Robot Drivetrain and Chassis

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Robot Drivetrain and Chassis

• Matt Hornung
• Team 1816

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• A bit about me

• Matt Hornung
• Drive train / Chassis
• Subteam leader
• Member since 2006
• Junior
• www.edinarobotics.com

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Safety First
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What is the most important?

• Drive Base
• Drive Base
• Drive Base
• - stolen from Andy Baker (team 45)

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Defining Drive Base

• Frame
• Wheels

• Gearbox
• Electronics

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Chassis Function

• Provides a platform for everything
• Strong
• Durable
• Accessible
• Light

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Weight

• 120 lbs robot weight limit
• Distribute evenly
• Track weight as you go
• Weight budget? chassis - 60 lbs
• tower 60 lbs
• How many ½ inch diameter holes in .100 Al are
  needed for 1 pound?
• 200!!

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Center of Gravity

• Keep it low.. or else

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Materials

• Metal
• Aluminum
• Steel
• Plastic
• Polycarbonate (Lexan) NOT Acrylic (Plexiglas)
• Wood

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Drivetrain Design

• What must the robot do?
• Power
• Maneuverability
• Speed
• Game rules and team strategy

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Materials Kit Chassis

• Standard Parts
• Lots of holes
• Durable
• Lightweight
• Comes with the kit

• Might not fit your design

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Materials 80-20 (T-Slot)

• Fits your design better than kit chassis
• Standard Parts
• Easy to use

• Heavy
• Expensive

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Materials Custom Frame

• Fits your design perfectly
• Light

• Expensive
• Requires extra time/money/effort
• Non-standard parts

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Wheels

• Driven or not?
• Traction or not?
• Steering
• Support
• and stability

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Traction Wheels
www.ifirobotics.com

• IFI Wheels
• Many sizes
• Changing tread
• is annoying
• Light weight and Traction
• Plaction Wheels
• Only 6
• Easier to change tread

www.andymark.biz
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Omni

• Less friction
• Sideways rollers

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Mecanum

• Used for Mecanum Drive
• Like omni wheels, but the rollers are at 45 angle

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Custom

• Make your own wheels!

Spinners!!
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Drive trains

• Many types
• Each one unique with many advantages and
  disadvantages
• There is no perfect drive train. Choose what is
  best for your team which may change from year to
  year.

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Tank

• Simple
• Light weight?
• Traction
• 2-6 wheels (usually)

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Omniaka Holonomic

• Move in any direction
• Harder to build and program
• Low traction
• Gets pushed around

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Mecanum

• Move in any direction
• Heavy
• Works with kit chassis

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Given the will, any configuration can work
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Car Driveaka Ackerman

• Drives like a car
• Larger turning radius
• Hard to build

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Swerveaka Crab

• Move in any direction
• Lots of traction
• Hardest to build
• Machining
• CAD

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Motors

• Limited
• Standard
• Specifications online
• www.usfirst.org
• www.chiefdelphi.com
• DC motors - speed is controlled via PWM

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Transmissions

• Come in the kit
• How many speeds?
• 1? 2? More?
• www.AndyMark.biz
• Mount securely

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Spacers and Chains

• PVC
• Metal tube
• Proper tension

• 35 or 25?
• www.mcmaster.com

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Im sure youre wondering

• How fast will my robot go?
• How much can my robot push?
• How do I find out the answer to these questions?

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Important Terms

• Coefficient of Friction
• Speed Loss Constant 90
• Drive train Efficiency 90
• Stall Torque
• Gear Ratio
• Current Draw

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Remember, its just a little volts and amps!
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Doing the Math

• Lets be honest, do you really want to do a lot
  of math?
• Spreadsheets
• Chris Lyddiatt from Team 1114
• www.chiefdelphi.com
• paper Feet Per Second / Misc Calculations

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Tradeoffs

• Speed vs. Force
• Max speed vs. Acceleration
• Be practical
• Average speed 5 15 fps (depends on game and
  strategy)

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Build season

• Only 6 weeks long
• Running chassis in about 2-4 weeks

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RememberIts no big deal!
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Resources

• www.edinarobotics.com
• www.mcmaster.com
• www.ifirobotics.com
• www.andymark.biz
• www.chiefdelphi.com
• www.mnfirstregional.org
• www.usfirst.org
• www.8020.net/