Design and development of receptionist robot

In Chapter 3, we will explain about kinematics and dynamics of robot mobile platform by analyze the interaction between wheels and ground.. Here, the wheeled robot is a 2-DOF mobile robo

BỘ GIÁO DỤC VÀ ĐÀO TẠO

TRƯỜNG ĐẠI HỌC SƯ PHẠM KỸ THUẬT TP HỒ CHÍ MINH

KHOA CƠ KHÍ CHẾ TẠO MÁY

ĐỒ ÁN TỐT NGHIỆP NGÀNH CÔNG NGHỆ KỸ THUẬT CƠ ĐIỆN TỬ

GVHD: PGS TS NGUYỄN NGỌC PHƯƠNG SVTH: ÐẶNG HẢI ÐĂNG MSSV: 12146040 NGUYỄN TRỌNG TUẤN MSSV: 12146223 NGUYỄN CÔNG LUẬT MSSV: 12146105 PHÙ TRUNG MƠ MSSV: 12146113

Tp Hồ Chí Minh, tháng 07 năm 2016

S KL 0 0 4 7 2 8

DESIGN AND DEVELOPMENT OF RECEPTIONIST

ROBOT

MINISTRY OF EDUCATION AND TRAINING HCMC UNIVERSITY OF TECHNOLOGY AND EDUCATION

MINISTRY OF EDUCATION AND TRAINING HCMC UNIVERSITY OF TECHNOLOGY AND EDUCATION

TRƯỜNG ĐẠI HỌC SƯ PHẠM KỸ THUẬT

TP HCM

CỘNG HOÀ XÃ HỘI CHỦ NGHĨA

VIỆT NAM

Độc lập - Tự do – Hạnh phúc

KHOA CƠ KHÍ CHẾ TẠO MÁY

Bộ môn Cơ điện tử

NHIỆM VỤ ĐỒ ÁN TỐT NGHIỆP

Giảng viên hướng dẫn: PGS TS NGUYỄN NGỌC PHƯƠNG

Sinh viên thực hiện: ĐẶNG HẢI ĐĂNG MSSV: 12146040

1 Tên đề tài:

Thiết kế, chế tạo và điều khiển robot tiếp tân

2 Các số liệu, tài liệu ban đầu:

Robot tiếp tân tự hành, có khả năng di chuyển, cung cấp thông tin và giao tiếp với người dùng thông qua màn hình cảm ứng và hệ thống nhận diện giọng nói

3 Nội dung chính của đồ án:

- Tính toán và thiết kế cơ khí

(Ký, ghi rõ họ tên) (Ký, ghi rõ họ tên)

 Được phép bảo vệ ……… (GVHD ký, ghi rõ họ tên)

- Địa chỉ sinh viên: Openlab

- Số điện thoại liên lạc: 01264655234

- Email: whitebot.openlab@gmail.com

- Ngày nộp khoá luận tốt nghiệp (ĐATN):

- Lời cam kết: “Tôi xin cam đoan khoá luận tốt nghiệp (ĐATN) này là công trình do

chính tôi nghiên cứu và thực hiện Tôi không sao chép từ bất kỳ một bài viết nào

đã được công bố mà không trích dẫn nguồn gốc Nếu có bất kỳ một sự vi phạm nào, tôi xin chịu hoàn toàn trách nhiệm”

Tp Hồ Chí Minh, ngày … tháng … năm 20…

Ký tên

ACKNOWLEDGMENTS

Firstly, we would like to acknowledge our thesis supervisor Assoc Pr Dr Nguyễn Ngọc Phương and Assoc Pr Dr Nguyễn Trườ ng Thi ̣nh for the continuous support of our project and related research, for their patience, motivation, and immense knowledge Their guidance helped us in all the time of research and writing of this thesis We could not have imagined having better advisors and mentors for our project

Besides our advisors, we would like to thank to our thesis committee ME Lê Thanh Tùng, for his insightful comments and encouragement, but also for the hard question which incented me to widen my research from various perspectives We would also thank to the members of OPENLAB who have supported us throughout our time in laboratory

Finally, we would like to thank the Department of Mechanical Engineering, for giving us the best opportunity to work on our final project

