Low Carbon Footprint Electric Lawn Mower Version 2

1
Low Carbon Footprint Electric Lawn Mower Version
2

• Jeff Garza
• Jason Gualandi
• Dustin Hohenbery
• Advisors
• Dr. Huggins
• Mr. Gutschlag

2
Project Summary

• Low carbon footprint
• Battery powered electric motor
• Photovoltaic charging system
• Comparable functionality and pricing to current
  gas powered models

3
Why Make the Change to Electric?
http//environment.about.com/od/pollution/a/lawnmo
wers.htm
4
Overview

• Mower system
• Motor Testing
• Simulations
• Field Testing
• Battery Sizing
• Charging System
• Photovoltaic Sizing
• Controller Functionality
• Experimental Results
• Project Schedule
• Future Recommendations

5
Mower Functional Requirements

• Mow a 10,000 ft2 area or operate for at least one
  hour
• Safety switch on the handle which will need to be
  held down for the mower to start spinning the
  blade.
• Weight of the mower shall not exceed 65 lbs.
• The size of the deck and blade shall yield a 19
  inch cutting swath.

6
Motor Selection
Table 1 Field Test from LCFELM 2008
7
Motor Selection

• Brushless vs. Brushed
• Scott 1 HP PM Brushed DC Motor

Figure 1 Scott Motor Characteristics
8
Mower System
Figure 2 Mower System Block Diagram
9
Mower System
Figure 3 Lawn Mower Block Diagram
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Motor Testing

• Why test the motor?
• Why make a motor simulation?
• Why simulate the motor with a load?

11
Motor Simulation
Figure 4 Motor Simulation
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Motor Simulation - EE Side
Figure 5 Motor Simulation For Electrical Side
13
Motor Simulation
Figure 6 Motor Simulation For Mechanical Side
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Motor Simulation
Table 2 Simulation vs Experimental Data for
Motor Only
Experimental Experimental Experimental Experimental Experimental Simulation Simulink vs. Experimental
Fraction of Voltage Voltage (V) Current (A) RPM w (rad/sec) w (rad/sec) error
1 24 3.60 3535 370.2 374.8 -1.25
3/4 18 3.18 2660 278.6 281.0 -0.88
2/3 16 3.10 2373 248.5 249.9 -0.56
1/2 12 2.80 1776 186.0 187.4 -0.76
1/3 8 2.56 1180 123.6 124.9 -1.08
1/4 6 2.45 883 92.5 93.7 -1.33
1/6 4 2.35 583 61.1 62.4 -2.21
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Motor Simulation
Figure 7 Graph of Simulation vs Experimental
Data
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Mower Simulation
Figure 8 Mower System Simulation
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Mower Simulation
Figure 9 Mower System Simulation For Blade
Information
18
Mower System Circuit
Figure 10 Mower System Wiring Diagram
19
Mower Components
Figure 12 Scott 1 HP PM DC Motor
Figure 11 Scott 1 HP PM DC Motor
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Mower Components
Figure 13 On/Off Switch and Circuit Breaker
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Lawn Mower Prototype
Figure 14 Lawn Mower Prototype
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Experimental Data Analysis

• 19 Blade
• Tspin 0.728 Nm
• Typical Power 450.8 W
• Cutting Power 106.2 W
• 22 Blade
• Tspin 1.433 Nm
• Typical Power 720.8 W
• Cutting Power 93.1 W

23
Battery Selection

• 19 blade
• Current 19.10 Amps
• Voltage 23.60 Volts
• 450.8 W
• 22 Amp Hour
• 18.8 lbs

http//www.npcrobotics.com/products/viewprod.asp?p
rod16cat15modegfx
24
Photovoltaic Panel

• BP 350
• 50 Watt panel
• 2.9A peak current
• 17.5V peak voltage
• 0.450543 m2

25
Minimum Solar Radiation For the Month of June
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Photovoltaic Sizing Equations

• (PVarea)(Minimum Radiation)(Eff)(Unit
  conversion) MJ/Day
• Calculation for 4 Kwh/m2/day radiation value

27
Photovoltaic Sizing Equations

• If 22 Amp hour batteries are used and dissipated
  80, the total energy needed to replaced by the
  charger is 1.63 MJ.
• Find the amount of days needed to charge

28
Charging System
Figure 15 Charging System Block Diagram
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Charging System Circuit
Figure 16 Charging System Wiring Diagram
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Charging System Subsystems

• Relays
• Tested functionality with the EMAC
• Current Sensors
• Tested the output with an oscilloscope
• AC/DC Power Supply
• Confirmed the output voltage and current
• Solar Charger
• Confirmed operation with DC Supply

31
Charging System - Requirements

• Duration of Charge
• Charge The batteries in 4 days.
• Minimize Use of AC/DC power supply.
• Easy Interface
• Easy to disconnect the batteries.
• Charger Controller
• Charger controller needs to be compatible with
  the battery technology.

