Skip to content

FLL Session 4: Sensor Navigation, Line Tracking, Mission Routing & Innovation Problem Selection — Lego Legends

Date: Saturday, October 4, 2026
Time: 1:00 PM – 4:00 PM
Attendees: Team Members, Mentors & Coaches
Season Phase: Training Camp 3 — Sensor Navigation, Field Mission Routing & Innovation Problem Narrowing

[!IMPORTANT]

🧭 Session 4 Coaching Architecture: Transitioning from Blind Guesswork to Sensor Intelligence

In Session 3, students mastered mechanical modularity and physical chassis building. Today marks a major technical leap: shifting from time/motor-degree dead-reckoning to closed-loop sensor feedback.

  1. Innovation Problem Narrowing (1:15 – 1:55 PM): While energy is fresh, synthesize midweek research findings, analyze existing solutions, and narrow the team's focus down to 1–2 high-potential problem statements ahead of the October 17 Zoo Field Trip.
  2. Dual-Station Sensor & Mission Lab (2:05 – 3:10 PM): Hands-on implementation of dual color sensors, line following, and line squaring subroutines, driven by the Peer Ambassador Handoff protocol.
  3. The "Sensor Blind Navigation" Core Values Challenge (3:10 – 3:35 PM): An experiential communication exercise that illustrates how robots perceive sensor thresholds, reinforcing trust, closed-loop callouts, and empathy.
  4. Roles in Action: Put the updated Team Roles Matrix into full practice—each student lead coordinates their domain!

📌 Coach's Prep & Materials Checklist

🕒 Master Timeline Overview (1:00 PM – 4:00 PM)

gantt
    title Session 4 Master Timeline (Saturday, Oct 4)
    dateFormat HH:mm
    axisFormat %H:%M

    section Kickoff
    Welcome & Role Briefing       :13:00, 15m

    section Innovation
    Midweek Research & Problem Selection :13:15, 40m

    section Recharge
    Bio Break & Energy Reset      :13:55, 10m

    section Robot Lab
    Station A/B Sensor & Code Camp :14:05, 30m
    Peer Ambassador Handoff       :14:35, 15m
    Reverse Handoff & Testing     :14:50, 20m

    section Core Values
    Sensor Blind Navigation Game  :15:10, 25m

    section Wrap-Up
    Clean-Up Protocol Sprint      :15:35, 15m
    Daily Learning Reflection     :15:50, 10m

📋 Minute-by-Minute Session Plan

1:00 - 1:15 PM | Welcome, Energy Check & Role Briefing (15 min)

  • Arrival & High-Five Welcome (5 min): Greet students as they enter. Check in on personal energy and verify team badges.
  • The 3 Mission Goals for Today (5 min):
  • Innovation: Narrow down from broad habitat ideas to our top 2 specific problem candidates.
  • Robot: Teach the robot to "see" using color sensors—mount sensors and code a line-stop program.

  • Core Values: Trust each other in the "Sensor Blind Navigation" team challenge.

  • Activating the Team Roles Matrix (5 min):

  • Remind the team: "Leads do not work alone—leads facilitate, organize, include everyone, and safely store our gear!"
  • Machamp (Presentation Lead): Keeps track of the master room clock and transition timers.
  • Alakazam (Research Lead): Keeps project discussions focused on specific evidence and citations.
  • Tinkaton (Prototype Lead): Manages building task assignments and LEGO sorting trays.
  • Dragonite (Outreach Coordinator): Compiles interview questions for our guest experts.
  • Jigglypuff (Creative Director): Captures photos/videos of robot testing and tracks design milestones.
  • Meowth (Budget Officer): Tracks supply wishlists and audits high-value electronic gear.
  • Greninja (Intelligence Scout): Leads test-run debriefs and records robot consistency scores.
  • Psyduck (Rubber Ducky): Sounding board for stuck teammates, ensures fair table turns, and monitors stress.

