ENGR 1110: Lego Car Project Final Design Presentation

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ENGR 1110 Lego Car ProjectFinal Design
Presentation

• Section 12 Team A
• John Langdon
• Clint Patterson
• Joseph Berrios
• Mustafa Ali
• Tim Aldridge

December 5, 2003
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Overview

• Introduction
• Basic concept
• Driving strategy
• Mechanical sub-system
• Electronic sub-system
• Materials and cost
• Reliability and safety
• Competition results and analysis
• Conclusion

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Introduction

• Drive a LEGO car around an oval track in the
  shortest net time
• Consider time penalties and bonuses
• Consider various trade-offs

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Basic Concept
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Driving Strategy
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Driving Strategy

• REAR-WHEEL DRIVE
• Drive 1 motor ? rear-axle
• Steering 1 motor ? rack pinion
• Rectangular path on course
• 1st run automated w/ manual backup
• 2nd and 3rd fully automated

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Mechanical Sub-system

• Rear wheel drive
• Tire traction
• Maintenance
• Construction

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Rear Wheel Drive
Mechanical Sub-System

• Drive motor
• 1 motor connected to rear-axle
• Both drive wheels connected to rear axle
• Rack pinion
• 1 motor connected to a linear rack
• Rack connected to pinion that pivots two steer
  wheels

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Rack and Pinion Close Up
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Maximized Tire Traction
Mechanical Sub-System

• Weight localized on each set of wheels
• Rubber radial tires
• Light-weight stranded wire

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Easy Maintenance
Mechanical Sub-System

• Both motors easily removable
• Quick transformation from pivot-steer to
  rear-wheel-drive and vice versa
• Hooks at end of each wire and diode
• Quick changes to circuit design
• No soldering required
• No electric tape required

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Sturdy Construction
Mechanical Sub-System

• LEGO friction pins
• Virtually impossible to break bricks apart
• Built-in tower to hold wire

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Close Up Shot 2
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Front
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Top
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Electronic Sub-system

• Frequency and Waveform
• Programming
• Wiring

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Frequency and Waveform
Electronic Sub-System

• 150 Hz frequency
• Square wave with positive duty cycles
• Circuit
• 1 diode on drive channel
• 1 diode on steering channel

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Programming
Electronic Sub-System

• Matlab to generate square wave .WAV
• Visual Basic for drive-by-wire driving
• Left channel drive motor
• Right channel rack-and-pinion motor
• Media source
• Primary CDRW with backups
• Backup floppy disks

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Wiring
Electronic Sub-System

• Requirements low resistance / low friction
• Wiring simulation runtimes using PSpice

• Empirical Choice 28-gauge stranded, 40 ft
• Actual Implementation 24-gauge stranded, 50 ft

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Materials and Costs

• Mandatory Supplies 57.25
• LEGO parts 20.42
• Wire 10.21
• Total Expenditure 87.88
• Mandatory Supplies 2 motors, 2 sets of wheels
  and tires, 8 diodes

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Reliability and Safety

• Redundant systems
• Multiple media sources
• Backup manual system if automation fails
• Insulated Wires
• Product not intended for children under the age
  of 10.

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Testing and Competition Results

• Practice times (average)
• Setup Time 15-25 seconds
• Automated 0-50 seconds setup
• Manual 102 seconds setup
• Actual time
• Setup Time 10-15 seconds
• Automated N/A
• Manual 78 seconds
• Final position in class 5th

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Issues During Competition

• Problem Automation on 1st run not possible with
  new amplifier setting
• Solution Manual recording saved
• Problem A glitch in 2nd runs 4th turn resulted
  in too sharp a turn
• Solution Corrected by delaying 4th turn by 1.5
  seconds
• Problem Setup error in 3rd run resulted in
  malfunction
• Solution Need to be careful in future about
  procedures

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Conclusion

• Car designed to meet user requirements
• First-ever rack pinion implementation
• Drive-by-wire software
• Predictable performance due to extensive testing