Reference Implementation of the PID Controller

The PID controller is the by far most frequently employed type of controller. As you read, billions of digitally implemented PID controllers are running, shaping the dynamic behavior of anything from the fan speed in your laptop to safety-critical components in nuclear power plants. Given the abundance of commissioned PID controllers, it is surprisingly hard to find a single source that provides a well-documented, and motivated reference implementation of the PID controller in text-based code. This work provides one. We use the incremental (velocity) form, motivated by its intrinsic integrator anti-windup and bumpless transfer behavior. In addition, we discuss our implementation in terms of measurement filtering, setpoint handling, and runtime environment, among other implementation aspects. Our reference implementation is a living "document", and a link to a GitHub repository hosting the latest version is provided.