1:15 - 1:55 PM | Block 1: Innovation Project Problem Narrowing & Expert Outreach Prep (40 min)

flowchart LR
    A["🔬 Alakazam & Team<br/>Share Midweek Facts"] --> B["⚖️ Decision Matrix<br/>Local vs. Specific Habitat"]
    B --> C["🎯 Top 2 Problem<br/>Candidate Finalists"]
    C --> D["📬 Dragonite Leads<br/>Draft Expert Questions"]

    style A fill:#fef08a,stroke:#eab308,stroke-width:1.5px;
    style B fill:#e0f2fe,stroke:#0284c7,stroke-width:1.5px;
    style C fill:#dcfce7,stroke:#16a34a,stroke-width:1.5px;
    style D fill:#fce7f3,stroke:#db2777,stroke-width:1.5px;
  • Midweek Research Synthesis (15 min):
  • Facilitated by Alakazam (Research Lead) and supported by mentors.
  • Teammates go around the table sharing one fascinating scientific fact or habitat challenge discovered during the week.

  • Capture ideas on the whiteboard grouped into ecosystem clusters:

    • Deep Benthic Zone / Hydrothermal Vents: Extreme pressure, darkness, unique chemosynthesis, light pollution from exploration subs.
    • Coastal Estuaries / Salt Marshes: Sediment runoff, artificial shoreline seawalls, microplastic biofouling.
    • Kelp Forests / Rocky Reefs: Wave energy damage, rising water temperatures, sea urchin imbalances.

  • Applying the FLL Problem-Narrowing Filter (15 min):

  • Guide students through the Socratic evaluation framework from our Mentor Innovation Rubric Guide:

    • "Is this problem too big for us to impact (e.g. 'clean the entire ocean') or specific enough to build a prototype for?"
    • "Can we find and interview a real human expert who works on this problem locally or regionally?"
    • "Can we explain who suffers from this problem in 2 sentences?"

  • Narrow the list down to 2 strong finalist problems.

  • Expert Outreach Prep for Zoo Field Trip (10 min):

  • Led by Dragonite (Outreach Coordinator).
  • The team is visiting the Zoo on October 17 to interview biologists.
  • Draft 3–4 open-ended, high-leverage questions to ask:
    • "What is the most difficult challenge you face when monitoring this habitat in the wild?"
    • "What tools do you currently use, and what is their biggest flaw?"
    • "If engineers could build any new tool to help your conservation work, what would it do?"

1:55 - 2:05 PM | Bio Break & Physical Energy Reset (10 min)

  • Hands off bricks and tablets immediately.
  • Water break, nutritious snack, bathroom check, and physical stretch.
  • Clear desks and prep the robot stations for engineering time.

2:05 - 3:00 PM | Block 2: Dual-Station Robot Engineering Camp (60 min)

💡 Why Dual Color Sensors?
Running on motor rotations alone causes errors due to wheel slip, battery drain, and mat friction variations. Adding two color sensors pointing down enables line tracking and line squaring (aligning perpendicular against field lines), resetting accumulated positioning errors to zero!

flowchart TD
    subgraph Part1["Part 1: Master Station Sprints (2:05 - 2:35 PM • 30 min)"]
        direction LR
        STA["🛠️ Station A: Hardware & Sensor Rigging<br/>(Tinkaton Lead + Builders)<br/>• Mount 2 downward sensors (8-10mm height)<br/>• Design quick-clip cable cable clips<br/>• Build front bumper alignment jig"]
        STB["💻 Station B: Code & Sensor Logic<br/>(Greninja Lead + Coders)<br/>• Calibrate light reflected % (White vs. Black)<br/>• Program 'Drive until Black Line'<br/>• Program Proportional Line Follower"]
    end

    subgraph Part2["Part 2: Peer Ambassador Handoff (2:35 - 2:50 PM • 15 min)"]
        direction LR
        AMB["🤝 Ambassadors Stay Behind to Onboard Incoming Group<br/>(Mentors in Shadow Mode • Zero Lecturing!)"]
    end

    subgraph Part3["Part 3: Reverse Handoff & Mat Testing (2:50 - 3:10 PM • 20 min)"]
        direction LR
        TEST["🚀 Combined Integration Run on Mat<br/>• Robot drives to Line 1 and squares itself flush<br/>• Greninja logs 5-run reliability stats"]
    end

    Part1 --> Part2 --> Part3

Station A: Mechanical Rigging & Sensor Mounting (Build Lab)

  • Lead: Tinkaton (Prototype Lead) & Builders.
  • Objective: Mount two SPIKE Prime Color Sensors to the front of the Advanced Driving Base.
  • Key Engineering Principles:
  • Ground Clearance: Sensors must sit 8 mm to 10 mm above the mat. Too high ($>15\text{ mm}$), and ambient room light introduces noise; too low ($<5\text{ mm}$), and the sensor will scrape mat wrinkles or seam lines.
  • Sensor Spacing: Space the two sensors wide enough apart to straddle standard mission lines (approximately 4–6 Technic studs apart).
  • Cable Management: Secure sensory cables tightly using Technic bush pins so wires cannot catch on mission models.
  • Sturdy Bracing: Perform the 2-finger tug test on the sensor bracket to ensure zero wobble.

