HUMAN ARM-LIKE MECHANICAL MANIPULATOR

The Design and Development of a Multi -Arm Mobile Robot for Nuclear

Decommissioning

Mohamed J. Bakari

Engineering Department, Lancaster University, Bailrigg, Lancaster LA1 4YR, UK

Derek W. Seward

Engineering Department, Lancaster University, Bailrigg, Lancaster LA1 4YR, UK

Keywords: Robotics, System Engineer

ing, Nuclear, Decommissioning.

Abstract: This paper reviews the design and development of a human arm-like mechanical manipulator, which is the

basis of research currently being undertaken at Lancaster University, in order to address the complex tasks

found in the rapidly expanding field of nuclear decommissioning. The requirements of multi-arm robot

architecture for use in decommissioning tasks are discussed. The manipulators are integrated to work

cooperatively and perform similar functions to humans in both scale and dexterity. The role that automation

and robotics can play in enabling quicker demolition and at the same time reducing the exposure of workers

to harmful radiation is examined. The key issues surrounding radioactive materials and safe dose levels are

explained. The different stages of a particular system engineering process are outlined together with the

essential physical steps. The paper will conclude by identifying the compliance of the system engineering

used here with the requirements of designing a multi-arm robot.

1 INTRODUCTION

Hundreds of nuclear facilities will come to the end

of their working lives over the next decades and will

require decommissioning. Much of the

decommissioning process utilises well established

demolition techniques, however the overwhelming

complication in the case of the decommissioning of

nuclear facilities is the exposure of workers to

radiation. The primary use of robotics in

decommissioning applications is to reduce the

radioactivity dose levels to which workers are

exposed. Nearly all Deactivation &

Decommissioning (D&D) activities that are too

hazardous for direct human contact are presently

executed using robotic systems; however many of

these systems are custom-designed for specific

projects and hence expensive, often unreliable and

limited (IAEA, 2001). The purpose of the research

being undertaken at Lancaster University is to

develop a generic tool that can be used for a wide

range of decommissioning tasks. The importance of

multi-arm robots has been noted by many

researchers (Cox,1995; Miyabe, 2004; Alford, 1984)

in the past two decades who have pointed out the

advantages of such robots as compared to the

“handicapped” single-arm robots. There is indeed a

real desire for such systems in decommissioning

robotics, undersea robotics and space robotics. For

example, manipulating flexible objects or fixtureless

assembly (Cox, 1995). A multi-arm robot has the

ability to perform two distinct operations

simultaneously or separately, they also have the

ability to perform the same processing operation in a

coordinated manner or share the task such as holding

and cutting an object (Miyabe, 2004). Cecil Alford

(1984) presents a case study of material handling by

two robot arms.

2 MULTI-ARM MANIPULATOR

SYSTEM

There has not been much research to date that has

reported on the simultaneous utilization of a multi-

arm robot configured on the basis of the size and

168

J. Bakari M. and W. Seward D. (2006).

HUMAN ARM-LIKE MECHANICAL MANIPULATOR - The Design and Development of a Multi -Arm Mobile Robot for Nuclear Decommissioning.

In Proceedings of the Third International Conference on Informatics in Control, Automation and Robotics, pages 168-175

DOI: 10.5220/0001214501680175

 SciTePress

relationship between two human arms, deployed

from a remote vehicle with a manipulator. Previous

studies concerning multi-arm robot systems have

been deployed by either a rigid boom overhead

transporter or by a crane rather than a remote

vehicle. I have given below two examples of these

forms of multi-arm robot systems: DAWM (Noakes,

1999) is a multi-arm robot platform equipped with

two schilling Titan II or Titan T hydraulic

manipulators and mounted to a 5-DOF base.

DAWM as shown in Figure 1, was developed at Oak

Ridge National Laboratory (ORNL) by the Robotics

Development Program (RTDP) as a development

test bed to study issues related to dual arm

manipulation, including platform configuration,

control, automation, operations, and tooling. These

activities were conducted under the Deactivation and

Decommissioning (D&D) Focus Area robotics

product line.

Figure 1: DAWM with Titan II and Titan T manipulators.

RODDIN multi-arm robot system is a crane-

deployed work platform and is equipped with two

hydraulic manipulators (SAMM or MAESTRO).

