FrankencarAgile is Not Just for Software

Matt Spradley

Outlaws Just Have to Fit

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Typical Dumb Outlaws

• Fan Powered • CO2 Powered

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I Want a MakerBot

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Frankencar

400 Watt Brushless Motor

Infrared Tach Sensor

Digital Readout

Arduino Nano Control Unit 3-Axis

AccelerometerLED “Bling”

60A Electronic Speed Controller (ESC)

1300 mAh 40C 11.1 V LiPo Power Pack

Start Sensor

30A 1-3/8” Extra Sticky Wheels

Robust Steel Chassis

Belt Drive4 Wheel Drive

It’s Fun: Arduino is Awesome – Learn about It

• Arduino Nano Specs– Atmel ATmega328– 32 KB Flash RAM– 2 KB SRAM– 1 KB EEPROM– 16 MHz– 14 Digital I/Os (6 PWM)– 8 Analog Inputs– 2 Interrupts– .73” X 1.7”

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Get a Napkin… or Spreadsheet

Pinewood Derby w/ 1.2” Wheels

• 2.6 seconds (50 ft)

• 13 mph average

• 3700 rpm

Outlaw Pipe Dream

• 1 second

• 34 mph average

• 9630 rpm

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Divide and Conquer

• Smart Control– Sensors– Interconnects

• Strong– What to use for structure?

• Fast– What motor?

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Arduino UNO for Control

• Open source• C-Based Dev Platform• ATmega328• 32 KB Flash RAM• 2 KB SRAM• 1 KB EEPROM• 16 MHz• 14 Digital (6 PWM)• 6 Analog• 2 Interrupts• 32 Single-Byte Registers• $18 BUCKS !!!

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Start with the Architecture… I Mean Chassis

• Turnkey or mod would be great. Would R/C cars work?

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Seed of an Idea for later!

VEX Robotics Design System to the Rescue

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Hardware and Metal Kit ($80)

No BDUF!

Brushless Outrunner = Awesome + Tons of Torque

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http://www.youtube.com/watch?v=gT6noEibnpgVideo:

Time to Build V1

• Major blocks validated • Refine• Now just software

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Block Diagram

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Changed these

FlowchartTach Interrupt

Calculate:Distance

SpeedAcceleration

Store global telemetry

data

End

Start

AccelerationMotor +2% Motor -1%

Update readout and LED display

Any limits reached

End

< Target > Target

= Target

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Leaky Abstraction

Back to That 4X Reduction

_g2R102 = (WHEEL_CIRCUMFERENCE_FT

/ (_lastRevMicrosBuffer[0] - _lastRevMicrosBuffer[1]) - WHEEL_CIRCUMFERENCE_FT

/ (_lastRevMicrosBuffer[2] - _lastRevMicrosBuffer[3]))

/ (_lastRevMicrosBuffer[0] - _lastRevMicrosBuffer[2]) * SF_G_102;

Use long instead of float and scale as needed per operation

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A Matter of Torque

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Fix that part… easy

Motor

Rotation

Car Chassis

Lift

• Validate and iterate• Big Design up Front (BDUF) a Waste of Time• Divide and Conquer• Modular is Good and Bad• Experience Counts• You Will Make Mistakes• On to V2

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What Did We Learn?

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Cost

• $20 Arduino Nano

• $80 VEX Hardware and Metal Kit

• $60 Various sensors and displays

• $20 400 watt brushless motor

• $50 60 amp ESC

• $75 Misc. electronic parts

• $100 Misc. mechanical parts

Total Cost: ~ $405

http://mattspradley.com/outlaw

http://www.arduino.cchttp://www.vexrobotics.comhttp://www.robotmarketplace.comhttp://www.hobbypartz.comhttps://www.epictinker.comhttps://www.sparkfun.comhttp://www.sainsmart.comhttp://www.seeedstudio.com

Specific Parts:Wheels - http://www.robotmarketplace.com/products/0-T40P-143BG-HS4.htmlShafts - http://www.robotmarketplace.com/products/0-70105.htmlBearings - http://www.fingertechrobotics.com/proddetail.php?prod=ft-bearing-blockMotor - http://www.hobbypartz.com/86ma07-2215-1950kv.html

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Links