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A Mobile Jack Robot for Rescue Operation

J.Tanaka, K.Suzumori, M.Takata, T.Kanda, and M.Mori

Okayama University3-1-1 Tsushima-naka, Okayama, 700-8530, Japan

AbstractThis paper reports a research and development of

a rescue robot using a high-pressure hydraulic actuator. We

developed a practical and simple rescue robot, which used a

high-pressure hydraulic actuator which generates 100kN

force at 70MPa to drive a mechanism of jack. The objective

of the robot is to jack up debris to keep or to make space of

moving courses for other rescue robots and rescue tools, and

to rescue victims under debris. The robot jacks up to 33kN

load. We demonstrated that the robot can jack up over 20kN

to jack up a fallen tree of 20kN.

keywords- high power rescue robot, hydraulic actuator

I. INTRODUCTION

Through the Great Hanshin earthquake and in order toprepare for a seismic hazard, researches on measures todeal with natural calamities are much emphasized.

New category of rescue works is researched in variousfields to rescue survivors as much as possible and to carryout rescue works quickly when a disaster is caused by amajor earthquake in urban city.

Researches of the rescue robots are in one of such newcategory of rescue works. The greatest advantage of using

rescue robots for rescue works is that rescue robots canprevent second disaster. Additionally the robots can carryon operation in dangerous disaster site. Thus we predictthat the rescue robots will assume important role in disastersite.

It is a big issue for rescue robots to move on theirregular ground of disaster site. A variety of robots havebeen developed to move on irregular ground or into rubblessuch as micro robots, snake-like robots, millipede robots,crawler drive robots, flying robots and so on [1]. It is oftenthe case that these rescue robots developed up to thepresent, which mounted some devices (sensors, cameras,lights etc.), aim at searching victims and collectinginformation. For the rescue works, it is very important forthe rescue robots to achieve such aims.

It is also very important to realize operations such astreating heavy debris and carrying victims, which need bigpower. The former type robot is being developed a lot, butthe latter is not so many. As high power rescue tools,hydraulic jack for motor vehicles [2] and X-jack [3] aredeveloped to use for rescue operations in the site, but thesetools must be operated beside them. Therefore, operatorssometimes face to the risk of second disaster. So, wepropose a support method for the rescue works which needhigh power robot using a high-pressure hydraulic actuatorto realize the latter operations.

As the first step, we have developed power rescue robot

[4], [5]. As the next stage, we developed the jack up rescue

robot. The features of the robot are simple structure, simplecontrol system and high power. The aim of this robot is tojack up debris and rubbles to rescue victims and to make aspace which rescue team, other robots and tools go in.Figure 1 shows a working image of the robot.

In following section, we report mainly about the outline,design of jack mechanism and field test of the robot.

Fig.1 Working image of the robot

II. OUTLINE OF THE ROBOT SYSTEM

A. Resume of the robot

The robot has two functions; moving between rubblesand jacking up debris in disaster site.

A driving method is based on a crawler drive. The robotis controlled through an electric wire and a hydraulic tube.The operating range is around 10m. An operator drives therobot watching it directly or watching view from a cameramounted on it.

The aim of the robot is to go into dangerous sites andnarrow spaces, where a rescue team can not work orapproach. Then the robot is to jack up debris. The robot canmake spaces for working and moving courses for otherrescue robots and tools, and can keep space so as not to

break up debris. When victims are pressured by debris, therobot releases them from the pressure as temporarysupports until deliverance.

High power is necessary for jacking up debris. Thisrobot uses a single-acting hydraulic cylinder whichgenerates 100kN force at hydraulic pressure of 70MPa. Touse the hydraulic cylinder, the robot can jack up a load ofmaximum 33kN.

B. System configuration

Figure 2 shows the system configuration. The travelingmechanism of the robot is driven by two DC motors. The

Proceedings of the 2005 IEEEInternational Workshop on Safety, Security and Rescue RoboticsKobe, Japan, June 2005

0-7803-8945-X/05/$20.00 2005 IEEE. 99

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hydraulic actuator for lifting is driven by a hand pump. Ahydraulic hand pump, controller and power supply are inoperator side.

