fyp control and automation of scara june 2011 nust eme

CONTROL AND AUTOMATION OF SCARA

(SELECTIVE COMPLIANT ASSEMBLY ROBOTIC

ARM)

A PROJECT REPORT

DE-29 (DEE)

Submitted by

NS AHMED HASSAN SYAN

NS S.M. DANIAL HAIDER

NS MUHAMMAD ZAIN

NS S.M. ZOHAIB ABBAS

BACHELORS

IN

ELECTRICAL ENGINEERING

2011

PROJECT SUPERVISOR

DR FAHAD MUMTAZ

COLLEGE OF

ELECTRICAL AND MECHANICAL ENGINEERING

PESHAWAR ROAD, RAWALPINDI

NUST COLLEGE OF


DE

-29

(DE

E)

YE

AR

20

11



ARM)

A PROJECT REPORT

DEGREE 29 (DEE)

Submitted by

NS AHMED HASSAN SYAN

NS S.M. DANIAL HAIDER

NS MUHAMMAD ZAIN

NS S.M. ZOHAIB ABBAS

BACHELORS

IN

ELECTRICAL ENGINEERING

Year

2011

PROJECT SUPERVISOR

DR. FAHAD MUMTAZ

COLLEGE OF



of 124



ARM)

Submitted by:

NS AHMED HASSAN SYAN 2008-NUST-BE-ELEC-26

NS S.M. DANIAL HAIDER 2008-NUST-BE-ELEC-64

NS MUHAMMAD ZAIN 2008-NUST-BE-ELEC-53

NS S.M. ZOHAIB ABBAS 2008-NUST-BE-ELEC-67

Project Supervisor:

______________________ Date:____________ Dr. Fahad Mumtaz

Head of Department:

______________________ Date:____________ Dr. Mojeeb Bin Ihsan

DEPARTMENT OF ELECTRICAL ENGINEERING

COLLEGE OF



NUST COLLEGE OF


of 124

DECLARATION

We hereby declare that no portion of the work referred to in this Project Thesis

has been submitted in support of an application for another degree or qualification of this

of any other university or other institute of learning. If any act of plagiarism found, we are

fully responsible for every disciplinary action taken against us depending upon the

seriousness of the proven offence, even the cancellation of our degree.

COPYRIGHT STATEMENT

Copyright in text of this thesis rests with the Ahmed Hassan, Danial Haider,

Muhammad Zain and Zohaib Abbas. Copies (by any process) either in full, or of

extracts, may be made only in accordance with instructions given by the author

and lodged in the Library of NUST College of E&ME. Details may be obtained

by the Librarian. This page must form part of any such copies made. Further

copies (by any process) of copies made in accordance with such instructions may

not be made without the permission (in writing) of the author.

The ownership of any intellectual property rights which may be described in this

thesis is vested in NUST College of E&ME, subject to any prior agreement to the

contrary, and may not be made available for use by third parties without the

written permission of the College of E&ME, which will prescribe the terms and

conditions of any such agreement.

Further information on the conditions under which disclosures and exploitation

may take place is available from the Library of NUST College of E&ME,

Rawalpindi.

of 124

ACKNOWLEDGEMENTS

We are thankful to Allah Almighty for enabling us to achieve our

goals. We are thankful to our parents, for their constant support, guidance

and affection. We are grateful to our Electrical Department and its members

for supporting us in completing this project. We are really indebted to our

project supervisor, Dr. Fahad Mumtaz, for his generous and kind support and

valuable guidance. We are also thankful to Dr. Khalid Munawar, for his

encouragement, support and help during the implementation of this project.

We are also thankful to all our friends, especially Hassaan Saadat and Sohaib

Afzal, for helping us completing this project.

of 124

ABSTRACT

This project deals with the control and automation of SCARA robotic

arm, which is widely used for industrial automation throughout the globe. It

is capable performing several tasks in an industry. We have specifically

designed it for automated drilling of a given PCB. The project is an amalgam

of microcontroller hardware, control systems, DSP and computer networks.

The final project takes a Gerber file/PCB layout from the user, applies image

processing techniques on it to get the coordinates of the holes, applies

inverse kinematics technique on them to get the angles for movement of the

arms of the robot, and sends these angles to the microcontroller through

serial communication. There the controller accordingly moves both the arms

by driving the motors through H-bridges. PID control has been implemented

for position control. Once the end effector has precisely reached the spot of

drilling, a third motor moves the drill up and down to drill the hole.

of 124

TABLE OF CONTENTS

Chapter no. Title Page no.

Declaration and Copyright Certificate 3

Acknowledgements 4

Abstract 5

Table of Contents 6

List of Figures 8

List of Tables 10

Chapter 1

Introduction

1.1 What is a Robot? 11

1.2 Industrial Applications of Robots 11

1.3 What is SCARA? 12

1.4 Comparison of SCARA with other Cartesian Robots 12

1.5 Industrial Applications of SCARA 12

Chapter 2

Mechanical Structure of SCARA

2.1 Links 14

2.2 Joints 15

2.3 Degree of Freedom 16

2.4 End Effector 16

2.5 Dimensions of the Structure 16

2.6 Motors 17

Chapter 3

Control of SCARA

3.1 Encoder Resolutions and Relations 18

3.2 H-bridge Design 19

3.3 System Identification 21

3.4 PID Realization 24

3.4.1 General PID Controller 24

3.4.2 Zeigler-Nichols Tuning 26

3.4.3 PID of our System 29

of 124

3.5 Software Simulations, Circuit Diagrams and PCB

Layouts

33

Chapter 4

Automation of SCARA

4.1 Interactive GUI 42

4.2 Gerber File Processing 68

4.3 Image Processing 70

4.4 Scaling 75

4.5 Transformation 76

4.6 Inverse Kinematics 77

4.7 Serial Communication 81

4.8 Remote access over the internet 88

Chapter 5

Summary/Limitations

5.1 Summary 96

5.2 Limitations 96

Chapter 6

Recommendations for Future Work

97

Appendix 98

of 124

LIST OF FIGURES

Sr. no. Figure no. Title Page no.

1 2.1 (a) Unary Link, (b) Binary Link, (c) Ternary Link 14

2 2.2 Side view of SCARA 14

3 2.3 Top view of SCARA 15

4 3.1 Circuit diagram of H-bridge 19

5 3.2 PCB Layout of the H-bridge 20

6 3.3 Fully fabricated H-bridge 21

7 3.4 Full open-loop block diagram 21

8 3.5 Simplified open-loop block diagram 22

9 3.6 Block diagram of parallel form of PID 24

10 3.7 Step response of PI controller 25

11 3.8 Ramp response of PD controller 25

12 3.9 Response Curve for Zeigler-Nichols First Method 27

13 3.10 Example system 28

14 3.11 Step Response for a System tuned via Second Method 29

15 3.12 „SISO design tool‟ toolbox 30

16 3.13 PID implementation in Simulink (step input) 30

17 3.14 Step response for PID implementation in Simulink 31

18 3.15 PID implementation in Simulink (ramp input) 31

19 3.16 Ramp response for PID implementation in Simulink 32

20 3.17 PID implementation in Simulink (sinusoidal input) 32

21 3.18 Sinusoid response for PID implementation in Simulink 33

22 3.19 PCB layout of the first board 34

23 3.20 PCB layout of the second board 34

24 3.21 Proteus simulation of the first board 35

25 3.22 Combined simulation of first and second board 41

26 4.1 GUI layout 42

27 4.2 Completed GUI 43

28 4.3 Selecting a file from the hard drive 43

29 4.4 Finding coordinates (a) from an image file (b) from a

gerber file

44

of 124

30 4.5 Finding the angles 44

31 4.6 Transmitting angles to the controller 45

32 4.7 Viewing coordinates and angles for a specific point 45

33 4.8 PCB Layout 70

34 4.9 PCB Layout with a white border around it 70

35 4.10 Dilated image 71

36 4.11 Image obtained after XORing 72

37 4.12 Scatter plot of the coordinates 72

38 4.13 Relation between the no. of pixels and distance in cms 75

39 4.14 Scatter plot of the coordinates after scaling and

transformation

76

40 4.15 Top view of SCARA 77

41 4.16 Top view of SCARA showing the dimensions 77

42 4.17 Top view of SCARA showing the dimensions 79

43 4.18 Detailed dimensions of the top view 80

44 4.19 Detailed dimensions of top view with bold right

triangle

81

45 4.20 DB9 male and female connectors 82

46 4.21 Schematic diagram of MAX-232 83

47 4.22 USB to serial converter with its cable 84

48 4.23 Proteus simulation of serial communication with

PIC18F452

87

49 4.24 PCB layout of serial communication board 88

50 4.25 Fully fabricated serial communication board 88

51 4.26 Website 89

52 4.27 Entering data in the website 89

of 124

LIST OF TABLES

Sr. no. Table no. Title Page no.

1 3.1 Truth table of the effect of W1 and W2 on motor 20

2 3.2 Experimental values of K and τm 23

3 3.3 Zeigler-Nichols Recipe – First Method 26

4 3.4 Zeigler Nichols Recipe – Second Method 27

5 4.1 Pin outs and pin functions of DB9 82

6 4.2 Transition table of RS-232 voltages and MAX-232

voltages

83

7 4.3 Parameter values of serial communication 84

SCARA Chapter 1 : Introduction

Page 11 of 124

Chapter 1:

INTRODUCTION

1.1 What is a Robot?

A robot is re-programmable, multipurpose, electromechanical machine which is

capable of performing a variety of tasks on its own, or with some human or computer

guidance. It is usually automated to perform a specific task, which is normally ascribed to

humans. Some robots are also used for research into human-like systems, such as ASIMO

and TOPIO.

1.2 Industrial Applications of Robots

An industrial robot is defined by ISO as an automatically controlled,

reprogrammable, multipurpose manipulator programmable in three or more axes. The use

of robots in industry commenced in the 1960s. Today, about 90% of the robots work in

industries and factories. They can perform critical tasks with greater accuracy, more

speed, and more efficiency as compared to humans. Rapid improvements are also being

made to make them more and more efficient. Some typical industrial applications of

robots are:

a) Welding applications

b) Milling and drilling applications

c) Painting applications

d) Pick and place applications

e) Assembly operations

f) Packaging and palletizing

g) Material handling

h) Dispensing operations

i) Screwing, wiring and fastening

j) Laboratory applications

k) Water jet cutting

l) Product inspection and testing


Page 12 of 124

1.3 What is SCARA?

SCARA is an acronym for Selected Compliant Assembly Robotic Arm.

Sometimes the term Articulated is also used instead of Assembly. By virtue of the

SCARA's parallel-axis joint layout, the arm is slightly compliant in the X-Y direction but

rigid in the „Z‟ direction, hence the term „Selective Compliant‟ is used. This is

advantageous for many types of assembly operations, i.e., inserting a round pin in a round

hole without binding.

