UNIVERSITI TEKNIKAL MALAYSIA MELAKA (UTeM)

Remote Control Lawn Mower

Thesis submitted in accordance with the partial requirements of the Universiti Teknikal Malaysia Melaka for the

Bachelor of Manufacturing Engineering (Robotics and Automation) with Honours

Nur Nazatul Nura Mohamed Fouzy

Faculty of Manufacturing Engineering

May 2008

ABSTRACT

The Remote Control Lawnmower is a machine to make cutting grass process easier.

The lawnmower's movement will be controlled using RF remote control, where the

transmitter circuit will be placed at the remote control while the receiver circuit will

be placed at the lawnmower. The signal will be transfer from the remote control to

the lawnmower by the antenna (joystick) and the signal transfer is using radio

fkequency signal (RF). RF is quite effective in long distance and the components are

cheap and easy to get in the market. In this project, transmitter and receiver circuit is

build to control the movement of the lawn mower, motor and the rotation of the

blade. H-Bridge connection is used in the circuit in order to control the lawnmower's

movement whether to be slow or fast. There are two types of motor used in this

project and both of it is dc motor. Two types of dc motor used in this project are

power window motor and a regular dc motor.

ABSTRAK

Remote Control Lawnmower adalah sebuah mesh pemotong rumput yang dibina

menjadikan aktiviti memotong rumput lebih mudah. Pergerakkan mesin

pernotong rumput akan dikawal mengunakan alat kawalan jauh RF dimana litar

transmitter akan diternpatkan di alt kawalan jauh manakala litar receiver akan

ditempatkan di mesh pemotong rumput. Signal akan di hantar dari alat kawalan jauh

kepada mesin pemotong rumpur menggunakan antenna dan pemindahan signal ini

menggunakan radio frequency signal (RF). Signal RF berkesan untuk jarak yang jauh

dan komponen untuk litar RF adalah lebih murah dan senang untuk didapati di pasar.

Untuk projek ini, litar transmitter dan receiver dibina bagi mengawal pergerakkan

pernotong nunput, motor dan putaran mata bilah pisau. Sambungan H-Bridge

digunakan dalam litar bagi mengawal pergerakan laju dan perlahan pemotong

rumput. Terdapat 2 jenis motor yang digunakan dalam projek ini, kesemua motor

yang digunakan adalah dc motor. Dua jenis dc motor yang digunakan adalah motor

power window dan motor dc yang biasa.

CHAPTER 1

INTRODUCTION

1.0 Introduction

Mowing can be a very dangerous job as it involves rotating blade. It also took a very

long time to finish. This project produce a machine that is controlled by use of a

radio control system that will allow the operator to stay a safe distance away from the

machine so if anything happen, no one will get injured. This invention is also to

make mowing activity to be more fun and easy. Remote control systems are

increasing popular and the introduction of pre-tuned radio modules and their steadily

falling prices has made radio a viable alternative to infia-red control. The remote

control can cover area around 100 ft range. This machine is user friendly because

user only controls the machine with remote control and people can handle this

machine by only readiig the instructions. This project is divided into two parts,

mechanically and electronically.

1.1 Problem Statements

~ o s t of lawnmower today operates manually where human needs to control the

machine directly in grass cutting activities. This requires a lot of energy if the area

was too wide. The available lawn mower today uses petrol to operate the engine; this

can contribute air pollution. Automatic mower today requires a wire that surrounds

the boundary of the yard. This wire was installed around the perimeter of the yard

and the mower can sense this wire as the boundary. The mower will then turn a

specified angle and then cut in a straight line until it hits either the boundary or an

object, such as tree. It turns at the same angle again and will continue the same

process. The mower will continue this process until the lawn is completely cut. There

are a few drawbacks to this design. First, it requires a wire that needs to be implanted

into the ground. Second, the lawn isn't cut in nice patterns that people wants. The

mower constantly runs across the lawn in a different direction until it covers all of it,

which will take hours to complete.

