Ironman Project - Design Of Electro-Mechanical Muscle For Elbow Exoskeleton Robot.

I

“I hereby declare that I have read through this report entitle “Ironman project - Design of electro-mechanical muscle for elbow exoskeleton robot” and found out that it has comply the partial fulfillment for awarding the degree of Bachelor of

Mechatronics Engineering”

Signature : ...

Supervisor’s Name : Encik Nur Latif Azyze Bin Mohd Shaari Azyze

II

IRONMAN PROJECT - DESIGN OF ELECTRO-MECHANICAL MUSCLE FOR ELBOW EXOSKELETON ROBOT

LIM CHEE AN

A report submitted in partial fulfillment of the requirements for the degree Of Bachelor of Mechatronic Engineering

Faculty of Electrical Engineering

UNIVERSITI TEKNIKAL MALAYSIA MELAKA

III

I declare that this report entitle “Ironman project - Design of electro-mechanical muscle for elbow exoskeleton robot” is the result of my own research except as citied in the reference. The report has not been accepted for any degree and is not

concurrently submitted in candidature of any other degree.

Signature : ...

Name : Lim Chee An

IV

ACKNOWLEDGEMENT

First and foremost, I would like to express my heartily gratitude to my supervisor, Encik Nur Latif Azyze Bin Mohd Shaari Azyze for the guidance and enthusiasm given throughout the progress of this project. My appreciation also goes to my family who has been so tolerant and supports me all these years. Thanks for their encouragement, love and emotional supports that they had given to me. Nevertheless, my great appreciation dedicated to my colleague and those whom involve directly or indirectly with this project. Without their continued support and interest, this project would not have been same as presented here.

V

ABSTRACT

This project is to design an actuation system of electro-mechanical muscle for elbow exoskeleton robot. The objectives is to design and fabricates a low complexity and low engineering and construction cost of a 1 DOF motion prototype upper arm(elbow joint) training/rehabilitation (exoskeleton) system. This project is mainly concerned on DC motor speed control system by using microcontroller PIC 16F877A. It is a open-loop real time system, where gyro sensor is attach to the end of elbow arm to collect angular velocity data. Pulse Width Modulation (PWM) technique is used where its signal is generated in microcontroller. The PWM signal will send to motor driver to vary the voltage supply to motor to maintain a constant speed. Through the project, integrating humans and robotic machines into one system offers multiple opportunities for creating assistive technologies that can be used in biomedical. The scope is integration of a human arm with a powered exoskeleton (orthotic device) and its experimental implementation in an elbow joint, naturally controlled by the human. The basic purpose of the exoskeleton system as an assistive device is to amplify the moment generated by the human muscles relative to the elbow joint, while manipulating loads. The exoskeleton‘s elbow joint was powered by a dc gear motor (WD21100) with a stall torque of 20 Nm equipped with a internal gearbox. The system integrated PIC and gyro to measure angular velocity at the human arm/exoskeleton and external load/exoskeleton interfaces. The exoskeleton structure under study was one DOF mechanism, corresponding to the arm limbs and joints, which were mechanically linked (worn) by the human operator. In the present setup the elbow joint was kept fixed at given positions and the actuator was mounted on the exoskeleton elbow joint. The operator manipulated an external weight, located at the exoskeleton tip, while feeling a scaled-down version of the load. The remaining external load on the joint was carried by the exoskeleton actuator. At the end of the project, a 1 DOF prototype upper arm (elbow joint) training/physiotherapy (exoskeleton) system for experimental purpose was developed and fabricated.