The second attribute of the SCARA is the jointed two-link arm layout similar to

our human arms, hence the often-used term, Articulated. This feature allows the arm to

extend into confined areas and then retract or fold up out of the way. This is advantageous

for transferring parts from one cell to another or for loading/unloading process stations

that are enclosed.

1.4 Comparison of SCARA with other Cartesian Robots

SCARA has many advantages over the normal Cartesian robots. The most useful

feature is their high speed. They are about two times faster than the Cartesian system

robots. Their standard cycle time is also about 20% less than the conventional robots.

Furthermore, since their footprint is very small, they require very less area to mount.

Their small base projection area and height also allow freedom in system design. They

provide absolute feedback, which eliminates the need for returning to the origin again and

again.

On the other hand, SCARA robots are much expensive as compared to other

robots. But considering all the advantages discussed above, cost is a fair tradeoff in this

case.

1.5 Industrial Applications of SCARA

SCARA was invented in 1960s, in Japan, and since then it has found several

different applications in the industry. Today, many different variants of SCARA are

available in the market, which serve different applications. Some of the applications of

SCARA are:

Pick and place


Page 13 of 124

Packaging

Automated drilling

Automated welding

Mechanical assembly

Material handling

Screw driving

Now, in this project, we have first controlled SCARA and then specifically

automated it for automated drilling of PCBs.

SCARA Chapter 2 : Mechanical Structure of SCARA

Page 14 of 124

Chapter 2:

MECHANICAL STRUCTURE OF SCARA

2.1 Links

A link can be formally defined as „A rigid body with at least one particular point,

called a node, which supports the attachment of the link with other link‟. According to the

number of nodes each link possesses, we can divide the links into 3 common categories:

Unary Link: A link with a single node.

Binary Link: A link with two nodes.

Ternary Link: A link with three nodes.

Figure 2.1: (a) Unary Link, (b) Binary Link, (c) Ternary Link

SCARA has four links as shown in the side view of SCARA below. Link - 1 and

Link - 2 are binary links, whereas Link - 3 and Link - 4 are unary links.

Figure 2.2: Side view of SCARA

(a) (b) (c)

Link - 2

Lin

k -

1

End effector

Link - 3

Link - 4


Page 15 of 124

2.2 Joints

A joint can be formally defined as „The connection between two or more links at

their nodes‟. It constrains the motions of the connected links. If a joint connects only two

links, the entity is also called a kinematic pair. Depending on the degrees of freedom

(DOF) allowed for the kinematic pair, a joint can be classified as: one-DOF joint, two-

DOF joint, three-DOF joint etc. In robotics, for the simplicity of kinematic and dynamic

analysis, we use one-DOF joints because any joint with a higher order of DOFs can easily

be treated as the combination of multiple one-DOF joints. In a kinematic pair, one degree

of freedom (DOF) needs one independent parameter, which uniquely determines the

relative geometry (position and/or orientation) of the two links in the kinematic pair.

In three-dimensional space, any complex motion with respect to a reference

coordinate system can be treated as the combination of two basic motions: translation and

rotation. Therefore, if a joint imposes a translational motion, it is called a prismatic joint.

If the constrained motion is rotational, it is called a revolute joint.

SCARA has three joints:

Two revolute joints; one each for rotating the link - 2 and the link - 3

One prismatic joint; for moving the end effector up and down along the z-axis

The top view of SCARA is shown below. The joints have been labeled.

Figure 2.3: Top view of SCARA

Revolute Joints

Prismatic Joint


Page 16 of 124

2.3 Degree of Freedom

Degree of freedom (DOF) can be formally defined as „The number of

independently controllable motions in a mechanical device‟. Generally speaking, a

mechanical system's degrees of freedom refer to the number of independent parameters,

which uniquely determine its geometry (or configuration) in space and time.

Now although SCARA has three joints, and three motors to control these joints,

but it Degree of Freedom is FOUR. It is considered as a specialty of SCARA. It is a 4-

DOF device because it covers all three dimensions (x,y,z) and also one angle (the angle

between x and y).

2.4 End Effector

End Effector can be formally defined as „An attachment at the end of a robot that

interacts with the environment‟. It is the last link or the end of the robot/robotic arm. It

has to perform the operation for which the robot was built, such as a claw for pick and

place.

Since we have automated our robot for automated drilling of PCBs, so we

attached a PCB drill to it as the end effector. It is a normal drill that operates on 12V DC.

Separate adaptor was used to provide power to this drill.

2.5 Dimensions of the Structure

The base (Link - 4) and the Link - 1 of SCARA are made up of steel for strength.

Whereas the Link - 2 and the Link - 3 are made up of aluminum alloy for less weight.

This increases speed, and also avoids the danger of falling on one side. The dimensions

are given below:

The base or the Link - 4 is 5cm high and 50x50cms in dimensions

The Link - 1 is 50x16.8x16.8cms. The thickness of the walls of two sides is 0.4cm

each, whereas that of the other two sides is 0.1cm each.

The Link - 2 is 52.8cm long, 10cm high, and 10cm wide. The thickness of the

walls is 0.4cm. The internal radius of the side curves is 5cm.

The Link - 3 is 31.8cm long, 10cm high, and 10cm wide. The thickness of the

walls is 0.4cm. The internal radius of the side curves is 5cm.


Page 17 of 124

2.6 Motors

Six motors have been used in the project. However, only three of them are

actually being used for moving the joints. The other three are being used to get the

feedback. We have used,

Two wiper motors, one each for rotating the Link - 2 and the Link - 3, about their

respective revolute joints.

One power window motor, at the prismatic joint, for moving the end effector up

and down.

Three servo motors, one at each joint, for taking the feedback.

Separate encoders were not available in the market, so we had to buy these three

servo motors which had optical encoders in them. The power pins of the servo motors

were disconnected at all times. Only the encoder was given power, and its feedback was

used.

SCARA Chapter 3 : Control of SCARA

Page 18 of 124

Chapter 3:

CONTROL OF SCARA

3.1 Encoder Resolutions and Relations

A rotary encoder, also called a shaft encoder, is an electro-mechanical device that

converts the angular position or motion of a shaft or axle to an analog or digital code. The

output of incremental encoders provides information about the motion of the shaft which

is typically further processed elsewhere into information such as speed, distance, RPM

and position. The output of absolute encoders indicates the current position of the shaft,

making them angle transducers. Rotary encoders are used in many applications that

require precise shaft unlimited rotation - including industrial controls, robotics, special

purpose photographic lenses, computer input devices (such as optomechanical mice and

trackballs), and rotating radar platforms. There are two main types:

Absolute

Incremental (Relative).

As discussed earlier, optical encoders were not available in the market. So we

bought servo motors instead, which already had encoders in them. The resolution of these

encoders was found to be:

Encoder - 1: 286

Encoder - 2: 100

Encoder - 3: 286

After studying the gears and belts of the joints, we found out the relations between

the degrees the arm turns and the number of pulses the encoder gives as feedback. Since

the third motor moves the end effector up and down, so we measured its encoder‟s

relation in terms of centimeters moved and the number of pulses received

correspondingly. The relations are:

Encoder - 1: 1 degree = 4 pulses

Encoder - 2: 1 degree = 1.5 pulses

Encoder - 3: 1 cm = 1410 pulses


Page 19 of 124

3.2 H-bridge Design

The name „H-Bridge‟ is derived from the actual shape of the switching circuit

which controls the motion of the motor. It is also known as „Full Bridge‟. Basically there

are four switching elements in any H-Bridge design. When these switches are turned on

in pairs motor changes its direction accordingly. This attribute can be used to rotate the

motor in either direction, and also to control its speed.

Now the normal H-bridge ICs available in the market had a low current rating,

which did not fulfill our requirements. So we had to design and fabricate our own H-

bridges for driving the motors.

The H-bridge we designed works with the help of TIP122 and TIP127 power

transistors, and is capable of supporting current upto 5 Amperes. It proved to be very

versatile and robust. It only requires four wires for 12V power supply and direction

control. And it allows bidirectional control, breaking and freewheeling. The schematic is

shown below. It consists of only two logic ICs and a bunch of transistors.

Figure 3.1: Circuit diagram of H-bridge


Page 20 of 124

Q1, Q2, Q3 and Q4 are all 2N2222 BJTs. Any generic switching transistor can be

used instead of them. In order to support high current, the resistors R2, R4, R5 and R10

we used were 1W rated.

The wires W1 to W4 are for power supply and the logic signals for controlling the

control. The wires W1 and W2 connected to the microcontroller for controlling the motor.

The table below shows the effect of different combinations of the wires W1 and W2:

Table 3.1: Truth table of the effect of W1 and W2 on motor

Inputs Effect on motor

W1 W2

0 0 Motor will be freewheeling

0 1 Motor will turn clockwise

1 0 Motor will turn anti-clockwise

1 1 Motor will break

Where,

1 = Logic high = 5V

0 = Logic low = 0V

The diodes D2 to D4 that are shown in the schematic diagram are simple rectifier

diodes, with the forward current rating of 4A. The LED D1 lights up when there is power

in the circuit.

The PCB layout of the H-bridge is shown below:

Figure 3.2: PCB Layout of the H-bridge


Page 21 of 124

The fully fabricated PCB came out to be just about 5cm x 5cm in dimension, and

is shown below:

Figure 3.3: Fully fabricated H-bridge

3.3 System Identification

The power window and wiper motors attached to the links were old Nissan

motors. No datasheet came along with them; neither could we find one on the internet. So

we had to manually find the transfer functions of all the motors/links.

We used the least-squares solution to identify the discrete open-loop transfer

functions of these motors. We used MATLAB for this procedure. We took the first motor

and followed the following steps:

1. Suppose that the open loop block diagram of the system is:

Figure 3.4: Full open-loop block diagram

Since the motor has only angular feedback (optical encoder), so we approximated

its velocity with the backwards difference rule.

PWM 𝐾

s(τms + 1)

z − 1

Tz

u(kT) u(t) ENC(t) Vel(kT)

DC Motor (Position) Velocity Approximation


Page 22 of 124

2. Suppose that the simplified block diagram of the system is:

Figure 3.5: Simplified open-loop block diagram

Here we assumed that our velocity approximation is exact and cancels the

integrator in Figure 3.4‟s motor position transfer function. This helped simplify

the identification but still allowed us to identify K and τm.

3. In general, we carefully applied chosen inputs and measured the plant output(s). In

our case, the model was quite simple and we found that a step input worked very

well. Using Figure 3.5 as a guide, we derived the discrete transfer function by

assuming a zero-order hold (ZOH) and taking the z-transform of the continuous

system:

( )

( ) (1 − ) {

1

( )

( )}

Then,

( )

( ) [1 − ]

−

and the corresponding difference equation came out to be

( T) ( T − T) + ( T − T) …..(A)

where,

and [1 − ]

4. In order to identify these two model parameters, and , we had to apply an

open-loop step input to the motor and stored the motor‟s velocity response in an

array. So we created a DSP application that outputs a constant step value to the

motor. This application also sampled the optical encoder of the DC motor and

used the radian values to estimate the speed of the motor in units of

radians/second.

