final project-of-exoskeleton-universiti-putra-malaysia-mechanical-student

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1 PROBLEM STATEMENT

Imagine spending days at a time hiking through the sweltering heat of the desert carrying heavy

backpacks and weaponry; Imagine loading two hundred pound missiles into aircraft and tanks

for hours. Exhaustion would quickly take over, diminishing the limits of the human body. These

are problems that military personnel face every day.

2 LITERATURE REVIEW

Military exoskeleton also known as powered exoskeleton, exoframe, or powered armor. The

main purposes of this exoskeleton are to support the wearer by increasing their endurance and

strength. This exoskeleton is controlled by using power motor system, hydraulic, pneumatics,

and electro-pneumatics. One of the main functions of military exoskeleton is to provide extra

support that enables a army to carry more weight. The military exoskeleton also can be used to

support firefighter and rescue squad in facing emergency situation. Nowadays, many big

countries in the world like United State (US), Germany, China and Japan try to develop the

military exoskeleton for their new power in military. For the example, the United State was

designed DARPA super-light exoskeleton and HULC exoskeleton.

The DARPA super-light exoskeleton was developed by Harvard’s Wyss Institute for Biological

Inspired Engineering, and received $2.9 million in development for DARPA. The HULC

exoskeleton is known as Lockheed Martin Human Universal Load Carrier/Berkeley Bionics. This

military exoskeleton could be a real benefit to the military field for the future.

The exoskeleton also designed for the medical use, heavy works in factory, and military use. For

the medical use, many exoskeletons was created like HAL (Hybrid Assistive Limb) the cyborg

robot from CYBERDYNE company to help people in the area of rehabilitation who suffer from

neuromuscular system, diseases of the brain, cerebrovascular diseases, traumatic brain injuries,

and spinal cord injuries, etc. The CYBERDYNE Company also manufactures HAL exoskeleton

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for non-medical use like welfare field, assistance for rescue activities on disasters site and heavy

work in factory.

The exoskeleton has limitations and design issues like a power supply, skeleton, actuators, and

power control and modulation. The exoskeleton was step up for walking, jumping and running

using more power supply. However, the power supply is one of the largest problem facing in

develop the exoskeleton. The power supply using nowadays is not sufficient energy density to

sustain a full-body powered exoskeleton for more than a few hours.

For the skeleton issues, before this the developers are commonly done using steel and aluminium

in exoskeleton project. But this material has a heavy weight and the exoskeleton must work harder

to overcome its own weight. Aluminium has light weight but it is easy to fail through fatigue. This

situation can give injury effect for the wearer. Some of the developers try to using other materials

like titanium to get some lightweight and strength but this material is more expensive to designed

exoskeleton.

3 OBJECTIVES

a) To create a soft and lightweight under-suit that protect wearers’ joint and helps increase

amount of weight a soldier can easily carry while using less energy and increase their

endurance.

b) To increase the strength and safety of the solder.

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4 MORPHOLOGY CHART

Table 1: Morphology chart

Option 1 Option 2 Option 3 Option 4 Option

5

1 Joint Movement

Method

Hydraulic Pneumatic electronic servomotor elastic

actuators

2 Joint

Connect/flexibiity

separate exterior

ball joint

hollow spherical

ball joint

A chain of external

ball joints

gasketed

hard shell

sections

joined with

free-

rotating

mechanical

bearings

suit

limbs

3 Suiting system Belt Sticky Clip Slider

4 Power source/energy

source

Internal

combustion

hydraulics engine

with electrical

system

Lithium ion

batteries

Electrochemical fuel

cells (SOFC: solid

oxide fuel cells)

Solar

5 Material (frame and

amour)

Titanium Carbon Fiber Steel Aluminum

6 Extra load picking

method/device

Back pack Clip/Hanger Clamp Waist pack

7 Exoskeleton balancer Gravity

balancing

Passive force

balancer

ZMP & CoP

9 Control system/ OS Based on

human

biological

signals

EMG

sEMG

PLC

PIC

Based on

human

non

biological

signals

Human

motion

using

sensor

Dynamic

model

Platform

independent

control

methods

Control

methods are

operates either

human

biological

signal or non-

biological

signal.

