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Annual Conference of Industrial Electronics Society

作者： R. Araujo A.T. De Almeida Institute for Systems and Robotics and Electrical Engineering Department University of Coimbra Coimbra Portugal

Autonomous robots must be able to learn and maintain models of their environments. This paper introduces a new approach, based on the fuzzy ART neural architecture, for on-line map building from actual sensor data collected with a mobile robot. This method is then integrated, as a complement, on the parti-game learning approach, allowing the system to make a more efficient use of collected sensor information. Also, a predictive on-line trajectory filtering method, is introduced in the learning approach. Instead of having a mechanical robot moving to search the world, the idea is to have the system analysing trajectories in a predictive mode, by taking advantage of the improved world model. The real robot will only move to try trajectories that have been predicted to be successful, allowing lower exploration costs. This results in an overall new and powerful method for simultaneous and cooperative construction of a world model, and learning to navigate from an initial position to a goal region in an unknown world. It is assumed that the robot knows its own current world location, and is able to perform sensor-based obstacle detection (not avoidance), and straight-line motions. Results of experiments with a real Nomad 200 mobile robot are presented, demonstrating the effectiveness of the proposed methods.

关键词： Navigation Robot sensing systems Trajectory Buildings Mechanical sensors Mobile robots Subspace constraints Sensor systems Filtering Predictive models

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Ground plane detection by fusing visual and inertial information

Ground plane detection by fusing visual and inertial informa...

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International Workshop on Advanced Motion Control (AMC)

作者： J. Lobo J. Dias Institute of Systems and Robotics Electrical Engineering Department University of Coimbra Coimbra Portugal

In mobile systems the position and attitude of the active vision system's cameras can be hard to determine. Inertial sensors coupled to the active vision system can provide valuable information, as happens with the vestibular system in human and other animals. We present our integrated inertial and vision systems. The active vision system has a set of stereo cameras capable of vergence, with a common baseline, pan and tilt, and an implemented process of visual fixation. An inertial system prototype, based on low-cost sensors, was built. The inertial sensor data is used to segment the ground plane in the images. It is used to keep track of the gravity vector, allowing the identification of the vertical in the images. By performing visual fixation of a ground plane point, and knowing the 3D vector normal to level ground, we can determine the ground plane. The image can therefore be segmented, and the ground plane along which the robot can move identified.

关键词： Machine vision Cameras Sensor systems Image segmentation Position measurement Humans Animals Prototypes Image sensors Gravity

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A new 3D optical triangulation sensor for robotics

A new 3D optical triangulation sensor for robotics

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International Workshop on Advanced Motion Control (AMC)

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

Describes an optical range sensor that measures distance and orientation from surfaces. The sensor uses three laser diodes and a position sensitive detector (PSD) camera. The lasers are parallel to each other in a way that their interception points with the surface define a triangle. The coordinates of each intersection point imaged on the camera can be determined by triangulation. The orientation of the triangular surface patch can be calculated by the cross product of any two sides of the triangle. Experimental results taken with a first prototype show distance accuracy of about 0.05 mm, and orientation accuracy of 0.1/spl deg/. The prototype can take measures from 60 mm to 750 mm.

关键词： Optical sensors Robot sensing systems Cameras Prototypes Robot kinematics Sensor phenomena and characterization Diode lasers Position sensitive particle detectors Robot vision systems Surface emitting lasers

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Integration of inertial information with vision

Integration of inertial information with vision

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Annual Conference of Industrial Electronics Society

作者： J. Lobo J. Dias Institute of Systems and Robotics Electrical Engineering Department University of Coimbra Coimbra Portugal

Active vision systems can be used in robotic systems for navigation. The active vision system provides data on the robot's environment. In mobile systems the position and attitude of the cameras relative to the world can be hard to determine. Inertial sensors coupled to the active vision system can provide valuable information to aid the image processing task. In human and other animals the vestibular system plays a similar role. In this article, we explain our steps in the integration of inertial data with an active vision system. The active vision system has a set of stereo cameras capable of vergence, with a common baseline, pan and tilt. A process of visual fixation has already been implemented, enabling symmetric vergence on any selected point. An inertial system prototype, based on low-cost sensors was built. It is used to keep track of the gravity vector, allowing the identification of the vertical in the images. By performing visual fixation of a ground plane point, and knowing the 3D vector normal to level ground, we can determine the ground plane. The image can therefore be segmented, and the ground plane along which the robot can move identified. For on-the-fly visualisation of the segmented images and the detected points a VRML (virtual reality modelling languages) viewer is used.

关键词： Machine vision Robot vision systems Robot sensing systems Cameras Sensor systems Image segmentation Navigation Position measurement Image sensors Image processing

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Short-range DGPS for mobile robots with wireless Ethernet links

Short-range DGPS for mobile robots with wireless Ethernet li...

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International Workshop on Advanced Motion Control (AMC)

作者： A. Valejo J. Lobo J. Dias Institute of Systems and Robotics Electrical Engineering Department University of Coimbra Coimbra Portugal

For outdoor mobile robot applications the satellite based GPS system is available for position estimation. Differential GPS can add to the precision but requires a fixed receiver at a known position and some communication link. Typically differential GPS data is sent over dedicated radio links or broadcast. For short-range applications, where multiple robots move around an outdoors workspace, a wireless Ethernet link with multiple access points, and supporting multiple robots, is a good and cost-effective solution. The net can be used, amongst other things, for sending the differential data from a local fixed receiver to the robots. In the article we present a client/server model that enables the mobile robot to sign-up with the server and receive the DGPS data over the Internet, allowing the calculation of a more precise position. This provides a simple and flexible method of implementing DGPS corrections. Some field tests are presented that show that this simple approach can provide good results, without being an expensive solution.