5. For the first two seconds of our run, we stored both the output value and the

velocity value in separate arrays.

PWM 𝐾

τms + 1

u(t) Vel(t) Vel(kT)

DC Motor (Velocity)

ZOH


Page 23 of 124

6. In MATLAB, we used the function C6X_getvar to upload our data to MATLAB‟s

workspace. Then we saved the run‟s data to a unique “*.mat” file so that we could

use it later.

7. Then we plotted the motor‟s response. From the plot, we found the value for K.

Using the 63% rule, we also found an approximate value for τm.

8. Using equation (A), and starting with k = 2 and ending with k = 2000, we

compiled the data into 1999 equations that were a function of and . i.e.:

( ) (1) + (1)

( ) ( ) + ( )

( ) ( − 1) + ( − 1)

9. Then we solved them for and by least-squares regression. And solved for K

and τm using the equations for and . The value we recorded for and

were precise upto six decimal places.

10. Then we repeated the experiment three times, and took mean values. The values

of K and τm are shown below:

Table 3.2: Experimental values of K and τm

K τm

1. 0.3013 0.1578

2. 0.2373 0.2190

3. 0.2801 0.1831

4. 0.2659 0.2304

Mean: 0.27115 0.1975

11. Then we simply found the transfer function of the motor using the formula:

+

and it came out to be

+


Page 24 of 124

12. Similarly, we repeated the procedure for the other two motors. And their transfer

functions came out to be,

T 1

s +

and,

1

+ 1

respectively.

3.4 PID Realization

3.4.1 General PID Controller

PID controllers are the most commonly used controller structures in industry.

They do, however, present some challenges to control and instrumentation engineers in

the aspect of tuning of the gains required for stability and good transient performance.

One is that proposed by Ziegler and Nichols in the 1940's. The PID controller

encapsulates three of the most important controller structures in a single package. The

parallel form of a PID controller is shown below:

(s) + s+ s

Figure 3.6: Block diagram of parallel form of PID

Where,

Kp = Proportional gain

Kd = Derivative gain

Ki = Integral gain

The proportional gain helps us in establishing system stability and improving the

transient response of the system, while the derivative gain is used when it is necessary to

Kp

Kds

Ki /s

+ E(s) U(s)


Page 25 of 124

improve the closed loop response speed even further. Conceptually the effect of the

derivative term is to feed information on the rate of change of the measured variable into

the controller action. The most important term in the controller is the integrator gain that

introduces a pole at s = 0 in the forward loop of the process. This makes the compensated

open loop system (i.e. original system plus PID controller) a type 1 system at least; our

knowledge of steady state errors tells us that such systems are required for perfect steady

state set point tracking. In other words, for a unity feedback system, the perfect set point

control can be achieved for the controller, C(s), if and only if

1. The open loop forward gain has a steady state gain of infinity i.e.

(s) (s)

2. The system is closed loop stable.

3. Neither C(s) nor G(s) have zeros at the origin.

The third point eliminates the possibility of the loop transfer function cancelling

the effect of the integrator pole. The reset and rate times are of special significance in this

regard:

The reset time is the time taken for the integrator term output to equal the

proportional term output in response to a step change in input applied to a PI

controller.

Figure 3.7: Step response of PI controller

The rate time is the time taken for the proportional term output to equal the

derivative term output in response to a ramp change input applied to a PD

controller.

Figure 3.8: Ramp response of PD controller


Page 26 of 124

3.4.2 Ziegler-Nichols Tuning

In 1942 Ziegler and Nichols, both employees of Taylor Instruments, described

two mathematical procedures, for the tuning of PID controllers. These procedures are

now accepted as standard in control systems practice. Both techniques make a priori

assumptions on the system model, but do not require that these models be specifically

known. Ziegler-Nichols formulae for specifying the controllers are based on plant step

responses.

The First Method:

The first method is applied to plants with step responses of the form displayed in

Figure 4. This type of response is typical of a first order system with transportation delay,

such as that induced by fluid flow from a tank along a pipe line. It is also typical of a

plant made up of a series of first order systems. The response is characterised by two

parameters, the delay time L, and the time constant T. These are found by drawing a

tangent to the step response at its point of inflection and noting its intersections with the

time axis and the steady state value. The plant model is therefore

(s)

Ts + 1

Zeigler and Nichols derived the following control parameters based on this model:

Table 3.3: Zeigler-Nichols Recipe – First Method

PID Type Kp Ti = Kp/Ki Td = Kd/Kp

P T

0

PI T

0

PID 1 T

2L 0.5L


Page 27 of 124

Figure 3.9: Response Curve for Zeigler-Nichols First Method

It can be noted that the response curve shown above is similar to that of the over

damped second order systems.

The Second Method:

The second method is usually used for the plants that can be rendered unstable

under proportional control. The technique is designed to result in a closed loop system

with 25% overshoot. This is rarely achieved as Ziegler and Nichols determined the

adjustments based on a specific plant model. The steps for tuning a PID controller via the

2nd method are as follows:

Using only proportional feedback control:

1. Reduce the integrator and derivative gains to 0.

2. Increase Kp from 0 to some critical value Kcr, at which sustained

oscillations occur. If they do not, then another method has to be applied.

3. Note the value of Kcr, and also the corresponding period of sustained

oscillation, Pcr.

The controller gains are now specified as follows:

Table 3.4: Zeigler Nichols Recipe – Second Method

PID Type Kp Ti Td

P 0.5Kcr 0

PI 0.45Kcr 1

0

PID 0.6Kcr


Page 28 of 124

Consider a process with transfer function (s)

( )( )( ) that is to be

placed under PID control. We can determine the limiting gain for stability (before

oscillation) by using Routh-Hurwitz condition. The characteristic equation p(s), with

proportional control is:

Figure 3.10: Example system

1 + KG(s) = 0

(s+1)(s+3)(s+5) + K = 0

p(s) = s3 + 9s

2 + 23s +15 + K = 0

The corresponding Routh array is

s3

1 23 0

s2 9 15 + K 0

s1 192 – K 0

s0 15 + K

From this we see that the range of K for stability is

15 + K > 0

K > –15

and 192 – K > 0

K < 192.

So,

Kcr=192.

When K = 192, we have imaginary roots since the s1 row is identically 0. The

corresponding auxiliary equation is

9s2 + 15 + 192 = 0

which has roots at s = ±j4.8. Since this is a quadratic factor of the characteristic

polynomial the sustained oscillation at the limiting value of K, Kcr, is at 4.8rad/s. Thus,

Pcr = 1.31sec and Kcr = 192. This gives for full PID control from the table as

Kp = 0.6Kcr = 115.2

Ki = 2Kp/Pcr = 177.2

and Kd = Kp Td = Kp/8 Pcr = 18.3

K G(s)

U(s) E(s) R(s) Y(s)

– +


Page 29 of 124

Analysis: The closed loop step response shows an overshoot performance of 50%,

100% over target. Given the dependence of the technique on a generic model, it is not

surprising that the design objectives will almost always not be met. The technique,

however, does provide an effective starting point for controller tuning.

\

Figure 3.11: Step Response for a System tuned via Second Method

3.4.3 PID of our System

We implemented PID control on our system using the Zeigler-Nichols Method in

MATLAB. In MATLAB, there is a toolbox named „SISO Design Tool‟. There in the tab

of Automated Tuning, is the option of Zeigler-Nichols Tuning in the Tuning Algorithm

drop down list. It automatically tuned our system.


Page 30 of 124

Figure 3.12: „SISO design tool‟ toolbox

After that, we implemented this PID controller on our system, in Simulink, in the

MATLAB. We gave a step input to the system, and observed the corresponding output. It

can be seen that the input is tracked to a very good level.

Figure 3.13: PID implementation in Simulink (step input)


Page 31 of 124

Figure 3.14: Step response for PID implementation in Simulink

Then we also checked it for ramp and sinusoidal input. The following diagrams

illustrate the results:

Figure 3.15: PID implementation in Simulink (ramp input)


Page 32 of 124

Figure 3.16: Ramp response for PID implementation in Simulink

Figure 3.17: PID implementation in Simulink (sinusoidal input)


Page 33 of 124

Figure 3.18: Sinusoid response for PID implementation in Simulink

3.5 Software Simulations, Circuit Diagrams and PCB Layouts

Apart from the three H-bridges, we designed and fabricated four other boards for

the microcontrollers, and serial communication between PC and the controllers. First we

fabricated a board for normal H-bridges which were available in the market. But since

they did not fulfill our requirements, we had to discard that board. Then we fabricated

two other boards of a similar design for the microcontrollers. At the same time, we

designed and fabricated a board for the serial communication. This board has been

discussed in detail in the serial communication portion of this report, so we will not

discuss it here. The PCB layouts of the first board that we had to discard later, as well as

of the boards that we used are given on the next page.


Page 34 of 124

Figure 3.19: PCB layout of the first board

Since we had to discard this design, so we will not discuss it in detail here. The

PCB layout of the other two boards that we used is:

Figure 3.20: PCB layout of the second board


Page 35 of 124

We fabricated two boards of this design, each for holding one of the

microcontrollers. We also simulated it on Proteus first. The Proteus simulation diagram is

shown below:

Figure 3.21: Proteus simulation of the first board

And the code that we wrote for this simulation is given below:

LIST P=18F452

#include <P18F452.INC>

CONFIG WDT=OFF;

angle EQU 0x22

STOP EQU 0x22

MVALUE EQU 0x23

COMVALUE EQU 0x24

LCD_DATA EQU PORTD ;LCD data port

LCD_CTRL EQU PORTA ;LCD control port

RS EQU RA3 ;data/ instruction

RW EQU RA2 ;read/write

EN EQU RA1 ;enable of LCD

org 0x00

clrf PCLATH

goto Main

org 0x008

btfss INTCON,INT0IF ;checking whether interrupt was due

to RB0


Page 36 of 124

retfie

goto INT0_ISR

org 0x0100

Main

st

bsf TRISB,RB0 ;INT0 external interrup

configuration

bsf INTCON,INT0IE ;INT0 interrupt enable

bsf INTCON,GIE ;global interrupt enable

call LCD_INITIAL ;LCD initialization

call LCD_MOTOR_STOP ;displaying data (for stop

condition)

bcf TRISB,RB3 ;INPUT2 FOR MOTOR

bcf TRISC,CCP1 ;configuring as output for PWM,11

for DC1B1:B0 input1

bcf TRISB,RB2 ;SPEED CONTROL

bcf PORTB,2

BCF PORTB,3

BCF PORTC,2

BRA st

;--------------------------------------------------------------------

org 0x400

INT0_ISR

call LCD_INITIAL ;LCD initialization

call LCD_MOTOR_ON ;displaying data (for ON condition)