4

5 CONCEPT GENERATION & CONCEPT SELECTION

5.1 EXOSKELETON BALANCER

Concept

A B C

Gravity

Balancing

Passive Force

Balancer

Zero Moment Point (ZMP) & Center of Pressure

(CoP)

Concept A and B are the concept to reduce weight of body acting on the wearer legs; Concept C

is avoid the wearer to fall down due to unbalance extra load carried.

Reference Model – Moon Walker

Figure 1: Moon Walker - a Lower Limb Exoskeleton able to Sustain Bodyweight using a Passive

Force Balancer

10 Sensors Force

sensor

Pressure

sensor

Ground

contact

sensor.

Muscle

sensor

fabric

bend

sensor

Angle

sensor

Gyroscope

sensor

Accelerometers

Bio electric

signal sensor.

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Concept Screening

Table 2: Concept Screening for Exoskeleton Balancer

Concept Variants

Selection Criteria A B C Ref.

Ease of controlling - 0 + 0

Ease balancing - + + 0

Ease of safety + 0 0 0

System reliability - + + 0

Passivity + 0 - 0

Ease of

maintenance

+ 0 - 0

Ease of power

consumption

+ + 0 0

Pluses 4 3 3

Sames 0 4 2

Minuses 3 0 2

Net 1 4 1

Rank 3 1 2

Continue? No Yes Yes

No concept scoring required for the chosen Concept A and B because both concepts can balance

the exoskeleton from different aspect. Concept B is to balance the wearer weight with a constant

spring so that the body weight acting on both legs of the wearer can be reduce. Concept C is to

balance the whole exoskeleton (with wearer), so that it will not easy fall down sue to unbalance

from extra loading. As a result, implement both together can make the exoskeleton better.

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5.2 Exoskeleton Lower Part

The design of our exoskeleton suit is based on a few criteria. As for joint movement method,

joint connectivity, suiting system and the material used,the selection of the best option is by

using screening process. Table bellows the option of specification

Table 3: Morphology chart

Option 1 Option 2 Option 3 Option 4

1 Joint Movement

Method

Hydraulic Pneumatic electronic servomotor elastic actuators

2 Joint

Connectivity

separate exterior

ball joint

hollow spherical

ball joint

A chain of external ball

joints

gasketed hard

shell sections

joined with free-

rotating

mechanical

bearings


4 Material (frame

and amour)

Titanium Carbon Fibre Steel Aluminium

Based on the morphology chart, we had combine the option then make four options of design’s

spefication

Design 1


1 Joint Movement

Method


2 Joint

Connect/flexibiity

separate exterior

ball joint

hollow spherical

ball joint


joints

gasketed hard

shell sections

joined with free-

rotating

mechanical

bearings


4 Material (frame

and amour)


Specification of Design 1

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Design 2


1 Joint Movement

Method


2 Joint

Connect/flexibiity

separate exterior

ball joint

hollow spherical

ball joint


joints

gasketed hard

shell sections

joined with free-

rotating

mechanical

bearings


4 Material (frame

and amour)



Design 3


1 Joint Movement

Method

Hydraulic Pneumatic electronic servomotor Elastic Actuator

2 Joint

Connect/flexibiity

separate exterior

ball joint

hollow spherical

ball joint


joints

gasketed hard

shell sections

joined with free-

rotating

mechanical

bearings


4 Material (frame

and amour)



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Design 4


1 Joint Movement

Method


2 Joint

Connect/flexibiity

separate exterior

ball joint

hollow spherical

ball joint


joints

gasketed hard

shell sections

joined with free-

rotating

mechanical

bearings


4 Material (frame

and amour)



Table 4 : Screening

Selection

Criteria

Concepts Design

Design 1 Design 2 Design 3 Design 4

Ease of

Handling

Ease of Use

Mobility

Durability

Costing

Weight

Maintenance

Power saving

Efficiency

0

0

0

0

0

0

0

0

0

0

-

-

0

0

-

0

+

+

0

0

0

0

+

-

+

+

+

0

0

+

-

0

-

0

+

0

-

+

+

-

Sum of +’s

Sum of 0’s

Sum of –‘s

0

7

0

2

5

3

5

4

1

3

3

4

Net Score

Rank

0 -1 4 -1

*Design 1 been set as parameter

Therefore, by using screening concept we have decided that Design 3 is selected as the best

options.