关键词： Global Positioning System Mobile robots Ethernet networks Satellite broadcasting Receivers Web server Mobile communication Radio link Radio broadcasting Internet

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RobChair - A Semi-Autonomous Wheelchair for Disabled People

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IFAC Proceedings Volumes 1998年第3期31卷 509-513页

作者： G. Pires U. Nunes A.T. de Almeida Institute of Systems and Robotics Department of Electrical Engineering University of Coimbra Polo II 3030 Coimbra Portugal

This paper describes the RobChair assistive navigation system. RobChair is a project under development which aims to assist disabled people to operate powered wheelchairs. RobChair is being developed in order to provide several levels of functionality to assist different users. This paper describes some reactive navigational strategies, namely the potential field method, used for local obstacle avoidance; presents a teleoperation environment to allow remote operation by Internet observers; and introduces a voice human-machine interface (HMI).

关键词： behavioural architecture obstacle avoidance human-machine interface

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Fuzzy ART based approach for real-time map building

Fuzzy ART based approach for real-time map building

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International Workshop on Advanced Motion Control (AMC)

作者： R. Araujo A.T. de Almeida Dept. of Electr. Eng. Coimbra Univ. Portugal Institute for Systems and Robotics (ISR) and Electrical Engineering Department University of Coimbra Coimbra Portugal

In order to perform complicated tasks in previously unknown indoor environments, autonomous mobile robots must be able to acquire models of their environments. The model or map, is often used for planning robot motions which perform a task while avoiding obstacles in the environment. Applications where there is no previously available world model usually rely on sensor systems, such as laser range finders, and infrared and sonar range sensors, to collect thousands of range points which are difficult to handle and interpret. The paper introduces an approach, based on the fuzzy ART neural architecture, for online map building. The map is incrementally constructed in real-time by fitting rectangular geometrical primitives to actual sensor data collected with a mobile robot. This results in a compact world model that is easy to integrate into planning approaches. A sensor data filtering approach is proposed to reject noisy range points. It is assumed that the robot knows its own current world location. Results of experiments with a real Nomad 200 mobile robot are presented, demonstrating the operation of the proposed map building method.

关键词： Subspace constraints Mobile robots Infrared sensors Indoor environments Motion planning Robot motion Sensor systems Laser modes Sonar applications Sensor systems and applications

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Navigation systems design: an application of multi-rate filtering theory

Navigation systems design: an application of multi-rate filt...

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OCEANS

作者： P. Oliveira A. Pascoal Institute for Systems and Robotics and Department of Electrical Engineering Instituto Superior Técnico Lisboa Portugal

A methodology is introduced for the design of multi-rate navigation systems for underwater vehicles. The design technique proposed borrows from Kalman filtering theory and leads naturally to multi-rate complementary filtering structures, the performance of which can be assessed using a frequency-like domain interpretation. An example illustrates the application of the new technique to the design of a multi-rate navigation system for an autonomous underwater vehicle.

关键词： Filtering theory Kalman filters Aircraft navigation Robots Underwater vehicles Frequency Stochastic resonance Acoustic noise Design methodology Contracts

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Automated facial expression recognition based on FACS action units

Automated facial expression recognition based on FACS action...

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3rd IEEE International Conference on Automatic Face and Gesture Recognition, FG 1998

作者： Lien, James J. Cohn, Jeffrey F. Kanade, Takeo Li, Ching-Chung Department of Electrical Engineering University of Pittsburgh Pittsburgh PA 15260 United States Vision and Autonomous Systems Center Robotics Institute Carnegie Mellon University Pittsburgh PA 15213 United States Department of Psychology University of Pittsburgh United States

ISBN: (纸本)0818683449

Automated recognition of facial expression is an important addition to computer vision research because of its relevance to the study of psychological phenomena and the development of human-computer interaction (HCI). We developed a computer vision system that automatically recognizes individual action units or action unit combinations in the upper face using hidden Markov models (HMMs). Our approach to facial expression recognition is based an the Facial Action Coding System (FACS), which separates expressions into upper and lower face action. We use three approaches to extract facial expression information: (1) facial feature point tracking;(2) dense flow tracking with principal component analysis (PCA);and (3) high gradient component detection (i.e. furrow detection). The recognition results of the upper face expressions using feature point tracking, dense flow tracking, and high gradient component detection are 85%, 93% and 85%, respectively. © 1998 IEEE.

关键词： Hidden Markov models

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FED-the free body diagram method. Kinematic and dynamic modeling of a six leg robot

FED-the free body diagram method. Kinematic and dynamic mode...

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International Workshop on Advanced Motion Control (AMC)

作者： J.P. Barreto A. Trigo P. Menezes J. Dias A.T. De Almeida Institute of Systems and Robotics Escola Superioir de Tecnologia e Gestao Instituto Politecnico de Leiria Leiria Portugal Institute of Systems and Robotics Electrical Engineering Department University of Coimbra Coimbra Portugal

The free body diagram method, based on the dynamic equations of isolated rigid bodies, is used to overcome the difficulties in dynamic modeling of legged robots. The article presents a simulator for a six leg machine. Both kinematic and dynamic models are developed. Kinematic equations are derived with the Denavit-Hartenberg method. The free body diagram method is used to obtain the dynamic model. Some results of simulation are presented.

关键词： Kinematics Leg Legged locomotion Vehicle dynamics Vehicles Equations Wheels Rough surfaces Surface roughness Mobile robots

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