VI

ABSTRAK

Projek ini adalah untuk mereka-bentuk suatu elektro-mekanikal sistem untuk menggerakkan otot siku dalam exoskeleton. Objektif adalah untuk mereka satu prototaip yang mempunyai kerumitan dan kos kejuruteraan pembinaan yang rendah bagi 1 DOF sistem latihan / pemulihan (exoskeleton) untuk bahagian siku. Projek ini adalah berkaitan pada sistem kawalan kelajuan motor dengan menggunakan mikropengawal PIC 16F877A. Ia adalah satu sistem gelung buka, di mana sensor Gyro adalah melampirkan pada hujung lengan siku untuk mengumpul data kelajuan sudut. Pemodulatan lebar denyut (PWM) digunakan di mana isyarat yang dijana dalam mikropengawal akan hantar ke pengawal motor untuk mengubah bekalan voltan kepada motor untuk mengekalkan kelajuan yang tetap. Melalui projek ini, mengintegrasikan manusia dan exoskeleton ke dalam satu sistem untuk mewujudkan teknologi bantuan yang boleh digunakan dalam bioperubatan. Skop adalah integrasi lengan manusia dengan exoskeleton berkuasa (peranti ortotik) dan pelaksanaan eksperimen di siku dan dikawal secara semulajadi oleh manusia. Tujuan asas sistem exoskeleton sebagai alat bantuan untuk menguatkan tenaga yang dihasilkan oleh otot manusia berbanding dengan sendi siku, semasa memanipulasi beban. Siku exoskeleton telah dikuasai oleh gear motor dc (WD21100) dengan tork sebanyak 20 Nm dilengkapi dengan gear dalaman motor. Sistem bersepadu PIC dan Gyro untuk mengukur kelajuan sudut di lengan manusia dan lengan manusia yang dibantu oleh exoskeleton. Struktur exoskeleton bawah kajian adalah satu mekanisme DOF, bersamaan dengan siku manusia dan exoskeleton yang dipasang dan mengendali oleh manusia. Dalam persediaan ini , bahagian siku ditetapkan pada kedudukan yang diberikan dan exoskeleton dipasang pada siku tangan. Exoskeleton dimanipulasi dengan tambahan beban yang terletak di hujung exoskeleton dan telah dijalankan oleh motor exoskeleton itu. Pada akhir projek, , satu 1DOF sistem latihan / pemulihan (exoskeleton) untuk bahagian siku bagi tujuan eksperimen telah dicipta dan direka.