Fig.2 Schematic configuration of the robot system

The motors are controlled independently. So thedriving mechanism is very simple. The robot goes forwardwhen both motors normally rotate, goes back when bothmotors reversely rotate, and turns right and left when twomotors rotate in different direction. The power source issupplied by AC 100V source.

C. The overview of the robot

Figures 3, 4 and 5 show the overview of the robot. Therobot shown in Fig.3 is in driving mode where the size is228mm in width, 564mm in length, and 170mm in height.Figure 4 shows the robot in jack up mode. The jack up

stroke is 245mm in height. The robot moves to destinationpoint in driving mode, and after that, jacks up the debris in

jack up mode.Figure 6 shows the hydraulic pump. The operator

drives the jack of the robot to operate the handle of thepump.

Fig.3 Robot in driving mode

Hydraulic tube and electric wire

Hand pumpRobot

AC 100V

Power supplyController

Fig.4 Robot in jack up mode

Fig.5 Over view of the robot

Pressure gauge

510mm

Fig.6 Hand pump

D. The specification of the robot

Table 1 shows major specification of the robot and the

hydraulic cylinder. Table 2 shows that of hand pump. Thestroke shown in Table 1 means the moving range of thejack mechanism.

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TABLE1MAJOR SPECIFICATIONS OF THE ROBOT AND THE HYDRAULIC CYLINDER

Power(kN)

Stroke(mm)

Weight(kg)

Velocity(m/s)

Robot 33 245 35 0.39

HydraulicCylinder

100 75 2.8 -

TABLE2MAJOR SPECIFICATIONS OF THE HAND PUMP

Maximum

pressure(MPa)

ank capacity

(mm2)

Weight

(kg)

Hand pump 70 700 4.8

III. THE DESIGN OF JACK MECHANISM

A. The jack mechanism

The jack mechanism consists of a stand, parallel links,triangle parts and pull links as shown in Fig. 7. The point Arepresents an axis where the pull links and the triangle partsare connected. Stand is connected to triangle parts, triangleparts are connected to parallel links and pull links, and pulllinks are connected to hydraulic cylinder. Triangle parts,parallel links and hydraulic cylinder are connected to the

robots body at each fixed rotation points.

Fig.7 Jack mechanism

When the hydraulic cylinder extends, the pull links aredriven by the cylinder. Then the triangle parts are pulled bythe pull links at the point A and are rotated around the fixedpoints above the point A. Consequently the stand rises. Inthis way the jack mechanism is realized. Additionally, asstand, triangle parts and parallel links make up parallellinkages, the stand rises keeping it parallel to the ground.

B. The design of jack mechanism

If the hydraulic cylinder was located at the backside ofthe triangle parts, the pull links became needless since thehydraulic cylinder can directly push the point A. But totallength of the robot becomes very long in this design.Therefore we designed the hydraulic cylinder to be locatedinside of the jack mechanism.

Dimensions of the parts of the jack mechanism weredecided using mechanical analysis software. Since thehydraulic cylinder can generate maximum force of 100kN,the robot was designed to jack up load of minimum 30kN.On the basis of the results of mechanical analysis, wedesigned the size of the triangle parts, the position of therotation points with their parts and the hydraulic actuator.

Figure 8 shows a simulation result of the mechanicalanalysis software. As a result of the simulation, we got thejack up force of 33kN force and the stroke of 223mm.Figure 9 shows a relationship between the stroke of the

hydraulic actuator and force when the simulation is best.As shown in Fig.10, the position of the hydrauliccylinder is not fixed uniquely in terms of mechanics sincethe both ends of the hydraulic actuator have the degree offreedom with rotation. However, the position of thehydraulic cylinder is fixed uniquely in terms of dynamics insuch a way that the point A, the bottom side of thehydraulic cylinder and the piston side become in a straightline when the stand is pressured by a load.

Fig.8 Simulation images of the jack mechanism

Fig.9 A relationship between the force andthe stroke of the jack

Load

Adjusted parts

Hydraulic cylinder

30

32

34

36

38Force (kN)

StandTriangle parts

Fixed rotation

points

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70

Strokes (mm)

Parallel links

Pull links

Hydraulic actuator

Expansion

Rotation

Point A

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Fig.10 Side view of the jack mechanism

C. The design of other parts

Figure 11 shows the view from the basement of therobot. The mechanism of the jack is fixed by the side partsas shown in Fig.11. The shafts A, B and the plates A, B areconnected on the side plates, resulting in the rigidity of the

structure. The jack parts rotate around shaft B, and thehydraulic cylinder rotates around shaft A.