Đặng Hải Đăng Nguyễn Trọng Tuấn Nguyễn Công Luật Phù Trung Mơ

TÓM TẮT ĐỒ ÁN

THIẾT KẾ, CHẾ TẠO VÀ ĐIỀU KHIỂN ROBOT TIẾP TÂN

Đặng Hải Đăng Nguyễn Trọng Tuấn Nguyễn Công Luật Phù Trung Mơ Trải qua những biến động thăng trầm của lịch sử, xã hội loài người đang có những tiến bộ vượt bậc đặc biệt là trong lĩnh vực khoa học kỹ thuật như: Cơ khí hóa, Tự động hóa, Cơ điện tử… Sự thay đổi chóng mặt của nền công nghiệp và kinh tế dẫn đến những nhu cầu về nguồn lực nhân tạo, điển hình là robot Robot đã và đang giúp ích con người trong rất nhiều lĩnh vực như dịch vụ, công nghiệp, y tế, … Sự ra đời của chúng mở ra một

kỷ nguyên mới, kỷ nguyên của khoa học kỹ thuật, của sự thông minh sáng tạo, trong đó sức lao động cơ bắp dần được thay thế bằng sức lao động của máy móc thiết bị Những công việc khó khăn, yêu cầu độ chính xác cao mà trước kia cần đến vài ngày để hoàn tất thì nay đã được robot thực hiện chỉ trong vài phút Với độ chính xác cao, khả năng hoạt động không ngừng nghỉ, cùng với tiềm lực đa tác vụ tốt, robot dần có thể giúp con người trong mọi lĩnh vực của cuộc sống

Chính vì những ưu điểm vượt trội nêu trên, nhóm chúng em quyết định triển khai đề tài “Thiết kế, chế tạo và điều khiển robot tiếp tân” Đây là một lĩnh vực đang phát triển mạnh trên thế giới nhưng còn khá mới ở nước ta, hy vọng qua đề tài này, nhóm có thể góp phần xây dựng nền tảng phát triển robot dịch vụ tại Việt Nam

Trong phần báo cáo chúng em trình bày về: Tình hình phát triển của công nghệ robot trên thế giới, giải thích và chọn phương án thiết kế phù hợp, quá trình gia công, thử nghiệm

độ bền vỏ composite và đế robot, tính toán các bài toán động học và động lực học robot, thiết kế và bố trí mạch điện, nền tảng lập trình và xử lý tín hiệu robot, …

ABSTRACT

DESIGN AND DEVELOPMENT OF RECEPTIONIST ROBOT

Through the ups and downs change of history, human communities have been having great progresses especially in the field of science and technology such as mechanization, automation, mechatronics The rapid changes of the industry and the economy led to the demand for artificial resources, especially robots Robot has been helping people in many fields such as service, industrial, medical, The exist of them opens a new era, the era of science and technology, the creative intelligence , in which the muscular labor was gradually replaced by the labor of machinery The hard work, requiring high accuracy that previously required several days to complete, robot can do it in just a few minutes With high accuracy, the ability to operate non-stop, with good multi-tasking capabilities, the robot can gradually help people in all areas of life

Because of the above advantages, we decided to implement the project "Designing,

manufacturing and controlling robot receptionist" This is a fast growing sector in the world

but is relatively new in our country, hopefully through the project, we can contribute to build the platform for developing service robot in Vietnam

In the report we presented to: The development of robotics technology on the world, explain and choose the appropriate design, processing, testing the strength of platform and composite shell of robot, calculate dynamical and kinematic math, design and circuit layout, programming background and signal processing of robot, We also present about the combination between the hardware and software and the testing process Base on the result of testing, we know about the strong point and weak point of the method that we have used, from that make plans for the future development