VII TABLE OF CONTENT

TITLE PAGE

ACKNOWLEDGEMENT ... IV ABSTRACT ... V ABSTRAK ... VI TABLE OF CONTENT ... VII LIST OF TABLE ... IX LIST OF FIGURE ... X

CHAPTER 1 ... 1

INTRODUCTION ... 1

1.1 Background ... 1

1.2 Problem statement ... 2

1.3 Objective of Project ... 2

1.4 Scope of Project ... 3

CHAPTER 2 ... 4

THEORY AND LITERATURE REVIEW ... 4

2.1 Introduction ... 4

2.1.1 Exoskeleton robot ... 5

2.1.2 Elbow complex ... 5

2.1.3 Classification of Upper-Limb Exoskeleton Robots ... 6

2.1.4 Actuation System ... 7

2.1.5 Power Transmission System ... 8

2.1.6 Speed Control by Using PWM ... 8

2.1.7 Speed Control by Full H Bridge Motor Driver ... 10

2.1.8 Speed Control by using MOSFET and delay ... 10

2.2 Theory ... 11

2.2.1 Hardware ... 11

2.2.1.1 Microcontroller ... 12

2.2.1.2 PIC microcontroller start-up kit ... 12

2.2.1.3 DC Motor ... 13

2.2.1.4 Gyro meter sensor ... 15

VIII

2.2.2.1 MikroC ... 17

2.2.2.2 Proteus ... 17

2.2.2.3 Arduino Software ... 18

2.2.2.4 Solid Works ... 19

CHAPTER 3 ... 20

METHODOLOGY ... 20

3.1 Introduction ... 20

3.2 Flowchart of project... 21

3.3 Literature Review / Technical Research ... 23

3.3.1 Hardware ... 23

3.3.1.1 Designing Electronics Circuit ... 23

3.3.1.2 PIC Microcontroller ... 24

3.3.1.3 Gyro sensor ... 24

3.3.1.4 Power Supply Circuit ... 26

3.3.1.5 DC Motor Driver ... 27

3.3.1.6 Relay ... 28

3.3.1.7 DC motor ... 29

3.3.1.8 Loading Unit (weight plate 1kg &2kg) ... 30

3.3.2 Software ... 31

3.3.2.1 MikroC and Proteus ... 31

3.3.2.2 Sensor position setup ... 34

3.3.2.3 Solid Works ... 36

CHAPTER 4 ... 38

RESULT ... 38

4.1 Introduction ... 38

4.2 Hardware Result ... 38

4.3 Experiment: Determine Relationship of angular rate and angle of movement ... 39

4.3.1 Experiment 1: Payload Experiment which using human arm ... 39

4.3.2 Experiment 2: Payload Experiment which elbow arm lever actuated by dc motor ... 41

CHAPTER 5 ... 49

ANALYSIS AND DISCUSSION OF RESULT ... 49

5.1 Introduction ... 49

IX

5.2 Discussion ... 54

CHAPTER 6 ... 56

CONCLUSION AND RECOMMENDATION ... 56

6.1 Conclusion ... 56

6.2 Recommendation ... 57

REFERENCES ... 58

APPENDIX ... 60

LIST OF TABLE TABLE PAGE Table 3.1 Pin connection of PIC16F877A for DC motor speed control system ... 24

Table 3.2: Logic function of motor driver ... 28

Table 3.3: Performance of motor (WD21100) ... 30

Table 3.4: direction control of DC motor ... 33

Table 3.5: Result for DC motor speed controlling ... 34

Table 4.1: Angle of Movement, θ (°) versus Angular velocity of lower arm (elbow joint), , (rad/sec) ... 41

Table 4.2: Angle of Movement, θ (°) versus Angular velocity of lower arm (elbow joint), , (rad/sec) for each motor speed condition - Without load ... 43

Table 4.3: Angle of Movement, θ (°) versus Angular velocity of lower arm (elbow joint), , (rad/sec) for each motor speed condition - With load (1kg weight plate) ... 44

Table 4.4: Angle of Movement, θ (°) versus Angular velocity of lower arm (elbow joint), , (rad/sec) for each motor speed condition - With load (2kg weight plate) ... 45

Table 4.5: Aaverage of Angular velocity, , (rad/sec), Force, F (N), Torque, T (Nm) for each angle of human hand elbow joint movement ... 47

Table 4.6: Desired Force/Torque for Elbow Joint which assists by dc motor (only consider medium speed -200) ... 48

X LIST OF FIGURE

FIGURE PAGE

Figure 2.1: Human Upper Limb Motion Assist Exoskeleton Robots. [2] ... 5

Figure 2.2: Elbow complex and elbow motions. (a) Elbow anatomy. (b) Elbow flexion/extension motion. (c) Forearm supination/pronation motion. [3] ... 6

Figure 2.5 Joint axis drive system. [5] ... 8

Figure 2.6: PWM (Pulse Width Modulation) [5] ... 9

Figure 2.7: Relation of supply voltage with motor speed [5] ... 9

Figure 2.8: Full H bridge motor drive [5] ... 10

Figure 2.9: A power-switching element (bipolar transistor, MOSFET) used to vary speed of motor. [5] ... 10

Figure 2.10: wiring diagram of delay [5] ... 11

Figure 2.11 Variety of microcontrollers available in the market ... 12

Figure 2.12: SK40C Start-up Kit ... 13

Figure 2.13: Construction of DC motor. [5] ... 13

Figure 2.14: Relationship between motor speed and torque for a DC motor. [5] ... 14

Figure 2.15: Effect of changing the applied voltage. [5] ... 14

Figure 2.16: Relationship among speed, torque, and output power. (a) Low speed. (b) Moderate speed. (c) High speed. [5]... 14

Figure 2.17 Joint axis drive system. [5] ... 15

Figure 2.18: Gyroscope Model [13] ... 15

Figure 2.19: (a) Top view of pin diagram and (b) axis definition of gyro sensor (ITG-3200) [13] ... 16

Figure 2.20: MikroC program window ... 17

Figure 2.21 Proteus program windows ... 18

Figure 2.22: Arduino Programming IDE ... 18

XI

Figure 3.1: Methodology Flowchart ... 21

Figure 3.2: K-Chart ... 22

Figure 3.3 Block diagram of DC motor speed control system ... 22

Figure 3.4: Integration of Circuit Board ... 23

Figure 3.5: PIC16F84A IC Pin Diagram ... 24

Figure 3.6: Arduino UNO top view [13] ... 25

Figure 3.7: Schematic of Arduino and Sensor Board Connection [13] ... 25

Figure 3.7 IC LM7805 ... 26

Figure 3.8 Schematic circuit of +5V power supply ... 26

Figure 3.10 DC motor operational controls [5] ... 28

Figure 3.11: Motor (WD21100) chosen for this project [12] ... 29

Figure 3.12: Mechanical data sheet of motor (WD21100) [12] ... 30

Figure 3.13: 1kg & 2kg weight plate [9] ... 30

Figure 3.14: Schematic of overall project ... 31

Figure 3.15 PWM output ... 32

Figure 3.16: Converting a PWM signal to DC motor voltage input: (a) Maximum forward speed, (b) 75% forward speed, (c) 50 % forward speed, (d) 20% reverse speed. ... 34

