Project Interim Report (Autosaved)

8/12/2019 Project Interim Report (Autosaved)

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Proposal Interim Report:

Design and Development of a Solar

Powered Automatic Lawn Mower

PROJE! ODE: "#P$%$&

!eam Mem'ers:

OMORO !O((IAS O)

SA*#A *OEL O+,+,

AI-A E,.E*E


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A(S!RA!

In Kenya today, most lawn owners either use manual workers or petroleum powered lawn

mowers to maw their lawns. The use of manual workers is a process that is expensive, fails to

employ technology, and also leads to inconsistent mowing of grass. The petroleum powered lawn

mowers require an operator, are noisy, and emit air pollutants from their exhausts. A solution to

these two methods is the use of an automatic solar powered lawn mower. In addition to using

green energy- solar power that the earth receives in vast amounts at any given instance, it

eliminates the necessity of employing operators it leads to consistent grass cutting, and employs

modern technologies in its operations. In Kenya automatic lawn mowers are very few and are not

afforda!le to a ma"ority of the population. Alternative methods to automatic lawn mowers have

therefore remained to !e the popular ways of tending grass in lawns and other grass surfaces.

This pro"ect aims to come up with a design that would !e cheaper and thus afforda!le to the

Kenyan population and also !e fully operational with high efficiency.

The lawn mower is to !e powered !y solar with a !attery used for charge storage. The

lawn mower should have a ro!ust and sta!le structure to carry all loads associated with its

structure and operation. #otion and change of directions on the surface should also !e achieved

!y the lawn mower. The lawn mower should also !e a!le to navigate a given area on its own

while avoiding o!stacles. Incorporated in it should !e a grass cutting mechanism.

The developed system at the end of the pro"ect should !e functional and meet all the

stated o!"ectives and should also !e within the !udget allocated for the pro"ect.


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!a'le of ontents$.% I&T'()*+TI(&...........................................................................................................................

/)/ (A+.RO,*D..................................................................................................................................

/)0 PRO(LEM S!A!EME*!..................................................................................................................

/)1 PRO(LEM J,S!I"IA!IO*..........................................................................................................

/)2 O(JE!I3ES....................................................................................................................................../

0.% 1IT2'AT*'2 '23I24................................................................................................................./

0)/ O3ER3IE4...................................................................................................................................... ..5

0)/)/ OMMERIALL# A3AILA(LE A,!OMA!I LA4* MO4ERS.......................5

Table 2.1 Technology Analysis........................................................................................................6

0)/)0 IO* A,!O*OMO,S LA4*MO4ER OMPE!I!IO*...............................................6

0)/)1 A*DROID O*!ROLLED LA4*MO4ER...........................................................$$

.% #2T7()(1(89..............................................................................................................................$

1)/ Overview.............................................................................................................................................$

1)0 ME-A*IAL DESI.*.................................................................................................................$

1)0)/ 5assis.......................................................................................................................... $

1)0)0 45eels.................................................................................................................................$/

1)0)0 .rass cutter 'lade...................................................................................................... ..$/

1)2 AL,LA!IO*S ,SI*. I*I!IAL ES!IMA!ES........................................................................0$

.% 2:;2+T2) (*T+(#2


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$.% I*!ROD,!IO*

/)/ (A+.RO,*D

The lawn mower was invented in $6% !y an engineer named 2dwin =eard =udding.

=udding o!tained the idea of the lawn mower after seeing a machine in a local cloth mill which

used a cutting cylinder mounted on a !ench to trim cloth to make a smooth finish after weaving.

=udding reali>ed that a similar concept would ena!le the cutting of grass if the mechanism could

!e mounted in a wheeled frame to make the !lades rotate close to the lawn?s surface. This

reali>ation allowed =udding to produce lawn mowers made of cast iron. These lawn mowers

featured a large rear roller with a cutting cylinder in the front. +ast iron gear wheels transmitted

power from the rear roller to the cutting cylinder @$.