The objective of this project was to:

A. Identify the features that need to be modified or added for the Remote

Control Lawn Mower :

wireless remote control

power window (dc motor)

transmitter and receiver circuit

lawnmower (body)

B. Fabricate the prototype of Remote Control Lawn Mower

material and design

C. Test and tune the lawnmower to working condition

1.3 Scope

The scope of this project was to design and develop lawn mower using remote

control. All the operation will be controlled using radio frequency (RF) remote

control. Basically, the project can be divided into two sections which are

mechanically and electronically. From here it can be divided into 5 parts. The first

part was the mower (body) and the second part was the transmitter and receiver

circuit and next was the remote control. The fourth part is the motor and lastly, the

fifth part was the power supply. This project was the result of the combination of

these 5 parts.

This project will only include a basic electronic component that we have seen

everyday, for example, remote control and DC motor. The mechanical movement of

this machine from right to left and from back to front will be using the motor control

H-Bridge.

( MECHANICAL ] ( ELECTRONIC ]

MOWER(B0DY) MOTOR POWER SUPPLY

pq CONTROL

Figure 1.1 : Section of the Project

CHAPTER 2

LITERITURE REVIEW

2.0 Introduction

In this study, previous researchers that were done by other researchers were

reviewed. The. study was related to the project. In this section those studies are

reviewed, cited and credited. The information was found in reference book,

magazines and electronics media such as in the internet.

2.1 Historic of Wireless Communication

Wireless signals proved effective in communication for rescue work when a sea

disaster occurred. Effective communication was able to exist between ships and ship

to shore points. A number of ocean liners installed wireless equipment, In 1899 the

United States Army established wireless communication with a lightship off Fire

Island, New York. Two years later the Navy adopted a wireless system. Up to then,

the Navy had been using visual signaling and homing pigeons for communication.

~n 1901, radiotelegraph service was instituted between five Hawaiian Island. By

1903, a Marconi station located in Wellfleet, Massachusetts, carried an exchange or

greetings between President Theodore Roosevelt and King Edward VII. In 1905 the

naval battle of Port Arthur in the Russo-Japanese war was reported by wireless, and

in 1906 the U.S Weather Bureau experimented with radiotelegraphy to speed notice

of weather conditions.

In 1909, Robert E. Peary, arctic explorer, radio telegraphed "I found the pole". In

1910, Marconi opened regular American-European radiotelegraph service, which

several months later enabled an escaped British murderer to be apprehended on the

high seas. In 1912, the first transpacific radiotelegraph service linked San Francisco

with Hawaii.

Overseas radiotelegraph service developed slowly, primarily because the initial

radiotelegraph set discharge electricity within the circuit and between the electrodes

was unstable causing a high amount of interference. The Alexanderson high

frequency alternator and the De Forest tube resolved many of these early technical

problems. The Navy made major use of radio transmitter, especially Alexanderson

alternators the only reliable long-distance wireless transmitter, for the duration.

During World War I, governments began using radiotelegraph to be alert of events

and to instruct the movement of troops and supplies. World War I1 demonstrated the

value of radio and spurred its development and later utilization for peacetime

purposes. Radiotelegraph circuits to other countries enabled persons almost

anywhere in the United States to communicate with practically any place on earth.

since 1923, pictures have been transmitted by wire, when a photograph was sent

from Washington to Baltimore in a test. The first transatlantic radiophoto relay came

in 1924 when the Radio Corporation of America beamed a picture of Charles Evans

Hughes fiom London to New York. RCA inaugurated regular radiophoto service in

1926.

TWO radio communication companies once had domestic networks connecting

certain large cities, but these were closed in World War 11. However, microwave and

other developments have made it possible for domestic telegraph communication to

be carried largely in part over radio circuits. In 1945, Western Union establishes the

first microwave beam system, connecting New York and Philadelphia. This has since

been extended and is being developed into a coast-to-coast system. By 1988 Western

Union could transmit about 2,000 telegrams simultaneously in each direction.

