Wall-Following Robot with LEGO SPIKE Prime 3

Introduction

Wall-following is one of the most important navigation techniques used in robotics. It is commonly used in maze-solving robots, autonomous vehicles, and educational robotics competitions. In this project, we will build a simple wall-following robot using the LEGO® SPIKE™ Prime 3 platform and the Mindsensors DIST-ToF (Time-of-Flight) distance sensor.

The robot continuously measures its distance from a wall and adjusts its steering to maintain a constant gap. This project introduces students to sensor feedback, proportional control, and autonomous navigation.

The mindsensors DIST-ToF sensor provides highly accurate distance measurements from approximately 3 cm to 200 cm with millimeter resolution, making it ideal for wall-following applications.

How Wall Following Works

The basic idea is simple:

1. Place the DIST-ToF sensor facing the wall.
2. Select a target distance from the wall (for example, 100 mm).
3. Continuously measure the actual distance.
4. Compare the measured distance with the target distance.
5. Adjust the motor speeds to move closer to or farther from the wall.

If the robot is too far from the wall, it steers toward the wall.

If the robot is too close, it steers away.

If the distance is correct, it drives straight.

Hardware Required

Components

• LEGO SPIKE Prime Hub
• Two SPIKE Prime motors
• Mindsensors DIST-ToF Sensor
• Robot chassis with two drive wheels
• Optional caster wheel

Sensor Placement

Mount the DIST-ToF sensor on the side of the robot facing the wall.

Wall
||||||||||||||||

[ToF] Robot
  |
 [Hub]

This orientation allows the robot to continuously monitor its distance from the wall while moving forward.

Why Use a ToF Sensor?

Traditional ultrasonic sensors can sometimes produce noisy readings when the wall surface is irregular or when operating in tight spaces.

The Mindsensors DIST-ToF sensor uses laser-based Time-of-Flight technology and provides distance measurements directly in millimeters with a range of 3 cm to 200 cm.

Benefits include:

• High accuracy
• Fast response time
• Millimeter resolution
• Reliable operation in narrow corridors
• Easy integration with SPIKE Prime

Wall Following Algorithm

The robot follows this logic repeatedly:

Read distance

Error = TargetDistance - MeasuredDistance

If error > 0
    Turn away from wall
Else if error < 0
    Turn toward wall
Else
    Drive straight

A proportional steering correction can be calculated as:

Correction = Error × Gain

The gain determines how aggressively the robot reacts.

SPIKE Prime Python Example

The following example assumes:

• Left motor on Port A
• Right motor on Port B
• DIST-ToF sensor on Port E
• Desired wall distance = 100 mm

• How It Works

  • The sensor measures the current distance from the wall.
  • The error is calculated.
  • A steering correction is generated.
  • Motor speeds are adjusted.
  • The robot continuously updates its path.

  The result is smooth wall tracking without requiring complex navigation software.

  Tuning the Robot

  If the Robot Oscillates

  Reduce the gain value.

  Example:

  GAIN = 1

  If the Robot Reacts Too Slowly

  Increase the gain value.

  Example:

  GAIN = 3

  If the Robot Hits Corners

  Reduce the base speed:

  BASE_SPEED = 200

  Testing several combinations of speed and gain helps achieve the best performance.

  Extensions and Challenges

  Once basic wall following works, students can add advanced features:

  Maze Navigation

  Follow the left wall or right wall to navigate a maze.

  Corner Detection

  Detect sudden distance increases and make turning decisions.

  Obstacle Avoidance

  Use a second front-facing distance sensor.

  PID Control

  Upgrade from proportional control to a full PID controller for smoother operation.

  Data Logging

  Record distance measurements and graph robot performance.

  Educational Concepts Learned

  This project teaches:

  • Sensor integration
  • Feedback control systems
  • Autonomous navigation
  • Robotics programming
  • Proportional control
  • Real-time decision making

  These concepts are widely used in industrial robots, warehouse automation systems, and self-driving vehicles.

  Conclusion

  Building a wall-following robot with SPIKE Prime 3 and the Mindsensors DIST-ToF sensor is an excellent introduction to autonomous robotics. The high-resolution ToF sensor provides accurate distance measurements, allowing the robot to maintain a consistent distance from a wall while navigating its environment. With a simple proportional control algorithm, students can create a robot that demonstrates many of the same principles used in professional robotic systems.

  As you gain experience, you can expand the project into maze solving, obstacle avoidance, and advanced PID-based navigation, making it a valuable learning platform for robotics enthusiasts of all ages.