Advanced Guided Vehicles

The following sections are included:

• Preface

• Contents

Towards the end of 1988 three of the stronger members of the Robotics Research Group struggled down the narrow stairs to our mobile robot laboratory under the weight of our first robotic vehicle. The advent of this vehicle, known as 'the AGV' or sometimes as 'the Turtle', marked the start in earnest of the Oxford AGV project, which had as its broad aim the investigation of robotic vehicle technology for industrial applications. This book describes some of the achievements of the first five years of the project, especially in sensing and planning. Although most of the material presented is at the frontiers of international research we have aimed to make the book comprehensible to a broad audience through including an amount of more general material and two tutorial chapters. The book is appropriate for courses at graduate and final year undergraduate level, as well as for workers in the field…

The following sections are included:

• On-board GEM80 Controller
  • Control Strategy
  • Laser System: Localisation
  • Guidance System

• Overview of the Control System for the AGV

• Functionality Addressed in the Oxford AGV Project

The following sections are included:

• Introduction

• Previous Work

• Distributed Design

• Real-time Computer Architecture
  • Conventional Approach
  • Transputer Approach

• Mapping onto a Network of Transputers
  • Modular Approach
  • Hardware Mapping
  • Software Mapping
  • Achieving Accurate Timing
  • Asynchronous Communication

• Sensor-based Control Structure

• Conclusions

The following sections are included:

• Introduction

• Framework for Planning
  • Environment and its Topological Map

• Sensor Configuration
  • Local Map and Collision Zone
  • Rule-based Interpretation of Sonar Data

• Global Path Planner
  • Cost Function
  • Updating the Global Model

• Changing Environment: Problem Formulation
  • Formulation of Loss Function
  • Obstacle Avoidance Implementation
  • Examples of Implementation
  • Example 1
  • Example 2

• Real-time Implementation

• Conclusions

The following sections are included:

• Sysyem Principles
  • Attenuation in the Path
  • Selection of Wavelength and Radiation Mode

• Sensor Configuration

• Choice of Sensor

• Sonar Sensors
  • Application in Reactive Planning
  • Advances through Modelling

• Low Cost Optoelectronic Sensors
  • Sensors Based on Amplitude Detection
  • AMCW Sensors: Ranging through Phase Detection
  • Assessment of Accuracy

• Summary

The following sections are included:

• Introduction

• Optical Triangulation Geometries
  • Conventional Scanning Geometries
  • Synchronised Scanning Geometries

• Image Position Sensing Devices
  • The Charge-Coupled Device (CCD)
  • The Lateral-Effect Photodiode (LEP)
  • CCD/LEP Comparison

• Optical Sources
  • Laser Diodes and LEDs
  • Spectral Frequency of Projection: Visible, UV, or IR?

• Sensor Design
  • Image Sensor and Optical Source
  • Electronic Design
  • Geometric Design

• Sensor Characterisation
  • Experimental Conditions
  • System Noise Estimation
  • Theoretical Noise Calculation

• Sensor Performance
  • Measured Accuracy
  • Predicted Accuracy

• Use of the Sensor within the Oxford AGV Project
  • The Use of Intensity Data
  • Active Sensing

• Conclusions

The following sections are included:

• Introduction

• Sonar Model
  • Region of Constant Depth Model
  • RCD-Monopulse Sonar
  • Differential Feature Model

• A Tracking Sonar
  • Differential Uncertainty and Real-time Tracking
  • Probabilistic Model and Error Analysis
  • Performance and Limitations

• Modular Navigation
  • Localization Algorithm
  • Localization Results

• Discussion and Summary

The following sections are included:

• Introduction

• Vision Algorithm: Droid

• PARADOX Architecture

• Implementation of Droid on PARADOX
  • Datacube
  • The Transputer Network
  • Control Flow in Droid on PARADOX

• Performance Evaluation
  • Execution Speed
  • Ego-motion and Vehicle Speed Estimation

• Conclusion and Future Work

The following sections are included:

• NEL Range Images and Features
  • Image Formation
  • Feature Interpretation and Extraction

• The Utility of Features for Recognition

• Feature Extraction and Matching Strategy
  • Pallet Recognition

• Summary

The following sections are included:

• The Railway Track Algorithm

• Moving off the Tracks

• Configuration Space

• Searching C-space
  • Visibility Graphs
  • A* Search
  • Getting Away from it All
  • Region Decomposition

• Recapitulation

• Rotations and Other Problems

• Following Your Nose

The following sections are included:

• Potential Field Path Planning
  • Defining the Form of the Field
  • Translation Only
  • With One Rotational Degree of Freedom

• Calculation of the Influence of An Artificial Potential Field upon a Polygonal Moving Object

• Potential Field Path Planning for Robot Vehicles

• Local Path Planning for Robot Vehicles Using a Potential Field Approach
  • Guiding a Car-like Robot Using Potential Fields

• Gross Motion Planning for Mobile Robots

• Summary

The following sections are included:

• Overview

• The Scheduler
  • Improving the Solution by Geometric Reasoning

• Initial Path Planning

• Refining the Scheduler
  • Voronoi Scheduling Graphs

• A GVD-based Path Planner for Mobile Robots
  • Heuristics to Smooth the Linkage

• Putting It All Together
  • Improving the solution by Heuristics
  • Optimisations
  • An Example of Running the System
  • Linking with External Path Planners

• Remarks

The following sections are included:

• Requirements

• The Oxford Robot Database
  • Design
  • Implementation
  • Architecture—Summary

• Routemap Extraction in an Environment having Manthattan Geometry
  • Extracting Corridors
  • Structure of the Corridor Graph
  • Computational Complexity
  • Searching the Routemap

• A Large Example

• Summary

The following sections are included:

• Epilogue

• Bibliography

• Index