A.G.I.L.EAutonomously Guided Intelligent Lawn Equipment

Team Members:• Brad Ramsey

• Derek Rodriguez• Dane Wielgopolan

Project Advisors:• Dr. Joel Schipper• Dr. James Irwin

Who wants to mow the lawn?Who wants to pay someone else to mow the

lawn?

Why Build It?

Project Goal

Create a proof of concept autonomous lawnmower

• Mow the lawn while– Staying in a defined area– Avoiding obstacles– Efficient mowing

Key Components

A.G.I.L.E.

•Compass

•Microcontroller

•Software

•Sensors

•Motors

•Batteries

Key Components

A.G.I.L.E.

•Compass

•Microcontroller

•Software

•Sensors

•Motors

•Batteries

Platform• Dimensions:• Length: 12.5’’• Width: 18.5’’• Height: 7’’

• Symmetrical• Dual 12V lead acid batteries• Dual Pittman DC motors• Differential turning

– Zero turning radius• All electronics designed to work off of 12VDC

Perception

• Radio frequency (RF) dog fence detectors

• Ultrasonic sensors to locate objects

“Ears”

Radio frequency circuitsSense by signal strength

RF Filter Flowchart

RF RECIEVER / BANDPASS

FILTER

AC

RF

A/D Converter

MICROCONTROLLER

DIGITAL SIGNAL LEVEL

RECTIFIER

Unity Gain Op-amp

DOG FENCE

GAIN

ANTENNA

1) Single-Frequency Band Pass Filter2) Gain stages3) Rectifier4) Unity Gain Op-Amp 5) ADC on Emac

RF Filter Design•Frequency - 333 KHz

• Low frequency (LF) spectrum•IC used is LM318D•High Slew Rate and Gain Bandwidth Product

• Within desired noise floor

“Eyes”

• Ultrasonic sensors• Projects sound wave• Listens for echo• Converts time to distance• SRF05 – 3m range• We only need 1m

Reading the Ultra-Sonics

• Software Counter• Returns Value from 0-250• 250 is approximately 1m

CLEAR COUNT

SEND PULSE IS RETURN PIN LOW?

YES

IS RETURN PIN HIGH?NOINCREMENT

COUNTYES

RETURN COUNT

NO

SELECT SENSOR

Obstacle Avoidance• Ultrasonic sensors scan environment

• Distance thresholds are used in software

• Environment is stored in memory

• Proper action is taken DB

MOWER CHASSIS

C

A E

Obstacle Avoidance

DB

MOWER CHASSIS

C

A E

DB

MOWER CHASSIS

C

A E

D

B

MO

WER

CH

ASSI

S

CA

E

D

B

MO

WER

CH

ASSI

S

CA

E

Key Components

A.G.I.L.E.

•Compass

•Microcontroller

•Software

•Sensors

•Motors

•Batteries

Navigation

• Digital compass

• Voltage regulator

• PWM signal

• Follows heading

• Precise 90 and 180 degree turns

• Difficult indoors

}

Compass Tracking

• Error = (Heading – Desired heading) x Gain

• Error modifies PWMsignals accordingly

Example: Turn LeftError = 90 = (45-0)*2

LEFT MOTOR – ERROR & RIGHT MOTOR + ERROR

0˚

90˚

180˚

270˚

45˚

Error

Motor Control• Utilizes the EMAC’s onboard DAC• 0V to 5V → 0% to 100% duty cycle• H-Bridges control direction

Key Components

A.G.I.L.E.

•Compass

•Microcontroller

•Software

•Sensors

•Motors

•Batteries

Intelligence

• Software uses sensors’ data

• Follow the border

• Cover the field twice

• Avoid static and dynamic obstacles

Basic Algorithm

• Uses dog fence as border

• Starts with border• Ideal for square field• More testing• Minimal areas

missed

Wall Following

• Ideal Signal Strength

• Error correction

• Containment

• All shapes

Wall Following

• When do I stop?

• Turn counter

• Switch modes

Double Cut

• Missed areas– Light blue/light green

• Up-Down pattern– Blue

• Left-Right pattern– Green

Software

• Execution time– 147mS – 160mS

• Human reaction time– 250mS

Safety Features

• Stay with in mowing area– Avoid unknown obstacles– Don’t cut neighbor’s yard

• Ultrasonic sensors– Don’t run over life forms– Don’t crash into walls

• Bump sensors– Last line of safety protection

• Kill switch– Manual cutoff

DB

MOWER CHASSIS

C

A E

System Block Diagram

RIGHT DRIVE MOTORLEFT DRIVE MOTOR

DIRECTION DIRECTION

MICROCONTROLLER

SENSOR INPUTS

OUTPUTS

DIGITALCOMPASS

ULTRASONIC SENSORS

H-BRIDGE

PWM

H-BRIDGE

PWM

DOG FENCE DETECTORS

ANALOG TO PWM

CONVERTER

ANALOGVOLTAGE

ANALOG VOLTAGE

Completed Mower

Questions?

Ultrasonic Error Correction

IS READING SIGNIFICANTLY

DIFFERENT THAN OLDREADING?

YES

NO

READING

OLDREADING = READING

RETURN OLDREADING

OLDREADING

YES

POS_BOGUS FLAG = 0?

NO

POS_BOGUS FLAG

POS_BOGUS FLAG = 0

RETURN READING

POS_BOGUS FLAG = 1

OLDREADING = READING

POS_BOGUS FLAG = 0

RETURN READING

Microcontroller Connections

EMAC MICROCONTROLLER

ADC1ADC0P4.6 P4.7

DOGFENCERF RXers

MOTOR CONTROLLER

DAC0 DAC1

2121Direction Pins PWM Adjustment

DIGITALCOMPASS

P1.1 P1.2 P1.4 P4.1P1.3 P4.2 P4.3 P4.4

ULTRASONICSENSORS

2 31

Feedback Pins

Pulse P

ins

4 1 2 3 45

P1.5 P4.5

5 1 2

P1.6

PW

M

P1.7

RESET

Compass Read Function

IS RETURN PIN LOW? IS RETURN PIN HIGH?NOINCREMENT

COUNTYES

CALCULATE HEADING

NO

YES

CHECK FOR ERROR

RETURN HEADING

Compass Read Code• int readcompass()• {•• unsigned int reading=0;

• while(compassPWM==1){} //if its already high, wait• while(compassPWM==0){} //if its low, wait• while(compassPWM==1) //if its high, start counting until it falls low, then return count• {• reading++;• }• reading = (reading/13)-10; //convert to value between 0 and 359• if(reading > 380){reading = comp_readingold;} //error checking ignore massive error • if(reading > 359){reading = 359;} //error checking• comp_readingold=reading;• return(reading);• //return(compass_lookup(reading)); //lookup table• }

Actions Truth Table

• Maximum reaction time of 200ms• Max Speed: 2 ft/s• Distance until reaction 0.4 ft/s or 0.12 meters

Distance to Stop