PROMOTION IN RESCUE ROBOT

According to the Experience Gained by Participating in Bam Earthquake

Rescue Operation

Pooya Heiraty, Aboozar Aghajani, Hojatollah Shirzadi Laskoukelayeh, Majid Zeraat Pisheh Fard

and Sayyed Mohammad Hosseini Monsef

Department of R&D, Sprooz International Co., Ltd., Flat No. 2, No.9, Eftekhar St.

Valiasr St., Next to Motahhari Junction, Tehran, Iran

Keywords: Four-Wheeled Robot, Locomotion, Control, Communication, Sensor, Navigation, Victim, Differential

Drive, Map Generating, Bam Earthquake, Rescue Robot, Operator.

Abstract: Nowadays rescue robots are used in some rescue operations. Increasing the speed and accuracy of victim

detection with sensors and equipment which are installed on the robot and yet increasing human safety

factor of rescuers are among the advantages of using rescue robots.

By the experience of rescue operation in Bam earthquake and participating in some robocup competitions, a

new four-wheeled robot has been designed which has highly operational capability. In initial part of this

article, robot locomotion and controlling in different situations and the method of connection operator with

robot are surveyed; then, sensors which are used in for navigation and victim detection are explained. At the

end, the method of generating the map of robot’s movement route, which is very important for identifying

the trapped victim's location in a rapid rescue operation, was studied.

1 INTRODUCTION

In December 2003, a severe earthquake destroyed

one southern Persian city called Bam. This

earthquake was the most devastating earthquake in

the Middle East. Writers of this article who have

been designing and building several robots, joined

the rescue teams with their rescue robots and

searching devices for detecting victims.

Figure 1: Robot navigation in Bam earthquake collapses.

By the experience of Bam earthquake, another

rescue robot was designed and built whose

characters would be describe in this article. This

robot has high movement capability which could

traverse the obstacles easily. The electronical and

software parts of the robot have the ability of

distance navigation, victim detection, and generating

the map of victim places.

Individual Height adjustment of each wheels,

carrying baby robot with ability of separating from

the main robot and going through the small hole

which the main robot could not goes, rapid ability

for changing from four-wheeled to the track

situation and mapping ability in both systems are

among interesting idea which are used on this robot.

2 ROBOT LOCOMOTION AND

OTHER MECHANISMS

The designed rescue robot is based on the

four-wheeled robot mechanism. The design and

production of it is so that the robot has a high

capability of movement so that it can traverse the

obstacles and unevenness easily. This robot is made

using modern technology

195

Heiraty P., Aghajani A., Shirzadi Laskoukelayeh H., Zeraat Pisheh Fard M. and Mohammad Hosseini Monsef S. (2009).

PROMOTION IN RESCUE ROBOT - According to the Experience Gained by Participating in Bam Earthquake Rescue Operation.

In Proceedings of the 6th International Conference on Informatics in Control, Automation and Robotics - Robotics and Automation, pages 195-201

DOI: 10.5220/0002203201950201

 SciTePress

Figure 2: The robot.

The designed robot has four moving wheels and

its dimensions are 87*50*80 cm. The weight of

robot is about 32 kilograms. Four DC 12 V engines

are used for the moving system of the robot each of

them acts independently. The velocity of the robot is

about 1 m/s and the rotation speed is 30 degrees per

second.

The central computer which has the duty of

processing, receiving and transmitting the data is an

industrial PC (PC-104). Four packs of batteries of

Ni-cadmium type are used to supply robot energy.

This robot uses the height adjustment system and

the height of each wheel can be adjusted separately.

By using this system the robot can easily climb the

obstacles. Also in those cases where the patrol area

is crowded, and there is a possibility for the bottom

of the robot to collide with the obstacles, the height

of robot could be increased to remove this problem.

The changing range of the height in this robot is

about 10 centimeters and the height is adjustable at

the speed of two centimeters per second.

Figure 3: The height adjustment system.

In order to increase the moving ability, an innovative

suspension system is used in this robot. This

suspension system is devised in the form of a joint at

the middle of the robot. This joint is capable of

being locked at any angle and can help robot to

traverse the obstacles and unevenness. The freedom

degree of the joint is between -20 to +20. The time

needed for the joint to be locked is about three

seconds.

Figure 4: Joint suspension system of the robot.

To control the robot, three moving cameras are

used. One of which is at the front the other at the

back and the last one is located on the top of robot.

The camera which is located on the robot is

equipped with two Omni-directional mirrors above

and under the camera. These mirrors give the robot

the opportunity to have a visual angle of 360 degrees

vertically.

Under the pedestal of the camera, there are 12

Sonar sensors which have the duty to help the robot

in measuring the distance

and also to obtain the map

of environment.

Figure 5: Pan-tilts and omni-directional mirrors.

