ortop workshop 3 welcome goal: extend your knowledge of lego robotics – this workshop is very...

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

6/20/2011 1Copyright 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


LS centered30mm tiresRear followerSomewhat

Complex


• 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 3rd motor for fork attachment• Structurally strong – do 3 “ drop test• 3rd 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)



• 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 3rd 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



• Worksheet 1: Design & Construction• Purpose: compare and contrast alternative designs• Follow steps:

1. Quickly sketch the workshop robot or alternative designa. Sketch only the wheels, brick and front endb. The goal is to quickly get design ideas down on paper

2. Measure wheel diameter and distance between wheelsa. Mission planning tools include ruler

3. Multiply the wheel diameter by pi 3.14 to determine circumferencea. So 1 rotation = (how many?) inches/cm of travel

4. Balance the robot in your hand to determine the center of balancea. 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



• 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



• 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


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


Going Straight & TurningGoing 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


Going Straight & TurningTurning• 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


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.6/20/2011 11Copyright 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


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?


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?


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.


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


Sensors

• Light Sensor review– Light Sensor returns values of reflected light

• White = • Trigger Value (programmed) =

((white – black)/2 + black)• Black =


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 < or less 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


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 lamps6/20/2011 19Copyright ORTOP 2011

Sensors

• Light sensor values:– Instructor measures values


Color AbsoluteValue

Un-calibrated %

Calibrated %

Max 1000

White 700 70 100

Green

Black 300 30 0

Min 0

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


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


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


Sensors• Body Forward Mission Example:

– Move Forward to Release the Syringe• Count rotations & follow black line (threshold 39)• Use 2nd LS to detect T crossing (threshold 40)

– Turn 180 degrees– Move forward to push pills into box

• Count rotations & follow black line• Use 2nd 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?


Color Next to window Conference table

White 75 69

Green 52 51

Black 44 38

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


NAV 101 & Missions

• Warm up– Engineering Problem: Break down mission field

into Zones and Tasks for each mission


NAV 101 & Missions• Mission Zones & Tasks1. Study the game missions

a. Coach & Teams study mission videos and rules on FLL websiteb. It’s OK for coach to warn teams if they are not interpreting rules

correctly2. Teams divide the playing field into 2-4 zones

a. Zones based on geographical location on the game table3. Teams write tasking list for the missions

a. Write task list for each mission4. Teams prioritize missions

a. by points, b. by ease of programming, c. by location, d. or what your team thinks is important


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


NAV 101 & Missions

• Worksheet 4a: Mission ZoningDivide the playing field into 2-4 zones based on geographical

location


NAV 101 & Missions

• Worksheet 4b: Mission TaskingTasking the mission


Mission Name Description Task List

Stent Place the stent into the artery

Move fwd, detect circleTurn left 45 degrees – spinMove fwd, detect black lineTurn left 90 degrees – R wheelTurn on R sensorMove fwd, follow line, detect T w R sensor – this should insert the Stent into the artery

Blood Draw Trip 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.


NAV 101 & Missions• Mission Planning Sheet


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?


NAV 101 & Missions• Thank you for your attendance in the ORTOP workshops• Please fill out workshop survey• Resources handout• Food Factor Challenge:

http://www.firstlegoleague.org/media/twocol.aspx?id=248• Contact Us:

– Roger Swanson, [email protected]– Jim Ryan, [email protected]– Dale Jordan, [email protected]– Ken Cone, [email protected]– Cathy Swider, [email protected]– www.ortop.org/fll


http://www.firstlegoleague.org/media/twocol.aspx?id=248

mailto:[email protected]

http://www.ortop.org/fll

ortop workshop 3 welcome goal: extend your knowledge of lego robotics – this workshop is very...

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