RODDIN as shown in Figure 2, was developed by

CYBERNETIX and it is used for pipe and metal

cutting in decommissioning.

Figure 2: RODDIN with Maestro manipulators.

Neither of the multi-arm robot system manipulators

described above is based on human-scale size or

dexterity, they are also not light weight.

In the research being undertaken at Lancaster

University we are focusing on the development of a

multi-arm robot system based on human-scale size

manipulators which can be deployed by a remote

vehicle. The focus on the development of human-

scale size manipulators is to undertake pipe-cutting

decommissioning tasks; reconfigure the system for

other necessary decommissioning tasks, such as

dismantling; and to use the system in small restricted

spaces that are too dangerous for humans, or in

which a bigger manipulator could not be deployed.

Because of radiation hazards there are specific

requirement for a robot to fulfil in order to undertake

decommissioning tasks. A reconfigurable, multi-arm

robot system needs to have the following operational

features (Cox, 1999).

Titan

Operational features:

Titan II

• Human scale reach and dexterity

• Force control

• Obstacle and collision avoidance

• Remote teleoperated control (both

manipulators)

• Cooperative manipulator ability

• High reliability

It is widely believed that human scale and

dexterity can satisfy many situations occurring in

decommissioning tasks. Operators have the

confidence to know that if a human can accomplish

the task, then the robot can also achieve it. It is also

necessary, however, to consider collision avoidance

and planning strategies which are in themselves

complex processes.

Forces and torques experienced at the end

effectors of robot manipulators should be reflected

back to the human operator at the manual control

station, thus the operator can feel the work in

process. The dynamic behaviour of the end-effector

is one of the most significant characteristics in

evaluating the performance of robot manipulator

systems. Adding force information to robot control

therefore improves robot interaction with the

environment in the presence of uncertainty

(Oussama, 1987).

The goal of collision avoidance is to permit a

robot to work in an obstacle-strewn environment

without damaging itself or any of the obstacles it

encounters. Obstacle avoidance in an obstacle-

strewn environment is needed to assist the operator

of a remote system and help avoid damaging

expensive equipment or, even worse, causing further

contamination of the environment from the

hazardous materials in the decommissioning sites.

HUMAN ARM-LIKE MECHANICAL MANIPULATOR - The Design and Development of a Multi -Arm Mobile Robot

for Nuclear Decommissioning

169

Furthermore, the robot must prohibit self-collision in

the case of a multi-arm robot.

Teleoperation has been successfully applied to

unstructured tasks such as nuclear facility

maintenance, cleanup, underwater operation and

microsurgery (Parker, 1999). A telerobotic system

consists of a human operator, a remote robotic

system, and a human-machine interface. No matter

how good the remote robot is, unless the human-

machine interface is properly designed, the system

will not perform well. A poorly designed human-

machine interface can also introduce mental stress to

the operator that will further deteriorate the system

performance.

Cooperative manipulation is an important

enhancement to robotic capabilities which enables a

multi–arm robot to perform more complex tasks,

manipulate greater payloads, and span a greater

workspace (Dauchez, 1988). The task performed by

cooperating manipulators can be achieved in either

teleoperated, semi-autonomous and, or autonomous

fashion.

An important deciding factor for use of robotics

and automation lies in the reliability of the overall

system. It is given that the robot makes it safer for

the human. Reliability is a serious concern in

hazardous environments. Task plans can be

developed to optimise the safety of the system by

avoiding situations that place components near the

edge of their performance envelopes. Integration of

operational software with fault-tolerance and

condition based maintenance can further enhance the

system reliability.

3 THE ROLE OF AUTOMATION

AND ROBOTICS

The primary use of robotics in decommissioning

applications is to reduce the radioactive dose levels

to which workers are exposed. There are many

situations where, owing to the degree of radiation

and the very long half-lives of the radioactive

materials involved, robotics is the only feasible

option.

Remote cutting for equipment dismantlement is a

common need in the deactivation and

decommissioning community. Where possible,

suited humans are used to complete the cutting, but

there is significant safety, health, and cost issues

involved. Robotic systems have also been used

where radiation levels eliminate the possibility of

using humans; however cost and task completion

time are major issues. A time-efficient, cost-

effective approach to safely complete D&D

operations without the use of humans in the

hazardous environment is a direct need.