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Charging System

• Timer implemented for counting
• DHHMMSS
• Manually able to
• Switch power source
• Stop the System
• Reset the System
• System Utilizes Optimum Solar power
• Only switches to AC power when required

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Why Implement A Smart Charger?

• Lowers the Carbon Footprint
• System detects when Solar Power is available
• Only uses AC when necessary after 3 days
• Charge completes in 4 days or less

34
Charging System Main
Figure 17 Charging System Controller Block
Diagram
35
Charging System Stop Mode
Figure 18 Stop Mode Block Diagram
36
Charging System Reset
Figure 19 Reset Block Diagram
37
Charging System
Figure 20 Image of System After Startup
38
Charging System
Channel 1 PV Relay-Yellow Channel 2 AC
Relay-Blue
Figure 21 System Initiated
Figure 22 Initial Condition of Relays (PV Power
On)
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Charging System
Figure 23 Reset Mode
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Charger System Operation Experimental
Verification
Figure 24 Video showing Relay switching
Figure 25 Video showing PV Power and AC Power
Switching
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Charger System Operation Experimental
Verification Contd
Figure 27 AC Power On
Figure 26 PV Power On
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AC/DC Converter

• Converts 110 Volt AC Wall Outlet into a 12Volt DC
  Plug
• Output 12V DC-5.8A
• Input 100-120VAC
• 50/60Hz 1.8A

43
Charge Controller

• Prostar-15
• 15A max
• Inline fuses used for protection

44
Project Schedule

• Weeks 1-3
• Motor Modeling and simulation for Mower (Jeff and
  Jason)
• Program microcontroller for PV system (Dustin)
• Update website (Dustin)
• Order remaining parts for both systems (Everyone)
• Weeks 4-6
• Start building hardware for PV System (Jason
  Dustin)
• Create simulation for mower system (Jeff Jason)
• Weeks 7-9
• Debug software for PV system (Jason and Dustin)
• Test PV system (Jason and Dustin)
• Connect hardware for mower system (Jeff)
• Test lawn mower system (Jeff)
• Weeks 10-13
• Integrate both systems (Jason, Dustin, and Jeff)
• Start presentation and final report (Jason,
  Dustin, and Jeff)
• Week 14
• Have working final prototype

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Recommendations

• Mower System
• Smaller mower deck and blade
• Operate at slower speed
• Different battery technology
• Charging System
• Design charger for different battery technology
• Better way to sense status of battery during
  charging

46
Review

• Mower system
• Motor Testing
• Simulations
• Field Testing
• Battery Sizing
• Charging System
• Photovoltaic Sizing
• Controller Functionality
• Experimental Results
• Project Schedule
• Future Recommendations

47
Questions
Special Thanks Mr. Mattus, Dr. Dempsey, Mr.
Schmidt
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Motor Testing

• Locked rotor condition to measure Ra and La

Equation 1
Equation 2
Figure 28 Motor Testing Circuit for Ra and La
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Motor Testing
50
Motor Testing
Figure 30 Motor Testing Circuit
51
Motor Testing

• Mid-Range no load speed (Vs 12V)

Equation 3
52
Motor Testing

• Static Friction (TSF) and Viscous Friction (b)
• with Vs 16V and 8V (2 equations, 2
  unknowns)

Equation 4
53
Motor Testing

• Coast down test to compute Mass Moment of Inertia
  (J)

Equation 5
Equation 6
Valid for ?(t) gt 0
54
Motor Testing
55
Motor Testing

• Coast down test to compute Mass Moment of Inertia
  (J)

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Mower Simulation
Figure 32 Mower System Simulation
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Field Test
Table 3 Field Test Data
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19 Inch Blade Data
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22 Inch Blade Data
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Charging System
Figure 33 Charger System Block Diagram
61
Component Testing
Figure 34 Block Diagram for Testing Relay
Switching
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Component Testing
Figure 35 Condition of Relays For No Power
Figure 36 Condition of Relays for AC Power On
63
Component Testing
Figure 37 Block Diagram for Testing Current
Sensor
64
Photovoltaic Sizing Equations
Equation 1

• Calculation for 4 Kwh/m2/day radiation value

65
Charging System Timer Reset
Figure 38 Timer Block Diagram
Figure 39 Reset Block Diagram
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Relative Pricing

• Possible Sell for 650 or 700