The speed of the cameras at the back and front

which are moved by RC Servos is about 50 degrees

per second and the speed of the camera on the above

is about 10 degrees per second.

For increasing the moving ability of the robot in

special environments, and the ability of changing the

moving system, four-wheeled tracked are used. It

could be very rapid to change this situation.

Figure 6: Track system.

In order to increase the searching ability of robot,

a baby robot is used which is located inside the robot

and it will exit whenever it is necessary. This baby

robot is linked to the main robot through a cable.

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The moving system of this robot is of the

four-wheeled type, its dimensions are 15*10*8 cm

and it weighs 1 KG. Two DC (12 V) engines are

used in its moving system. The moving speed of the

robot is about 0.2 m/s.

Figure 7: Baby robot.

3 CONTROL METHOD AND

HUMAN-ROBOT INTERFACE

Controlling the robot is a partial autonomy. The

major part of the controlling effort is performed by

the operator and some movement decisions are made

by the robot itself with the prior permit of the

operator (which will be activated in the robot

guiding software). Some of these decisions are: to

automatic prevent collisions with the surrounding

environment and to automatic return the robot to the

starting point. But the software is designed so that

the human decisions are considered prior to the

robot decisions. For instance, in a narrow place the

operator may deem it reasonable for the robot to

collide with the walls so that it can pass the narrow

entrance; therefore the orders of the operator are

considered prior to the automatic decisions of the

robot.

Regarding the mechanical specifications and the

moving situation of the robot, three situations are

defined for its movement: slow speed, medium

speed and fast speed. The operator determines which

of the above mentioned speeds shall be selected. But

when the robot moves on a slope, the robot's

movement will be set automatically according to the

angle of the slope (which will be measured by

ADXL330 accelerometer) and the software setting

in which speed of the robot, while moving on the

slope, is determined.

Moreover the PID controller is used to correct

the mechanical errors and to adjust the exact speed

of the robot in different situations.

4 COMMUNICATION

Regarding the fact that the robot is a PC base,

W-Lan was used to establish connection between the

robot and the computer (operator). Moreover, since

in some regions it is impossible to establish wireless

connections because of the high rate of noise, the

capability of making connections through wire was

added to the above system so that establishing the

connection is practical even for long distances

(several kilometres). A wire gathering system is

devised inside the robot which could spread the long

wire simultaneous with the robot's movement when

connections shall be established through wire. In this

way the wire will not hinder the robot while moving

and it does not interfere with the robot's movement.

Table 1: W-Lan Specification.

Frequency Channel/Band Power (mW)

5.0 GHz - 802.11a

4 100

Through displacing a few simple jumpers which

are devised on the robot and also through activation

of the multiple choices exist in the provided

software, we can easily determine the method for

establishing connection with the robot.

To transmit the video pictures and voice, the 3W

video transmitter with 2GHz frequency are used.

5 SENSOR FOR NAVIGATION

AND LOCALIZATION

The baseline of navigation in a robot is to use

graphical and video pictures sent by various cameras

and Sonar system installed on the robot. Processing

data, sent by cameras, is performed by the operator

and the data sent by sonar system will be processed

by a central microcontroller.

In addition to sonar system, several photo

sensors are also installed on the robot's critical

movement points which prevent robot colliding with

the surrounding environment. According to the robot

maximum speed, the identifying distance of obstacle

by sensor is adjustable in a way that the robot will

not collide the obstacles.

In order to locate the robot, a combination of

data sent by various sensors are used which reduce

the errors (that are inevitable). Increasing the rate of

certainty in identification, grouping and also

eliminating of the ambiguities & conflicts are among

the benefits of this work. To perform the data

combining system, it requires selecting and using the

PROMOTION IN RESCUE ROBOT - According to the Experience Gained by Participating in Bam Earthquake Rescue

Operation

197

group of techniques harmoniously to achieve the

best answer.

In order to apply the intelligent combination of

data from the viewpoint of data processing, the high

level method is used.

These sensors include:

 Four encoders which are mounted onto the

motor shafts.

 Digital compass plus µ-metal to eliminate the

noise of engines which could completely

disable the digital compass sensor.

 the accelerometer sensor which obtains the

robot's vertical angle in two vertical directions

robot (using ADXL330 IC which most

importantly is used to obtain the vertical angle

(zx, zy) of the robot and to measure the height

of the distance traversed by the robot).

To use the data provided by these sensors for

illustrating the map, the following definitions shall

be considered.

The break points: whenever the command for the

robot's movement sent by operator through PC is

interrupted or the Stop command is transmitted to

the robot, that place will be considered as break

point.

Figure 8: Break points for drawing map of robot's

movement.

Note 1: the angle and the measure of the

traversed distance from the previous break point and

also the vertical distance of the robot from the

horizontal line of the starting point will be desirable

at the break point.