The Nuclear Regulatory Commission’s regulation

10 CFR 20 states that an occupational worker cannot

receive more than 50 mSv per year for the full body

dose (NRC), once this dose has been reached the

worker has to stop working immediately. This

necessitates an increased number of workers to be

employed in order to accomplish the necessary task.

By using robots the number of workers is

minimised, this in turn creates many additional

savings including a reduction in the quantity of

protective clothing needed, and a decreased

administration.

4 RADIOACTIVE MATERIALS

AND SAFE DOSE LEVELS

The effect of radiation on the human body is

measured in Sieverts (Sv). The International

Commission on Radiological Protection (ICRP) has

set public dose limits for exposure to radiation; this

is linked to the requirement to keep radiation

exposure as low as possible.

The radiation limits are usually set at 1mSv per year

above background (Burk, 2001). In most countries

the current maximum permissible dose to radiation

workers is 20 mSv a year averaged over 5 years,

with a maximum of 50 mSv in any one year. The

following table indicates the physical effects on

human of excessive exposure to radiation:

Table 1: Health Effects of Nuclear Radiations Doses.

Dose Health Effects

0.5 Sv Possible minor blood changes, no

obvious effect

0.5-1 Sv Radiation sickness, vomiting and

nausea. No death anticipated

4-5 Sv

Radiation sickness more severe. 50%

deaths in 3-8 weeks from infection or

anaemia. Survivors convalesce for

about 6 months

≈ 10 Sv

Vomiting and nausea within 1-2 hrs.

Probably no survivors. Death within

3-5 days following damage to lining

of small intestine

≈ 50 Sv

Tremors, convulsions almost

immediately. All deaths in less than

2 days due to brain damage

Decontamination and decommissioning (D&D)

of all nuclear facilities produces radioactively

contaminated materials. Some of these materials

continue to have economic value because they are in

ICINCO 2006 - ROBOTICS AND AUTOMATION

170

forms that can be recycled or reused. Others will

have little or no economic value and thus constitute

waste that has to be disposed of or stored if no

acceptable method of disposal exists.

The radioactive waste classification and disposal

routes (IAEA, 1994) are as follows:

1. Very low-level waste (VLLW). This waste can be

disposed of in normal landfill sites.

2. Low-level waste (LLW). This waste contains 1%

of the radioactivity but accounts for over 80% of the

volume and is stored in containers at a dedicated

site.

3. Intermediate-level waste (ILW). This waste

contains higher amounts of radioactivity than LLW

and requires shielding. There are no dedicated

facilities in the UK at present, so it is currently

stored on the site of the decommissioning facility in

a specially constructed facility.

4. Higher-level waste (HLW). This waste contains at

least 95% of the radioactivity in radiation waste but

no more than 3% of the volume and requires special

storage with cooling facilities.

In order to illustrate the above proportions of

radioactive waste, 1 tonne of spent fuel from fuel

processing gives rise to 0.1m

HLW, 1m

ILW and

LLW.

5 SYSTEMS ENGINEERING

PROCESS

The systems engineering process, as shown in

Figure 3, derives from the consideration of a specific

concept, and the consequent selection of appropriate

technology. Defining the user requirements is the

first step in the development process using the

system engineering principles and the finished

products should satisfy these requirements (Zied,

2004). The user requirement in this research is the

creation of a robot manipulator with the operational

features of human scale and dexterity.

The system requirements are an intermediate step

between the user requirements and the design stage,

which aim to show what the system is going to do.

In this research, the system requirements derive

from the multi-arm robot configuration which needs

to have the capacity for force control, collision

avoidance, remote controlled, cooperativeness and

high reliability.

The architectural design is the system design that

defines the major components, their arrangements,

decompositions and interrelationships. The human

scale manipulator developed in the research is called

Hydro-Lek which is a six degree of freedom robot

manipulator and consists of six links with a gripper,

four linear actuators and two rotary actuators.

The component development step is the detailed

design of the individual Hydro-Lek manipulator

links including functionalities, interfaces and

layouts. The given information is enough to

manufacture the robot components or to purchase

off-the-shelf components. The manipulator links

then have to be tested, assembled and finally

accepted.

