Tutorial 2 - Automatic Emergency Braking

• AEB Theory of Operation
  • 1️⃣ Learning Goals
  • 2️⃣ Overview
    • The LaserScan Message
    • The Odometry Message
    • The AckermannDriveStamped Message
  • 3️⃣ Time-to-Collision (TTC) vs. Distance-Based Braking
    • Distance-Based Braking (Threshold Approach)
    • Time-to-Collision (TTC) - A Smarter Alternative
    • Example: Comparing Both Approaches
    • Key Takeaways
  • 4️⃣ Understanding Time to Collision (TTC)
    • Basic TTC Concept
    • Example: Why TTC Matters
  • 5️⃣ Time to Collision Using Laser Scan Data
    • What Data the Vehicle Uses
    • Range Rate: Closing Speed Along a Beam
    • Calculating Range Rate (Recommended Method)
    • Computing TTC Per Beam
    • Why the Sign Matters
    • Using TTC for AEB Decisions
  • 6️⃣ Automatic Emergency Braking with TTC
• LaserScan Data
  • Finding the /scan Topic
  • Checking the Message Type
  • Inspecting the LaserScan Message Definition
  • Echoing Live Scan Data
  • Understanding /scan Output (LaserScan)
    • What ranges[] Means
    • How Many Samples Are in One Scan?
    • Mapping an Index to an Angle
    • “Straight Ahead” Index
    • Interpreting Range Values
  • Scan Timing and Health
  • Confirming Frame Information
  • Hardware: Hokuyo UST-10LX LiDAR
    • Key Specifications
    • Physical Characteristics
    • Connecting Hardware to Software
• AEB Package Creation
  • 1️⃣ Create the Safety Package
  • 2️⃣ Modify package.xml
  • 3️⃣ Modify CMakeLists.txt (If Using C++)
    • 4️⃣ Install Dependencies Using rosdep
    • 5️⃣ Implement the Safety Node
  • 6️⃣ Make It Executable
    • 7️⃣ Build & Run
• AEB Scan Example
  • 🚀 How safety_node.py Identifies Front Readings from LiDAR
    • 🔹 Problem Before Fix
    • ✅ Fix: Filter Only Front Readings
    • 1️⃣ Understanding LiDAR Data
    • 2️⃣ Extracting Front Readings
    • 📌 Explanation of Code
    • 3️⃣ Why This Fix Works
    • 4️⃣ Summary
    • 5️⃣ Full Code Example
• AEB Drive Example
  • Code Explanation: DriveForwardNode
    • 1️⃣ Shebang & Imports
    • 2️⃣ Class Definition: DriveForwardNode
    • 3️⃣ Node Initialization (__init__)
    • 4️⃣ Creating a Publisher
    • 5️⃣ Creating a Timer
    • 6️⃣ Logging Node Startup
    • 7️⃣ Drive Command Callback (drive_callback)
    • 8️⃣ Main Function
    • 9️⃣ Running the Script
    • 💡 Summary
  • Full Code
• Quality of Service (QoS) in ROS 2
  • QoS for Sensor Data
    • Using Sensor QoS in Python
  • Common QoS Profiles in ROS 2
  • Considerations When Using QoS
• Speed Adjustment Using PID Control for TTC
  • Overview
  • 1️⃣ Why Use PID Control for Speed Adjustment?
  • 2️⃣ PID Control Formula for Speed Adjustment
  • 3️⃣ How the Derivative Term Helps
  • 4️⃣ Example: PID-Based Speed Control
    • Scenario: Adjusting Speed Based on TTC
  • 5️⃣ Considerations & Tuning
  • 6️⃣ Summary