Note2: B3 is also defined as a break point here

because the robot's movement in the straight

direction is interrupted although it continued to

move without changing its direction.

Note3: having the data about the robot's location

(angle and the distance) at the break points, in an

ideal condition we could illustrate the route map of

robot in an accurate and simple way. This is the

advantages of the break point definition.

The movement route: the robot's route of movement

is obtained through connecting the vectors of break

points.

Note4: the specifications stated in note 1, will be

stored in the side memory of the robot in a special

arrange. Whenever the investigating operation is

finished, returning to the starting point could be

automatically delegated to the robot by using the

reversed combination of the stored data and

real time data provided by the sensors

simultaneously. (Obviously facing changes in the

environment is unavoidable thus just in the ideal

situation saved break points are used for returning to

the start point and in real situation the real time data

of sensors which could rectify the previous errors

are used to obtain the new break points.)

Note5: Advantages of storing the data about

break points in the side memory:

 The automatic returning of robot even in cases

when the operator and the robot are

disconnected.

 Access to the data in different steps of

movement in order to perform the combining

operation of the data provided by sensors

(sensor fusion) to obtain a relatively accurate

mapping.

 Access to the complete information of the route

stored inside the memory so that in case the

robot and PC are disconnected, the

information could be transferred to PC (after

returning of the robot).

6 SENSORS FOR VICTIM

IDENTIFICATION

The most important method to identify the victim, is

using pictures transmitted by the cameras which are

installed on the robot (three cameras are installed on

the robot but by using an analog switcher, the

operator selects one of the pictures provided by one

of these cameras to be transmitted.

And besides we can use:

 CO2 gas sensors for detecting the victim's

breathing.

 Installation of highly sensitive stereo

microphones on the robot helps the operator to

find the victim.

 LM75 IC for measuring the temperature of the

environment.

 The non-contact thermometer sensor model

IL301, with D:S (30:1) for measuring the

body temperature of the victim from a far

distance.

 Also a motion detector is installed on the robot

which is sensitive to any trivial movement in

the environment.

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7 ROBOT MECHANIC AND

LOCALIZATION

Firstly, we describe the mathematical equations of

localization differential mechanism and then by

using those equations, we could generate

four-wheeled robot and tracked robot equations with

acceptable accuracy.

7.1 Differential Drive

Figure 9 shows a typical differential drive mobile

robot. In this design incremental encoders are

mounted onto the two drive motors to count the

wheel revolutions. The robot can perform dead

reckoning by using simple geometric equations to

compute the momentary position of the vehicle

relative to a known starting position.

Figure 9: A typical differential drive mobile robot

(top view).

20 Part I Sensors for Mobile Positioning For

completeness, we rewrite the well-known equations

for odometry below. Suppose that at sampling

interval I the left and right wheel encoders show a

pulse increment of N

L and NR, respectively. Suppose

further that:

m = π Dn / n Ce (1)

where:

m = conversion factor that translates encoder pulses

into linear wheel displacement

n = nominal wheel diameter (in mm)

Ce = encoder resolution (in pulses per revolution)

n = gear ratio of the reduction gear between the

motor (where the encoder is attached) and the drive

wheel.

We can compute the incremental travel distance

for the left and right wheel, ΔU

L,i and ΔUR,i

according to:

ΔU

L/R,i = Cm NL/R,i (2)

And the incremental linear displacement of the

robot's center point C, denoted ΔU

i, according to:

ΔU

i = (ΔUR + ΔUL)/2 (3)

Next, the robot's incremental change of

orientation was computed:

Δθ

i = (ΔUR - ΔUL)/b (4)

Where b is the wheelbase of the vehicle and

ideally measured as the distance between the two

contact points between the wheels and the floor.

The robot's new relative orientation θ

i can be

computed from:

i = Δθi-1 + Δθi (5)

And the relative position of the center point

is:

i = xi-1 + ΔUi cos θi (6)

yi = yi-1 + ΔUi sin θi (7)

where:

i, yi = relative position of the robot's counterpoint c

at instant i.

7.2 Tracked Vehicles

Yet another drive configuration for mobile robots

uses tracks instead of wheels. This very special

implementation of a differential drive is known as

skid steering and is routinely implemented in track

form on bulldozers and army vehicles. Such

skid-steer configurations intentionally rely on track

or wheel slippage for normal operation (Figure 10),

and as a consequence provide rather poor

dead-reckoning information. For this reason, skid

steering is generally employed only in tele-operated

as opposed to autonomous robotic applications,

where the ability to surmount significant floor

discontinuities is more desirable than accurate

odometry information. An example is seen in the

track drives popular with remote-controlled robots

intended for explosive ordnance disposal.