MOVLW d'1410' ; pulses for 1 cm approx

MOVWF angle

MOVF angle,W

MULLW d'4' ; moving 4 cm

CALL TIMER1_COUNTER

BCF PORTC,2

BSF PORTB,3

MOVF PRODH,W

BACK

CPFSEQ TMR1H

BRA BACK

MOVF PRODL,W

BACK2

CPFSEQ TMR1L

BRA BACK2

BCF PORTB,3


Page 37 of 124

BCF PORTC,2

;*********************END OF FORWARD DIRECTION********

MOVLW d'1410'

MOVWF angle

MOVF angle,W

MULLW d'4'

CALL TIMER1_COUNTER

BSF PORTC,2

BCF PORTB,3 ;CHANGE DIRECTION

MOVF PRODH,W

BACK3

CPFSEQ TMR1H

BRA BACK3

MOVF PRODL,W

BACK4

CPFSEQ TMR1L

BRA BACK4

BCF PORTB,3

BCF PORTC,2

CALL SERIAL_TRANSMIT

bcf INTCON,INT0IF

retfie

;-----------------------------------------------------------------------

-

delay_2_sec ;creating 2 seconds delay using

timer 0,no prescalar,

;internal clock

movlw 0x04

movwf T0CON

bcf INTCON,TMR0IF

movlw 0x0B

movwf TMR0H

movlw 0xDC

movwf TMR0L

bsf T0CON,TMR0ON

tmr

btfss INTCON,TMR0IF

bra tmr

bcf T0CON,TMR0ON

bcf INTCON,TMR0IF

RETURN


Page 38 of 124

;---------------------------------------------------------------------

TIMER1_COUNTER

MOVLW 0x02

MOVWF T1CON

MOVLW 0x00

MOVWF TMR1L

MOVLW 0X00

MOVWF TMR1H

BSF T1CON,TMR1ON

RETURN

;**************************************************************

;*****************SERIAL TRANSMIT******************

SERIAL_TRANSMIT

MOVLW B'00100000' ;enable receive and serial port

MOVWF TXSTA

MOVLW D'12' ;4800 baud rate

MOVWF SPBRG

BCF TRISC,TX

BSF RCSTA,SPEN

r2 MOVLW A'S'

r1 BTFSS PIR1,TXIF

BRA r1

MOVWF TXREG

RETURN

;***********************************************************************

***

;EL Cee Dee Ka Kam

LCD_INITIAL

MOVLW b'00001110'

MOVWF ADCON1 ;configuring ADCON1 for LCD

operation to digitize

;port pins

CLRF TRISA ;making output

CLRF TRISD ;making output

BCF PORTA,1 ;making enable low

CALL LDELAY

MOVLW 0X38 ;INITIALIZE 2 LINES OF LCD, 5X7

MATRIX

CALL COMD_WRT

CALL DELAYLCD

MOVLW 0X01 ;CLEAR DISPLAY


Page 39 of 124

CALL COMD_WRT

CALL DELAYLCD

MOVLW 0X0C ;DISPLAY CURSOR

CALL COMD_WRT

CALL DELAYLCD

MOVLW 0X80 ;BRING CURSOR TO BEGINNING OF LINE 1

CALL COMD_WRT

CALL DELAYLCD

return

;------------------------------------------------------

COMD_WRT

MOVWF LCD_DATA ;GIVING COMMANDS TO THE LCD

BCF LCD_CTRL,RS

BCF LCD_CTRL,RW

BSF LCD_CTRL,EN

CALL DELAYLCD

BCF LCD_CTRL,EN

RETURN

DATA_WRT

MOVWF LCD_DATA ;DISPLAYING DATA ON THE LCD

BSF LCD_CTRL,RS

BCF LCD_CTRL,RW

BSF LCD_CTRL,EN

CALL DELAYLCD

BCF LCD_CTRL,EN

MOVLW 06H

CALL COMD_WRT

CALL DELAYLCD

RETURN

LDELAY

MOVLW D'255'

CALL DELAY2

CALL DELAY2

CALL DELAY2

CALL DELAY2

CALL DELAY2

CALL DELAY2

CALL DELAY2

CALL DELAY2


Page 40 of 124

CALL DELAY2

CALL DELAY2

RETURN

DELAYLCD

MOVLW D'10' ;GENERATING A DELAY OF 10ms

FOR ISSUING NEW CHARACTERS

CALL DELAY2

RETURN

;DELAY OF 0.5 MS

DELAY

MOVLW D'165'

MOVWF STOP

LOOP

DECFSZ STOP,F

GOTO LOOP

RETURN

;DELAY = MULTIPLE OF 0.5 MS

DELAY2

MOVWF MVALUE

LOOP2

CALL DELAY

DECFSZ MVALUE,F

GOTO LOOP2

RETURN

;------------------------------------------------

;displaying "STOP" when MOTOR is stationary

LCD_MOTOR_STOP

movlw A'S'

call DATA_WRT

movlw A'T'

call DATA_WRT

movlw A'O'

call DATA_WRT

movlw A'P'

call DATA_WRT

return

;**********************************************

;displaying "DRILLING" when MOTOR is ON

LCD_MOTOR_ON

movlw A'D'


Page 41 of 124

call DATA_WRT

movlw A'R'

call DATA_WRT

movlw A'I'

call DATA_WRT

movlw A'L'

call DATA_WRT

movlw A'L'

call DATA_WRT

movlw A'I'

call DATA_WRT

movlw A'N'

call DATA_WRT

movlw A'G'

call DATA_WRT

return

END

After simulating and testing this design, we also simulated the combined working

of both the microcontrollers in Proteus. The simulation diagram is given below:

Figure 3.22: Combined simulation of first and second board

SCARA Chapter 4 : Automation of SCARA

Page 42 of 124

Chapter 4:

AUTOMATION OF SCARA

4.1 Interactive GUI

In the process of automating the SCARA Robot, we developed an interactive,

user-friendly Graphical User Interface using MATLAB. It has five push buttons:

„Open File‟ - Opens the browser for user to select and open a Gerber File, or an

image file containing the PCB layout

„Find Coordinates‟ - Runs the image

Figure 4.1: GUI layout


Page 43 of 124

Figure 4.2: Completed GUI

User can select and open any desired file from his/her hard drive. It can accept

either a Gerber File, which is generated by the PCB designing software being used, or it

can accept any type of image file (.jpg, .png, .bmp etc.) containing the PCB layout. In

both these cases, the coordinates of the holes to be drilled in the PCB are calculated using

image processing techniques.

Figure 4.3: Selecting a file from the hard drive


Page 44 of 124

(a)

(b)

Figure 4.4: Finding coordinates (a) from an image file (b) from a gerber file

After that, it finds the angles to be transmitted, using inverse kinematics

technique, and then transmits those angles to the controller through serial communication.

Figure 4.5: Finding the angles


Page 45 of 124

Figure 4.6: Transmitting angles to the controller

We can also select any specific point from the scatter plot and view its respective

coordinates, and angles.

Figure 4.7: Viewing coordinates and angles for a specific point


Page 46 of 124

The MATLAB code for this GUI is given below:

function varargout = testing(varargin)

% TESTING M-file for testing.fig

% TESTING, by itself, creates a new TESTING or raises the existing

% singleton*.

%

% H = TESTING returns the handle to a new TESTING or the handle to

% the existing singleton*.

%

% TESTING('CALLBACK',hObject,eventData,handles,...) calls the local

% function named CALLBACK in TESTING.M with the given input

arguments.

%

% TESTING('Property','Value',...) creates a new TESTING or raises

the

% existing singleton*. Starting from the left, property value

pairs are

% applied to the GUI before testing_OpeningFcn gets called. An

% unrecognized property name or invalid value makes property

application

% stop. All inputs are passed to testing_OpeningFcn via varargin.

%

% *See GUI Options on GUIDE's Tools menu. Choose "GUI allows only

one

% instance to run (singleton)".

%

% See also: GUIDE, GUIDATA, GUIHANDLES

% Edit the above text to modify the response to help testing

% Last Modified by GUIDE v2.5 29-May-2011 18:26:21

% Begin initialization code - DO NOT EDIT

gui_Singleton = 1;

gui_State = struct('gui_Name', mfilename, ...

'gui_Singleton', gui_Singleton, ...

'gui_OpeningFcn', @testing_OpeningFcn, ...

'gui_OutputFcn', @testing_OutputFcn, ...

'gui_LayoutFcn', [] , ...

'gui_Callback', []);


Page 47 of 124

if nargin && ischar(varargin{1})

gui_State.gui_Callback = str2func(varargin{1});

end

if nargout

[varargout{1:nargout}] = gui_mainfcn(gui_State, varargin{:});

else

gui_mainfcn(gui_State, varargin{:});

end

% End initialization code - DO NOT EDIT

% --- Executes just before testing is made visible.

function testing_OpeningFcn(hObject, eventdata, handles, varargin)

clc;

guidata(hObject,handles);

handles.err = wavread ('error.wav');

handles.tada = wavread ('tada.wav');

handles.first = 0;

handles.gerber_chk = 0;

filename = 'new.jpg';

%str = strcat(PathName,FileName);

I = imread (filename);


axes (handles.axes1)

imshow(I);

% This function has no output args, see OutputFcn.