&owadays, lawn mowers are useful pieces of machinery that employ a revolving !lade to

cut a lawn very smoothly. ed to mow

the lawn regularly due to the userBs timely schedule. The lawn mower can also !e programmed to


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mow grass at the desired height. The mechanism of a ro!otic lawn mower contains wheels which

allow the lawn mower to navigate the lawn, along with sensors which are used to detect changes

in terrain, fences, and other foreign o!"ects which should not !e mowed. Typically,

the ro!ot includes a charging station which can !e installed anywhere where there is an electric

outlet. #ost of these ro!ots are equipped with containers for clipping collection so that the

lawn does not need to !e raked after mowing @.

/)0 PRO(LEM S!A!EME*!

The standard motor powered push lawn mower is not considered user friendly. The young, old,

handicapped, or people who are disa!led would have issues using a typical push lawn mower.

Another draw!ack when using a standard motor powered push lawn mower is that this lawn

mower is not environmentally friendly as it would cause air and noise pollution. The electric

lawn mower is environmentally friendly since there is no noise pollution due to engine noises,

and no fumes !ut is expensive. An electric corded lawn mower is limited in range !y its trailing

power cord, which may limit its use with lengthy lawns. There is the additional ha>ard with these

machines of accidentally mowing over the power ca!le. The programma!le ro!otic lawn mower

is very expensive. (ne can pay upwards of C,%%% to purchase their own. Also, this lawn mower

requires the user to set up a !order wire around the lawn that defines the area to !e mowed. This

timely process must also !e done correctly or else the ro!otic lawn mower will not operate

properly DE. (ur main goal is to design and create a lawn mower that incorporates all of the

!enefits of the previous mentioned lawn mowers and eliminate all of the previously mentioned

draw!acks. 4ith all of these lawn mower designs mentioned, our plan is to create a solar-

propelled electric automatic lawn mower. (ur design will !e more hardware set with software

controls like a predicta!le navigation algorithm while still maintaining the efficiency andrelia!ility of regular lawn mower.


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/)1 PRO(LEM J,S!I"IA!IO*

#ost autonomous lawn mowers already created generate a random pattern that will encompass

the entire area desired to !e mowed at the end, !ut ends up consuming a lot of energy and time.

This "ustifies our push for a predicta!le navigation pattern that is more efficient in terms of

energy consumption and time spent. An electric wire is needed for most autonomous mowers to

create a mowing !oundary for the machine. 7owever, if the electric line is not properly placed,

the mower could potentially cross over the line and travel where it is not supposed to. The

perimeter wire increases time required for set up whenever a lawn is to !e mowed. This pro"ect

design will eliminate this guide wire and will instead incorporate a few sensors to carry out the

same function more efficiently. The overall goal for this mower pro"ect is to create an automated

solar powered lawn mower that is very effective and efficient while at the same time the machine

is safe, simple and not expensive.

/)2 O(JE!I3ES

The main o!"ective is to create an automated solar powered lawn mower that will mow a lawn,

navigate and perform o!stacle avoidance autonomously while !eing very simple to use,

effective, and efficient as well as incorporating safety, and simplicity inexpensively.

To achieve the main o!"ective the following specific o!"ectives will !e addressedF

$E To design a simple and fa!ricate the grass cutting mechanism and the chassis for

housing the electrical system and support the mechanical elements of the lawn

mower

0E To design and develop electronic control circuitry for the lawn mower

E To develop control code for the lawn mower controller

E To perform experiments that will test the performance of the lawn mower


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0.% 1IT2'AT*'2 '23I24

0)/ O3ER3IE4

There are past developments that have gone on to develop !etter solutions for mowing. As a

result, the literature review for this pro"ect is divide into three main areas namely commercially

developed automatic lawn mowers review, I(& ro!otics +ompetition pro"ect designs and a

ho!!yist pro"ect, the Android +ontrolled lawn mower.

0)/)/ OMMERIALL# A3AILA(LE A,!OMA!I LA4* MO4ERS

The technology ta!le 0.$ shown !elow gives a snapshot of the commercially availa!le lawn

mowers and their characteristics like cost, weight, dimensions, cutting strategy, navigation

system, sensor system and typical chargingGrunning time. The models outlined here include

'o!o#ow, 7usqvarna Automower


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the existing automated lawnmowers have good solutions for low noise emission, in the range of

/ to 6d=.