2.2 Radio Frequency (Transmitter and Receiver)

In order to carry useful information, radio waves must be modulated, in other word;

the signal must be superimposed on the radio wave (carrier wave). With

amplitude modulation transmission, it is the amplitude of the carrier wave that is

made to change in accordance with the required signal. It is reasonable to generate

but can suffer from interface. With Frequency Modulation transmission, it was the

frequency of the carrier wave that was made to change in accordance with the

required signal. The F.M modules described here tend to be more expensive than the

A.M modules, but they were almost immune to interference, can carry higher data

rate and have longer range.

Figure 2.1 : Transmitter and receiver modules

Joystick Atmel 44 14 - Modcm

I I

I l l 1 I I I l l I I I I I I I t I

;*: I I

Speed Control * v

Car % Atmel Modcm Steering Control

d

2.2.3 Coded Transmitter

~ l l remote control system was more reliable if a coded message was sent, and used

of an encoder integrated circuit is suggested. AX5326p-4 is use in this project. It can

operate up to 12V and it does not produce a modulated output. In other word, the IC

encodes the signals but modulation was performed inside the radio module.

2.2.4 Decoding Receiver

Details how the receiver module may be used with an AX decoder. Signals detected

by the receiver module IC are output to the decoding device. The signal was only

decoded if the setting on the dip switch S 1 was matching those of the transmitter.

When a correctly coded signal was received the pin on IC2 switched to positive. The

only pin remains positive for the duration of the decoded signal.

2.3 TIG Welding

2.3.1 TIG Basics

Gas Tungsten Arc Welding (GTAW) was frequently referred to as TIG welding. TIG

welding was a commonly used high welding process. TIG welding has become a

popular choice of welding processes when high quality, precision welding was

required.

In TIG welding an arc was formed between a nonconsumable tungsten electrode and

the metal being worked. Gas was fed through the torch to shield the electrode and

molten weld pool. If filler wire was used, it was added to the weld pool separately.

Although TIG welding was a relatively slow process, it provides high quality welds.

Typical applications are for aluminum irrigation pipes, stainless steel sprayer tanks

and aluminum engine parts.

TIG was the perfect welding method for materials such as stainless steel, titanium

alloy, aluminum alloy and high-temperature alloy steel. It was most often used for

general repairs and sometimes for assembly. For example, conventional TIG would

be used for welding or laminating multiple tooling parts.

Conventional TIG would also be a choice to repair damage caused by knockout pin

breakage, or to repair parting line flash and to weld gate areas. Dimensional

corrections can be made to get a mold back into tolerance, and can be used to apply a

permanent shim on the back or bottom of an insert or cavity and core.

2.3.2 Advantages of TIG Welders

While using a TIG welder requires that separate filler material be used when

additional material is needed, TIG welding has a number of advantages over other

welding processes.

The sharp and rigid tungsten allows for high precision welding.

The small arc produced by TIG welding was ideal for welding thin materials.

No material was added to the weld unless it is required.

The inert gas shielding the weld creates no slag or splatter, making TIG

welding a much cleaner and time-efficient process.

Nozzl 7

w e l i ~ e t a l wild Pool

Figure 2.2: TIG Illustration

2.3.3 Shielding Gases

Argon

Argon + Hydrogen

ArgonMelium

Helium was generally added to increase heat input (increase welding speed or weld

~enetration). Hydrogen will result in cleaner looking welds and also increase heat

input; however, Hydrogen may promote porosity or hydrogen cracking.

2.3.4 TIG Welding Problems

Erratic arc

Excessive electrode consumption

Oxidized weld deposit

Arc wandering

Porosity

Difficult arc starting

2.4.1 Introduction

In general an H-bridge was a rather simple circuit, containing four switching

element, with the load at the center, in an H-like configuration:

Figure 2.3: H-Bridge Connection

The switching elements (41 ..Q4) are usually bi-polar or FET transistors, in some

high-voltage applications IGBTs. Integrated solutions also exist but whether the

switching elements are integrated with their control circuits or not was not relevant

for the most part for this discussion. The diodes (Dl ..D4) are called catch diodes

and are usually of a Schottky type. Though they are mentioned in most documents

dealing with H-bridges, their role is usually neglected. They are of key importance

for most of the discussion on this page.