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6 EXOSKELETON CONCEPT SKETCHES

Figure 2: Exoskeleton concept sketch 1

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11


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Figure 5: Exoskeleton final concept sketch

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7 MATERIAL SELECTION

The method use to select the main materials is by comparing few materials using CES

EduPack and then using scoring concept based on their performance index. Material is selected

based on the required criteria. The criteria for body materials should be low in density, high in

young modulus, high in yield strength and low in price. The reference material is Cast iron, nodular

graphite, EN GJS 450 10.

Table 5: List of properties of reference material and selected materials for crankshaft

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Figure 6: Graph of Young’s Modulus VS Density

Figure above shows 8 of the materials that have been filtered out based on the required criteria.

Table 6: formula for performance index

Young Modulus, E Shear Modulus, G Yield Strength, σ

Performance

Index

calculation

Mass Price Mass Price Mass Price

𝐸12

𝜌

𝐸12

𝜌𝐶

𝐺12

𝜌

𝐺12

𝜌𝐶

𝜎23

𝜌

𝜎23

𝜌𝐶

Where,

𝐸 = 𝑀𝑜𝑑𝑢𝑙𝑢𝑠 𝑜𝑓 𝐸𝑙𝑎𝑠𝑡𝑖𝑐𝑖𝑡𝑦 (N/𝑚2)

𝐺 = 𝑀𝑜𝑑𝑢𝑙𝑢𝑠 𝑜𝑓 𝑅𝑖𝑔𝑖𝑑𝑖𝑡𝑦 (𝑃𝑎)

𝜌 = 𝑑𝑒𝑛𝑠𝑖𝑡𝑦 (𝑘𝑔

𝑚3)

𝑐 = 𝑚𝑎𝑡𝑒𝑟𝑖𝑎𝑙 𝑐𝑜𝑠𝑡 (𝑅𝑀

𝐾𝑔)

Density (kg/m^3)2000 5000 10000

Yo

un

g's

mo

du

lus

(GP

a)

10

20

50

100

200

500

Cast iron, nodular graphite, EN GJS 450 10

Titanium, alpha-beta alloy, Ti-6Al-2Sn-4Zr-6Mo (6-2-4-6)

Titanium, alpha alloy, Ti-8Al-1Mo-1V, solution treated & stabilized

Aluminum, 8019, rapid solidification

Beryllium-aluminum alloy, Beralcast 310, cast

Beryllium, Standard Grade, hot pressed

Aluminum, 6061, wrought, T6

Aluminum, 7075, wrought, T6

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Table 7: Performance index Scoring for Exoskeleton materials

Results shows that Berylium is the best performance material that we can use. Since the price of

Berylium is too expensive, so we had choose the second best material, which is Titanium alpha-

beta. Therefore, here is the mechanical properties of the materials.

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8 PARAMETERS DESIGN AND CALCULATIONS

Figure 7: Average body dimension

𝐴𝑣𝑒𝑟𝑎𝑔𝑒 𝑚𝑎𝑠𝑠 𝑜𝑓 𝑔𝑟𝑜𝑢𝑝 𝑚𝑒𝑚𝑏𝑒𝑟 =50 + 67 + 58 + 58 + 55

5= 57.6𝑘𝑔

𝑇ℎ𝑒 𝑏𝑜𝑑𝑦 𝑤𝑒𝑖𝑔ℎ𝑡 𝑎𝑐𝑡𝑖𝑛𝑔 𝑜𝑛 𝑡ℎ𝑒 𝑒𝑥𝑜𝑠𝑘𝑒𝑙𝑒𝑡𝑜𝑛 = 57.6𝑘𝑔 × 9.81𝑚𝑠−2 = 565.06𝑁

The exoskeleton should carry extra payload which is twice of the body weight,

So,

𝑃𝑎𝑦𝑙𝑜𝑎𝑑 = 2 × 𝑏𝑜𝑑𝑦 𝑤𝑒𝑖𝑔ℎ𝑡 = 2 × 565.06𝑁 = 1130.112𝑁 ≈ 1131𝑁

8.1 STATIC ANALYSIS

The final sketch is then simplified into free body diagram. Then, from the free body diagram, the

internal load and the direction of load in each member is determined as below.