% hObject handle to figure

% eventdata reserved - to be defined in a future version of MATLAB

% handles structure with handles and user data (see GUIDATA)

% varargin command line arguments to testing (see VARARGIN)

% Choose default command line output for testing

handles.output = hObject;

% Update handles structure

guidata(hObject, handles);

% UIWAIT makes testing wait for user response (see UIRESUME)

% uiwait(handles.figure1);


Page 48 of 124

% --- Outputs from this function are returned to the command line.

function varargout = testing_OutputFcn(hObject, eventdata, handles)

% varargout cell array for returning output args (see VARARGOUT);

% hObject handle to figure



% Get default command line output from handles structure

varargout{1} = handles.output;

% --- Executes on button press in pushbutton1.

function pushbutton1_Callback(hObject, eventdata, handles)


handles.check=0;

[FileName,PathName] = uigetfile({'*.*'},'Select File');

handles.str = strcat(PathName,FileName);

filename_length = length (FileName);

if ( (FileName(filename_length) == 't') || (FileName(filename_length) ==

'T') )



set (handles.edit5,'String','---------');


imshow('gerber.jpg');

else if ( (FileName(filename_length)) == 'g' ||

(FileName(filename_length) == 'p') || (FileName(filename_length) == 'P')

|| (FileName(filename_length) == 'G') )


handles.I = imread (handles.str);


set (handles.edit5,'String','PCB Layout');


imshow(handles.I);

end

end

set (handles.edit7,'ForegroundColor',[0.078 0.169 0.549]);

set (handles.edit7,'String',' Ready for next operation');

set (handles.listbox1,'String','');


Page 49 of 124

set (handles.listbox2,'String','');

if (handles.first==1)


axes(handles.axes3);

scatter(1,1,1,[0.859 0.933 0.957]);

set (handles.axes3,'Visible','off');

set (handles.edit6,'String','');

handles.first = 0;

end


set(handles.pushbutton2,'Enable','on')

set(handles.pushbutton3,'Enable','off')



% hObject handle to pushbutton1 (see GCBO)






handles.first = 1;

if (handles.gerber_chk == 1)

text = textread(handles.str, '%c');

ll = length(text);

x=[];

y=[];

n=1;

for i = 1:ll

if (text(i)=='X')

sign_x = text(i+1);

x(n) =

str2num(text(i+7))+(str2num(text(i+6)))*10+(str2num(text(i+5)))*100+(str

2num(text(i+4)))*1000+(str2num(text(i+3)))*10000+(str2num(text(i+2)))*10

0000;

if (sign_x == '-')

x(n)=x(n)*(-1);

end

n=n+1;

end


Page 50 of 124

end

n=1;

for i = 1:ll

if (text(i)=='Y')

sign_y = text(i+1);

y(n) =

str2num(text(i+7))+(str2num(text(i+6)))*10+(str2num(text(i+5)))*100+(str

2num(text(i+4)))*1000+(str2num(text(i+3)))*10000+(str2num(text(i+2)))*10

0000;

if (sign_y == '-')

y(n)=y(n)*(-1);

end

n=n+1;

end

end

axes (handles.axes3);

scatter (x,y);

else

set (handles.edit7,'ForegroundColor',[0.847 0.161 0]);

set (handles.edit7,'String',' Busy (Please Wait)');

pause(0.00001);

th = 0.625;

im = im2bw(handles.I,th);

imsize = size(im);

imh = imsize(1);

imw = imsize(2);

im1 = padarray(im, [3 3], 1);

h = [0 1 0; 1 1 1; 0 1 0];

im2p = zeros(imh+6, imw+6);

im2 = im2p;

im2(1, 1) = 1;

tt=0;

bb=-1;

while(sum(sum(im2p - im2)) ~= 0)


Page 51 of 124

im2p = im2;

im2 = imdilate(im2, h);

im2 = im1 & im2;

if (rem(tt,65)==0)

if (bb==-1)


pause(0.00001);

else if (bb==0)

set (handles.edit7,'String',' Busy. (Please Wait)');

pause(0.00001);

else if (bb==1)

set (handles.edit7,'String',' Busy.. (Please

Wait)');

pause(0.00001);

else if (bb==2)

set (handles.edit7,'String',' Busy... (Please

Wait)');

pause(0.00001);

bb=-2;

end

end

end

end

bb=bb+1;

end

tt=tt+1;

end;

im3 = xor(im1,im2);

bwl = bwlabel(im3);

areas = regionprops(bwl,'Area');

center_points = regionprops(bwl,'Centroid');

no_of_holes = size(areas);

aa=[];

for rr=1:no_of_holes(1)

aa (rr)=areas(rr).Area;

if (aa(rr)<2)

pixel=find(bwl==rr);

im3(pixel)=0;

end


Page 52 of 124

if (aa(rr)>25)


im3(pixel)=0;

end

end

bwl = bwlabel(im3);


handles.new=[];

s2=size(center_points);

for ii=1:s2(1)

handles.new(ii,:) = center_points(ii).Centroid;

end

handles.i = ii;

handles.new(:,2)=imh-handles.new(:,2);

handles.new(:,3)=(1/43.2)*handles.new(:,1);

handles.new(:,4)=(1/43.2)*handles.new(:,2);

handles.new(:,5)=handles.new(:,3)+40;

handles.new(:,6)=handles.new(:,4);



scatter(handles.new(:,5),handles.new(:,6));

end

set (handles.edit6,'String','Scatter Plot of the Coordinates');









Page 53 of 124




handles.check=1;



pause(0.001);

l1=52;

l2=31;

for vr=1:handles.i

handles.new(vr,8)=acos((handles.new(vr,5)^2+handles.new(vr,6)^2-

l1^2-l2^2)/(2*l1*l2));

handles.new(vr,10)=round(handles.new(vr,8)*(180/pi));

handles.new(vr,7)=atan(handles.new(vr,6)/handles.new(vr,5))-

atan((l2*sin(handles.new(vr,8)))/(l1+l2*cos(handles.new(vr,8))));

handles.new(vr,9)=round(handles.new(vr,7)*(180/pi));

end


set (handles.listbox1,'String',num2str(handles.new(:,9)));

set (handles.listbox2,'String',num2str(handles.new(:,10)));
















% serial_obj = serial('COM3');

% set(serial_obj,'BaudRate',9600);


Page 54 of 124

% set(serial_obj,'FlowControl','none');

% set(serial_obj,'Parity','none');

% fopen(serial_obj);

% fprintf(serial_obj,'%d',30);

% fclose(serial_obj);

for nt=1:3


set (handles.edit7,'String',' Sending angles to the controller

(Please Wait)');

pause(0.67);

set (handles.edit7,'String',' Sending angles to the controller.

(Please Wait)');

pause(0.67);

set (handles.edit7,'String',' Sending angles to the controller..

(Please Wait)');

pause(0.67);

set (handles.edit7,'String',' Sending angles to the controller...

(Please Wait)');

pause(0.67);

end


set (handles.edit7,'String',' All angles have been sent !');






pause(0.000001);

wavplay(handles.tada,44100);







set(handles.pushbutton5,'Enable','inactive')

set(handles.pushbutton5,'String','Return')





Page 55 of 124



set (handles.edit7,'String',' Click on a point to select it');

pause(0.00001);

set(handles.figure1,'CurrentAxes',handles.axes3);

while (1)

[x,y]=ginput(1);

if ( (x>36.5 && x<186) && (y>489.5 && y<529.4) )

break;

end

xclosest = 0.2;

yclosest = 0.2;

for tt=1:handles.i

if ( ((abs(x-handles.new(tt,5)))<xclosest) && ((abs(y-

handles.new(tt,6)))<yclosest) )

xclosest = abs(x-handles.new(tt,5));

xplot = handles.new(tt,5);

if (handles.check==1)

anglel1 = handles.new(tt,9);

end

yclosest = abs(y-handles.new(tt,6));

yplot = handles.new(tt,6);


anglel2 = handles.new(tt,10);

end

end

end

if ((xclosest<0.2) && (yclosest<0.2))




hold on;

scatter(xplot,yplot,'filled','CData',[1 0 0]);

hold off;

set (handles.edit1,'String',num2str(xplot));

set (handles.edit2,'String',num2str(yplot));


set (handles.edit3,'String',num2str(anglel1));

set (handles.edit4,'String',num2str(anglel2));

end



Page 56 of 124

set (handles.edit7,'String',' Click on another point, or click

Return button to return');

pause(0.00001);

else



set (handles.edit7,'String',' INVALID SELECTION ! Click on a

point !');

pause(0.00001);

wavplay(handles.err,44100);

end

end



set(handles.pushbutton5,'String','Select a Point')






end





set (handles.edit1,'String','x');

set (handles.edit2,'String','y');

set (handles.edit3,'String','theta 1');

set (handles.edit4,'String','theta 2');




function edit1_Callback(hObject, eventdata, handles)

% hObject handle to edit1 (see GCBO)



% Hints: get(hObject,'String') returns contents of edit1 as text


Page 57 of 124

% str2double(get(hObject,'String')) returns contents of edit1 as

a double

% --- Executes during object creation, after setting all properties.

function edit1_CreateFcn(hObject, eventdata, handles)



% handles empty - handles not created until after all CreateFcns

called

% Hint: edit controls usually have a white background on Windows.

% See ISPC and COMPUTER.

if ispc && isequal(get(hObject,'BackgroundColor'),

get(0,'defaultUicontrolBackgroundColor'))

set(hObject,'BackgroundColor','white');

end

% --- Executes on selection change in listbox1.

function listbox1_Callback(hObject, eventdata, handles)

% hObject handle to listbox1 (see GCBO)



% Hints: contents = get(hObject,'String') returns listbox1 contents as

cell array

% contents{get(hObject,'Value')} returns selected item from

listbox1


function listbox1_CreateFcn(hObject, eventdata, handles)




called

% Hint: listbox controls usually have a white background on Windows.






Page 58 of 124

end

% --- Executes on selection change in listbox2.

function listbox2_Callback(hObject, eventdata, handles)




% Hints: contents = get(hObject,'String') returns listbox2 contents as

cell array

% contents{get(hObject,'Value')} returns selected item from

listbox2


function listbox2_CreateFcn(hObject, eventdata, handles)




called

% Hint: listbox controls usually have a white background on Windows.





end

% --- If Enable == 'on', executes on mouse press in 5 pixel border.

% --- Otherwise, executes on mouse press in 5 pixel border or over

edit1.

function edit1_ButtonDownFcn(hObject, eventdata, handles)









Page 59 of 124



a double






called






end







a double






called






end


Page 60 of 124







a double






called






end







a double






called


Page 61 of 124






end







a double






called






end







a double


Page 62 of 124






called






end


function axes2_CreateFcn(hObject, eventdata, handles)

% hObject handle to axes2 (see GCBO)



called

% Hint: place code in OpeningFcn to populate axes2

% --- Executes during object deletion, before destroying properties.

function axes2_DeleteFcn(hObject, eventdata, handles)




% --- Executes on mouse press over axes background.

function axes2_ButtonDownFcn(hObject, eventdata, handles)









Page 63 of 124



a double






called






end







a double






called







Page 64 of 124

end







a double






called






end







a double






called


Page 65 of 124






end







a double




% e ventdata reserved - to be defined in a future version of MATLAB


called






end







a double


Page 66 of 124






called






end







a double






called






end




Page 67 of 124





a double






called






end







a double






called




Page 68 of 124




end







a

% double






called






end

4.2 Gerber File Processing

Every PCB designing software has an option for generating a „Gerber File‟, which

contains the complete information about the holes, layers, wires etc. of the PCB layout.

We used Proteus v7.6 for designing our PCBs. It generates different gerber files for

different attributes of the layout, all in .txt format. The file named as „xxxxx - CADCAM

Drill.txt‟ contains the information about the holes of the PCB to be drilled, where „xxxxx‟

is the name of the file. We simply read this file using MATLAB, and found the

coordinates using it. The MATLAB code for doing so is given on the next page.