User Requirements

System Requirements

Architectural Design

Component Development

Integration & Verification

Installation & Validation

Operational Capability

System identification

(Office based work)

System creation

(Workshop production)

Operational validation

(Laboratory work)

Figure 3: Sequential development model (Stevens, 1998).

HUMAN ARM-LIKE MECHANICAL MANIPULATOR - The Design and Development of a Multi -Arm Mobile Robot

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171

Wrist Roll

Forearm

Roll

Wrist

Pitch

Azimuth

Yaw

Elbow

Pitch

Shoulder

Pitch

Figure 4: Hydro-Lek 6 DOF Arm.

Figure 4 above, shows the six joints Hydro-Lek

manipulator layout. Joint one rotates with axis

perpendicular to plane XY. Joint two rotates

perpendicular to joint one. Joint three rotates parallel

to joint two and is offset by the link indicated as A.

Joint four is perpendicular to joint three and is offset

by the link indicated as B. Joint five is perpendicular

to joint four, parallel to joint three and is offset by

the link indicated as C. Joint six is perpendicular to

joint five and is offset by the link indicated as D.

Verification can be performed in two stages. The

first stage is design verification in which the design

is certified against the requirements and it assures

that the product will work properly if it is

manufactured. Computer simulation provides a

means of viewing robot motion to aid in human

perception and decision making for both design and

operation. Interactive software packages that

generate computer animations have found wide

acceptance for programming and simulating

industrial robots. Animated work-cell design

involves graphically placing the robot in its

environment, also called the work-cell.

Machines, tools, parts and any other objects that the

robot manipulators will interact with are also placed

in the workcell. Computer animation is then used to

visually simulate these interactions as the robot

manipulator performs its task. The verification step

in this research was carried out using a CAD/CAM

software package which included Pro/ENGINEER

Wildfire 2.0, used for modelling, modification and

animation of the Hydro-Lek arm components; and

robot simulation software, Workspace 5.04, in order

to assemble and integrate the imported arm

components from the Pro/Engineer software, and

carry out the necessary kinematics simulations by

defining all of the arm joint translations and

orientations.

Table 2 explains the Hydro-Lek manipulator arm

functions.

Table 2: Hydro-Lek arm functions.

Joint Actuator

Function

Type Nom.

Range

1 Azimuth

Yaw

Linear 90

2 Shoulder

Pitch

Linear 120

3 Elbow

Pitch

Linear 120

4 Forearm

Pitch

Rotary 180

5 Wrist

Pitch

Linear 180

6 Wrist Roll Gerotor 360

ICINCO 2006 - ROBOTICS AND AUTOMATION

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Figure 5: Denavit-Hartenberg Configuration for the Hydro-Lek arm.

Robot manipulators can be considered as a set of

bodies, or links, connected in a kinematic chain by

joints. Each joint of the robot manipulator exhibits

one degree of freedom.

Hydro-Lek manipulator specification:

• Human size arm (900 mm long)

• Approximately 30 kg weight

• 6 function + gripper

• Potentiometer sensor for each joint

• Gripper with force sensor

• Closed loop position control

Both Hydro-Lek manipulators are in the

manufacturing stage, they are due to be delivered in

two months time. Multi-arm configuration will be

set up in order to be mounted to the Brokk 40

friendly mount point.

The Hydro-Lek manipulator structure is

kinematically defined by giving each link four

parameters (d

, θ

, a

and α

). The four given

parameters shown in Table 3, describe how to get

from one joint to another. Neighbouring links have a

common joint axis between them.

Table 3: The D-H Parameters.

Joint

1 θ

2 θ

0 a

3 θ

- 90

-a

4 θ

-d

5 θ

-a

6 θ

+ 90

180

0 d

The distance along the common axis from one link

to the next link is offset d

. The amount of rotation

about the common axis between one link and its

neighbour is joint angle θ

The definition of mechanisms by means of these

four parameters is a convention called Denavit-

Hartenberg (Fu, 1987). The location and orientation

of each joint frame is shown in Figure 5 above. In

this research, the installation step can be conceived

as an integration step within the systems engineering

process. This integration step couples the two

Hydro-Lek manipulators in a test bed in order to

form a multi-arm configuration as shown in Figure

4. A similar project has been undertaken by Daniel

Cox (2004).