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Figure 8: The free body diagram of Exoskeleton

The static analysis is done separately of Part 1, Part 2 and Part 3 with Assumptions:

The weight of each rigid member is negligible.

Part 1

Part 2

Part 3

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8.1.1 STATIC ANALYSIS OF PART 1 (TRUNK & HIP)

Figure 9: Free body diagram of part 1 – trunk and hip

Part 1, determine responding force, FA and FB:

∑ 𝑀𝐵 = 0, +𝐶𝑊:

80𝐹𝐴 − 1131(125 + 80) = 0

𝑭𝑨 = 𝟐𝟖𝟗𝟖. 𝟏𝟗𝑵 𝒇𝒐𝒓𝒄𝒆 𝒖𝒑𝒘𝒂𝒓𝒅

∑ 𝑀𝐴 = 0, +𝐶𝑊:

564.04(80) − 1131(125) − 𝐹𝐵(80) = 0

𝑭𝑩 = −𝟏𝟐𝟎𝟑. 𝟏𝟓𝑵 = 𝟏𝟐𝟎𝟑. 𝟏𝟓𝑵 𝒇𝒐𝒓𝒄𝒆 𝒖𝒑𝒘𝒂𝒓𝒅

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Part 1, Joint A,

∑ 𝐹𝑦 = 0, +𝑢𝑝𝑤𝑎𝑟𝑑 ∶

−2898.19 + 𝐹2 𝑠𝑖𝑛 28.68 = 0

𝑭𝟐 = 𝟔𝟎𝟑𝟖. 𝟗𝟒𝑵 (𝑪)

∑ 𝐹𝑥 = 0, +𝑡𝑜 𝑟𝑖𝑔ℎ𝑡 ∶

𝐹1 − 𝐹2 cos 28.68 = 0

𝑭𝟏 = 𝟓𝟐𝟗𝟖. 𝟎𝟒𝑵 (𝑻)

Part 1, Joint B,


−5298.04 + 𝐹3 sin 45 = 0

𝑭𝟑 = 𝟕𝟒𝟗𝟐. 𝟓𝟔𝑵 (𝑪)

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1203.15 + 7492.56 sin 45 − 𝐹5 = 0

𝑭𝟓 = 𝟔𝟓𝟎𝟏. 𝟏𝟗𝑵 (𝑻)

Part 1, Joint C,


𝐹4 cos 7.44 − 6038.9 sin 28.68 − 7492.56 sin 45 = 0

𝑭𝟒 = 𝟖𝟐𝟔𝟓. 𝟖𝑵 (𝑪)

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Part 1, Joint D,


𝐹6 + 6501.19 − 8265 cos 7.44 = 0

𝑭𝟔 = 𝟏𝟔𝟗𝟓. 𝟎𝟐𝑵 (𝑪)

8.1.2 STATIC ANALYSIS OF PART 2 (CALF)

Figure 10: Free body diagram of part 2 – calf

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Part 2, Joint A,


𝐹1 sin 45 = 0

𝑭𝟏 = 𝟎 𝑵


𝐹2 + 𝐹1 cos 14.64 − 1695.02 = 0

𝑭𝟐 = 𝟏𝟔𝟗𝟓. 𝟎𝟐𝑵 (𝑪)

Part 2, Joint C,


𝑭𝟑 = 𝟎 𝑵


𝑭𝟓 = 𝟏𝟔𝟗𝟓. 𝟎𝟐𝑵 (𝑪)

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Part 2, Joint D,


𝑭𝟒 = 𝟎 𝑵


𝑭𝟔 = 𝟏𝟔𝟗𝟓. 𝟎𝟐𝑵 (𝑪)

8.1.3 STATIC ANALYSIS OF PART 3 (FOOT)

Figure 11: Free body diagram of part 3 – foot

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𝑭𝟏 = 𝑭𝟐 = 𝑭𝟔 = 𝑭𝟕 = 𝟏𝟔𝟗𝟓. 𝟎𝟐𝑵 (𝑪)

𝑭𝟑 = 𝑭𝟒 = 𝑭𝟓 = 𝟎 𝑵

8.2 MEMBER THICKNESS IDENTIFICATION

From the above calculation, maximum compression and tensile force in the member have been

detected, as shown below,

Table 8: The maximum tensile and compression load in the member

Maximum force Location

Compression 8265.8 N Part 1, Joint B

Tensile 6501.19 N Part 1, Joint C

These 2 maximum force is then used to determine the suitable dimension for hip, calf, and foot.