Page 69 of 124

MATLAB Code:

text = textread('Board 2 - CADCAM Drill.TXT', '%c');

size = length(text);

x=[];

y=[];

n=1;

for i = 1:size

if (text(i)=='X')

sign_x = text(i+1);

x(n) = str2num(text(i+7)) + (str2num(text(i+6)))*10 +

(str2num(text(i+5)))*100 + (str2num(text(i+4)))*1000 +

(str2num(text(i+3)))*10000 + (str2num(text(i+2)))*100000;

if (sign_x == '-')

x(n)=x(n)*(-1);

end

n=n+1;

end

end

n=1;

for i = 1:size

if (text(i)=='Y')

sign_y = text(i+1);

y(n) = str2num(text(i+7)) + (str2num(text(i+6)))*10 +

(str2num(text(i+5)))*100 + (str2num(text(i+4)))*1000 +

(str2num(text(i+3)))*10000 + (str2num(text(i+2)))*100000;

if (sign_y == '-')

y(n)=y(n)*(-1);

end

n=n+1;

end

end

figure;

scatter (x,y);


Page 70 of 124

4.3 Image Processing

As mentioned before, the GUI can also take an image file as input. It then applies

image processing on it to get the coordinates of the holes to be drilled. The steps we

followed in image processing are as under:

1. Read an image file from the hard drive.

Figure 4.8: PCB Layout

2. Convert it into a black and white binary image using threshold of 0.625

3. Put a white border around that image. Store it separately for further use.

Figure 4.9: PCB Layout with a white border around it


Page 71 of 124

4. Now make another completely black image of exactly the same size and make its

topmost left pixel white

5. Now dilate this image using the following sectioning element

[ 1 1 1 1 1

]

and then take its AND with the image obtained in step 3

6. Repeat step 5 in a loop until the whole image has been dilated.

Figure 4.10: Dilated image

7. Observe that the image obtained after dilation is similar to the one in figure 4.9,

only difference is that the holes in this one have been blacked out. Take its XOR

with the image in figure 4.9. The resulting image will have white pixels for holes

and the rest of the area will be all black, as shown on the next page.


Page 72 of 124

Figure 4.11: Image obtained after XORing

8. Apply „bwlabel‟ command on it. It will divide all the white areas into separate

regions.

9. Using „regionprops‟ command, the „centroid‟ property will give us the coordinates

of all the holes.

Figure 4.12: Scatter plot of the coordinates

50 100 150 200 250 300 350 400 450 500 5500

50

100

150

200

250

300

350


Page 73 of 124

10. We can also observe the area of each hole, using the „area‟ property. We made use

of this property to remove single pixel noise, and also to remove any unwanted

areas that were part of the PCB layout.

The MATLAB code for image processing is given below:

close all;

clear all;

clc;

%threshold

th = 0.625;

%name of image file

filename = 'PIC Board 2.jpg';

%read image

I=imread(filename);

im = im2bw(I,th);

figure;

%get size

imsize = size(im);

imh = imsize(1);

imw = imsize(2);

%put white border around image

im1 = padarray(im, [3 3], 1);

subplot(2,2,1);

imshow(im1);

%make sectioning element

h = [0 1 0; 1 1 1; 0 1 0];

%make images containing unwanted white area

im2p = zeros(imh+6, imw+6);

im2 = im2p;

im2(1, 1) = 1;

while(sum(sum(im2p - im2)) ~= 0)

im2p = im2;

im2 = imdilate(im2, h);

im2 = im1 & im2;

end;

subplot(2,2,2);

imshow(im2);

%put unwanted white area to black


Page 74 of 124

im3 = xor(im1,im2);

%remove single pixel noise

bwl = bwlabel(im3);

areas = regionprops(bwl,'Area');


no_of_holes = size(areas);

aa=[];

for rr=1:no_of_holes(1)

aa (rr)=areas(rr).Area;

if (aa(rr)<2)


im3(pixel)=0;

end

if (aa(rr)>25)


im3(pixel)=0;

end

end

subplot(2,2,3)

imshow(im3);

subplot(2,2,4)

imshow(im3);

bwl = bwlabel(im3);


new=[];

s2=size(center_points);

for i=1:s2(1)

point = center_points(i).Centroid;

new(i,:) = center_points(i).Centroid;

rectangle('Position',[fix(point(1))-3,fix(point(2))-3,6 ,6],

'FaceColor','r')

end

new(:,2)=imh-new(:,2);

figure;

scatter(new(:,1),new(:,2))


Page 75 of 124

4.4 Scaling

After image processing, we found the relationship between the no. of pixels of the

image and the distance in centimeters on the PCB. An example is shown below:

Figure 4.13: Relation between the no. of pixels and distance in cms

This gives us the relation,

2.5cm = 108 pixels

=> 1cm = 43.2 pixels

In MATLAB,

% SCALING

% 1cm = 43.2pixels

% or

% 1pixel = 0.02314814815

% size of the image

new(:,3)=(1/43.2)*new(:,1);

new(:,4)=(1/43.2)*new(:,2);

figure;

scatter(new(:,3),new(:,4));


Page 76 of 124

4.5 Transformation

Now we cannot place the PCB right at the base of SCARA, because the end

effector cannot reach there. So we placed it at some distance and also correspondingly

transformed our plane. In MATLAB,

% TRANSFORMATION

new(:,5)=new(:,3)+40;

new(:,6)=new(:,4);

figure;

scatter(new(:,5),new(:,6))

After scaling and transformation, the scatter plot of the coordinates came out to be

the one shown below:

Figure 4.14: Scatter plot of the coordinates after scaling and transformation

40 42 44 46 48 50 52 541

2

3

4

5

6

7

8


Page 77 of 124

4.6 Inverse Kinematics

First, we studied the studied the forward kinematics of the SCARA Robot. Below

is given a diagram showing the top view of SCARA.

Figure 4.15: Top view of SCARA

Figure 4.16: Top view of SCARA showing the dimensions

Let‟s suppose that the length of the first arm (link - 2) of SCARA is L1, length of

the second arm (link - 3) is L2, the angle between the first arm and the x-axes is θ1, and

the angle between the second arm and the first arm is θ2. Now we know that the

transformation matrix for the transformation from frame (i-1) to frame i is given by the

one shown on the next page.

θ1

θ2


Page 78 of 124

[

s −s s s s s −s −s s s s s − s − s

1

]

The 3x3 matrix formed by the intersection of first three rows and the first three

columns of this matrix is the rotation matrix which shows the 3-D rotation in the x, y and

z directions. The last row is always [ 1] as shown above. And the first three entries

of the last column constitute the translation matrix. The three entries show the translation

in the x, y and z-directions respectively.

Now for transformation from frame-0 to frame-1, we only need to rotate the frame

of reference by and this rotation is only in the xy-plane. Furthermore, no translation is

required so the translation matrix will be 0. Hence the transformation matrix will be

[

s −s s s 1 1

]

For transformation from frame-1 to frame-2, we first need to translate it by L1

along the x-axis, and then we have to rotate it by and this rotation is only in the xy-

plane. Hence the transformation matrix will be

[

s −s s s 1 1

]

For transformation from frame-2 to frame-3, we only need to translate it by L2

along the x-axis. No rotation is required, so the rotation matrix will be identity matrix.

Hence the transformation matrix will be

[

1 1 1 1

]

The net transformation matrix for the transformation from frame-0 to frame-3 will

be equivalent to the product of these three matrices.


Page 79 of 124

This transformation matrix will bring us from the origin (base of the SCARA) to

the edge of the second arm (link-3). In order to reach the tip of the drill, we will have to

translate it further by multiplying it with the P matrix

Where P matrix is the translation matrix

[ ]

Now in order to study the inverse kinematics of SCARA, consider the top view of

SCARA once again.

Figure 4.17: Top view of SCARA showing the dimensions

On the next page, are given the detailed dimensions of this top view

θ1

θ2


Page 80 of 124

Figure 4.18: Detailed dimensions of the top view

The point (x,y) is given to us and we have to find the angles θ1 and θ2. It can be

seen from the figure that,

x = L1 cosθ1 + L2 cos(θ1+θ2)

y = L1 sinθ1 + L2 sin(θ1+θ2)

Squaring and adding these two equations, we get,

x2

+ y2 = L1

2cos

2θ1 + L2

2cos

2(θ1+θ2) + 2L1L2cosθ1cos(θ1+θ2) + L1

2 sin

2θ1 +

L22

sin2(θ1+θ2) + 2L1L2sinθ1sin(θ1+θ2)

x2

+ y2 = L1

2 [cos

2θ1+sin

2θ1] + L2

2 [cos

2(θ1+θ2)+sin

2(θ1+θ2)] +

2L1L2[cosθ1cos(θ1+θ2)+sinθ1sin(θ1+θ2)]

x2

+ y2 = L1

2 + L2

2 + 2L1L2{ cos[θ1-(θ1+θ2)] }

cos(-θ2) = (x2

+ y2 - L1

2 + L2

2) / (2L1L2)

θ2 = cos-1

[(x2

+ y2 - L1

2 + L2

2) / (2L1L2)]

Consider the figure 4.18 shown below. A right triangle has been marked in bold,

it will help us in finding other angle.

θ1

L1 cosθ1

L2 cos(θ1+θ2)

L1 sinθ1

L2 sin(θ1+θ2)

( x,y )


Page 81 of 124

Figure 4.19: Detailed dimensions of top view with bold right triangle

It can be seen that

θ = θ1 + θ‟

or θ1 = θ – θ‟ …….(B)

by simple geometric formulae,

θ = tan-1

(y/x)

θ‟ = tan-1

[L2sinθ2/(L1+L2cosθ2)]

putting these values in equation (B), we get

θ1 = tan-1

(y/x) – tan-1

[L2sinθ2/(L1+L2cosθ2)]

4.7 Serial Communication

Serial Communication was performed with MATLAB. RS-232 was employed as

standard for communication, since it is the most known serial port used in transmitting

the data in communication and interface. Even though serial port is harder to program

than the parallel port, this is the most effective method in which the data transmission

requires less wires that yields to the less cost. The RS232 is the communication line

which enables the data transmission by only using three wire links. The three links

provides „transmit‟, „receive‟ and common ground.

The „transmit‟ and „receive‟ line on this connecter send and receive data between

the computers. As the name indicates, the data is transmitted serially. The two pins are

TXD & RXD. There are other lines on this port as RTS, CTS, DSR, DTR, and RTS, RI.

θ

θ‟

θ1

( x,y )


Page 82 of 124

The „1‟ and „0‟ are the data which defines a voltage level of 3V to 25V and -3V to -25V

respectively.

The electrical characteristics of the serial port as per the EIA (Electronics Industry

Association) RS232C Standard specifies a maximum baud rate of 20,000bps, which is

slow compared to today‟s standard speed. For this reason, we have chosen the new RS-

232D standard, which was recently released.