HUMAN ARM-LIKE MECHANICAL MANIPULATOR - The Design and Development of a Multi -Arm Mobile Robot

for Nuclear Decommissioning

173

6 THE MULTI-ARM ROBOT

CONFIGURATION

The ongoing research work in robotics at Lancaster

University is concerned with advancing the semi-

autonomous tele-operated robot for D&D tasks.

Figure 6 shows the layout of the two Hydro-Lek

arms. The left arm is a complete arm with a gripper

and the right arm has no gripper but a simple flange

where a cutting tool will be fixed. The purpose of

developing the multi-arm robot in this research work

is for the arms to have the ability to perform two

distinct operations simultaneously or separately. The

decommissioning task considered here is pipe

cutting where the left arm holds a straight pipe while

the right arm cuts it. The left arm then places the cut

piece in a suitable waste disposal vessel.

At this stage of the project, the aim is to attach

the multi-arm robot on to a Brokk 40 friendly mount

point as shown in Figure 7. The primary aim of the

research is to develop intelligence in the robot that is

similar to the cooperation and communication

between the human brain and its two arms; hence the

human arm is adopted as the starting point to

establish the size and functionality of the proposed

system. The next stage of this research work is the

identification and development of hardware and

software systems such as the National Instruments

robotic platform (Lewis, 2004). The NI robotic

platform combines hardware interfacing, stepper or

servo control, trajectory generation, task level

programs, a graphical user interface 3D simulation

and a math library. The NI robotic platform

implements all these components in a homogeneous

architecture that will utilise a single hardware

platform (a standard PC), a C programming

language and an operating system (LabVIEW Real-

Time). This design will lead to a less complex

architecture, easier to use and easier to extend.

Figure 6: Hydro-Lek arms configuration.

Figure 7: Multi-arm mobile robot.

7 CONCLUSION

Nuclear decommissioning provides a particularly

fruitful sector for the advancement of automation

and robotics. Earlier generations of nuclear facility

have now been closed and many are waiting

effective decommissioning. There is a multi-billion

pound world-wide market for companies who have

the skills and technology to engage with the task. In

addition to traditional hazards such as asbestos and

PCBs, the key hazard is obviously the presence of

significant quantities of radioactive waste material.

It is the effective management of this waste which is

the crux of nuclear decommissioning. Many projects

have been successfully completed and valuable

lessons learned. This is a great driver to the further

use of automation and robotics in order to reduce the

radiation dose to which workers are subjected.

This paper has outlined and discussed the design

and development of a human arm-like mechanical

manipulator in order to address the complex tasks

found in the rapidly expanding field of nuclear

decommissioning and the requirements of multi-arm

robot architecture for use in decommissioning tasks.

The stage so far reached is a manufacturing and

integration stage, the next stage of this research will

involve carrying out experimentation in order to

execute pipe cutting tasks.

ACKNOWLEDGEMENTS

The authors are grateful for the support of the

Engineering and Physical Science Research Council

EPSRC.

Hydro-Lek multi-arm

ed test b

Brokk 40 Robot

Left ar

ht ar

Test be

ICINCO 2006 - ROBOTICS AND AUTOMATION

174

REFERENCES

Burk, R. J., 2001. Ionizing Radiation-Safety Standards for

the General Public – Position Statement of the Health

Physics Society [online]. Health Physics Society.

Available from:

http://hps.org/documents/publicdose.pdf [accessed

January 2006]

Brokk 40 robots information [online]. Available from:

http://www.brokk.com/ [accessed February 2006]

Cox, D., Cetin, M., Pryor, M., and Tesar, D., 1999.

Requirements for Modular Dual-Arm Robot

Architecture for Use in Deactivation and

Decommissioning Tasks. ANS 8

International

Topical meeting on Robotics and Remote Systems,

9(4), pp. 1-14, American Nuclear Society.

C. O. Alford., and S. M. Belyeu., 1984. Coordinate control

of two robot arms. IEEE International Conference of

Robotics, pp. 468-473.

Cox, J. D., Rackers, K., and Tesar, D., 1995. Cooperative

Manipulation Experiments Using a Dual-Arm Robot.

