ORTOP Workshop 3 Welcome Goal: Extend your knowledge of LEGO robotics – This workshop is very hands-on and will run 3 hours. You will be working in teams of 3-4 members, so be prepared to take notes and share your ideas. – Introductions – How did the Can-Do challenge go last week? The workshop is divided into four modules and a challenge: – Robot Design & Construction – Going Straight & Turning – Reliably! – Using Sensors in Navigation – Focus on the Light Sensor – Nav 101 & Mission Planning – Buoy Mission 6/20/20111Copyright ORTOP 2011

Robot Design & Construction Warm up Compare the two robots at your table, noting: – Complexity – Sensors & their locations – Balance & center of gravity – Screen & control panel location – Beam & pin structural design – Anything else that stands out Appoint a team leader, (each exercise has a different team leader), and What features are common, what are unique? Fill in a Venn diagram or 3 column table as a group. GO – 5 min Let’s get 1-2 comments from each team 6/20/20112Copyright ORTOP 2011 LS centered 30mm tires Rear follower Somewhat Complex

Robot Design & Construction The Engineering Problem to solve is to build a robot to run Food Factor missions. Here are some design alternatives: – 3 motor design Built in workshop 1 Light sensor not on centerline of robot Has 3 rd motor for fork attachment Structurally strong – do 3 “ drop test 3 rd wheel – discuss alternatives Low Center of Gravity – Basic tri-bot design (show outreach bot example) Simple to build Screen & controls backward Light sensor centered but not mounted vertically – Kangaroo’s robot Third year team, won overall state championship – Handout: NXT Reference Books for FLL, Dale Jordan (workshop 2) 6/20/20113Copyright ORTOP 2011

Robot Design & Construction Design Considerations: – Using LEGO bricks - tend to fall apart under stress – use beams & pins for strength (w3 bag of parts) – Use gears for driving or for attachments bevel, straight, worm (transfers power one way), pulley – all provide torque transfer Note: Gears on 3 rd motor for lifting fork – Position of light sensor With respect to: Robot Centerline - tracking is under the sensor With respect to: Turning Pivot Point - affects line tracking wobble – Small wheels, large wheels or tracks What are + and – of large wheels? – Quick connect Interface for probes, grippers, or bumpers 6/20/20114Copyright ORTOP 2011

Robot Design & Construction Worksheet 1: Design & Construction Purpose: compare and contrast alternative designs Follow steps: 1.Quickly sketch the workshop robot or alternative design a.Sketch only the wheels, brick and front end b.The goal is to quickly get design ideas down on paper 2.Measure wheel diameter and distance between wheels a.Mission planning tools include ruler 3.Multiply the wheel diameter by pi 3.14 to determine circumference a.So 1 rotation = (how many?) inches/cm of travel 4.Balance the robot in your hand to determine the center of balance a.What happens if the robot is heavy on one side? 5.Discuss in your team “Similarities” and “Differences” between the workshop robot and the outreach robot 6.GO 10 min 6/20/20115Copyright ORTOP 2011

Robot Design & Construction Compare & Contrast Results – How are they Similar, how are they Different? Each workshop team present one “Similarity” and one “Difference” in the designs your team evaluated GO – 5 min 6/20/20116Copyright ORTOP 2011

Robot Design & Construction Wrap up, conclusions, next steps – See Resources Handout for robot design ideas – Have your teams build 2-3 different robots then select the best features for their final design – Keep a good engineering notebook (robot diary) of team designs, what worked, what did not work, show to judges – Robot design is an evolving process, e.g. Kangaroo’s robot over three years – 2 min stretch break, gather around the Body Forward field 6/20/20117Copyright ORTOP 2011

Going Straight & Turning Warm up Body Forward Stent Demo – Move 18” from start box, to circle, – Spin turn 40 deg Left, – Move 13” to black line, – One wheel turn 70 deg left, – Follow black line with Left Light Sensor for 5 sec, – Turn Right Light Sensor ON to move forward to detect T while inserting the Stent into the artery – The Engineering Problem is to reliably insert the stent into the vein 6/20/20118Copyright ORTOP 2011

Going Straight & Turning Going Straight Purpose: – Discover inherent inaccuracy in robot movement – Understand how and when to correct errors Simple test: – Move 2 feet, stop, record robot position – Mark a pencil line on paper where cow catcher lands – Run test 5-10 times, record results of each run – Why is this important? We want to learn to predict where the robot will move to, and how accurately it will move. More runs may show wider deviation. – We will run this experiment in a few minutes 6/20/20119Copyright ORTOP 2011

