (ICRA)

作者： J. Batista P. Peixoto H. Araujo ISR-Institute of Systems and Robotics Department of Electrical Engineering University of Coimbra Coimbra Portugal

We describe a focusing-by-vergence system combining a flow based vergence process with an off-line pre-calibration of the focusing odometry. The vergence process is controlled by the retinal optical flow disparity and the target depth velocity is directly obtained from this disparity. The relationship between the target depth (focused target distance) and the focusing odometry of the motorized lens is obtained by an off-line focusing calibration, using a bivariate polynomial to model the relationship between these parameters. The focusing system is velocity controlled and the focusing velocity is dependent on the target focusing depth velocity and the focal distance velocity. The influence of the focal distance velocity that arise due to the focusing process itself is compensated by the adjustment of the zoom parameter based on a constant magnification approach, or through the modeling of the focal distance as a function of the zoom and focus lens settings.

关键词： Motion control Control systems Retina Velocity control Lenses Optical control Process control Image motion analysis Calibration Polynomials

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A surveillance system integrating visual telepresence

A surveillance system integrating visual telepresence

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International Conference on Pattern Recognition

作者： P. Peixoto J. Goncalves H. Antunes J. Batista H. Araujo ISR-Institute of Systems and Robotics Department of Electrical Engineering University of Coimbra Coimbra Portugal

ISBN: (纸本)0769507506

We describe an indoor surveillance system which enables the control of a binocular active vision system by a remote operator wearing a head mounted display. Visual feedback to the head mounted display is obtained using the images captured by the active vision system. To maximize the 3D perception of the operator the system is able to adjust the vergence angle of the active vision system in order to maintain fixation on the objects in the center of the image. A wide-angle lens static camera located on the surveillance area is also used to enable the detection and tracking of intruders. In case of an intrusion a map with the location of the detected targets is displayed on top of the images shown on the head mounted display. This information allows the remote operator to redirect his attention to where the target is.

关键词： Surveillance Head Machine vision Displays Humans Delay Cameras Lenses Sensor phenomena and characterization Mechanical sensors

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Binocular tracking and accommodation controlled by retinal motion flow

Binocular tracking and accommodation controlled by retinal m...

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International Conference on Pattern Recognition

作者： J. Batista P. Peixoto H. Araujo ISR-Institute of Systems and Robotics Department of Electrical Engineering University of Coimbra Coimbra Portugal

ISBN: (纸本)0769507506

Describes a tracking and accommodation system controlled by retinal motion flow. The tracking system decomposes two basic behaviors: smooth-pursuit and vergence. Both behaviors are optical flow based. The eye's accommodation (focusing) is based on a focusing-by-vergence approach combining a flow based vergence process with an off-line pre-calibration of the lens focusing odometry. The focusing and tracking system run in parallel and are both velocity controlled.

关键词： Tracking Motion control Retina Focusing Velocity control Geometry Angular velocity Control systems Equations Lenses

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Sensor fusion for skill transfer systems

Sensor fusion for skill transfer systems

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IEEE International Workshop on Intelligent Robots and systems (IROS)

作者： R. Cortesao R. Koeppe Electrical Engineering Department Institute of Systems and Robotics (ISR) University of Coimbra Coimbra Portugal German AeroSpace Center (DLR) Institute for Robotics and Systems Dynamics Wessling Germany

Describes how to design a data fusion module for skill transfer purposes. The data fusion paradigm is addressed. It consists of two independent modules for optimal fusion and filtering. A new interpretation of the Kalman filter equations is done, to achieve a "model-free" equation capable of following arbitrary variables. An engineering approach is used to tune the parameters of interest for a certain task. The fusion algorithm presented is global, and could easily be extended to any arbitrary system. It was successfully tested in the institute of robotics and System Dynamics at the DLR.

关键词： Sensor fusion Robot sensing systems Humans Filtering Equations Vehicle dynamics Aerodynamics Sensor systems Intelligent robots Training data

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