page 1  (8 pages)
2to next section

Laser Range Vision for Tele-Excavation

Michael Greenspan
National Research Council of Canada

Michael Lipsett
Atomic Energy Canada Limited

John Ballantyne
Spar Aerospace Limited

Pam Renton, Eric Gagnon and Nestor Burtnyk National Research Council of Canada

Abstract

This paper presents the development of a teleexcavation system which uses a laser range scanner and a virtual environment to aid a typical remote excavation process. The system includes : a commercial excavator which has been modified for remote operation, a remotely operated sensorized scout vehicle, and a graphical computer workstation. The laser range scanner is attached to a pan-tilt unit on the scout vehicle; the scanner acquires accurate 3D geometric data about the terrain. The scanned data and the excavator telemetry are inputs to the virtual environment that yield an accurate visual model of the worksite that includes the excavator.

One focus of the work is the construction of the virtual environment from a collection of acquired range images, which are processed to register their relative positions within the scene. A number of control schemes have also been implemented to test and compare the effectiveness of various modes of teleexcavation. In particular, virtual barriers are constructed from an analysis of the range data. These barriers can be used both to prevent collisions of the excavator with obstacles, and to guide excavation.

The system has been developed and preliminary integration tests were performed.

Introduction

The remote operation of heavy machinery is a technology which is essential for the cleanup of highlevel waste sites, where there is no safe way to protect an operator on the machine. The issues encountered are

similar to those of telerobotics in general. Because a remote operator is removed from the machine, the absence of direct visual and other sensory queues makes safe and effective operation difficult.

One way to improve the effectiveness of teleoperation is through the use of a virtual environment, a rich 3D graphical model of the worksite and the device under control. The virtual environment provides the operator with an overview of the worksite, to facilitate analysis, planning, and simulation of the operations, with the goal of improving efficiency.

The U.S. Department of Energy has committed to cleaning hazardous waste sites which exist in many nuclear research and weapons production facilities throughout the United States [1]. The high levels of radiation and toxicity make it dangerous for humans to remain very long in the vicinity of these sites, which rules out conventional site restoration practices.

The use of remote machinery, where the operator is physically removed from the device under control, is a promising approach. The issues involved in operating remote machinery are similar to those which have been well addressed in the field of telerobotics [2]. In this case, there is the added difficulty that the out of the line of sight of the worksite and must rely entirely on sensor feedback. Unlike the case of ground operated control of space robotics, there is not necessarily a significant time lag between the operator and the equipment.

The objective of the work described in this paper is to demonstrate the utility of laser range imagery for the effective teleoperation of a remote excavator. Laser