Fig.11 The view from downside of the robot

IV. DRIVE MECHANISM

A. Motors and gears

TABLE3

SPECIFICATIONS OF MOTOR AND REDUCTION GEAR

Motor Reduction gear

Body length 57mm Body length 44mm

Voltage 32V Reduction ratio 72.3

Rotationalspeed with no

lead6100rpm Length 106.9

Starting torque 720mNm

Static

maximumtorque

20Nm

Maximumelectrical

current2.3A

Reductionefficiency

0.65

The robot uses two high-torque DC geared motors. Themotion of the motors is decelerated by spur gears toincrease the torque. The rear sprockets rotated by the gearsdrive the crawlers. The gears connected on the motors arewith 1.0 module and 20 teeth. These gears mesh with the

other gears of 1.0 module and 80 teeth. The sprockets arewith 1.0 module and 38 teeth.

Points of bottom side

of the hydraulic cylinder

Table 3 shows the specifications of the motors and thereduction gear. Figure 12 shows the design detail aroundthe motors.

Points of piston side

of the hydraulic cylinder

Point A

Spur gears

Geared motor SprocketShaft B

Fig.12 Mechanism around motors

B. Crawler belt

As shown in Fig.13, the crawler belt has rollersmeshing the sprocket teeth and studs. Studs increasegripping force on the ground, and work also to spike the

body on the ground when the robot jacks up the debris.

Fig.13 Crawler belt

C. Analysis of driving statics

As shown in Fig.14, a static analysis was made forclimbing steps.

The theoretical equation is obtained as follows; F1+ F2cos> w sin (1),

where l, , F1, F2 and w represent the length between thecenters of the gears and the center of gravity, the angle ofthe steps, the driving force of the rear back wheel, thedriving force of the front wheel, and the weight of the robot,respectively.

Studs

Side platesShaft APlate APlate B

Crawler Belts

Rollers

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This equation leads the criteria for climbing stairs.

Fig.14 The model of the robot

V. FIELD TESTS

We carried out two field tests to make the potential ofthe robot clear: a driving test and a jack up test.

A. Driving test

The aim of driving test is to evaluate the performanceof traveling. In disaster site, road condition is not so good,because many debris and rubbles are on the roads. Rescuerobot needs to travel under such condition. To determine

how high the robot can go over, we made this robot 1)driveon a bumpy road, and2)climb stairs.

1) Bumpy road test

The bumpy road has bumps from 10 mm to 50 mm high.The robot could run smoothly. Figure 15 shows this test.

Fig.15 Running on the bumpy road

2) Bump and stairs tests

Table 4 shows the experimental results of bump tests. Itshows the height of the bumps which the robot went over.

Figure 16 shows the schematic diagram of bump test.As shown in table 4, the robot could go over 150mm bumpin dry condition and 100mm bump in wet condition.

Figure 17 shows stairs test. The stairs we used for thistest have three steps. Each step except the first step is 300mm wide and 140 mm high. The first step is 40 mmlower than the other steps. The ground under the stairs isgravel. As show in this figure, the robot climbed stairs

smoothly.From a result of these tests, we found the robot can

drive bumpy road and climb stairs.

TABLE 4THE HEIGHT OF BUMP WHICH THE ROBOT GETS OVER

Fig.16 The diagrammatic illustration of experiment which the

robot gets over a bump

Fig. 17 Climbing stairs

B. Jack up test

We made two types of jack up tests: the one was to jackup a car, and the other was to jack up a fallen tree.

1) Jack up a car

This experiment was carried out to run on an asphaltpavement and to jack up a car front. The weight of the caris about 10kN. A corrugated cardboard is used between thecar and the robot to prevent the car from being scratched.

As a result of this jack up test, the robot was fount tojack up the car front side easily. The weight jacked up bythe robot is estimated to be over 5kN since the engine of

this car is located at the front side.

Roadcondition

Dry Wet

h 150mm 100mm

F2

F1

h

140

300

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