CHAPTER 1: INTRODUCTION 1

1.1 DESCRIPTION 1

1.2 SEVERAL SERVICE ROBOTS 4

1.2.1 Robot Fetch 4

1.2.2 Robot Relay 4

1.2.3 OSHbot 5

1.2.4 Robot Techi 6

1.2.5 ENON 7

1.3 OBJECTIVES 8

1.4 PROCEDURES 8

1.5 SYSTEM OVERVIEW 8

1.6 PROJECT TIMELINE (By week) 9

CHAPTER 2: MECHANICAL DESIGN 10

2.1 PLATFORM DESIGN 10

2.1.1 Design requirement 10

2.2 MAKING MOLD AND COMPOSITE 12

2.2.1 Design requirement 12

2.2.2 Choosing and making robot cover 13

2.3 ROBOT’s ARM 15

CHAPTER 3: KINEMATICS AND DYNAMICS 16

3.1 KINEMATICS MODEL 16

3.1.1 Introduction 16

3.1.2 Kinematics 16

3.1.2.1 Representing Robot's Position 16

3.1.2.2 Kinematic Wheel Model 17

3.1.3 Kinematics Robot arm 22

3.2 DYNAMIC MODEL 26

CHAPTER 4: ELECTRONICS AND ELECTRICAL SYSTEM 29

4.1 CALCULATE MOTORS 29

4.1.1 Introduction 29

4.1.2 Calculate the electric motor 29

4.1.3 The shoulder motor 32

4.2 ELECTRONICS 34

4.2.1 Encoder 34

4.2.2 Driver 34

4.3 CALCULATE THE BATTERIES 35

4.4 AUTOMATION CHARGING DOCK 37

5.1 SOFTWARE OF CONTROL 39

5.1.1 Communications 39

5.1.3 PID controller 41

5.2 IMAGE PROCESSING 42

5.2.1 EmguCV: Face detection using Haar Cascades 43

5.2.1.1 About Haar Cascades 43

5.2.1.2 Result 43

5.2.2 Face Identify and Emotion Recognition 43

5.2.2.1 Microsoft Cognitive Services (Project Oxford) 43

5.2.2.2 Face API: Face Identification 43

5.2.2.3 Emotion API 44

5.2.2.4 Result 44

5.2.3 Face Recognition and Emotion Detection Programming Logic Graphic 45

5.2.4 Detect and track object by color using AForge.NET Framework: 46

5.3 MAPPING TRAJECTORY PLANNING 49

5.4 OBSTACLE AVOIDING 50

5.4.1 Ultrasonic sensors 50

5.4.2 Kinect 51

5.5 HUMAN COMMUNICATION 52

5.5.1 Google Speech API 53

5.5.2 Stanford Parser for NET 53

5.5.3 Voice Processing Programming Logic Graphic 55

CHAPTER 7: EXPERIMENTS, DISCUSSION & CONCLUSION 56

7.1 STRAIGHT MOVEMENT TEST 56

7.2 45 DEGREE MOVEMENT TEST 56

7.3 FREE MOVEMENT TEST 56

7.4 DISCUSSION 57

7.5 SUMMARY OF PROJECT 57

7.6 FUTURE WORK 58

CONTENT TABLES

Page

Table 1.1 Project timeline 9

Table 3.1 DH parameter representation 23

Table 4.1 Gear motor features and standard data 31

Table 4.2 Shoulder motor’s specification 33

Table 4.3 Parameters of the control circuit for DC Servo MSDE1 35

Table 4.4 Power usage of equipment on robot 36

Table 7.1 Error for each 10 meter distance (Unit: mm) 56

Table 7.2 Error of 45 degree movement test (Unit: mm) 56

Table 7.3 Error of free movement test (Unit: mm) 56

CONTENT FIGURE

Page Figure 1.1 Estimated operational stock of industrial robots 2013 – 2014 and forecast for