In general all four switching elements can be turned on and off independently,

though there are some obvious restrictions. Though there's no theoretical restriction

like that, by far the most pervasive load used with H-bridges are brushed DC or

bipolar stepper motors (steppers need two H-bridges per motor).

2.4.2 Basic operation

The basic operating mode of an H-bridge was fairly simple: if 4 2 and 4 3 are turned

on, the left lead of the motor will be connected to ground, while the right lead was

connected to the power supply. Current starts flowing through the motor which

energizes the motor in (let's say) the forward direction and the motor shaft starts

spinning. If Ql and Q4 are turned on, the converse will happen, the motor gets

energized in the reverse direction, and the shafi will start spinning in that way. If

less than full-speed (or torque) operation was intended one of the switches are

controlled in a PWM fashion. The average voltage seen by the motor will be

determined by the ratio between the 'on' and 'off time of the PWM signal.

Current flow in the forward direction Current flow in the backward direction

Figure 2.4: Basic Operation

2.5 DC Motor

DC motors consist of rotor-mounted windings (armature) and stationary windings

(field poles). In all DC moton, except prmanent magnet motors, current must be

conducted to the armature windings by passing current through carbon brushes that

slide over a set of copper surfaces called a commutator, which was mounted on the

,tor. The commutator bars are soldered to armature coils. The brushlcommutator

combination makes a sliding switch that energizes particular portions of the

armature, based on the position of the rotor. This process creates north and south

magnetic poles on the rotor that are attracted to or repelled by north and south poles

on the stator, which are formed by passing direct current through the field windings.

It was this magnetic attraction and repulsion that causes the rotor to rotate.

2.5.1 The Advantages

The greatest advantage of DC motors may be speed control. Since speed was directly

proportional to armature voltage and inversely proportional to the magnetic flux

produced by the poles, adjusting the armature voltage andlor the field current will

change the rotor speed. Today, adjustable frequency drives can provide precise speed

control for AC motors, but they do so at the expense of power quality, as the solid-

state switching devices in the drives produce a rich harmonic spectrum. The DC

motor has no adverse effects on power quality.

2.5.2 The drawbacks

Power supply, initial cost, and maintenance requirements are the negatives associated

with DC motors.

Rectification must be provided for any DC motors supplied from the grid. It

can also cause power quality problems.

The construction of a DC motor was considerably more complicated and

expensive than that of an AC motor, primarily due to the commutator,

brushes, and armature windings. An induction motor requires no commutator

or brushes, and most use cast squirrel-cage rotor bars instead of true windings

- two huge simplifications.

. Maintenance of the brush/commutator assembly was significant compared to

that of induction motor designs.

In spite of the drawbacks, DC motors are in wide use, particularly in niche

applications like cars and small appliances.

Permanent mamet motors

Here, permanent magnets instead of armature windings are mounted on the rotor.

Since the magnetic field produced on the rotor is limited in strength and was not

controllable, permanent magnet motors are typically small and produce little

horsepower.

Series motors

Series motors connect the field windings in series with the armature. Series motors

lack good speed regulation, but are well-suited for high-torque loads like power tools

and automobile starters because of their high torque production and compact size.

Shunt motors

Shunt motors use high-resistance field windings connected in parallel with the

armature. Varying the field resistance changes the motor speed. Shunt motors are

prone to armature reaction, a distortion and weakening of the flux generated by the

poles that result in commutation problems evidenced by sparking at the brushes.

Installing additional poles, called interpoles, on the stator between the main poles

wired in series with the armature reduces armature reaction.

Compound motors

Here, the concept of the series and shunt designs are combined. The Figure above

shows one way of wiring a compound motor with interpoles. The blue lines indicate

the shunt field, the red lines designate the series field and the green lines show the

interpole windings in series with the armature.