Figure 3.17: Sensor placing position on arm ... 35

Figure 3.18: block diagram of experimental setup ... 35

Figure 3.19: Flowchart for program gyro ... 35

Figure 3.20: Data send and display on PC... 36

Figure 3.21: Four view viewport with 3rd _{angle projection of elbow arm for experimental} purpose ... 37

Figure 4.1: Hardware parts ... 38

Figure 4.2: (a) Elbow movement (b) Location to attached sensor and weight (c) Angle of elbow movement ... 40

XII Figure 4.3: Electro-mechanical elbow orthotics ... 42 Figure 4.4: Position of elbow Arm Movement of Lower Arm (Elbow Joint) ... 42 Figure 5.1: Tri-axial angular rate for different load at each angle of movement ... 49 Figure 5.2: The definitions of the gyro sensor attach on reference frame. The unit y-axis is defined along the segment, upwards, the z-axis point in dorsal direction and the x-axis laterally. ... 50 Figure 5.3: Tri-axial gyroscope raw data for different load which assist using dc motor. .. 51 Figure 5.4: Result of Average of angular velocity, force, and torque for each angle of elbow movement ... 52 Figure 5.5: Result of Average of angular velocity, force, and torque for each angle of elbow movement ... 53

LIST OF APPENDICES

TITLE PAGE

Appendix A - 3D view of a 1 DOF prototype upper arm (elbow joint)

training/physiotherapy (exoskeleton) system ... 60 Appendix B - MikroC Coding written for DC Motor: ... 61 Appendix C - Arduino Coding written for gyroscope: ... 62

1

CHAPTER 1

INTRODUCTION

1.1 Background

An exoskeleton is an external structural mechanism whose joints correspond to those of the human body. It is worn by the human and the physical contact between the operator and the exoskeleton allows direct transfer of mechanical power and information signals. This project is about to design an actuation system of electro-mechanical muscle for elbow exoskeleton robot. To design a simple mechanism for dc motor as actuator of elbow exoskeleton and fabricate a low cost actuator and driving system for elbow joint, a direct current (DC) motors have variable characteristics and can provide a high starting torque have been choose. It is important to make a motor driver to control the speed of DC motor in desired speed, where the load on the DC motor varies over a speed range. To make the motor operate, first must make the program on PIC. The PWM (Pulse Width Modulation) function of PIC is used for the electric current control to drive a motor. In utilizing the exoskeleton as a human power amplifier, the human provides control signals for the exoskeleton, while the exoskeleton actuators provide most of the power necessary for performing the task. The human becomes a part of the system and applies a scaled-down force compared with the load carried by the exoskeleton. For example, if the exoskeleton manipulates an object, the human may feel 10% of the load while the exoskeleton carries 90% of the load. The main purpose of the powered exoskeleton system is to amplify the load carrying capacity of a healthy operator; however, it can also be used as an upper limb orthotic for physically impaired humans At the end of this project, a Gyro meter sensor for detecting the angular rate to find desired force and torque on elbow movement have produced. The measurement of arm movement is important for load

2 estimation. Gyroscopes measure angular velocity, which can be used to estimate a change in orientation.

1.2 Problem statement

1. Complicated and hard to use by patient/aged people for existing mechanism of elbow rehabilitation exoskeleton.

2. Expensive cost in mechanical structure of elbow joint actuator for weight training. 3. Complexity of comparison method of kinematic and dynamic data for elbow

movement in active mode and passive mode.

1.3 Objective of Project

Basically, these projects are listing three main objectives. The objectives are a guideline and goal in order to complete this project. This project is conducted to achieve the following objectives:

1. Design and fabricates a low complexity and low engineering and construction cost of a 1 DOF motion prototype upper arm(elbow joint) training/rehabilitation (exoskeleton) system

2. To design a dc motor system for electro-mechanical structure of elbow joint

3. To provide a simple method for force/torque measurement using Gyro meter sensor system.

3 1.4 Scope of Project

In order to achieve the objective of the project, there are several scope had been outlined. There are two scopes in this project which is hardware development and software development.