Figure 10: The effective point of contact for a skid-steer

vehicle is roughly constrained on either side by a

rectangular zone of ambiguity corresponding to the track

footprint. As is implied by the concentric circles,

considerable slippage must occur in order for the vehicle

to turn.

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Operation

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7.3 Four-wheeled Vehicles

Obtaining the robot route map is one of the issues

about which designer really concern. For this, there

are simple mathematic equations. The robot route

map equations parameters are described below.

These equations are valid while wheels revolutions

are equal, it means that the robot should go forward,

backward or rotate at its place and could not use

these equations in complicate movement. In rotation,

robot changing angle is calculated and it has no

movement.

Table 2: Parameters of movement route for four-wheeled

robots.

Dimensional distance traveled by wheel

for each encoder pulses

Effective width of robot divided by two O

Incremental travel distance for the left and

right wheel in the straight movement

ΔUR1 = ΔUL1

Incremental travel distance for the left and

right wheel in u turn movement

ΔUR2 = ΔUL2

Number of pulses received by left and

right encoder

NR,i = NL,i

Wheelbase of the vehicle, measured as the

distance between the two contact points

(wheels & floor)

The mathematic equations of robot route

movement are described below:

Sin α = O / b

(8)

m = лDn / nCe

(9)

ΔU

L1 = Cm NL,i

(10)

ΔU

R1 = Cm NR,i

(11)

t = Cm × Sin α

(12)

ΔU

L2 = Ct NL,i

(13)

ΔU

R2 = Ct NR,i

(14)

ΔU

i = (ΔUR1 + ΔUL1 ) / 2

(15)

ΔӨ

i = ΔUR2 / b

(16)

i = Өi-1 + ΔӨi

(17)

i = Xi-1 + ΔUi cos Өi

(18)

i = Yi-1 + ΔUi sin Өi

(19)

If compass sensor or gyroscope use more

than encoders, ΔӨ

i parameter is directly obtained

from sensors and other movement route equations

shall use without change.

Figure 11: A typical four-wheeled drive mobile robot

(top view).

8 MAP GENERATION

The map generation process, for illustrating the

route of robot's movement is studied on this part.

The recorded data, observed by cameras and also the

piece of information were received by various

sensors, illustrated on the map of robot movement

(in form of a general report for the robot

performance). This part consists of two parts called

automatic mapping and manual mapping which the

automatic mapping is chosen as the default. The

work procedure is as follows:

Data about shaft encoders exist on the robot, and

the data received through the digital compass sensor

are transmitted continuously from robot. The

computer firstly combines the received data and

applies a series of error correcting algorithms to

reduce the errors of shaft encoders (sensor fusion)

and then the coordinates of the robot in each second

will be obtained. By using these coordinates, two

dimensional routes of robot's movement will be

illustrated. Meanwhile, the data provided by gas and

voice sensors, transmitted by the robot, will be saved

in the computer and they will be illustrated on the

map at the place which they were received. In

addition, some tools are designed for the operator by

which the operator can record its observations and

insert information in the map.

Figure 12: The scheme of the software used to illustrate

the route map.

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200

Figure 13: Symbols which are used in map generating.

Whenever the operator realizes that at the place

where the robot locates or at its surroundings, there

is a stair, wall, door, slope, or a victim, it can locate

a symbol of what it observes on the route map.

By using observed environment button and while

navigating the robot, the operator will mark the

places visited by the robot to prevent the repetitive

visiting and then, saves time. For returning to the

previous situation the operator just need to press

undo button.

While working, whenever the robot and the

computer are disconnected or whenever major errors

in the coordinates data or the data provided by

sensors are observed which may caused as a result of

robot damage, the operator can select the manual

mapping choice to illustrate the route. In this way,

he can enjoy the benefits of software in controlling

the robot and will face fewer errors.

In case that operator uses each of the above

objects in a wrong place, the software has the ability

to delete the object by a right click or to replace it by

a left click. The places in white colour show that

they are observed by the operator.

While observing an injured person, and placing

its symbol on the route map, another form will

appear for the operator in which the operator should

enter the related data to be recorded and also to be

used for the next reportages.

Figure 14: Form for recording the victim data.

9 CONCLUSIONS

Height adjustment and suspension systems enrich

the robot to go through the entirely destructed

buildings; however, it is not possible for it to cross

some obstacles such as steps. Robot mapping system

acts perfectly inside the buildings, but in the open

areas or the rubble it needs to improve. In the

improvement plan, these limitations must be

removed. In its final version, laser scanner and radio

positioning will be installed. The received

information plus the other sensors data result in a

better mapping achievement. It order to accelerate

its movement on the steps and through the obstacles,

some changes will be applied on the wheels and the

motion system.

ACKNOWLEDGEMENTS

Prof. Caro Lucas.

Dr. Soleiman Farshid Fam.

Dr. Sayyed Hassan Mir Hosseini.

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