After more than a century, DC motors are still in .widespread use, and thanks to niche

applications that show no signs of disappearing, they'll be around for many years to

come.

CHAPTER 3

METHODOLOGY

3.0 Introduction

This Remote Control Lawn Mower was divided into 5 parts, lawn mower (body),

motor, power source, circuit and the last part was the remote control. The project was

divided according to this part so that all the work can be done according to schedule

and it will be easier to arrange all the work.

Radial Diagram

DEBUGGING

Figure 3.1 : Radial Diagram

f REMOTE CONTROL

LAWN MOWER

Figure 3.2: Remote Control Lawnmower Project

3.1 Lawn Mower (Body)

For the final design of the Lawnmower, it was decided that the best solution was to

construct a frame design for the ease of implementation of the objectives. The design

allowed an idea to build a desired mobility and mounting platform into the model

without the limitations or unnecessary components associated with recycling a used

mower chassis. This allows for a safe design that can protect the operator and allow

for remote operation.

This section was to detail the mechanical construction of the Lawnmower's

mounting frame and how the blade and other parts are mounted to it. For this

Lawnmower, the hollow steel was used to be the mower's body.

3.1.1 Part 1: Frame Construction

The metal used for the body frame was stainless steel (hollow steel % inch x % inch)

and to build the entire fiame it uses approximately 3 meters of the steel. In

determining the width of the body frame of this project, it was planned that the

overall width of the chassis rails is the same width as the distance between the bases

of the axles. This width must also consider if it clear the motor and other accessories.

More important was to choose the overall length of the chassis rails. This must be

done very carellly, and must consider the following points when designing this part:

At all times/height adjustments the front swivel wheels

must not touch the body of the mower

A little extra at the back must be added because it is better

to have too much than too little.

Figure 3.3: The frame

3.1.2 Front Wheels Supports

The front wheel consists of two 5 cm diameter caster wheels welded to the main

h e . The wheels were made of nylon and can move freely in any direction.

It was welded slightly back fiom the fiont edge of the frame so the mower has the

tendency to move straight. It would be better to put them as far forward on the frame

as possible to get best usage out of the chassis.

The wheels were welded to the fiame using TIG Welding. The wheels were welded to

the frame using TIG welding because the frame was made of stainless steel.

Figure 3.4: The front wheels

3.1.3 Rear Wheels

The rear wheel uses standard tyres that were bought in hardware store which was

normally used in remote control car. The wheel was normally called caster wheels.

But the caster wheel had been modified where only the wheel was used in the project

instead of the metal. Both tyres were connected together with the power window

motor using the adapterlshaft and boost (left and right). First of all, the gear from the

power window was welded to the screw from the caster wheel because this was the

only way the power window motor can be connected to it. In this way the motor can

moves the wheel. The shaft then is welded to a boost. This was to give some space

between the wheel and the power window motor. There was a flat metal sheet fiom a

stainless steel (1.2 mm) between the motor and the wheel. The wheel will only move

if the motor was connected to the power supply. Refer figure 3.1.3(a).

Figure 3.5: Rear Wheels

Figure 3.6: Mounting of the rear wheels to frame

3.1.4 Mower (Blade Casing/Blade)

For this project, the blade casing uses a thin metal sheet to cover the blade and expose

only the cutting part of the blade to the ground. The casing was mounted on the fimne

of the mower while the blade is mounted on the casing. The design for the casing was

slightly different than any other lawnmower in the market where the shape of the

mower was square instead of round. The mower was a little bit lower than the top of

the lawnmower to make cutting grasses to be more efficient and neat. And on top of

the mower, there was a 1 cm diameter holes, drilled, to let the dc motor to be mounted

to it and so the blade can be mounted to the dc motor. Refer figure 3.1.4(a).

Figure 3.7: Casing Blade

CASING BLADE DC MOTOR

Figure 3.8: The mounting of the blade's motor