For the first scope which is hardware development are three main sections and those section are:

1. Design and fabricate an actuation system for elbow which using dc motor as experimental purpose.

2. Design a speed control DC motor circuit using PIC Microcontroller

For the second scope which is the software development, there are two main sections and that section are:

1. To simulate the dc motor control system using Proteus software.

2. Program and communicate with an Arduino board to collect measurement data from gyro sensor.

3. Design mechanical structure using solid work software of 1 DOF prototype upper arm training/physiotherapy (exoskeleton) system for experiment purpose.

4

CHAPTER 2

THEORY AND LITERATURE REVIEW

2.1 Introduction

This chapter introduces and explains the source of idea for design, concept, specification and other information that related to the project. It is found base on the product that have been develop or research by institutions before this project and some of them may be available in market nowadays. This study should be done to ensure that project is being developed to run efficiently while achieving the desired objective. All the theories of all devices and compatible software that are used in this project will also be discussed in this chapter.

Outline

this chapter includes the study of exoskeleton robot, elbow complex, classification of upper-limb exoskeleton robots, actuation system, power transmission system, dc motor, speed control by using PWM, full H bridge motor drive, delay and principle of gyro meter sensor‘s operation. It‘s also included some study about all related hardware and software that are used during process of completing this project, like microcontroller, PIC start-up kit, dc motor, gyro sensor, Proteus, MikroC, Arduino and Solid works.

5 2.1.1 Exoskeleton robot

An exoskeleton robot is a wearable motion assist device consisted with actuators and sensors whose joints correspond to those of the human body .It is worn by the human and the physical contact between the user and the exoskeleton allows direct transfer of mechanical power and information signals. In utilizing the exoskeleton robot, the user provides the control signal for the exoskeleton, while the exoskeleton actuator provides most of the power necessary for performing the power assist [1]. Figure 2.1 show a 7 DOF exoskeleton robot developed at University of Washington, USA. [2]

Figure 2.1: Human Upper Limb Motion Assist Exoskeleton Robots. [2]

2.1.2 Elbow complex

The elbow complex allows 2DOF, flexion/extension and supination/pronation .In the elbow flexion motion, the angle between the forearm and the upper arm is decreased where as in extension motion the angle is increased [see Fig. 2.2(b)]. Average movable ranges of the human elbow are 5 degrees in extension, 145 degrees in flexion. Forearm supination and forearm pronation each has average movable range of 90 degrees [3].

6

Figure 2.2: Elbow complex and elbow motions. (a) Elbow anatomy. (b) Elbow flexion/extension motion. (c) Forearm supination/pronation motion. [3]

2.1.3 Classification of Upper-Limb Exoskeleton Robots

Upper-limb exoskeleton robots can be classified in several ways considering features of their mechanical designs and/or control methods. It‘s classified according to [4]:

a) Applied segment of the upper-limb

 Classified as hand exoskeleton robot, forearm exoskeleton robot, upper-arm exoskeleton robot or combined segment exoskeleton robot.

b) DOF

 Classified according to the number of active or passive joints or in other words DOF as 1DOF, 2DOF, 3DOF, etc.

c) power transmission methods

 Gear drive, cable drive, linkage mechanism or other method. d) Applications of the robot

 Classified according to the intended purpose namely rehabilitation robots, assistive robots, human amplifiers, haptic interfaces or other uses.

e) Control methods

 Impedance control, force control, fuzzy-neuron control or other control methods.

7

Figure 2.3: Classification of exoskeleton robots. (a) Methods of classification of upper-limb exoskeleton robots. [4]

Figure 2.4: Classification of exoskeleton robots. (b) A classification of upper-limb exoskeleton robots based on the actuators used in mechanical designs. [4]

2.1.4 Actuation System

Several actuation technologies are available for actuating a system. Electric motors, pneumatic actuators, hydraulic actuators, ultrasonic motor, IC engines, static electric actuators, and shape memory alloy are some of them. DC motors are the commonly used actuator for upper-limb exoskeleton robots. It has high speed and precision. Therefore, DC motors can be used to actuate upper-limb exoskeleton robots from advanced motion control methods. However, gears are required to obtain required torques for upper-limb motions using less weight and small sized DC motors. Otherwise heavy motors causing a burden for the function of upper-limb exoskeleton robot have to be used for generating required upper-limb joint torques. [4]