Table 2.1 Technology Analysis

Product ost 4eig5tDimension in

inc5es

utting

Strateg6

*avigation

S6stemSensor S6stem

!6pical

5arging

!ime an

Running

!ime

Ro'oMow 789 C0,$J $. kg &GA


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0)/)0 IO* A,!O*OMO,S LA4*MO4ER OMPE!I!IO*

The I(& Autonomous 1awnmower +ompetition was an annual competition hosted !y

the


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need for the mower to have a >ero turn radius. )uring the second semester several additions and

modification were made to prototype lawnmowers. 8enerally, the lawnmowers that participated

in the competition consisted of seven su!systemsF Lrame


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The overall system consists of a mechanical su!system, consisting of the frame design, weather

enclosure, digital encoder mounts, mower !lade and shroud and wheel mounts. The mechanical

su!system was designed using multiple software suites in order to develop a sound frame design,

determine suita!le material selection and determine the environmental impact of the design.

Ligure 0.$.0.0 !elow shows the development stages of design through the development of

several prototypes.

"igure 0)/)0)0


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0)/)1 A*DROID O*!ROLLED LA4*MO4ER

The !asis of this pro"ect was to design a lawnmower that can !e controlled with oneBs android device. The

constituents used to create this includeF a lawnmower, motors, motor controller, !atteries, wheels, staple

components for the frame and wheels, Arduino, 4iLly shield, and a wireless camera. The techniques used

to create and manipulate the machine includedF


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powered !y a car !attery the car !atteryBs output voltage was stepped down from $03 to 3 using a

linear regulator !ecause higher voltages caused malfunctions with the ;4# pins. Numper wires are used

to connect the Arduino to the 4iLly module.

As can !e derived, most of the commercial autonomous lawnmowers use perimeter wire sensors

to control their motion within the assigned area. There are two different types of perimeter wire

sensors one is a !oundary loop-wire sensor used to prevent the lawn mower from going outside

the assigned area. Another type is a guide wire sensor which is used to guide the mower to its

charging station and return to its last finishing position after !eing fully charged. =ut this

solution has some weaknesses the mower consumes more energy and time since it operates

randomly within the !oundary loop until the entire green area is mowed, and the lawn will not

look nice after mowing. 4hile the I(& 'o!otics +ompetition tries to eliminate the perimeter

wire, these pro"ects are very expensive as they are heavily funded hence introduce complex

technologies like laser scanning and 8;< triangulation. (n the other hand, ho!!yists try to solve

the same pro!lem !ut not to very successful execution.


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1); ME!-ODOLO.#

1)/ Design Overview

The design of the overall system will !e !roken down into three fundamental areasF the

mechanical platform, the electrical system, and the software implementation. The mechanical

platform will consist of a sturdy aluminium chassis !ase that is driven !y four wheels using

differential steering from the rear. Inside the ro!ot, a mower deck occupies the !ase of this frame.

It is important to use the correct type of mower deck since vi!rations are of great concern here.

The shroud is used to separate the mower deck area from the rest of the ro!ot to prevent grass

clippings from !lowing into the upper compartment of the ro!ot. The solar panels inclined in a

3-shape arrangement are the main power source for the !atteries via a charge controller. There

are two separate 03G$/A drive motors to provide thrust mo!ility to the ro!ot. In the !ack, two

$03 !atteries, connected in series, supply 03 to the motor powering the mower and the dual h-

!ridge, which controls !oth drive motors. )rive motors, electronics and !atteries are located

toward the rear of the ro!ot to provide more traction. The electrical system is created in two

independent sections. The first will consist of the electronics portion of the ro!ot hardware. This

includes the sensory devices Di.e. ultrasonic sensors, encoders, etc.E and the microcontroller that

will handle processing of the received data. The second section will !e made of the motors and

motor drives. The software associated with this pro"ect is categori>ed into navigation and

o!stacle avoidance su!systems. Ligure .$.$ !elow shows the high level design of the overall

system.


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"igure 1)/)/ !5e overall s6stem design

1)0 ME-A*IAL DESI.*

The primary concern when designing this lawn mower is its simplicity and low cost, which

affected the types of materials considered for the chassis. The mechanical design was focused on

the materials needed to construct a custom frame and housing that would !e the !asis for a ro!ust

and functional lawn mower. Ligure .0.$ shows the mechanical design as designed using


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screwed onto the frame such that one is at the front of the frame !etween the spindle wheels and

one on each side of the frame, all of which are pointing outwards to help sense o!stacles at the

!est Hviewing angle. The chassis design is shown in figure .0.0 !elow.