IEEE Priceedings.

Cox, D., 2004. Cooperative manipulation Testbed

Development-Kinematics. 17

Annual Florida

Conference on the Recent Advances in Robotics

(FCRAR), Florida.

Cox, D., 2002. Mock-up of Hazards Material Handling

Taks Using a Dual-Arm Robotic System. Proceedings

World Automation Congress, Orlando.

Dauchez, P., Fournier, A., and Jourdan, R., 1988. Hybrid

Control of a Two-Arm Robot for Complex Tasks. 2

International Symposium on Robotics and

Manufacturing (ISRAM), New Mexico.

Fu, K.S., Gonzalez, R.C., and Lee, C.S., 1987. Robotics

Control, Sensing, Vision, and Intelligence. Singapore:

McGRAW-HILL.

Hydro-Lek Manipulator information [online]. Available

from:

http://www.hydro-lek.com/ [accessed October

2005]

International Atomic Energy Agency (IAEA), 2001. State

of The Art Technology of Decommissioning and

Dismantling of Nuclear Facilities. Technical Report,

no. 395, Vienna.

International Atomic Energy Agency (IAEA), 2001.

Methods for The Minimization of Radioactive Waste

From Decontamination and Decommissioning of

Nuclear Facilities . Technical Report, no. 401, Vienna.

International Atomic Energy Agency (IAEA),

1994.Classification of Radioactive Waste. A safety

guide, Vienna.

Lewis, F.L., Dawson, D.M., and Abdallah, C.T., 2004.

Robot manipulator Control Theory and Practice, 2

ed. New York: Marcel Dekker.

Measson, Y., David, O., Louveau, F., and Friconneau, J.

P., 2002. Technology and Control For Hydraulic

Manipulator. 22

Symposium on Fusion Technology

(SOFT), Helsinki.

Miyabe, T., Konno, A., Uchiyama, M., and Yamano, M.,

2004. An Approach Toward an Automated Object

Retrieval Operation with a Two-Arm Flexible

Manipulator. The International Journal of Robotics

Research, 23(3), pp. 275-291.

Noakes, M. W., 1999. Dual Arm Work Module

Development and Applications. Proceedings of The

American Nuclear Society Eighth ANS Topical

Meeting on Robotics and Remote Systems, Pittsburgh.

National Instruments product information [online].

Available from: http://www.ni.com/ [accessed January

2006]

Oussama, Khatib., 1987. A unified approach for motion

and force control of robot manipulators: The

operational space formulation. IEEE Journal of

Robotics and Automation, RA-3 (1), pp. 43-53.

Parker, L.E., and Drapper, J.V., 1999. Robotics

Application in Maintenance and Repair, 2nd ed. New

York: Wiley.

RODDIN, Crane-deployed work platform information

[online]. Available from:

http://www.cybernetix.fr/modules.php?&op=modload

&name=cybernetix&file=product&topic=14&bt=nucl

eaire&newlang=eng [accessed November 2005]

Roman, H.T., 1992. Nuclear Plant – Experience and

Future Projections. 40

Conference on Remote System

Technology.

SAMM Manipulator information [online]. Available from:

http://www.cybernetix.fr/modules.php?&op=modload

&name=cybernetix&file=product&topic=14&bt=nucl

eaire&newlang=eng [accessed November 2005]

Stevens, R., Brook, P. Jackson., K. and Arnold, S., 1998.

Systems engineering, coping with complexity. London:

Prentice Hall Europe.

Seward, D., 1999. The development of intelligent mobile

robot. Thesis (PhD). Lancaster University.

Titan Manipulators information [online]. Available from:

http://www.sub-atlantic.co.uk/products.html [accessed

March 2006]

U.S. Nuclear Regulatory Commission [online]. Available

from: http://www.nrc.gov/reading-rm/doc-

collections/cfr/part020/ [accessed November 2006]

Zied, Khaled., 2004. Investigation of processes and tools

for rapid development of intelligent robotic systems.

Thesis (PhD). Lancaster University.

HUMAN ARM-LIKE MECHANICAL MANIPULATOR - The Design and Development of a Multi -Arm Mobile Robot

for Nuclear Decommissioning

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