Station B: Sensor Calibration & Navigation Logic (Code Lab)

  • Lead: Greninja (Intelligence Scout) & Coders.
  • Objective: Create modular Scratch/Python blocks for sensor-based navigation.
  • Programming Milestones:

  • Light Reflection Threshold Test:

    • Place sensor over white mat surface: record value (typically ~80–90%).
    • Place sensor over black line: record value (typically ~10–20%).
    • Calculate midpoint threshold: $\text{Threshold} = \frac{\text{White} + \text{Black}}{2} \approx 50\%$.

  • Block 1: "Drive Until Black Line" (Stop at Line):

    • Start motors forward $\rightarrow$ Wait until Color Sensor $< 35\%$ $\rightarrow$ Stop motors.

  • Block 2: "Line Squaring" (Self-Alignment):

    • Drive forward until either sensor detects black.
    • Pivot the opposite wheel until the second sensor also detects black.
    • Result: Robot is now aligned 100% perpendicular to the line, regardless of starting angle!

2:35 - 2:50 PM: The Peer Ambassador Handoff (15 min)

  • Exactly at 2:35 PM, stations switch.
  • 1–2 Ambassadors stay at Station A to teach the incoming group how the sensors are mounted and calibrated.
  • 1–2 Ambassadors stay at Station B to guide incoming coders through the threshold math.
  • Coaching rule: Mentors stand back in shadow mode. Let the kids explain and teach in their own words!

2:50 - 3:10 PM: Integration & Mat Reliability Trials (20 min)

  • Both halves re-unite at the official table.
  • Psyduck ensures every teammate gets an active role during testing (launcher, spotter, data logger).
  • Perform 5 trial runs of the Line Squaring routine from the Launch Area:
  • Greninja logs success rate in the team notebook (e.g. 4/5 clean squares).
  • Jigglypuff films slow-motion video of the sensor behavior to verify detection timing.

🥊 3:00 - 3:45 PM | The CRM Stress Gauntlet (30 min)

💡 Coaching Note: We do not need to run all 4 challenges in every session! Running 2 focused challenges per session keeps the exercises crisp, prevents sensory fatigue, and keeps students on their toes. Today, we run Challenge 1 and Challenge 2 (with Challenge 3 & 4 reserved for future rotations).

The Golden CRM Rule: "Aviate, Navigate, Communicate"

Before starting, gather pairs and review the 3-word pilot axiom (see CRM Guide): 1. 🛩️ Aviate: Control the physical piece first—hold it steady! 2. 🧭 Navigate: Check the clock and know what piece is missing or needed next. 3. 📢 Communicate: Speak loud and clear so your partner acts as one brain!

The Universal Ground Rule: The One-Handed Duo Constraint

  • Each student puts their non-dominant hand firmly in their pocket (or behind their back).
  • They may only use ONE hand!
  • Why: One child cannot take over. One student must act as the Anchor (holding the beam steady) while the other acts as the Builder (inserting pins and sliding gears).
flowchart LR
    C1["⚡ Challenge 1<br/>The Fast Clock<br/>(60s Time Pressure)"] --> C2["🧩 Challenge 2<br/>The Missing Pin<br/>(Assertive Callouts)"]
    C2 -.->|Future Rotation| C3["🔄 Challenge 3<br/>The Tactical Swap<br/>(Partner Rotation)"]
    C3 -.->|Future Rotation| C4["🔦 Challenge 4<br/>Lights Out / Sound<br/>(Sensory Shock)"]

    style C1 fill:#e1f5fe,stroke:#0284c7,stroke-width:2px;
    style C2 fill:#fff9c4,stroke:#fbc02d,stroke-width:2px;
    style C3 fill:#f1f5f9,stroke:#94a3b8,stroke-dasharray: 5 5;
    style C4 fill:#f1f5f9,stroke:#94a3b8,stroke-dasharray: 5 5;