2015 – 2018 2

Figure 1.2 Service robots for professional use 3

Figure 1.3 Robot Fetch 4

Figure 1.4 Robot Relay 5

Figure 1.5 OSHbot 6

Figure 1.6 Adept’s Robots 7

Figure 1.7 ENON 7

Figure 2.1 Von Mises Stress of Robot platform 11

Figure 2.2 Displacement of Robot platform 12

Figure 2.3 Basic Robot cover 13

Figure 2.4 Making mold and composite 14

Figure 2.5 From mold to composite 15

Figure 2.6 Workspace of robot arm 15

Figure 3.1 Four wheeled differentially driven mobile robot 17

Figure 3.2 Wheel moving in a plane 18

Figure 3.3 Coordinate position of each member of the robot 19

Figure 3.4 Differential drive motion 20

Figure 3.5 Kinematic Arm Model of service robot 22

Figure 3.6 Force on robot 27

Figure 4.1 The forces of moving robot 29

Figure 4.2 Forces on the robot’s arms 32

Figure 4.3 Structure of Encoder 34

Figure 4.4 Control circuit for DC Servo MSDE1 35

Figure 4.5 Automation charging dock 37

Figure 5.1 Control system of robot 39

Figure 5.2 Diagram of communication between the control blocks in robot 40

Figure 5.3 Cascade controller 41

Figure 5.4 Block diagram of PID controller 42

Figure 5.5 RC motor control 42

Figure 5.6 Result of face detection 43

Figure 5.7 Person identify and emotion detection 44

Figure 5.8 Face Recognition and Emotion Detection Programming Logic Graphic 45

Figure 5.9 Detect and track object by color 46

Figure 5.10 Model of a pinhole camera 47

Figure 5.11 Tracking and Picking Object Programming Logic Graphic 49

Figure 5.12 Ultrasonic sensor on robot 50

Figure 5.13 Depth stream in image 51

Figure 5.14 Main program and virtual face 52

Figure 5.15 Interaction between robots and humans 53

Figure 5.16 Stanford Parser 54

Figure 5.17 Voice Processing Programming Logic Graphic 55

Figure 7.1 Experiment at the central building 57

experts

The service robotics industry has long been the subject of science fiction, with robot maids, like Rosie from the Jetsons, or cleaners, like Wall-E Or medical assistants and all round helpers like Baymax from Big Hero 6 Baymax was actually modeled on the latest in soft robotics research, but there’s still a big gap between research and commercialization So far there have been very few successful service robotics

companies

Until now, industrial robotics has been the dominant sector for robots, particularly

in the car industry and consumer electronics The industrial robotics sector is worth more than $32 billion dollars in sales, software and service, although there are only 1.5 million industrial robots in the world, compared to more than 10 million Roombas! There has been steady growth in industrial robotics for the last five years and this trend shows no signs of slowing (as Figure 1.1.)

of the total forecast of service robots at the current time

A strongly growing sector will be mobile platforms in general use Service robot suppliers estimate that about 16,000 mobile platforms as customizable multi-purpose platforms use will be sold in the period 2015-2018 Also, sales of logistic systems will increase considerably in this period More than 14,500 units are estimated, thereof, about 13,300 automated guided vehicles About 700 robots for rescue and security applications will be sold between 2015 and 2018 mainly surveillance and security robots Robots for professional cleaning will increase to about 6,650 units in the same period, mainly systems for floor cleaning About 7,800 medical robots will be sold plus 4,000 robots for inspection and maintenance

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These forecasts are, as mentioned earlier, based mainly on individual sales projections by companies and professional organizations It is the opinion of the IFR Statistical Department that the forecasts should be seen as trends concerning market direction rather than actual and precise sales forecasts

The cost of service robotics systems is dropping significantly, putting service robots

in reach of many new market partners But these new market opportunities are also arising due to continual improvements in the safety and compliance of robot systems, alongside their more intuitive user interfaces

Figure 1.2 Service robots for professional use

What is also clear is that none of these robots replace workers, but they supplement work at critical bottle neck times/tasks or improve health outcomes making jobs more attractive, especially in areas where there is a chronic shortage or high turnover of staff

At the end of the day, the value proposition for service robotics is in supporting workers to work better, faster and safer But these new robot assistants offer a tantalizing glimpse of a reshaped work paradigm, where humans gravitate to managerial jobs, leaving more of the menial and repetitive jobs to robots

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1.2 SEVERAL SERVICE ROBOTS

1.2.1 Robot Fetch

Figure 1.3 Robot Fetch

Fetch Robotics builds robot systems for the logistics industry The company was founded in 2014 and is headquartered in San Jose, CA Unveiled in April 2015, the Fetch Robotics system is comprised of a mobile base (called Freight) and an advanced mobile manipulator (called Fetch) Fetch and Freight use a charging dock for autonomous continuous operations, allowing the robots to charge when needed and then continue on with their tasks In addition, the system includes accompanying software to support the robots and integrate with the warehouse environment The robots are designed to work independently alongside human workers, performing repetitive tasks such as warehouse delivery, pick and pack, and more Fetch was awarded a GameChanger award by Robotics Business Review for Best Industrial Productivity Solution

1.2.2 Robot Relay

Savioke is creating autonomous robots for the services industry The company aims to improve the lives of people by developing and deploying robotic technology

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in human environments Savioke was founded in 2013 and is headquartered in Santa Clara, CA Savioke is the creator of Relay, state-of-the-art robot designed for autonomous delivery of items between people Relay’s first application is in the hospitality industry