Going Straight & Turning Turning Purpose: – Understand two types of turns – Understand turning accuracy Steps: – A Spin turn = position the Move block Slider to L or R end. A spin turn uses 2 wheels. (Instructor show this) The robot “spins” around the center point between the two wheels Used for turning in tight spots – A One Wheel turn = use Move block, Turn off one motor, one wheel moves, one is stationary (Instructor show this) The robot “turns” around the stationary wheel – Run a Spin test 5-10 times to understand turning accuracy – Mark a pencil line where the cow catcher lands – Have your teams run these tests and record their observations – Turns with the slider in the intermediate positions may not be repeatable 6/20/201110Copyright ORTOP 2011

Going Straight & Turning Worksheet 2: Going Straight & Turning – Attachments for 2 foot test Use cow catcher - for starting point alignment, and for marking robot landing points – Write a Go Straight Characterization Program Two blocks: Move 2 feet, Move stop Given your wheel circumference, how many wheel rotations equal 2 feet? – Select a new team lead – Collect data Run tests 5-10x, marking each landing point on paper DRAW A BOX around the landing points to show X and Y move errors List 2-3 factors that influenced X and Y errors Discuss results in team and report the SIZE of you box to the class Run Tests at different speeds: Team A 30, Team B 50, Team C 70 – For extra credit: Add to your program a 90 degree “one wheel” turn and repeat test – GO 15 Min. 6/20/201111Copyright ORTOP 2011

Going Straight & Turning Going Straight & Turning Variables – Starting position: e.g. home base – Speed: faster = less accuracy – Battery charge: more = faster moves – Tire size: larger = faster but less accuracy – Robot balance: lean to one side = less accuracy – “Spin” turns vs. “one wheel” turns Other variables – Motor friction, mechanical gear play – NXT Software: tries to keep both wheels moving at same speed 6/20/201112Copyright ORTOP 2011

Going Straight & Turning Going Straight The S curve inaccuracy – A Move block rotates the B & C axles to the programmed position using the built-in rotation sensors as feedback – If one wheel slows down, the other wheel will also slow down causing the robot to move in an S curve – Did you observe this in your tests? 6/20/201113Copyright ORTOP 2011

Going Straight & Turning Compare & Contrast Results – What did you discover about the variables that affect robot motion? – How can you identify & isolate the variables to make the robot more predictable? Other forms of navigation – Wall follower (wheels) – Wall Feelers (touch sensor) – Back against a wall or into a corner – Any other ideas? 6/20/201114Copyright ORTOP 2011

Going Straight & Turning Conclusions & Next Steps – Use navigation to know where the robot is at all times – Understand variables and how they influence robot movement – >>Long dead reckoning moves are not necessarily bad - if your robot can re-align or compensate for move inaccuracies, e.g.: Width of the cow catcher, width of the buoy pickup fork Backing into a wall or corner to re-align the robot – Apply move & turn knowledge to missions! Break 10 min. 6/20/201115Copyright ORTOP 2011

Sensors Warm up – Engineering Problem: Stop on green or black reliably (10 out of 10 times) – Run stop on black program Re-run test with different lighting conditions What affect does room light have on the sensor/program? – Review how to read light sensor values using view mode From NXT-G 6/20/201116Copyright ORTOP 2011

Sensors Light Sensor review – Light Sensor returns values of reflected light White = Trigger Value (programmed) = ((white – black)/2 + black) Black = 6/20/201117Copyright ORTOP 2011

Sensors Light Sensor Review – Sensor “Wait Until” program action – note hour glass in Light Sensor “Wait” icon – This program: Runs the Move block, then Waits on the Light Sensor block, Until sensor trigger value is crossed, then Continues to the next program step Note: Until = threshold value AND greater than Read light sensor value in lower left corner of the light sensor control panel – High to low (light to dark) transition use < – Low to high (dark to light) transition use > – Light Sensor Values range from 100 (white) to 0 (black) So, lets measure white, green, & black values, then run some experiments 6/20/201118Copyright ORTOP 2011

Sensors Color Light Sensor See Color Sensor Block ? for programming details Detects color(s) within a defined range Also works as black & white light sensor Wait for Color Sensor example: Turn on motor Wait for color sensor Stop motor Color Lamp Block – for turning on/off RGB lamps 6/20/201119Copyright ORTOP 2011

Sensors Light sensor values: – Instructor measures values 6/20/201120Copyright ORTOP 2011 ColorAbsolute Value Un-calibrated % Calibrated % Max1000 White Green Black Min0