By using the material buckling and tensile equation, the dimension of exoskeleton can be

determined.

Compression force can cause a member to buck. By inverse calculation, substitute the maximum

compression force of 8265.8N into equation of buckling to determine the right dimension to

prevent buckling of member.

𝑆𝐹 × 𝑃𝑐𝑟 =𝜋2𝐸𝐼

(𝐾𝐿)2

Where,

𝑆𝐹 = 𝑠𝑎𝑓𝑒𝑡𝑦 𝑓𝑎𝑐𝑡𝑜𝑟 = 3 (𝑓𝑜𝑟 𝑑𝑦𝑛𝑎𝑚𝑖𝑐 𝑖𝑚𝑝𝑎𝑐𝑡)

𝑃𝑐𝑟 = 𝑡ℎ𝑒 𝑐𝑟𝑖𝑡𝑖𝑐𝑎𝑙 𝑐𝑜𝑚𝑝𝑟𝑒𝑠𝑠𝑖𝑜𝑛 𝑙𝑜𝑎𝑑 = 8265.8𝑁

𝐸 = 𝑡ℎ𝑒 𝑦𝑜𝑢𝑛𝑔′𝑠 𝑚𝑜𝑑𝑢𝑙𝑢𝑠 𝑜𝑓 𝑚𝑎𝑡𝑒𝑟𝑖𝑎𝑙 = 28𝐺𝑃𝑎 𝑓𝑜𝑟 𝑡𝑖𝑡𝑎𝑛𝑖𝑢𝑚

𝐼 = 𝑚𝑜𝑚𝑒𝑛𝑡 𝑜𝑓 𝑖𝑛𝑒𝑟𝑡𝑖𝑎

𝐾 = 𝑑𝑒𝑠𝑖𝑔𝑛 𝑓𝑎𝑐𝑡𝑜𝑟 𝑏𝑎𝑠𝑒𝑑 𝑜𝑛 ℎ𝑜𝑤 𝑡ℎ𝑒 𝑚𝑒𝑚𝑏𝑒𝑟 𝑏𝑒𝑒𝑛 𝑓𝑖𝑥𝑒𝑑 𝑎𝑡 𝑏𝑜𝑡ℎ 𝑒𝑛𝑑

= 1 𝑓𝑜𝑟 𝑏𝑜𝑡ℎ 𝑝𝑖𝑛𝑛𝑒𝑑 𝑒𝑛𝑑

𝐿 = 𝑡ℎ𝑒 𝑙𝑒𝑛𝑔𝑡ℎ 𝑜𝑓 𝑚𝑒𝑚𝑏𝑒𝑟

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Rearrange the equation to I as subject,

𝐼 =𝑆𝐹 × 𝑃𝑐𝑟 × (𝐾𝐿)2

𝜋2𝐸

So,

𝐼 =(24797.4)(0.2186)2

𝜋2(113 × 109)

𝐼 = 1.0625 × 10−4 𝑚4

Taking width, b = 60mm = 0.06m

𝐼 =(𝑤𝑖𝑑𝑡ℎ, 𝑏) × (𝑡ℎ𝑐𝑖𝑘𝑛𝑒𝑠𝑠, ℎ)3

12+ 𝐴𝑑𝑥

Rearrange the equation to h as subject,

ℎ = √12𝐼𝑦𝑦

𝑏

3

= √12 ×1.0625 × 10−9

0.06

3

= 4.61 × 10−4𝑚 = 𝟎. 𝟒𝟔𝟏𝒎𝒎

Furthermore, tensile force can cause a member to fracture. By inverse calculation, substitute the

maximum tensile force of 6501.19 N into equation of axial tensile to determine the right dimension

to prevent tensile failure of members.