8 2.1.5 Power Transmission System

Power transmission method of upper-limb exoskeleton robot depends on the actuator. With an electric motor, gear drives, cable (wire) drives and/or linkage mechanisms can be used to transmit power. Although electric motors can be used as direct drives, they are rarely used as direct drive in upper limb exoskeleton robots, since the size of the existing motors which can generates required upper-limb joint torques are rather large. Gear drives and/or cable drives have commonly been used in present upper-limb exoskeleton robots. Gear drives do not create slip as in the case of some cable drives. Also bevel gear drives can be used to transmit power between non-parallel axes. Therefore, compact joints can be designed for the upper-limb exoskeleton robot. Compact joints are important to the upper-limb exoskeleton robots used in daily motion assist. Backlash is inherent in gear drives. Also it is difficult to obtain precise back-drivability with gears. Therefore, gear drives should be carefully designed for the upper-limb exoskeleton robots. Since gear drives cannot be used to transmit power over relatively long distances, motors should be fixed near the actuated axis when gear drives are used for power transmission. [4]

Figure 2.5 Joint axis drive system. [5]

2.1.6 Speed Control by Using PWM

DC motor speed is controlled by controlling its driving voltage. In many applications, a simple voltage regulation would cause lots of power loss in the control circuit, so a PWM method is used in many DC motor-controlling applications. In basic PWM method, the operating power to the motors is turned on and off to modulate the current to the motor. The ration of on time to off time is what determines the speed of the motor. A PWM circuit can be implemented by using discrete components. However, this

9 approach cannot provide the desired flexibility and controllability is expensive. A better implementation method for PWM circuitry is to use the PWM functions available in many microcontrollers today. Most of the PIC 16 devices have PWM functions. Controlling the speed of the motor is an important area to be considered. The speed of motor is directly proportional to the DC voltage applied across its terminals. A PWM (Pulse Width Modulation) wave can be used to control the speed of the motor. Here the average voltage given or the average current flowing through the motor will change depending on the ON and OFF time of the pulses controlling the speed of the motor. The duty cycle of the wave controls its speed.

Figure 2.6: PWM (Pulse Width Modulation) [5]

As the amount of time that the voltage is on increases compared with the amount of time that it is off, the average speed of the motor increases and vice versa. The time that it takes a motor to speed up and slow down under switching conditions is depends on the inertia of the rotor (basically how heavy it is), and how much friction and load torque there is. Figure 2.7 shows the speed of a motor that is being turned on and off fairly slowly:

10 2.1.7 Speed Control by Full H Bridge Motor Driver

A full bridge circuit is shown in the diagram below. Each side of the motor can be connected either to battery positive, or to battery negative and through a on-off switching MOSFET (Metal Oxide-Semiconductor Field Effect Transistor) which can turn very large currents on and off under the control of a low signal level voltage. Only one MOSFET on each side of the motor must be turned on at any one time otherwise they will short out the battery and burn out.

Figure 2.8: Full H bridge motor drive [5]

To make the motor go forwards, Q4 is turned on, and Q1 has the PWM signal applied to it. Meanwhile, to make the motor go backwards, Q3 is turned on, and Q2 has the PWM signal applied to it.

2.1.8 Speed Control by using MOSFET and delay

Figure 2.9: A power-switching element (bipolar transistor, MOSFET) used to vary speed of motor. [5]

11 The purpose of motor speed control is to control the speed, direction of rotation or position of the motor shaft. This requires that the voltage applied to the motor is modulated in some manner. Understanding the ratings of the motor is an important step in the process as it is often the corner points of operation that will determine the choice of the power switching element. The startup current (sometimes given as stall current or locked-rotor current) value can be up to three times the value of the steady-state operating current. This is where the power-switching element (bipolar transistor, MOSFET) is used in this project. By turning the power-switching elements on and off in a controlled manner, the voltage applied to the motor can be varied in order to vary the speed or position of the motor shaft. A relay (or magnetic relay or magnetic switch) is a switch operated by an electromagnetic action. The relatively small current flowing through a coil of an electromagnet inside pulls (or pushes) a lead contact to make (or break)a circuit. No current would push (or pull) back the contact by the mechanical spring attached to the mechanism

Figure 2.10: wiring diagram of delay [5]

2.2 Theory

This section includes the study about all related hardware and software that are used during process of completing this project. This theory section is divided into hardware and software and will be explain briefly.

