DESIGN OF A ROBOT TEAM FOR SEARCH IN CENTRAL

EUROPEAN FORESTS

Santi Esteva, Antoni Martorano

Institut d’Inform`atica i Aplicacions, Girona University, C/ Santal´o S/N, Girona, Spain

Albert Figueras

Institut d’Inform`atica i Aplicacions, Girona University, C/ Santal´o S/N, Girona, Spain

Keywords:

Autonomous robots, Surveillance, Robot exploration, Robot team design.

Abstract:

Security incidents are a new topic for the autonomous robot task. Robots, sensors and intelligence make a

great combination to achieve speciﬁc goals in this area. This paper proposes a methodology to design the size

and the exploration form for a group of robots in the typical Central European forest. The objective is to ﬁnd

victims hidden into the fallen leaves. A statistics of the trouble situations is the starting point to design the

team to displace at the objective. The robots are autonomous but is necessary one human supervisor to solve

some critical situations. The results show the partition and the area covered by a simple group of equal robots.

1 INTRODUCTION

In the last years, security incidents, like terrorism,

have raised new research areas focused in surveil-

lance issues, the automation of these tasks is an im-

portant research area using robotic platforms and sen-

sors. The use of a team of robots and sensors is an

approach that has many advantages and difﬁculties

over a single robot platform. In this paper it is pro-

posed a framework to develop a multi-robot surveil-

lance platform (Caballero D., 2010), (Caballero D.,

2009). Surveillance is the act to close watch kept over

someone. Robotic surveillance is the topic to refer at

close watch on the relevant events. The automation

of the surveillance task are the approaches oriented

to the formalization of the problem (Everett H. R.,

1999), (Everett H. R., 2003).

Related works to segment the space to explore for

a multi-robot teams, several authors uses Voronoi di-

agrams of the space exploration to assign rectangu-

lar polygons strategies to segment the space explo-

ration (Matcovschi M. H., 2008). Other works uses

the agent entities and discuss the ability of the agent

to explore determined area (Rybski P. E., 2000). And

other determine an algorithm to achieve optimized re-

gion partition and coverage according the energy and

some constraints (Hao Wu, 2008).

This work analyzes the optimum partition of the

space exploration according probabilistic information

of the abnormal situations for the robot, which is nec-

essary a human operator support. Optimizing the efﬁ-

ciency of the whole team, robots and support and also

taking information from the biological communities

(Martorano, 2010) is the objective of the presented

work.

2 THE TERMITES

The Termites colonies are groups of social insects

composed by a social organization to share tasks in a

specialized form. The Workers, the Soldiers and Re-

productives elements are a self-organized system in a

decentralized form for a common collective behavior.

The Caste system of the Termite cologne depends

on the environmental scenarios and depredators, from

a 2% of soldiers in Africa zones to 12% of soldiers in

a Formosa Island.

Genetic information characterizes the Caste, size

and composition. Also stress situations can adapt the

system to the new changes, as temperature, depreda-

tors, etc. The biological process into the live of the

Termite insect evolves the colonies adapting at the

evolution phase of the group. The differences of the

Caste proportion are justiﬁed to improve the colony

survival at different conditions; the analysis of this in-

325

Esteva S., Martorano A. and Figueras A..

DESIGN OF A ROBOT TEAM FOR SEARCH IN CENTRAL EUROPEAN FORESTS.

DOI: 10.5220/0003570603250328

In Proceedings of the 8th International Conference on Informatics in Control, Automation and Robotics (ICINCO-2011), pages 325-328

ISBN: 978-989-8425-75-1

 2011 SCITEPRESS (Science and Technology Publications, Lda.)

Figure 1: Proportion of soldiers depending on the geo-

graphic area.

Figure 2: Graph of efﬁciency as the number of workers-

soldiers.

formation induces to propose different size and Caste

of a team of robots for each scenario.

Some experiments for one deﬁned scenario with

different Castes show the result of the improvement

for the colony survival. The improvements are done

when the size of the colony is small and the Caste

ratio is at the lower rates. From these results is trans-

formed to other representation the improvement at in-

terchanging the role between one Worker to a Soldier.

Figure 3: Gain performance by the number of workers-

soldiers.

In this representation indicates the minimum size

and composition of the team to gather these best im-

provements.

3 TEAM OF ROBOTS

The robot team can be similar to the Termite colony

taking account several similarities or equivalences in

order to transport the termite results to the robot team:

The different role of the termite elements can be

viewed as robots specialization. Depredators in Ter-

mites are the blocking situations in the robot area.

Nest of termite is the operation centre on the robots

ﬁeld.

There are also several aspects with big differences,

as size of the colony, objectives, movement, etc. The

main result of this comparison is: there exist one

Caste relation and size that will be optimal for a one

deﬁned task and area.

4 THE ROBOT

The team of robots are composed by several units of a

specialized robot to autonomously navigate in forest

areas, coordinated by an operation center, where a hu-

man operator controlled all the system, the positions,

the ﬁnding targets, the stopped or blocked robots.

Figure 4: Unit of our autonomous robot.

The robot characteristics are:

Size: 51cm x 58 cm x 32 cm.

Weight: 5 Kg.

Batteries: 12V 14 Ah.

Autonomy: 2 hours.

The robot is equipped by:

- DGPS with 15 cm. global position accuracy.

- Laser Range Finder with 240 and 4m range obstacle

detection.