𝜎𝑠𝑦 =𝑆𝐹 × 𝑃

𝐴=

𝑆𝐹 × 𝑃

𝑏ℎ

Where,

𝜎𝑠𝑦 = 𝑦𝑖𝑒𝑙𝑑 𝑠𝑡𝑟𝑒𝑛𝑔𝑡ℎ 𝑜𝑓 𝑡𝑖𝑡𝑎𝑛𝑖𝑢𝑚 = 1120𝑀𝑃𝑎

𝑃 = 𝑡ℎ𝑒 max 𝑡𝑒𝑛𝑠𝑖𝑙𝑒 𝑙𝑜𝑎𝑑 𝑎𝑐𝑡𝑖𝑛𝑔 𝑜𝑛 𝑡ℎ𝑒 𝑚𝑒𝑚𝑏𝑒𝑟 = 6501.19𝑁

𝑆𝐹 = 𝑠𝑎𝑓𝑒𝑡𝑦 𝑓𝑎𝑐𝑡𝑜𝑟 = 3 (𝑓𝑜𝑟 𝑑𝑦𝑛𝑎𝑚𝑖𝑐 𝑖𝑚𝑝𝑎𝑐𝑡)

𝑏 = 𝑤𝑖𝑑𝑡ℎ 𝑜𝑓 𝑡ℎ𝑒 𝑚𝑒𝑚𝑏𝑒𝑟

ℎ = 𝑡ℎ𝑖𝑐𝑘𝑛𝑒𝑠𝑠 𝑜𝑓 𝑡ℎ𝑒 𝑚𝑒𝑚𝑏𝑒𝑟

Take width, b = 60mm = 0.06m, rearrange the equation to find thickness, h,

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ℎ =𝑆𝐹 × 𝑃

𝑏 × 𝜎𝑠𝑦=

3 × 6501.19

0.06 × 1120 × 106= 2.9 × 10−4 = 𝟎. 𝟐𝟗𝒎𝒎

As a comparison, the minimum thickness of the member to withstand compression and tension

force are 0.461mm and 0.29mm respectively. To be safe, the thickest of the member must be bigger

the 0.461mm

8.3 BOLT DIAMETER IDENTIFICATION

From the previous static analysis, the maximum load acting on the member is shown in tale below:

Table 9: The maximum tensile and compression load in the member

Maximum force Location

Compression 8265.8 N Part 1, Joint B

Tensile 6501.19 N Part 1, Joint C

Following is the calculation to determine the suitable bolt diameter, d with 8265.8 N

compression force.

𝑆ℎ𝑒𝑎𝑟 𝑆𝑡𝑟𝑒𝑠𝑠 𝑜𝑓 𝑡𝑖𝑡𝑎𝑛𝑖𝑢𝑚, 𝜏 =𝑆𝐹 × 𝐹𝑜𝑟𝑐𝑒, 𝐹

𝐴𝑟𝑒𝑎, 𝐴=

𝑆𝐹 × 𝐹 × 4

𝜋𝑑2

Rearrange the equation to bolt diameter, d as subject,

𝑏𝑜𝑙𝑡 𝑑𝑖𝑎𝑚𝑒𝑡𝑒𝑟, 𝑑 = √𝑆𝐹 × 𝐹 × 4

𝜋 × 𝜏= √

3 × 8265.8 × 4

𝜋 × 1120 × 106= 5.31 × 10−3𝑚 = 𝟓. 𝟑𝟏𝒎𝒎

To achieve minimum SF of 3, both diameter should be equal or bigger than 5.31mm, but the bigger

and available bolt diameter in the industry is 5.5mm. So, 5.5mm bolt diameter is chosen.

27

9 FINAL DESIGN

Figure 12: Front isometric view of Exoskeleton

Foot

Payload Shoulder

Spline

Hip

Calf

Trunk

28

Figure 13: Back isometric view of Exoskeleton

The detail dimension for every parts are shown in Attachment.

10 ANALYSIS AND SIMULATION

The overall image of the Exoskeleton is shown in the figures below. Simple FEM are to be done

in static condition. The body weight and payload are applied on the trunk, the result is observed.

The important parameter need to be observe in from the result are:

Maximum Von Mises stress

Maximum displacement

Minimum safety factor

29

Figure 14: Applied weight of 565.04N and payload of 1131N

As shown in Figure above, body weight (565.04N) and payload (1131N) are applied to the main

trunk. At the same time, fix constraint is applied to both foot base of Exoskeleton. Finally,

frictionless constraint applied to the back of Exoskeleton to avoid it falling backward and

forward during simulation.

30

Figure 15: Mesh view of Exoskeleton

Then, Auto Mesh is applied to the whole Exoskeleton geometry.