2.2.1 Hardware

There are several hardware or electronics component that are used in this project which are microcontroller, PIC microcontroller start-up kit, DC motor and gyro sensor .Brief explanations are given about all these hardware in the next proceeding section

12 2.2.1.1 Microcontroller

Basically, microcontroller is a small computer on a single integrated circuit containing a processor core, memory, and programmable input/output peripherals. The PIC microcontroller consist of over 400 variations consists of a number of memory configurations, amount of support hardware required, different I/O pin arrangements, packaging, and available peripheral functions.

Microcontroller input and output pins are available to communicate with the outside world or peripheral devices such as sensor, motor and LCD. The number of I/O pins per controllers varies greatly, plus each I/O pin can be programmed as an input or output (or even switch during the running of a program). The load (current draw) that can be driven by each pin is usually low. Therefore, it is important to use a driver chip or transistor buffer if the output is expected to be a heavy load.

There are a lot of advantages in using microcontroller such as the low cost factor which makes it very popular among students and hobbyists. Another advantage of microcontroller is the variety of programming software available and most of them are distributed as freeware such as MPLAB, MikroC, PICC and CCS.

Figure 2.11 Variety of microcontrollers available in the market 2.2.1.2 PIC microcontroller start-up kit

For this project, 40 pins PIC start-up kit or SK40C will be used as a main board which is come with a proper feature for this project. One of the features is compact, powerful, flexible and robust start-up platform which is very suitable for this project as a compact and portable camera application tool. SK40c also come with 33 I/O label pins for interface process between PIC and external component. Connector for UIC00A (low cost

Figure 2.3: Classification of exoskeleton robots. (a) Methods of classification of upper-limb exoskeleton robots. [4]

Figure 2.4: Classification of exoskeleton robots. (b) A classification of upper-limb exoskeleton robots based on the actuators used in mechanical designs. [4] 2.1.4 Actuation System

Several actuation technologies are available for actuating a system. Electric motors, pneumatic actuators, hydraulic actuators, ultrasonic motor, IC engines, static electric actuators, and shape memory alloy are some of them. DC motors are the commonly used actuator for upper-limb exoskeleton robots. It has high speed and precision. Therefore, DC motors can be used to actuate upper-limb exoskeleton robots from advanced motion control methods. However, gears are required to obtain required torques for upper-limb motions using less weight and small sized DC motors. Otherwise heavy motors causing a burden for the function of upper-limb exoskeleton robot have to be used for generating required upper-limb joint torques. [4]

2.1.5 Power Transmission System

Power transmission method of upper-limb exoskeleton robot depends on the actuator. With an electric motor, gear drives, cable (wire) drives and/or linkage mechanisms can be used to transmit power. Although electric motors can be used as direct drives, they are rarely used as direct drive in upper limb exoskeleton robots, since the size of the existing motors which can generates required upper-limb joint torques are rather large. Gear drives and/or cable drives have commonly been used in present upper-limb exoskeleton robots. Gear drives do not create slip as in the case of some cable drives. Also bevel gear drives can be used to transmit power between non-parallel axes. Therefore, compact joints can be designed for the upper-limb exoskeleton robot. Compact joints are important to the upper-limb exoskeleton robots used in daily motion assist. Backlash is inherent in gear drives. Also it is difficult to obtain precise back-drivability with gears. Therefore, gear drives should be carefully designed for the upper-limb exoskeleton robots. Since gear drives cannot be used to transmit power over relatively long distances, motors should be fixed near the actuated axis when gear drives are used for power transmission. [4]

Figure 2.5 Joint axis drive system. [5] 2.1.6 Speed Control by Using PWM

DC motor speed is controlled by controlling its driving voltage. In many applications, a simple voltage regulation would cause lots of power loss in the control circuit, so a PWM method is used in many DC motor-controlling applications. In basic PWM method, the operating power to the motors is turned on and off to modulate the current to the motor. The ration of on time to off time is what determines the speed of the motor. A PWM circuit can be implemented by using discrete components. However, this

approach cannot provide the desired flexibility and controllability is expensive. A better implementation method for PWM circuitry is to use the PWM functions available in many microcontrollers today. Most of the PIC 16 devices have PWM functions. Controlling the speed of the motor is an important area to be considered. The speed of motor is directly proportional to the DC voltage applied across its terminals. A PWM (Pulse Width Modulation) wave can be used to control the speed of the motor. Here the average voltage given or the average current flowing through the motor will change depending on the ON and OFF time of the pulses controlling the speed of the motor. The duty cycle of the wave controls its speed.

