Active Robot Vision

The following sections are included:

• CONTENTS

The following sections are included:

• INTRODUCTION

• ACTIVE VISION

• MODEL BASED ROBOT NAVIGATION

• REACTIVE ROBOT CONTROL

• HIGHLIGHTS

• REFERENCES

The ability to dynamically control the imaging parameters such as camera position, focus, and aperture is satisfied through the use of special purpose hardware such as a robotic head. This paper presents the design and control aspects of the Harvard Head, a binocular image acquisition system. We present three applications of the head in vision tasks concentrating on the computation of depth from controlled camera motion.

Active vision systems can be considered as systems that integrate visual sensing and action. Sensing includes detection of actions/events and results also in specific actions/manipulations.

This paper mainly addresses the basic issues in the design of a head-eye system for the study of active-purposive vision. The design complexity of such a head is defined by the activeness of the visual system. Although we have not had the motivation to exactly reproduce the biological solutions in a robot, we claim that the designer should carefully consider the solutions offered by evolution.

The flexibility of the behavioral pattern of the system is constrained by the mechanical structure and the computational architecture used in the control system of the head. The purpose of the paper is to describe the mechanical structure as well as the computational architecture of the KTH-head from this perspective.

We present the design of a controllable stereo vision head. TRISH (The Toronto IRIS Stereo Head) is a binocular camera mount, consisting of two fixed focal length color cameras with automatic gain control forming a verging stereo pair. TRISH is capable of version (rotation of the eyes about the vertical axis so as to maintain a constant disparity), vergence (rotation of each eye about the vertical axis so as to change the disparity), pan (rotation of the entire head about the vertical axis), and tilt (rotation of each eye about the horizontal axis). One novel characteristic of the design is that each camera can rotate about its own optical axis (torsion). Torsional movement makes it possible to minimize the vertical component of the two-dimensional search which is associated with stereo processing in verging stereo systems.

Active vision involving the exploitation of controllable cameras and camera heads is an area which has received increased attention over the last few years. At LIA/AUC a binocular robot camera head has been constructed for use in geometric modelling and interpretation. In this manuscript the basic design of the head is outlined and a first prototype is described in some detail. Detailed specifications for the components used are provided together with a section on lessons learned from construction and initial use of this prototype.

This paper presents the design and development of a real-time eye-in-hand stereovision system to aid robot guidance in a manufacturing environment. The stereo vision head comprises a novel camera arrangement with servo-vergence, focus, and aperture that continuously provides high-quality images to a dedicated image processing system and parallel processing array. The stereo head has four degrees of freedom but it relies on the robot end-effector for all remaining movement. This provides the robot with exploratory sensing abilities allowing it to undertake a wider variety of less constrained tasks. Unlike other stereo vision research heads, the overriding factor in the Surrey head has been a truly integrated engineering approach in an attempt to solve an extremely complex problem. The head is low cost, low weight, employs state-of-the-art motor technology, is highly controllable and occupies a small-sized envelope. Its intended applications include high-accuracy metrology, 3-D path following, object recognition and tracking, parts manipulation and component inspection for the manufacturing industry.

This paper describes a layered control system for a binocular stereo head. It begins by a discussion of the principles of layered control. It then describes the mechanical configuration for a binocular camera head with six degrees of freedom. A device level controller is presented which permits an active vision system to command the position of a binocular gaze point in the scene. The final section describes the design of perceptual actions which exploit this device level controller.

A Simulation, Animation, Visualization and Interactive Control (SAVIC) environment has been developed for the design and operation of an integrated robotic manipulator system. This unique system possesses the abilities for (1) multi-sensor simulation, (2) kinematics and locomotion animation, (3) dynamic motion and manipulation animation, (4) transformation between real and virtual modes within the same graphics system, (5) ease in exchanging software modules and hardware devices between real and virtual world operations, and (6) interfacing with a real robotic system. This research is focused on enhancing the overall productivity of an integrated human-robot system. This paper describes a working system and illustrates the concepts by presenting the simulation, animation and control methodologies for a unique mobile robot with articulated tracks, a manipulator, and sensory modules.

Simulations have traditionally been used as off-line tools for examining process models and experimenting with system models for which it would have been either impossible or too dangerous, expensive, or time-consuming, to perform with physical systems. We propose a novel way of regarding simulations as part of both the development and the working phases of systems. In our approach simulation is used within the processing and control loop of the system to provide sensor and state expectations. This minimizes the inverse sensory data analysis and model maintenance problems. We refer to this mode of operation as the verification mode, in contrast to the traditional discovery mode.

In order to provide simulations and planning that are intertwined with the control of a physical system, temporal issues have to be considered. By limiting the focus of the system to small portions of complex models which are temporarily relevant to the system's operation, the system is able to maintain its models and respond faster. For this we employ the Context-based Caching (CbC) mechanism within our Mobile Platform Control and Simulation Program (MOSIM). CbC is a knowledge management technique which maintains large knowledge bases by making the necessary information available at the right time.

New methods for producing avoidance behavior among moving obstacles within the context of reactive robotic control are described. These specifically include escape and dodging behaviors. Dodging is concerned with the avoidance of a ballistic projectile while escape is more useful within the context of chase. The motivation and formulation of these new reactive behaviors are presented. Both simulation and experimental results using a robot in a cluttered and moving world are provided.