31

Figure 16: Result of Von Mises Stress

The maximum Von Mises Stress is 38.04 MPa and it happen at the knee joint. 38.04 MPa is

lower than yield strength of titanium which is 1120 MPa. Therefore, the material is operate under

safe region.

32

Figure 17: Result of displacement

Due to the loading, the maximum displacement happen at the knee again. The value of maximum

displacement is 0.07405mm, which is a not visible displacement. And, it is a very acceptable

displacement.

33

Figure 18: Result of safety factor

Finally and the most important result is the minimum safety factor. The minimum safety factor

that shows from the result is 8.16. Safety factor of 8.16 is more than what expected. In short, the

Exoskeleton passed the static load test.

34

11 COST ESTIMATION

The total weight of the frame is 71.59kg

Material used : Titanium, alpha-beta alloy, Ti-6Al-2Sn-4Zr-6Mo(6-2-4-6)

Table 10: Cost item

Cost Item Price

(RM)

Quantity Total

Cost

Raw material 85.20 71.590 6099

Battery (Lithium polymer) 500 1 500

Actuator 90 4 360

Equipment 10 1 10

Manufacturing 300 1 300

Summary 7269

Since no allocation budget:

Estimated hours: 670 Planned hours: 720 Imputed hours: 470 Hour rate: RM2.50/h

Table 11: Total cost

Category Estimated Planned Hour

cost

Total cost

Coordination 40 40 40 100

Analysis 100 100 100 250

Design 120 140 130 325

Draft 40 40 40 100

Template 40 60 40 100

Apply design 40 40 40 100

Development 190 200 195 487.5

Product Management 50 50 50 125

Testing 50 50 50 125

Summary RM 1712.5

Estimated cost summary=7269+1712.5= RM8981.5

35

12 REFERENCES

http://en.wikipedia.org/wiki/Powered_exoskeleton

http://www.digitaltrends.com/cool-tech/darpa-invests-super-light-exoskeleton-soldiers/

http://www.defensereview.com/lockheed-martin-hulc-human-universal-load-carrier-

anthropomorphic-exoskeleton-for-future-military-special-operations-forces-sof-warfare-at-sofic-

2012-video/

http://www.kurzweilai.net/book-review-science-fiction-bots-becoming-fact

http://en.wikipedia.org/wiki/Powered_exoskeleton

http://www.digitaltrends.com/cool-tech/darpa-invests-super-light-exoskeleton-soldiers/

http://www.defensereview.com/lockheed-martin-hulc-human-universal-load-carrier-anthropomorphic-exoskeleton-for-future-military-special-operations-forces-sof-warfare-at-sofic-2012-video/



http://www.kurzweilai.net/book-review-science-fiction-bots-becoming-fact

36

13 ATTACHMENT

37

Contents

1 PROBLEM STATEMENT ...................................................................................................... 1

2 LITERATURE REVIEW ........................................................................................................ 1

3 OBJECTIVES .......................................................................................................................... 2

4 MORPHOLOGY CHART ...................................................................................................... 3

5 CONCEPT GENERATION & CONCEPT SELECTION ...................................................... 4

5.1 EXOSKELETON BALANCER ...................................................................................... 4

5.2 Exoskeleton Lower Part ................................................................................................... 6

6 EXOSKELETON CONCEPT SKETCHES ............................................................................ 9

7 MATERIAL SELECTION .................................................................................................... 13

8 PARAMETERS DESIGN AND CALCULATIONS ............................................................ 16

8.1 STATIC ANALYSIS ..................................................................................................... 16

8.1.1 STATIC ANALYSIS OF PART 1 (TRUNK & HIP) ............................................ 18

8.1.2 STATIC ANALYSIS OF PART 2 (CALF)............................................................ 21

8.1.3 STATIC ANALYSIS OF PART 3 (FOOT) ........................................................... 23

8.2 MEMBER THICKNESS IDENTIFICATION .............................................................. 24

8.3 BOLT DIAMETER IDENTIFICATION ....................................................................... 26

9 FINAL DESIGN .................................................................................................................... 27

10 ANALYSIS AND SIMULATION .................................................................................... 28

11 COST ESTIMATION ........................................................................................................ 34

12 REFERENCES .................................................................................................................. 35

13 ATTACHMENT ................................................................................................................ 36