Figure 2.6: PWM (Pulse Width Modulation) [5]

As the amount of time that the voltage is on increases compared with the amount of time that it is off, the average speed of the motor increases and vice versa. The time that it takes a motor to speed up and slow down under switching conditions is depends on the inertia of the rotor (basically how heavy it is), and how much friction and load torque there is. Figure 2.7 shows the speed of a motor that is being turned on and off fairly slowly:

2.1.7 Speed Control by Full H Bridge Motor Driver

A full bridge circuit is shown in the diagram below. Each side of the motor can be connected either to battery positive, or to battery negative and through a on-off switching MOSFET (Metal Oxide-Semiconductor Field Effect Transistor) which can turn very large currents on and off under the control of a low signal level voltage. Only one MOSFET on each side of the motor must be turned on at any one time otherwise they will short out the battery and burn out.

Figure 2.8: Full H bridge motor drive [5]

To make the motor go forwards, Q4 is turned on, and Q1 has the PWM signal applied to it. Meanwhile, to make the motor go backwards, Q3 is turned on, and Q2 has the PWM signal applied to it.

2.1.8 Speed Control by using MOSFET and delay

Figure 2.9: A power-switching element (bipolar transistor, MOSFET) used to vary speed of motor. [5]

The purpose of motor speed control is to control the speed, direction of rotation or position of the motor shaft. This requires that the voltage applied to the motor is modulated in some manner. Understanding the ratings of the motor is an important step in the process as it is often the corner points of operation that will determine the choice of the power switching element. The startup current (sometimes given as stall current or locked-rotor current) value can be up to three times the value of the steady-state operating current. This is where the power-switching element (bipolar transistor, MOSFET) is used in this project. By turning the power-switching elements on and off in a controlled manner, the voltage applied to the motor can be varied in order to vary the speed or position of the motor shaft. A relay (or magnetic relay or magnetic switch) is a switch operated by an electromagnetic action. The relatively small current flowing through a coil of an electromagnet inside pulls (or pushes) a lead contact to make (or break)a circuit. No current would push (or pull) back the contact by the mechanical spring attached to the mechanism

Figure 2.10: wiring diagram of delay [5] 2.2 Theory

This section includes the study about all related hardware and software that are used during process of completing this project. This theory section is divided into hardware and software and will be explain briefly.

2.2.1 Hardware

There are several hardware or electronics component that are used in this project which are microcontroller, PIC microcontroller start-up kit, DC motor and gyro sensor .Brief explanations are given about all these hardware in the next proceeding section

2.2.1.1 Microcontroller

Basically, microcontroller is a small computer on a single integrated circuit containing a processor core, memory, and programmable input/output peripherals. The PIC microcontroller consist of over 400 variations consists of a number of memory configurations, amount of support hardware required, different I/O pin arrangements, packaging, and available peripheral functions.

Microcontroller input and output pins are available to communicate with the outside world or peripheral devices such as sensor, motor and LCD. The number of I/O pins per controllers varies greatly, plus each I/O pin can be programmed as an input or output (or even switch during the running of a program). The load (current draw) that can be driven by each pin is usually low. Therefore, it is important to use a driver chip or transistor buffer if the output is expected to be a heavy load.

There are a lot of advantages in using microcontroller such as the low cost factor which makes it very popular among students and hobbyists. Another advantage of microcontroller is the variety of programming software available and most of them are distributed as freeware such as MPLAB, MikroC, PICC and CCS.

Figure 2.11 Variety of microcontrollers available in the market 2.2.1.2 PIC microcontroller start-up kit

For this project, 40 pins PIC start-up kit or SK40C will be used as a main board which is come with a proper feature for this project. One of the features is compact, powerful, flexible and robust start-up platform which is very suitable for this project as a compact and portable camera application tool. SK40c also come with 33 I/O label pins for interface process between PIC and external component. Connector for UIC00A (low cost