Sensors Example: Light Sensor Calibration Blocks Turn on sensor, wait, calibrate white, then black – Program Steps: Turn on light sensor Say “white” Wait 3 seconds Sample and store the “white” value Say “Black” Wait 3 seconds Sample and store the “black” value Wait 1 second and end the program – Why is this important? Calibrating the light sensor provides widest range of values between white and black, making it easier to use the sensor in a variety of lighting conditions 6/20/201121Copyright ORTOP 2011

Sensors Worksheet 3: Light Sensor – Engineering Problem: Write a program to stop reliably on a Black or Green line – Measure white, green, and black values – Determine a Threshold Value – Run your program in room light and high intensity light – Calibrate your light sensor – Re-run the test and compare results Team A 30, Team B 50, Team C 70 (ken run the tests) – GO – 15 min 6/20/201122Copyright ORTOP 2011

Sensors Light Sensor Variables (try these back home) – Sensor Distance from the mat – Sensor position with respect to robot center line – Sensor position with respect to robot pivot center – Robot speed – Sensor mounting angle – Shroud to protect sensor from ambient light – Colored lines using a color light sensor – Line width – angle of approach Distance Sensor: Uses Threshold same as light sensor, greater than > or less than < a distance 6/20/201123Copyright ORTOP 2011

Sensors Body Forward Mission Example: – Move Forward to Release the Syringe Count rotations & follow black line (threshold 39) Use 2 nd LS to detect T crossing (threshold 40) – Turn 180 degrees – Move forward to push pills into box Count rotations & follow black line Use 2 nd LS to detect T crossing – The demo failed because of “different’ lighting conditions. – Why did it fail? – What can we do to make this demo reliable? 6/20/201124Copyright ORTOP 2011 ColorNext to windowConference table White7569 Green5251 Black4438

Sensors Compare & Contrast Results – Discuss test results in your teams – What is the most important factor in using the light sensor – predictably? 2 min stretch break 6/20/201125Copyright ORTOP 2011

NAV 101 & Missions Warm up – Engineering Problem: Break down mission field into Zones and Tasks for each mission 6/20/201126Copyright ORTOP 2011

NAV 101 & Missions Mission Zones & Tasks 1. Study the game missions a.Coach & Teams study mission videos and rules on FLL website b.It’s OK for coach to warn teams if they are not interpreting rules correctly 2.Teams divide the playing field into 2-4 zones a.Zones based on geographical location on the game table 3.Teams write tasking list for the missions a.Write task list for each mission 4.Teams prioritize missions a.by points, b.by ease of programming, c.by location, d.or what your team thinks is important 6/20/201127Copyright ORTOP 2011

NAV 101 & Missions Mission Planning Variables – Mission difficulty – Mission programming time – Mission run time – Mission points – Design time for probes, grippers, or bumpers – Other FLL goals, e.g. research project 6/20/201128Copyright ORTOP 2011

NAV 101 & Missions Worksheet 4a: Mission Zoning Divide the playing field into 2-4 zones based on geographical location 6/20/201129Copyright ORTOP 2011

NAV 101 & Missions Worksheet 4b: Mission Tasking Tasking the mission 6/20/201130Copyright ORTOP 2011 Mission NameDescriptionTask List StentPlace the stent into the artery Move fwd, detect circle Turn left 45 degrees – spin Move fwd, detect black line Turn left 90 degrees – R wheel Turn on R sensor Move fwd, follow line, detect T w R sensor – this should insert the Stent into the artery Blood DrawTrip the syringe allowing it to roll back into base

NAV 101 & Missions Worksheet 4c: Buoy Mission Planning Sheet Engineering Problem: Move the Buoy from its current position into the box, then park the robot on the black finish line Write a mission plan (moves & turns), then write a program to execute your plan Go: 20 min. 6/20/201131Copyright ORTOP 2011

NAV 101 & Missions Mission Planning Sheet 6/20/201132Copyright ORTOP 2011 s Start here End here Place buoy here

NAV 101 & Missions Examples of team discussions to be facilitated by the coach – Discuss and record results in team notebooks – What did you like about your solution? – What went wrong with your solution? – Are there variables you can control? – What would you change next time? 6/20/201133Copyright ORTOP 2011

NAV 101 & Missions Thank you for your attendance in the ORTOP workshops Please fill out workshop survey Resources handout Food Factor Challenge: Contact Us: – Roger Swanson, – Jim Ryan, – Dale Jordan, – Ken Cone, – Cathy Swider, – 6/20/201134Copyright ORTOP 2011