⚡ Challenge 1: The Fast Clock (60 Seconds)

  • The Scenario: You have exactly 60 seconds on the big screen timer to assemble the complete pivoting Technic lever arm.
  • What Mentors Will Observe: Kids rushing, dropping pins, fumbling with one hand, getting quiet, or frantically yelling "Hurry up!"
  • The Rules:
  • Timer starts with an official match buzzer: "3, 2, 1, LEGO!"
  • Build until the horn sounds at 0:00.
  • The 2-Minute Debrief:
  • "Raise your hand if your heart beat faster when you heard the countdown!"
  • "Did rushing make you faster or did it make pins slip out of your fingers?"
  • Coach Takeaway: In FLL, smooth is fast. When you rush silently, you drop parts. Next time, tell your partner: "Hold beam grey flat!" then slide the pin calmly.

🧩 Challenge 2: The Missing Pin (Unforeseen Obstacle)

  • The Secret Setup: Before starting, the mentor quietly removes one black connector pin from every team's tray without telling them!
  • The Scenario: 60-second timer starts. Kids attempt to finish the arm, but quickly realize: the final beam cannot be secured because a pin is missing!
  • What Usually Happens: Kids freeze, search through the carpet, blame their partner ("Did you drop it?!"), or stand paralyzed.
  • The Expected CRM Behavior:
  • Aviate: Finish what can be assembled.
  • Navigate: Realize a required piece is physically absent.
  • Communicate: Raise a hand, look at the mentor/referee, and assertively call: "Supply! We are missing one black friction pin!"
  • Mentor immediately tosses them the missing pin.
  • The 2-Minute Debrief:
  • "Was it your fault the pin was missing?" (No!).
  • "Did blaming your partner help?" (No!).
  • Coach Takeaway: At tournaments, models jam and parts break through no fault of your own. Don't waste 20 seconds freezing. Aviate, Navigate, Communicate! Speak up assertively!

(Challenges 3 & 4: Tactical Mid-Build Swap and Lights-Out Sensory Shock are held in reserve for upcoming sessions!)

3:45 - 3:50 PM | The Clean-Up Protocol Sprint (15 min)

  • Stop immediately at 3:35 PM. Enforce clean-up discipline cleanly.
  • Role Leadership in Action:
  • Tinkaton (Prototype Lead): Inspects table surface, checks sorting trays, and ensures modular attachment frames are packed in padded bins.

  • Meowth (Budget Officer): Performs electronics inventory:

    • 2 SPIKE Prime Hubs plugged into charging cables.
    • 4 Color Sensors verified and accounted for.
    • Tablets placed in storage dock and plugged in.

  • Machamp (Presentation Lead): Ensures whiteboard notes are photographed and research binders are filed in the cabinet.

  • Floor Sweep Challenge: Two-minute group sprint to ensure zero Technic pins or beams remain on the floor.

3:50 - 4:00 PM | Daily Learning Circle & Reflection (10 min)

  • Gather team in a seated circle with all materials put away.
  • Machamp monitors the 1-minute-per-speaker time.
  • Each team member answers:
  • "What was one 'Aha!' moment you had about color sensors or our project today?"

  • "Who is one teammate you saw using a FIRST Core Value (Discovery, Innovation, Impact, Inclusion, Teamwork, Fun) today?"

  • Mentors Hand Out Recognition Tokens / Pokémon Cards: Celebrate grit, thoughtful questions, and clean handoffs.

  • Quick parent dismissal check-in.

🎯 Coach's Success & Evaluation Criteria

By 4:00 PM, Session 4 is a complete success if:

  • The team evaluated their research ideas and agreed on top 2 finalist problem statements.
  • At least 3 specific questions were drafted for domain experts on the upcoming Zoo trip.
  • Both SPIKE Prime robots have dual color sensors rigidly mounted at 8–10 mm clearance.
  • Students programmed and verified a functioning "Stop at Line" or Line Squaring routine.
  • The Peer Ambassador Handoff was executed with students leading the explanation without mentor lecturing.
  • Every child participated in the "Sensor Blind Navigation" challenge.
  • Clean-up protocol completed 100% with all batteries on charge.
  • Every student shared a takeaway in the Daily Learning Circle.