Robot Construction Basics Les Turner Director of Technology, Northern Indiana ESC Head Coach, Bremen Botz!

Bremen Botz! Team Members Preston Huffman – Lead Builder – Robot Base Zac Ericson – Lead Builder – Attachments Josh Turner – Lead Programmer Cordall Schoning – CAD Design / Programmer Revised 12/4/2010 Robot Construction Basics Les Turner, Northern Indiana ESC 1

MINDSTORMS NXT SYSTEM Lego NXT consists of: Lego NXT Controller Servo Motors Sensors (Light, Color, Sound, Touch, Ultrasonic) Software to program the NXT Controller Lego gears, beams, pins, wheels, & other parts. Revised 12/4/2010 Robot Construction Basics Les Turner, Northern Indiana ESC 2

Get To Know The Parts Not all Lego parts are the same: – Connecting Pins Black Connecting Pins(Friction – Hold Tight) Gray Connecting Pins(Free – Will Rotate) Blue Axle Pins(Friction – Hold Tight) Grey and Yellow Axle Pins(Free – Will Rotate) – Friction Gear(Allow axle to rotate when bound) – Other Specialized Parts are available! Revised 12/4/2010 Robot Construction Basics Les Turner, Northern Indiana ESC 3

Objectives for Construction Usually revolves around an FLL tournament: Robot to accumulate as many points as possible in 2 min 30 seconds. No human interaction with the robot outside of the defined base. Highest Score wins, ties are broken with 2 nd highest scores (or sometimes time) Revised 12/4/2010 Robot Construction Basics Les Turner, Northern Indiana ESC 4

Robot Construction Three R’s Robustness: The robot needs to be quick enough to accomplish all tasks within time. Rigidness: The robot needs to be constructed solidly to eliminate play and slop. Repeatability: The robot needs to use landmarks and other techniques for accuracy. Revised 12/4/2010 Robot Construction Basics Les Turner, Northern Indiana ESC 5

R1 - Robustness Understanding Motion and Measurement – Wheel Size Has An Impact Larger is Faster, but less Accurate Smaller is More Accurate, but is Slower Gearing may help, but changes Torque (Power) – Wheelbase Issues (Distance Between Wheels) Greater the Distance, Greater the Accuracy Allows more degrees of rotation for same movement Any sideways movement of wheel introduces error Revised 12/4/2010 Robot Construction Basics Les Turner, Northern Indiana ESC 6

R1 - Robustness Gearing (Standard Gears) – Large Gear Driving a Small Gear Can Achieve High Speeds at the Expense of Power – Small Gear Driving a Large Gear Higher Torque at the Expense of Speed – Worm Gears Very Slow with Extreme Torque – Flat Gears Extended Range of Motion (Speed Set by Drive Gear) Revised 12/4/2010 Robot Construction Basics Les Turner, Northern Indiana ESC 7

R2 - Rigidness Solid Construction – Multiple points of connection (drive wheels) – Use Axle Clamps to hold items tight on axles – Can’t use too many pins, only wrong ones – Keep all gear meshing tight to minimize slop – Brace robot structure so parts do not detach easily – Route cabling so it doesn’t interfere with robot – Don’t forget access to charging and USB ports! Revised 12/4/2010 Robot Construction Basics Les Turner, Northern Indiana ESC 8

R3 – Repeatability (Robot-Based) Minimize Friction – Wall Following Wheels – Third Point of Contact (Fixed or Pivot Wheel) Use Physical Limits on Robot for Arms – Always ‘Home’ the Arm Against Limit – Use Limit to establish operating position Use Sensors to Establish Limits / Position – Touch / Ultrasonic Sensors to Detect Limits Revised 12/4/2010 Robot Construction Basics Les Turner, Northern Indiana ESC 9

R3 – Repeatability (Table-Based) Establish Points of Reference on Table – Don’t Overlook Anything on Table (Tissue Box?) – Walls make great alignment tools and limits – Lines or other markings on table for reference – Even Table Elements may be used for alignment! The Light Sensor is Your Friend! – FIRST almost always put lines where needed! – Use the black lines around base as initial reference – Build a shield for the Light Sensor (Ambient Light) Revised 12/4/2010 Robot Construction Basics Les Turner, Northern Indiana ESC 10

Lets Build a Robot! Front Sheet 10 – Sturdy Motor Attachment – Left Motor Wire to Output B on NXT – Right Motor Wire to Output C on NXT Back Sheet 20 – Long Front Setup – Modify to attach to existing beams from step 1 – Add a wheel to bottom of front arm. Think about ways to ‘solidify’ this robot! Revised 12/4/2010 Robot Construction Basics Les Turner, Northern Indiana ESC 11

Programming The robot doesn’t do much without a program We will write a basic move and turn program The NXT-G Programming Environment is very easy to use and is very powerful. Programming details are for another session! Revised 12/4/2010 Robot Construction Basics Les Turner, Northern Indiana ESC 12

QUESTIONS & ANSWERS Contact Info: Les Turner Revised 12/4/2010 Robot Construction Basics Les Turner, Northern Indiana ESC 13