- Inertial Measurement Unit, which combines 3 gyros

and 3 accelerometers.

- Thermal sensor with 1m. range measure.

- Methane sensor.

- Digital camera.

ICINCO 2011 - 8th International Conference on Informatics in Control, Automation and Robotics

326

- WI-FI communication.

- Four-Wheeled Driver 60W.

5 EXPLORATION

The robot ability to explore unknown areas is demon-

strated, using D-GPS in outdoor scenarios and

equipped by four strong wheeled drive, and the robot

can easily navigate by typical Central European for-

est, due by their characteristics.

Some handicaps can be found in this kind of ter-

rains, holes, climbs, obstacles, water, etc. and cannot

be over passed by the robot.

Four typical blocking situations for the robot:

Figure 5: Lateral climbing.

Figure 6: Obstacle not detected.

A 2D Laser range sensor is useful to detect and

predict some of these troubles, the others can cause

problems to the robot and will be necessary the use of

other kind of support to solve these handicaps.

To deﬁne the support for the robots according the

number of the explorers will be deﬁned according the

obstacle proportions for the exploring area.

Figure 7: Hole and slipping situation.

Figure 8: Changes in the ﬁeld.

6 EXPERIMENTATION

One forest is necessary to be explored to ﬁnd a victim,

dead or alive. The area is divided in circles or squares

where the robots are working, jointly with one human

operator to restore the robot at blocking situations.

Each area where the robots are moving is organized

to be covered in 2 hours of autonomy batteries for a

group of N robots. The velocity of the robot is 1 m/s

and during this time is covered 1 square meters of ex-

ploration. The objective is to conﬁgure the surfaces

to cover by a group of N robots, maintained by only 1

human operator. The probability of the blocking sit-

uation is 1 over 400, this means during 400 sec. one

abnormal situation appears. And the operator needs

the distance in time to arrange the situation.

With all this premises the analysis over square ar-

eas or circular is the following:

Figure 9: Square or circular areas.

The gravity center of a circular sector is 2/3R, and

DESIGN OF A ROBOT TEAM FOR SEARCH IN CENTRAL EUROPEAN FORESTS

327

over Diagonals of the square is L/

√

2, and in Verti-

cal or Horizontal lines is L/2, the mean result 0.6 L.

Assigning this distance for same surface covered re-

sult R=L/

√

π, and combined with the gravity center,

resulting the distance for circular areas 73% less than

square areas. This means the time to recover the robot

improves using areas limited by circles.

Once the shape of the areas is deﬁned, is also nec-

essary to deﬁne the number of the robots working in

and the size of the area.

The number of robots is deﬁned by the working

limit of the human operator, as much robots much

work to restore the operability of the robot front a

blocking situations.

Time between abnormal situation appears each

400 sec/ N , and during this time the operator uses

2/3 R in time to restore the robot:

400 / N = 2/3 R

And using the other formula to solve the problem, the

time to cover this area is 2 hours:

R2/N = 2∗3600

Resulting a N = 8 robots and R = 135 m

Figure 10: The areas can be rearranged at hexagonal forms

maintaining the results.

7 CONCLUSIONS

The ability of the robot for this subject is the accurate

measure of the Methane or Thermal information and

their interpretation, the persistence and the working

journey. The humans have ability on the movements,

but not at the inspection and data interpretation, and

also are affected by the fatigue.

This article try to import some information from

the evolution process over the adaptation of the ter-

mites at different mediums in millions of years, and

incorporate any information as improvements for a

team of robots designed to exploring a forest area.

The characteristics of the distribution, and the

caste particularities of the termites colonies are the

principal focus where this work is centered, and the

results show one possible characterization of the team

of robots specialized on search in a forest area.

REFERENCES

Caballero D., Esteva S., e. a. (2009). Designing The Size

Of a Robot Team For Search And Rescue. ISSN1454-

8658.

Caballero D., Esteva S., e. a. (2010). Fleet size of robots

for rescue missions. Proceedings of IEEE Interna-

tional Conference on Automation, Quality and Test-

ing, Robotics.

Everett H. R., e. a. (1999). From Laboratory to Ware-

house: Security Robots Meet the Real World. The In-

ternational Journal of Robotics Research 1999, DOI:

10.1177/02783649922066448.

Everett H. R., e. a. (2003). Robotic Security Systems. IEEE

Instrumentation and Measurement Magazine.

Hao Wu, Guohui Tian, X. L. (2008). Research on opti-

mized partition algorithm for multi robots collabora-

tion coverage. Intelligent Control and Automation,

2008. WCICA 2008. 7th World Congress on.

Martorano, A. (2010). Required to incorporate SWARM in-

telligence into the equipment design of robot rescue

teams. Master Tesis, Mster MIIACS, University of

Girona, Director: Santi Esteva.

Matcovschi M. H., P. O. Stability and Set-Invariance Test-

ing for Interval Systems. Journal of Control Engineer-

ing and Applied Informatics, Vol.10, No.3 , pp.18-26,

2008, ISSN: 1454-8658.

Rybski P.E., e. a. (2000). A Team of Robotic Agents

for Surveillance. AGENTS ’00 Proceedings of

the fourth international conference on Autonomous

agents, ACM New York, NY, USA 2000., isbn: 1-

58113-230-1 edition.

ICINCO 2011 - 8th International Conference on Informatics in Control, Automation and Robotics

328