Figure 1.4 Robot Relay

Relay delivers snacks and amenities to hotel guests, enabling hotel staff to focus on other guests’ needs With successful deployments in the U.S at hotel groups such as Starwood and InterContinental Group, Relay has a proven record of more than five thousand deliveries Savioke (pronounced “savvy oak”) was awarded

a GameChanger award by Robotics Business Review for Best Consumer Solution

1.2.3 OSHbot

When a customer comes in and says, “Hey, I’m looking for nails and paint” then the robot can tell that customer where to find those items It shows customers that it understands what is said It displays on-screen the products that the store has

in stock It has a touch screen so customers can just navigate on the screen and see the pictures of the products and then click on the one that they actually want to see OSHbot then tells the customer that the product is located in Aisle 15, for example, whether it’s in stock and some more information about the item Customers can

click on a button and follow OSHbot to the location of the item in the store

The robot actually guides customers by its own fully autonomous navigation

to the product location Meanwhile customers are following OSHbot, there’s a

screen on the back and that’s for engagement

If customers don’t want to follow the robot, OSHbot can just show them the product location on the map The customer can decide to go on their own

Techi is a new service robot configured to serve food in restaurants

When they released the Lynx, it was an entirely new design optimized for high reliability and flexibility The software also evolved during those years From this newer generation of the OEM platform we created the Lynx Handler SEMI, which

is the semiconductor specific vehicle The Lynx Handler incorporates a collaborative SCARA robot on top of the Lynx mobile base

ENON has a built-in camera that allows high-resolution vision and real-time image upload suited for monitoring and patrolling It can navigate easily through winding corridors using its map localization software and obstacle detection sensors

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The robot also has speech recognition features as well as speech synthesis ability ENON can connect itself to the internet and hence it might have its own pc based remote control pretty soon

1.3 OBJECTIVES

 Design and development of autonomous service robot based on mobile platform

to communicate interactive people in open environment as universities, hotels, buildings

 Robot can communicate with human using image processing and voice processing and provide information to the human

 Robot can move on smooth floor and avoid the statics and dynamics obstacles Robot can find its charge base since the energy is low

1.4 PROCEDURES

In the following chapters we will discuss the steps we took towards fulfillment of

my project In Chapter 2, we will present the mechanical design of all components on robot In Chapter 3, we will explain about kinematics and dynamics of robot mobile platform by analyze the interaction between wheels and ground In Chapter 4, we will discuss about electronics and electrical system we used in robot, for distribute electric

to all electrical equipment In Chapter 5, we will explain the control system for our robot Finally, in Chapter 5, we will summarize our accomplishments and discuss the future of the Service Robot

1.5 SYSTEM OVERVIEW

Receptionist robot, will be located in the public area, serving as a receptionist The robot is designed with 23 degrees of freedom The main components of the robot are platform, body, 2 arms and 2 hands Robot is driven by 4 wheels: 2 driving wheels and

2 passive wheels Actuators are DC motors and the maximum speed of robot is 5 km/h

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1.6 PROJECT TIMELINE (By week)

Table 1.1 Project timeline

 Two wheeled platforms: The differential drive is a two-wheeled drive system with independent actuators for each wheel The benefits of this wheel configuration is its simplicity A differential drive system needs only two motors, one for each drive wheel Often the wheel is directly connected to the motor with internal gear reduction Despite is simplicity, the controllability is rather difficult Especially to make a differential drive robot move in a straight line Since the drive wheels are independent, if they are not turning at exactly the same rate the robot will veer to one side

 Three wheeled platforms: one of the three wheel configuration is synchro drive

The synchro drive system is a two motor drive configuration where one motor rotates all wheels together to produce motion and the other motor turns all wheels to change direction This mechanical guarantee of straight line motion

is a big advantage over the differential drive method where two motors must be dynamically controlled to produce straight line motion Wheel alignment is critical in this drive system, if the wheels are not parallel, the robot will not translate in a straight line

 Four wheeled platforms: Generally stability can be further improved by adding

more wheels, although once the number of contact points exceeds three, the hyper static nature of the geometry will require some form of flexible

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suspension on uneven terrain to maintain wheel contact with the ground A car type drive is one of the simplest locomotion systems in which separate motors control translation and turning, this is a big advantage compared to the differential drive system There is one condition: the turning mechanism must

be precisely controlled A small position error in the turning mechanism can cause large odometry errors This simplicity in in line motion is why this type

of locomotion is popular for human driven vehicles

Figure 2.1 Basic Robot cover

To build an autonomous mobile robot, which will be used for different tasks in

an indoor environment With the knowledge we picked up in some wheeled mobile platform above, we decided to design a new mechanical platform conform our requirements that forms the base of the entire robot The robot is shown in Fig 2.1