The RS-232D has existed in two types. i.e., D-TYPE 25 pin connector and D-

TYPE 9 pin connector. We have used the D-TYPE 9 pin connector. The pin outs and pin

configurations of DB9 are shown below:

Figure 4.20: DB9 male and female connectors

Table 4.1: Pin outs and pin functions of DB9

Pin no. Pin outs Function

1 DCD Data Carrier Detect (This line is active when modem

detects a carrier)

2 TD Transmit Data (Serial data output)

3 RD Receive Data (Serial data input)

4 DTR Data Terminal Ready

5 SG Signal Ground

6 DSR Data Ready State (UART establishes a link)

7 RTS Request To Send (acknowledge to modem that UART is

ready to exchange data)

8 CTS Clear To Send (i.e., modem is ready to exchange data)

9 RI Ring Indicator (becomes active when modem detects

ringing signal from PSTN)


Page 83 of 124

The IC that we used for voltage level transition from RS-232 to TTL level is

MAX-232. Below is shown the schematic diagram and the transition table. All the

capacitors in the diagram are of 22uF.

Figure 4.21: Schematic diagram of MAX-232

Table 4.2: Transition table of RS-232 voltages and MAX-232 voltages

RS-232 Line Type & Logic Level RS-232

Voltage

TTL Voltage to/from MAX-232

Data Transmission (Rx/Tx) Logic 0 +3V to +15V 0V

Data Transmission (Rx/Tx) Logic 1 -3V to -15V 5V

Control Signals (RTS/CTS/DTR/DSR)

Logic 0

-3V to -15V 5V

Control Signals (RTS/CTS/DTR/DSR)

Logic 1

+3V to +15V 0V

Since Serial ports are not available with new PCs and laptops, we used a USB to

serial converter and installed its driver.


Page 84 of 124

Figure 4.22: USB to serial converter with its cable

The values of the parameters used for serial communication are as under:

Table 4.3: Parameter values of serial communication

Parameter Value

1. Baud Rate 4800

2. Timeout 2 sec

3. Parity None

4. Flow Control None

5. Data Bits 8

6. Stop Bits 1

7. Handshaking None

8. Buffer Size 512 bytes

9. Terminator LF

The PIC coding for transmitting the data is given below:

LIST P=18F452


org 0x00

clrf PCLATH

goto Main

org 0x200

Main


MOVWF TXSTA


MOVWF SPBRG

BCF TRISC,TX

BSF RCSTA,SPEN


Page 85 of 124

r2 MOVLW A'G'

r1 BTFSS PIR1,TXIF

BRA r1

MOVWF TXREG

BRA r2

END

And for receiving the data is:

LIST P=18F452


org 0x00

clrf PCLATH

goto Main

org 0x200

Main


MOVWF RCSTA


MOVWF SPBRG

BSF TRISC,RX

CLRF TRISB

MOVLW 0x00

MOVWF PORTB

r1 BTFSS PIR1,RCIF

BRA r1

MOVFF RCREG,PORTB

BRA r1

END

The MATLAB code that we wrote for transmitting the angles is:

%serial communication to send angles

s_obj=serial('com3');

set(s_obj,'BaudRate',4800);

set(s_obj,'timeout',2);

fopen(s_obj);

fprintf(s_obj,'%s',out_1(1));

pause(1)

if(out_1(1)>0)

fprintf(s_obj,'%s',80);

pause(1)


Page 86 of 124

else


pause(1)

end

fprintf(s_obj,'%s',out_2(1));

pause(1)

if(out_2(1)>0)


pause(1)

else


pause(1)

end

ang=2;

while(1)

sent=0;

ss=fscanf(s_obj,'%s');

if(ss=='S')

display('ok')

sent=1;

final_out_1=out_1(ang)-out_1(ang-1);

fprintf(s_obj,'%s',final_out_1);

pause(1)

if(final_out_1>0)


%pause(1)

else


%pause(1)

end

final_out_2=out_2(ang)-out_2(ang-1);

fprintf(s_obj,'%s',final_out_2);

pause(1)

if(final_out_2>0)


%pause(1)

else


%pause(1)

end

ang=ang+1;


Page 87 of 124

else

display('S not received')

end

if(ang>size(out_1,2))

break;

end

end

fclose(s_obj);

delete(s_obj);

Before implementing it on hardware, we simulated the serial communication in

Proteus, and it worked perfectly. Then we designed and fabricated the PCB for serial

communication in Proteus. It also worked perfectly on hardware.

Figure 4.23: Proteus simulation of serial communication with PIC18F452


Page 88 of 124

Figure 4.24: PCB layout of serial communication board

Figure 4.25: Fully fabricated serial communication board

4.8 Remote access over the internet

Internet has become a necessity now-a-days. One can access anything half way

across the globe using the internet. It has reduced the world to a „global village‟. Keeping

this trend in mind, we have also added an interactive feature in our project. We developed

a website and interfaced it with SCARA, via MATLAB. Through this website, one can

send the input to SCARA even if he is sitting thousands of miles away.


Page 89 of 124

Figure 4.26: Website

All one has to do is to enter his name, location, email address and his PayPal

account no. for the deduction of charges. Then he can upload any desired file from his

hard drive for drilling. The file may be a Gerber file, or an image file containing the PCB

layout.

Figure 4.27: Entering data in the website

Page 90 of 124

The software we used for developing the website is „Adobe Dream Weaver‟. The

codes we wrote for developing and formatting the site, and for uploading a file are both

given below:

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"

"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">

<html xmlns="http://www.w3.org/1999/xhtml">

<head>

<meta name="keywords" content="" />

<meta name="description" content="" />

<meta http-equiv="content-type" content="text/html; charset=utf-8" />

<title>Diminishing by Free CSS Templates</title>

<link href="style.css" rel="stylesheet" type="text/css" media="screen"

/>

</head>

<body>

<div id="wrapper">



<div id="header">

<div id="logo">

<h1>SCARA</h1>

</div>

</div>

<div id="splash"> </div>



<div id="page">

<div id="page-bgtop">

<div id="page-bgbtm">

<div id="content">

<div class="post">

<h2 class="title">Welcome to Automated Drilling </h2>

<div class="entry">

<div class="formm">

<form action="upload.php" method="post"

enctype="multipart/form-data">

<p><br/>

Name:

<p>

<input type="text" name ="name"tabindex="1" class="inp-text"/>

<br/>

<br/>

Page 91 of 124

<p > Location:</p>

<input type="text" name

="location"tabindex="2" class="inp-text"/>

</p>

<p> <br/>

Email:</p>

<p>


="email"tabindex="3" class="inp-text"/>

<br/>

</p>

<p>PayPal Account No.:</p>

<p>


="paypal"tabindex="4" class="inp-text"/><br/>

</p>

<p>

<label for="file" class="float">Select

File:</label>

</p>

<p> </p>

<p>

<input type="file" name="file" id="file"

"tabindex="5" class="inp-text"/>

</p>

<p> </p>

<p> </p>

<p><br />

<input type="submit" name="submit"

value="Submit" style="margin-left:230px"/>

</p>

</form>

</div> </div>

</div>

<div class="post">

</div>

<div style="clear: both;"> </div>

</div>



<div id="sidebar">

Page 92 of 124

<ul>

<li>

<h2>Introduction</h2>

<p>We have designed this

website in the wake of commercializing our project. Please

upload a layout image file from ARES.</p>

</li>

<li>

<h2>Group Members</h2>

<ul>

<li><a >Syed Muhammad Zohaib Abbas</a></li>

<li><a >Syed Muhammad Danial Haider</a></li>

<li><a >Muhammad Zain</a></li>

<li><a>Ahmad Hassan Syan</a></li>

</ul>

</li>

<li>

<h2>Project Supervisor</h2>

<ul>

<li><a >Dr. Fahad Mumtaaz</a></li>

</ul>

</li>

</ul>

</div>




</div>

</div>

</div>



</div>

</div>

</body>

</html>

<html xmlns="http://www.w3.org/1999/xhtml">

<head>

<meta name="keywords" content="" />

<meta name="description" content="" />

Page 93 of 124

<meta http-equiv="content-type" content="text/html; charset=utf-8" />

<title>Diminishing by Free CSS Templates</title>

<link href="style.css" rel="stylesheet" type="text/css" media="screen"

/>

</head>

<body>

<div id="wrapper">



<div id="header">

<div id="logo">

<h1>SCARA</h1>

</div>

</div>

<div id="splash"> </div>



<div id="page">

<div id="page-bgtop">

<div id="page-bgbtm">

<div id="content">

<div class="post">

<h2 class="title">Welcome to Automated Drilling </h2>

<div class="entry">

<?php

if ($_FILES["file"]["error"] > 0)

{

echo "Error: " . $_FILES["file"]["error"] . "<br />";

}

else

{

}

?>

<?php

if ((($_FILES["file"]["type"] == "image/gif")

|| ($_FILES["file"]["type"] == "image/jpeg")

|| ($_FILES["file"]["type"] == "image/pjpeg"))

&& ($_FILES["file"]["size"] < 20000000))

{


{

echo "Error: " . $_FILES["file"]["error"] . "<br />";

}


Page 94 of 124

else

{

}

}

else

{

echo "invalid file";

}

?>

<?php

if ((($_FILES["file"]["type"] == "image/gif")

|| ($_FILES["file"]["type"] == "image/jpeg")

|| ($_FILES["file"]["type"] == "image/pjpeg"))

&& ($_FILES["file"]["size"] < 20000000))

{


{

echo "Return Code: " . $_FILES["file"]["error"] . "<br />";

}

else

{

echo "Size: " . ($_FILES["file"]["size"] / 1024) . " Kb<br />";

if (file_exists("upload/" . $_FILES["file"]["name"]))

{

echo $_FILES["file"]["name"] . " already exists. ";

}

else

{ echo "file Uploaded sucessfully";

move_uploaded_file($_FILES["file"]["tmp_name"],

"upload/" . $_FILES["file"]["name"]);

echo "Stored in: " . "upload/" . $_FILES["file"]["name"];

}

}

}

else

{

echo "b";

}

?>

<br /><br /><br /><br /><br />

<a href="index.html">Back </a> </div>

Page 95 of 124

</div>

<div class="post">

</div>


</div>



<div id="sidebar">

<ul>

<li>

<h2>Introduction</h2>

<p>We have designed this

website in the wake of commercializing our project. Please

upload a layout image file from ARES.</p>

</li>

<li>

<h2>Group Members</h2>

<ul>

<li><a >Syed Muhammad Zohaib Abbas</a></li>

<li><a >Syed Muhammad Danial Haider</a></li>

<li><a >Muhammad Zain</a></li>

<li><a>Ahmad Hassan Syan</a></li>

</ul>

</li>

<li>

<h2>Project Supervisor</h2>

<ul>

<li><a >Sir Fahad Mumtaaz</a></li>

</ul>

</li>

</ul>

</div>




</div>

</div>

</div>



</div>

</div>

</body>

</html>

SCARA Chapter 5 : Summary and Limitations

Page 96 of 124

Chapter 5:

SUMMARY AND LIMITATIONS

5.1 Summary

We successfully accomplished all the objectives of our project. By the end of the

semester, we were able to fully control the revolute movement of both the arms, as well

as the prismatic movement of the end effector. The movement was also very refine due to

the implementation of PID. We also successfully automated our project. Image

processing, gerber file processing, inverse kinematics, serial communication and remote

access, all were successfully implemented.

