Level 4 — Sensors
How robots perceive the physical world
Sensors are the robot’s sensory organs. Without reliable sensing, even the best mechanics and control algorithms fail. Sensors convert physical phenomena into electrical signals that control systems can process.
This level focuses on understanding sensor types, signal quality, and limitations — not on blindly trusting raw values.
Sensor categories
- Position sensors — encoders, potentiometers
- Motion sensors — gyroscopes, accelerometers
- Distance sensors — ultrasonic, infrared, time-of-flight
- Contact sensors — limit switches, bump sensors
- Environmental sensors — temperature, light, pressure
Encoders
Encoders measure rotation or position and are fundamental for precise control. They enable speed calculation, position tracking, and closed-loop feedback.
- Incremental encoders — relative movement tracking
- Absolute encoders — direct position measurement
- Resolution defines measurement precision
- Mounting accuracy affects data quality
Inertial sensors (IMU)
Inertial Measurement Units combine accelerometers and gyroscopes. They measure linear acceleration and angular velocity.
- Accelerometers sense acceleration and gravity
- Gyroscopes sense angular rate
- Drift accumulates over time
- Orientation estimation requires filtering
Distance sensing
Distance sensors allow robots to detect obstacles and navigate safely. Each technology has trade-offs in range, accuracy, and reliability.
- Ultrasonic — simple, affected by surface and angle
- Infrared — fast, sensitive to lighting conditions
- Time-of-flight — higher precision, limited field of view
Analog vs digital signals
Sensors may output analog voltages or digital data. Understanding this difference is essential for correct interpretation.
- Analog signals require filtering and calibration
- Digital sensors provide processed data but hide raw behavior
- Resolution and sampling rate limit usable information
Calibration and errors
All sensors have errors. Calibration defines the relationship between real physical values and measured data.
- Offset error shifts measurements
- Scale error distorts values
- Noise introduces randomness
- Temperature affects accuracy
What you should know after Level 4
- how different sensors work and where to use them
- why raw sensor data is never perfect
- how calibration improves reliability
- why sensing quality limits control performance
Next: Level 5 — Control Systems