The platform we want to design is shown in Fig 2.2 Because of Robot’s height (about 1330mm), we decided to take a two wheeled platform with two

Figure 2.2 Mobile robot platform

2.2 MAKING MOLD AND COMPOSITE

2.2.1 Design requirement

The goal of this project is to make and run a Robot that can serve everybody

So It can be interacted, mobility and less occupied area The requirements were selected by looking at the different features implemented by other robot designs, and selecting the common minimum features we deemed necessary for most cooperative AI systems The following list shows the selected requirements with an explanation of each point

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 Cheap – In research and create Robot for final project, it doesn’t have any donation So we must consider which materials is the best suit with our project and finance

 Lightweight – For a long-life battery and mobility Optimization space of the cover is considered very carefully, for robot can contains many components inside

 Durable – In duty of serve everybody Many situations that we can’t predict

so Robot must have prepare for any situation

 Expandability - Since we can not predict all of the hardware requirements for all experiments that researchers want to conduct, the only logical step if

we want the price to be low is to enable specific hardware to be added when needed This requirement also works great with the open source model If a researcher requires a specific sensor or actuator she is free to design and add this feature at any time The extension may then be freely adopted by other

researchers that have similar requirements at a later date

2.2.2 Choosing and making robot cover

Figure 2.3 Robot in virtual world

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For all of the reason that given above Our team decided to choose Composite for making Robot cover It’s a mixture of polyester and fiber glass Very suit with our finance and easy to use

The average of height of Vietnamese is 1.62 meter of men and 1,468 meter of women To people can interact with Robot, the touch screen must be within easy reach

 The mold is made from foam and plaster Foam inside and plaster outside (Fig 2.4)

Figure 2.4 Making mold from foam and plaster

 When achieving sufficiently fry of plaster, we mix polyester, fiber glass and then coated on plaster surface

 Mixture of polyester and fiber glass is called composite Composite will dry after a half-day

 After released mold We have the basic cover, then we must make the surface smooth for paint (Fig 2.5 a & b)

to the information supplied by camera systems automatically or through interaction with the operator

is concerned with the rotational movement of each wheel's axis

The basic element of every mobile robot is the wheel, which can be simplified

to the kinematics of a rolling disk Kinematic parameters include radius of the wheel, length of the wheel axle, location of the mass center, etc The kinematic model of this thesis is simplified and is similar to the model of a unicycle Here, the wheeled robot is a 2-DOF mobile robot, a three wheeled robot with two drive wheels and one castor wheel The states of the mobile robot with differential driving mechanism change according to the two wheel velocities, when the mobile robot moves from current location to where the robot is to be located

3.1.2 Kinematics

3.1.2.1 Representing Robot's Position

Kinematic model of the wheeled robot assumes that the robot is placed on

a plane surface and the contacts between the wheels of the robot and the rigid horizontal plane have pure rolling and non slipping conditions during the motion This nonholonomic constraint can be written as

The center position of the robot is expressed in the inertial coordinate frame (x,y,θ) Here x and y are the position of the robot and θ is the orientation of the robot with respect to inertial frame Suppose the robot moves on a plane with linear and angular velocities, the state vector can be expressed asq  ( x y q )T The differential drive mobile robot has two drive wheels which are independently driven for getting desired path The robot’s motion on linear trajectories is given by constant velocities of the wheels and the motion on

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circular trajectories is determined by the difference between the angular velocities of the two drive wheels The state of the robot is defined by its position and orientation and by the speeds of the two drive wheels (x, y, θ, φl, φr) A simple structure of differentially driven three wheeled mobile robot is shown in Figure 3.1 For the robot’s movement, the linear velocity υ and the angular velocity ϴ are chosen by the path planner These values are converted into the velocities of the left and right wheels The kinematic model is formulated by using these wheel speeds and geometric constraints of the vehicle also

Figure 3.1 Four wheeled differentially driven mobile robot

3.1.2.2 Kinematic Wheel Model

To simplify the analysis of the rolling and contact constraints, the assumptions are made such that the wheels remain vertical to the plane of motion and have a point or line contact to the ground plane Likewise, the model will assume that there is no sliding motion orthogonal to the rolling motion at the wheel's single point of contact The wheel coordinate frame is positioned at the center of the wheel, on the axle At times it may be convenient to define this frame at the wheel contact point and it may be useful to have it rotate with the wheel Each wheel has its own frame as shown in Figure 3.2