"igure 1)0)0 5assis design

The 1atitude and 1ongitude of Nu"a locality is -$.$%00 and 5.%$$J0/ respectively. (n the

0$st )ecem!er, the sun will rise J$O east of due south and set J$O west of due south. The chassis

design is in such a way that it can hold the cutter motor securely and at the same time hold the 3-

configuration of the solar panels at an angle of 0%O.

Fault Analysis

As shown in Ligure .0.0, the frame of the lawn mower was drawn in


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where the most stress is happening on the frame and dark !lue is where the least stress is

showing on the frame.


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The motors !eing used are two )+ electric motors. 2ach of the motors came with their

own mounting !rackets and gear !oxes. The two drive motors are !olted onto aluminum 1-

!eams with four hex screws. The 1-!eams are welded on either side of the frame of the

autonomous lawnmower. The motors also have a gear switch located at the top of the housings.

3.2.5 Final Mower Specifcations

Ta!le .0.0F #ower


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Electronics Co!part!ent Len&t'( -5./2 c! Wi%t'( 2+.3/ c! ei&'t( 2,.32 c!

C0ttin& %ec4 wi%t' ,.,3c!

C0tter len&t'-).,2c!

otal !ass -.+/4&

Mechanical Design Validation


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The lawn mower will consist of three motors- two to drive the wheels and one to run the grass

cutter mechanism. The wheel motors should !e a!le to provide sufficient torque to move the

lawn mower in various types of lawn terrain. The motor controller and drives should !e a!le to

vary the performance of the motors to achieve the events of !raking, starting, maintaining

motion, differential power to select motion direction and reversing. Lor the grass cutter the

motors and motor controllers will achieve the functions of starting and stopping the motors

depending on the directions presented though the microcontroller program. The motors would !e

interfaced to the system micro controller from which the system code will !e run to control the

entire system. The ratings of components in the motor drive circuits will !e calculated as per the

design specifications.

The figure .0 !elow shows some dc motor controllers and some of their parameters and

features.

Ligure .0 types of dc motor controllers considered

1)1)0)0 Microcontroller

The micro controller will act using its program code to change the manner of operation of

different components of the drive circuit. The microprocessor through its program code would


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influence starting the drive mechanisms, maintaining the drive mechanisms in motion, changing

direction of the lawn mower through differential wheel powering, reversing the lawn mower and

!reakingG stopping the lawn mower. The micro controller using its code will determine whether

the grass cutter motor starts or stops.

1)1)1 O*!ROL IR,I!S

The control circuit will !e implemented to achieve its functions through the interaction of

sensors and the micro controller. The sensors !eing considered are proximity sensors to detect

the presence and proximity of o!stacles, grass detection sensors to detect the presence or a!sence

of grass. The sensors will !e interfaced to the micro controller so that an appropriate action is

implemented according to the program code.The figure . !elow shows roughly the interaction of various components of the electronic

module


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Ligure . Interactions of components in the control model.1)1)2 ODE DE3ELOPME*!

+omputer


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faster. The "oystick also has the power !utton which is needed for !oth the controller and the

computer su!system.

The computer su!system contains the !asic stamp 0 microcontroller which directs the

mower?s movement, sensors, and the on and off functions. As the frame of the mower moves the

microcontroller receives signals from the ultra-sonic ping sensors and the infrared sensors. Theping sensor sends out a pulse and when the pulse !ounces !ack the sensor sends the amount of

time it took to receive the pulse to the microcontroller. Then the microcontroller depending on

the distance it calculates reroutes around the o!"ect. The infrared sensor sends a frequency out

that is set to detect a certain color and if it gets reflected !ack then the infrared sends the signal

!ack to microcontroller. Lor sensor location see )rawing T$. The wheels on the lawnmower

have a !uilt-in encoder which sends a signal to the microcontroller which gets interpreted as a

distance. (nce the distance is reached the !asic stamp 0 sends the signal to the controller. As

the mower moves across the microcontroller saves the distance from the encoder so it can

compare against the dimensions of the field. The microcontroller could receive signal for an

automatic shut off, either from a wired red !utton or from the wireless controller.

