Computing · Automated systems · 20 suggested minutes
01 · Sensors, data and feedback
Learning objective: Describe input–process–output and explain feedback.
A sensor measures a physical condition and provides data. A controller processes that data using an algorithm. An actuator produces a physical action, such as a motor changing speed. This input–process–output chain helps explain a robot without suggesting it has human thoughts. Feedback occurs when measurements of the system influence later action.
A threshold controller compares a measurement with a chosen value. For example, if distance is below 20 cm, command a stop. The virtual robot follows a rule; changing the threshold changes the rule’s condition. Sensor resolution, delays, noise and missing readings affect a real design. A comparison sign matters: “less than” differs from “less than or equal to”.
A controller needs a specified response to invalid data, not just the happy path. An emergency-stop system is a separate safety concern. The virtual stop rule cannot prove a real robot will avoid collision; real stopping also depends on speed, braking capability, latency and many other factors.
Worked example · follow the reasoning
For the condition distance < 20 cm, a reading of 19 cm triggers stop and 20 cm does not. With distance ≤ 20 cm, both trigger stop. Testing the boundary checks the actual rule.
Common misconception
A sensor reading is not automatically correct, and a threshold rule does not guarantee safety.