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When the wheel is rolling along a curved line, the linear velocity of its center (x, y, θw, w) in the base coordinate system OXY depends on the wheel orientation in the plane defined by the angle θw

x

 w

Figure 3.2 Wheel moving in a plane

Figure 3.2 are called nonholonomic WMR and represented by Equations (3.2) and (3.3) The angular speed of each wheel is calculated by

The methodology of the kinematic model of the robot is to develop a model

of the robot's motion as a function of time that will predict the position and orientation of the robot due to wheel velocities and initial body pose The kinematic model is conducted through a two step process that involves determining the position and velocity of the robot body followed by analysing the position, orientation and wheel velocities of the robot

Each member of the robot is constructed on a two dimensional, Cartesian based coordinate system known as the global frame (Figure 3.3) For a robot with known dimensional constraints on the body, the position of the body can

be defined in the global frame (X, Y) by the location of the center of axle and

w

r

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the angle θ between the two angular positions A rotation matrix Rm is used to map the motion of the body in the global frame through a rotation about the Z-axis

Figure 3.3 Coordinate position of each member of the robot

Given the rotational speeds of the left and right wheels, their respective radii

r and the distance l/2 to the center of the robot, the model can predict the velocity of the robot For this differentially driven mobile robot, the two drive wheels are fixed so that a positive angular rotation produces a positive displacement along the axis Rolling and sliding constraints for a fixed standard wheel ensures that all rotational motion exerted by the wheels produce

an accompanied translation and rotational motion of the robot In case of differential drive, to avoid slippage and have only a pure rolling motion, the robot must rotate around a point that lies on the common axis of the two driving wheels This point is known as the instantaneous center of rotation (ICR) By changing the velocities of the two wheels, the instantaneous center of rotation will move and different trajectories will be followed (Figure 4.4)

Figure 3.4 Differential drive motion

From the model of each wheel, the robot translational velocity is the average linear velocity of the wheels

xcos sin l/ 2

ycos sin l / 2

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If υl = υr the then the radius R is infinite and the robot moves in a straight line (Figure 4.5 (a)) For different values of υl and υr the mobile robot does not move in a straight line but follows a curved trajectory around a point located at

a distance R from the centre of rotation, changing both the robot's position and orientation If υl = -υr then the radius R is zero and the robot rotates around its center

The motion of the robot could be described with two modes, either pure rotation or pure translation The path consists of circular arcs with a specified radius and turning angle and a straight tangent line The circular arc and straight tangent line are used to avoid stoppage and provide continuity for the robot To achieve controlled trajectory, the linear and angular velocities υ and ω are calculated by Equation (4.17) and (4.18) through fuzzy logic controller

00

x y

x y

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3.1.3 Kinematics Robot arm

Figure 3.5 Kinematic Arm Model of service robot

This manipulator has for degrees of freedom (DOF) and located at the left and right of the robot Manipulator is necessary to perform humans-like motion for robots Especially, it requires grasping action for service robot as well There are two motors on the shoulder (Roll q1, Pitch q2), one motor on the elbow (Pitch q3), and one motor on the wrist (Roll q4) The end effecter also has one motor

to drive the worm gear that controls the gripper The dimensions of robot are shown

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respectively The joint variables are denoted by qi In the case of prismatic joint, qirepresents the displacement, similarly qi represent the angle of rotation for the revolute joint

Obtain the DH parameters: To describe the kinematics of any robot, four parameters are given for each link Li, Di, θi, αi where two of them described the link, and the others describe the connection with other links In the case of revolute and prismatic robots, the variable qi and Di are denoted as joint variable DH parameter is computed manually or using computer programs such as MATHEMATICA or MATLAB programs Table (3.1) shows the DH parameters for i-link robot manipulator

Table 3.1 DH parameter representation

A  Rot(z, q ) Trans(z, D ) Trans(x, L ) Rot(x,  ) (3.12) After the homogeneous matrix has been defined for each link of the robot manipulator, simple solution to find the total homogeneous matrix for robot manipulator with i-links is accomplished by multiplying all the transformation matrices from A1 to Ai as follows:

l l A

x y z