5.2 Limitations

We faced many problems and limitations during the course of making this project.

Some of the problems that faced are:

No information about the motors and encoders was given to us. The datasheets of

the motors were not available, not even on the internet. So we had to manually

check and find all the connections and determine the transfer functions of the

motors.

We did not design the mechanical structure ourselves. It was designed by our

seniors. It was a bit old-fashioned and we could not make any changes in it.

SCARA Chapter 6 : Recommendations for future work

Page 97 of 124

Chapter 6:

RECOMMENDATIONS FOR FUTURE WORK

Control and automation are two huge fields. A lot of research is being done in

these areas all around the world, and there is still a large area waiting to be explored.

Even in the particular case of our project, a lot of research can be done, and a lot of

improvements can be made in it. If someone wants to pursue and carry on this project, we

would to recommend that:

Improvements can be made in the web-SCARA interface.

SCARA has many several industrial applications, as discussed in the first chapter.

We, however specifically automated our project for automated drilling of PCBs.

Its end effector can be changed to serve other industrial applications. And for

automation, programming would have to be done accordingly.

Improvements can also be made in the mechanical structure. It bulky size and

weight can be reduced to make it more practical. Mechanical brakes can also be

installed and used for more accuracy.

SCARA Appendix

Page 98 of 124

APPENDIX

PIC18F452 Features utilized:

SCARA Appendix

Page 99 of 124

SCARA Appendix

Page 100 of 124

SCARA Appendix

Page 101 of 124

SCARA Appendix

Page 102 of 124

SCARA Appendix

Page 103 of 124

SCARA Appendix

Page 104 of 124

SCARA Appendix

Page 105 of 124

SCARA Appendix

Page 106 of 124

Serial Communication in MATLAB:

Associate Professor Joel M. Esposito

[email protected]

Systems Engineering Department

United States Naval Academy,

Annapolis, MD 21402

http://www.usna.edu/Users/weapsys/esposito/

Basic Concepts

Serial Message: You litterally send or recive data over this cable on a single pin

as a series of bytes (1 byte = 8 bits or 0 – 255).

o Example: [0] [12] [27] [42] [112]

Terminators: Just as we use a period in English to dentote the end of a sentence,

we use a "terminator" to indicate the end of a series of bytes that constitute a

message.

o The terminator can be anything the sender and receiver agree on but a

"carrage return" (\r) is a common choice.

mailto:[email protected]

SCARA Appendix

Page 107 of 124

Buffer: If you don't understand how a buffer works, you will never understand

serial communication. Say a sensor is streaming back data to your program, more

frequently than your program reads it. On your computer this data gets stored in

something called a buffer, until you decide to read it. Think of a buffer as a list.

o As new data values come in they get added to the bottom of the list (most

recent data).

o If your program reads a value from the buffer, it starts at the top of the list

(oldest data). Once you read a byte of data, it is no longer in the buffer;

and the data in the second position on the list moves up to the top position,

etc.

o The buffer has a finite length (you set it). This means there is a limit to

how long the list can get. Once the buffer is totally full, what happens

when the sensor tries to send new data to the buffer? The oldest data (top

of the list) gets discarded forever, and all the entries move up, to make

room on the bottom of the list for new data.

o If you'rer smart about using the buffer, you can make sure you never miss

any data. If your not smart about it, it is easy to loose data or use old data.

What You Need to Know Before You Continue

Go the computer you will use, your device, and all the documentation that came with it.

Find the Serial Port on the PC. If there is none, use a USB-to-Serial Converter.

You may have to install drivers for it. Connect the device to the PC.

COM Port Number: Each serial port on the PC is labeled COM1, COM2, etc.

You need to figure out which one you're attached to.

o If there is a serial port at the back of the computer, chances are it's COM1.

However, even if there is only 1 serial port visible in the back, its possible

its COM2, or COM3 especially if there is a modem.

o If you use a converter or blue tooth the port number gets assigned in

software and may change each time you disconnect or reconnect the

device. On Windows XP (or vista classic view), go to Control

Panel/System/Hardware/DeviceManager/Ports/Comm Ports and verify

which port your device was assigned

Device Settings: Go to the documentation that came with your device and

identify the Communication settings. We'll need this for the next section. Here is

an example:

o Baud Rate

o Timeout.

o Buffer size etc.

Setting up Serial port objects

Basic Concepts

Matlab uses a special variable type to keep track of serial connections – the Serial

Object.

Unlike nornal variables which have a single value, objects have many "attributes"

or parameters that can be set. (ex. port number, baud rate, buffersize, etc)

One of those attributes is the port number. A label that cooresponds to which port

your device is connected to.

SCARA Appendix

Page 108 of 124

In order to actually send or recieve data through the serial port object it must be

open. When not in use it can be closed (not the same as deleting it)

You can have many different serial objects in memory. They can all send and

receive data at the same time as long as they are each on a different port.

There can even be several objects associated with the same physical port.

However, only one of those objects associated with a given port can actually be

open (sending or receiving data) at any time.

Creating a Serial Port Object

Here is an example of how to do this. the only piece of information you must supply is

which com port to use. The rest of the attributes are set to some default values:

serialPort = serial('com1')

Setting the Parameters

set(serialPort, 'BaudRate', 19200)

get(serialPort, 'BaudRate')

This method is cumbersome if you have a lot of things you want to change. A better way

to to set them when you create the Serial Object.

serialPort_new = serial('com1', 'baudrate', 19200, 'terminator', 'CR')

The Parameters

To see a list of parameters and their current values

get(serialPort)

ByteOrder = littleEndian

BytesAvailable = 0

BytesAvailableFcn =

BytesAvailableFcnCount = 48

BytesAvailableFcnMode = terminator

BytesToOutput = 0

ErrorFcn =

InputBufferSize = 512

Name = Serial-COM1

ObjectVisibility = on

OutputBufferSize = 512

OutputEmptyFcn =

RecordDetail = compact

SCARA Appendix

Page 109 of 124

RecordMode = overwrite

RecordName = record.txt

RecordStatus = off

Status = closed

Tag = GarminGPS

Timeout = 0

TimerFcn =

TimerPeriod = 1

TransferStatus = idle

Type = serial

UserData = []

ValuesReceived = 0

ValuesSent = 0

SERIAL specific properties:

BaudRate = 19200

BreakInterruptFcn =

DataBits = 8

DataTerminalReady = on

FlowControl = none

Parity = none

PinStatus = [1x1 struct]

PinStatusFcn =

Port = COM1

ReadAsyncMode = continuous

RequestToSend = on

StopBits = 1

Terminator = LF

SCARA Appendix

Page 110 of 124

Good Idea To Set

Your device will work without setting these but you can set these to make your life easy

later.

Tag: The tag is like giving the serial port object a nickname. If have a few

different serial ports open this a good way to keep track of them. Example,

serialPort is configured to talk with a garmin GPS.

set(serialPort, 'tag', 'GarminGPS')

TimeOut: If you try to read data from the serial port and there is no data in the

buffer matlab will keep trying to read for "Timeout" seconds (default 10 sec):

get(serialPort, 'Timeout')

ans =

10

This might really slow down your code. There are ways around this, but if there

is no data there you probably don't want to sit there for 10 seconds, so consider

making it smaller. On the other hand, it does take some time for messages to pass

over the wire, so setting it to zero means you will probably miss a lot of messages.

InputBufferSize: This specifies how long the buffer is. The default is 512 bytes.

That might not be long enough for your messages. Especially if you think the

sensor will be streaming data back more frequently than you plan on reading the

buffer. Remember if the sensor tries to send data and the buffer is full it will

discard some old data and it will be gone forever. On the otherhand, having an

unessecarliy large buffer can be cumbersome.

Closing Serial Port Objects

Concepts

When you are done with a serial port object it doesn't go away. Also, closing it, deleting

it from memory and clearing it from the workspace are three separate actions.

Example Code

For technical reasons you have to use this syntax to properly get rid of it:

delete(serialPort_new)

clear serialPort_new

Writing To The Serial Port

Before you can write to your serial port, you need to open it:

fopen(serGPS)

SCARA Appendix

Page 111 of 124

Now you need to figure out two things from the Serial Command Interface (SCI) that

came with your device:

1. Will you send binary data (bytes) or text (ascii)?

2. What will you send to it?

If your SCIs messages look like a list of numbers (ex: [4][253][1][1])), its probably the

first choice. Note that even though what you send is actually binary, the documentation

might list it as numbers between 0 and 255, or hexidecimal numbers.

If your SCIs messages look like a mix of text and numbers (ex: 'MOVE 31'), its probably

the second choice.

Writing Binary Data

Use the command fwrite to send four bytes of binary data

fwrite(serGPS, [0, 12, 117, 251]);

Writing ASCI Commands

Use the command fprintf to send asci data. You can use a mix of text in single quotes

and variables values.

moveNum = 98; pauseTime = 2; % just some example data

fprintf(serGPS, 'MOVE %d, PAUSE %d', [moveNum, pauseTime] ) ; % note

Its important to understand that a number, (ex. 98) is not sent as a number. Its actually

the asci code for the characters '9' and '8'.

Reading From The Serial Port

Streaming vs Polling: Flushing the Buffer

If you are going to poll the device (send it a request each time you want to get data) you

don't want to read any old data that might be left over in the buffer. This is a useful and

quick way to clean it out

N = serRoomba.BytesAvailable();

while(N~=0)

fread(serRoomba,N);

N = serRoomba.BytesAvailable();

end

SCARA Appendix

Page 112 of 124

H-Bridge L298n datasheet:

SCARA Appendix

Page 113 of 124

SCARA Appendix

Page 114 of 124

SCARA Appendix

Page 115 of 124

TIP127 datasheet:

SCARA Appendix

Page 116 of 124

SCARA Appendix

Page 117 of 124

SCARA Appendix

Page 118 of 124

SCARA Appendix

Page 119 of 124

SCARA Appendix

Page 120 of 124

TIP122 datasheet:

SCARA Appendix

Page 121 of 124

SCARA Appendix

Page 122 of 124

SCARA Appendix

Page 123 of 124

SCARA Appendix

Page 124 of 124

fyp control and automation of scara june 2011 nust eme

Documents