Ingles

Variable Geometry Tracked Vehicle (VGTV) prototype : conception, capability and problems
Jean-Luc PAILLAT (jlpaillat@gmail.com), Philippe LUCIDARME (philippe.lucidarme@istia.univ-angers.fr), and Laurent HARDOUIN (laurent.hardouin@istia.univ-angers.fr)
Laboratoire d'Ingenierie des Systèmes Automatisés Angers, France

This paper presents a prototype of tracked UGV (Unmanned Grounded Vehicles)called B2P2. This tele-operated robot has been designed to intervene in unstructured environments like for example battleeld or after an earthquake. This robot based on an original system of multiple articulations can be classied into the VGTV (Variable Geometry Tracked Vehicle) category. The proposed concept allows the robot to adapt its shape in order to increase its clearing capability. Unlikeexisting robots, the tension of the caterpillars is actively controlled and can be turned o to increase the robot/ground contact surface needed for some special kind of obstacles. After a short state of the art, the paper presents the detailed architecture of the robot. The third part introduces the data and video transmission materials tested during the conception of the robot. The behaviour ofthe robot over several obstacles (staircase, curb and bumper) is analysed and the necessity of releasing the tracks is discussed.
Abstract.

1

Introduction

The use of robots in dangerous environment like partially collapsed buildings or nuclear power station is currently a research topic of prime interest. Designing generic robots well suited to a large variety of missions andenvironments is still challenging : the challenge is thus to design the smallest robot as possible (able to pass into narrow openings) and with the best clearing capabilities. The prototype called B2P2 presented in this paper is a tracked vehicle based on an actuated chassis (Fig. 1). It has been designed to maximize the clearing capability to the robot size ratio. Unlike existing robots the track's tensioncan be controlled on our prototype. Experiments presented in the following will discuss of the interest of controlling the track's tension. This article is organized as follows. Section 2 presents an overview about a selection of existing robots. Section 3 gives the technical description of our prototype. Next section is dedicated to the data and video transmission materials tested during theconception of the robot. The last section discusses about real experiments performed with the robot over three obstacles : a curb, a staircase and a bumper. A general conclusion ends the paper and presents some perspectives.

Fig. 1.

B2P2 prototype

2
2.1

Existing UGVs
Wheeled and tracked vehicles with xed shape

(a) ATRV-Jr robot. Photo Courtesy of AASS, Örebro University.
Fig. 2.(b) Talon-Hazmat robot (Manufacturer : FosterMiller)

Two UGV with xed shape models

This category gathers non variable geometry robots. Theoretically, this kind of vehicles are able to climb a maximum step twice less high than their wheel diameter. Therefore their dimensions are quite important to ensure a large clearing capability. This conception probably presents a high reliability [1]but those robots are not well suited for unstructured environments like after an earthquake [2].

Fig. 2(a) and 2(b) present two vehicles dedicated to reconnaissance and surveillance.
2.2 Variable Geometry Tracked Vehicle

A solution to ensure a large clearing capability and to reduce the dimensions consists in developing tracked vehicles which are able to modify their geometry in order tomove their center of mass and climb higher obstacles than half their wheel's diameters. The Micro VGTV Fig. 3(a) is a good example of the possibility of this kind of UGVs. Indeed, with a wheel diameter of only 6.5 cm, it is able to climb a step of 25 cm. [3] provide endurance tests results for this UGV. Another solution consists in using ippers as the Packbot (Fig. 3(b)). This kind of VGTV can...