What is a Control loop?
A control loop (or controller) is a process in which a system is continuously driven and adjusted based on measurements, in order to reach and maintain a desired target — the Setpoint.
Control loops are essential in automation, the process industry, HVAC, machines and many other technical applications.
🔧 What does a control loop do?
A control loop compares the actual value (measured by a Sensor) with the desired value, also called the Setpoint. Based on the difference (the control error), the controller drives the system to correct this.
🧱 Basic components of a control loop
Setpoint → Comparator → Controller → Actuator → Process → Sensor → back to the Comparator
| Component | Description |
|---|---|
| Setpoint | The desired target value of the process (e.g. 100 °C, 2 bar pressure, 500 rpm) |
| Sensor | Measures the actual process value |
| Controller | Determines how strongly to correct (e.g. a PID controller) |
| Actuator | Carries out the correction (e.g. a valve, motor or heating element) |
| Process | The system or device you are controlling |
📌 Example
When controlling the temperature in an oven:
- Setpoint = 180 °C (desired temperature)
- Sensor measures the actual temperature
- Controller compares the measured value with the Setpoint
- Heating element is switched on or adjusted to bring the temperature up to the Setpoint
🔄 Types of control
| Control type | Description |
|---|---|
| Open-loop (feedforward) | No feedback, only reacts to the input |
| Closed-loop (feedback) | Measures the output and corrects based on the deviation (most commonly used) |
| PID control | Proportional–Integral–Derivative: the most widely used algorithm in industry |
🎯 Aim of a control loop
- Stable and safe process operation
- Efficient use of energy and raw materials
- Preventing deviations, errors or damage
- Automatic correction without human intervention
📌 In summary
A control loop ensures that a system reaches and maintains its desired state (Setpoint) by continuously adjusting based on real-time measurements.