A.G.I.L.E Autonomously Guided Intelligent Lawn Equipment

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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

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Why Build It?

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

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Project Goal

• Create a proof of concept autonomous lawnmower
• Mow the lawn while
• Staying in a defined area
• Avoiding obstacles
• Efficient mowing

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Key Components

Navigation
Perception

• Compass

• Sensors

Intelligence
Platform

• Microcontroller
• Software

• Motors
• Batteries

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Key Components

Navigation
Perception

• Compass

• Sensors

Intelligence
Platform

• Microcontroller
• Software

• Motors
• Batteries

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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

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Perception

• Radio frequency (RF) dog fence detectors
• Ultrasonic sensors to locate objects

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Ears

• Radio frequency circuits
• Sense by signal strength

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RF Filter Flowchart
1) Single-Frequency Band Pass Filter 2) Gain
stages 3) Rectifier 4) Unity Gain Op-Amp 5) ADC
on Emac
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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

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Eyes

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

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Reading the Ultra-Sonics

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

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Obstacle Avoidance

• Ultrasonic sensors scan environment
• Distance thresholds are used in software
• Environment is stored in memory
• Proper action is taken

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Obstacle Avoidance
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Key Components

Navigation
Perception

• Compass

• Sensors

Intelligence
Platform

• Microcontroller
• Software

• Motors
• Batteries

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Navigation

• Digital compass
• Voltage regulator
• PWM signal
• Follows heading
• Precise 90 and 180 degree turns
• Difficult indoors

167
90
180
257
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Compass Tracking

• Error (Heading Desired heading) x Gain
• Error modifies PWM
• signals accordingly
• Example Turn Left
• Error 90 (45-0)2
• LEFT MOTOR ERROR RIGHT MOTOR ERROR

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Motor Control

• Utilizes the EMACs onboard DAC
• 0V to 5V ? 0 to 100 duty cycle
• H-Bridges control direction

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Key Components

Navigation
Perception

• Compass

• Sensors

Intelligence
Platform

• Microcontroller
• Software

• Motors
• Batteries

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Intelligence

• Software uses sensors data
• Follow the border
• Cover the field twice
• Avoid static and dynamic obstacles

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Basic Algorithm

• Uses dog fence as border
• Starts with border
• Ideal for square field
• More testing
• Minimal areas missed

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Wall Following

• Ideal Signal Strength
• Error correction
• Containment
• All shapes

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Wall Following

• When do I stop?
• Turn counter
• Switch modes

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-45
45
-45
90
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Double Cut

• Missed areas
• Light blue/light green
• Up-Down pattern
• Blue
• Left-Right pattern
• Green

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Software

• Execution time
• 147mS
• 160mS
• Human reaction time
• 250mS

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Safety Features

• Stay with in mowing area
• Avoid unknown obstacles
• Dont cut neighbors yard
• Ultrasonic sensors
• Dont run over life forms
• Dont crash into walls
• Bump sensors
• Last line of safety protection
• Kill switch
• Manual cutoff

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System Block Diagram
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Completed Mower
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Questions?
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Ultrasonic Error Correction
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Microcontroller Connections
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Compass Read Function
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Compass Read Code

• int readcompass()
• unsigned int reading0
• while(compassPWM1) //if its already high,
  wait
• while(compassPWM0) //if its low, wait
• while(compassPWM1) //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 gt 380)reading comp_readingold
  //error checking ignore massive error
• if(reading gt 359)reading 359 //error
  checking
• comp_readingoldreading
• return(reading)
• //return(compass_lookup(reading)) //lookup
  table

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Actions Truth Table
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Distance to Stop

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