T.


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T. 2quipment 1ist

-=asic


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the program needs to !e changed so the program can accurately stop. If the constant is wrong it

could cause it to inaccurately read the o!"ect distance and either hit the o!"ect or avoid it too

soon causing the lawnmower to not cut some of the grass.

Also, if the program has a memory error it could affect the encoder and have it go longer or

shorter and go out of the !ounds of the cutting field. There is no way to prevent this. The!ackup is the infrared sensor which is also running and it detects the !oundaries in case the

encoder fails.


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: P ;ing *ltra-


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The coding language will !e selected in accordance to the final micro controller that will !e

selected. The code will !e involved in the process of navigation and o!stacle avoidance.

1)1)2)/ *avigation

The code should ensure that the microprocessor controls the drive mechanisms and circuitry to

move the mower around from a given start point during the process of grass cutting. The motion

will !e in a linearG nonrandom manner.

1)1)2)0 O'stacle avoidance

Through the microprocessor program code will direct the drive circuit on how to ena!le the lawn

mower to avoid the o!stacles. (!stacle sensors would inform the microprocessor of the presence

of an o!stacle. The microprocessor through its program code would then determine the path to !e

followed in avoiding the o!stacle. e the code, testing will then !e done on the lawn mower to see how the lawn

mower operates when running the specific program code.

1)2 AL,LA!IO*S ,SI*. I*I!IAL ES!IMA!ES


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4heel )iameter P$6.cm=aterry ;ack P $kg.+hasis 4eight P kg.4heel #otors P kg.+utter #otor 4eight P 0kg.

+utter P$kg.


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2); E=PE!ED O,!OMES

To develop an automated solar powered lawn mower that will mow a lawn, navigate and perform

o!stacle avoidance autonomously while !eing very simple to use, effective, and efficient as wellas incorporating safety, and simplicity inexpensively.

Fig 3.3 Schedule


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8); RE"ERE*ES

@$ =ender, )aniel. 8uthrie, Andrea. 8oode, Nason. 7ayashi, #asato. Thomas, Anthony.Thomas, 8eorge. D0%$$, &ovE. 'o!otic 1awnmower )esign. @(nline.Availa!le LT;FhttpFGGro!omow.ion.orgGwpcontentGuploadsG0%$$G$0G0%$$W+levelandW'o!oticW1awnmowerW)esign.pdf. DAccessedF 0%$, Nune $E

@0 7all-8eisler, Kristen. D0%$E. 7ow can lithium-ion !atteries improve hy!ridsQ@(nline.Availa!leF httpFGGauto.howstuffworks.comGlithium-ion-!atteriesimprove-hy!rids$.htm.DAccessedF 0%$, Nune $E

@ =ender, )aniel. 8uthrie, Andrea. 8oode, Nason. 7ayashi, #asato. Thomas, Anthony.

Thomas, 8eorge. D0%$$, &ovE. 'o!otic 1awnmower )esign. @(nline.Availa!le LT;FhttpFGGro!omow.ion.orgGwpcontentGuploadsG0%$$G$0G0%$$W+levelandW'o!oticW1awnmowerW)esign.pdf. DAccessedF 0%$, #ay 05E

@ D0%$E.=est #owerF Nohn )eer Tango 2. @(nline. Availa!leFhttpFGG!estmower.comGproductsGNohn-)eere-Tango-2.html. DAccessedF 0%$, Nune $E

@ =osch, 'o!erts. =osch Idego. @(nline. Availa!leFhttpFGGwww.!oschindego.comGg!GenGproductGtheXindego.html. DAccessedF 0%$, Nune $E

@/D0%%E. =osch Idego 'o!otic 1awn #ower. @(nline.Availa!leFhttpFGGalltoolsgarage.comGindex.phpQroutePproductGproductYproductWidP0/)DAccessedF 0%$, Nune $0E

@5 +ar!a"al, #artin, #allman, #ike, ;orter, +urtis, Zurinskas, 2rik. Team


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DAccessedF 0%$, Nune $E

@$$ D0%$0E. 'o!ot +enterF 'o!otic

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Project Interim Report (Autosaved)