Real-time control systems are systems where the controlling logic has only two ways of interacting with the system: reading sensor input, and writing to physical outputs. This field includes robotics, telescope control systems, and most applications involving a physical system being driven by a digital controller.

An approximate description of a real time system.

This diagram roughly describes the control systems of a modern real-time system. The user generates a set of input data, either by giving information through input devices such as controllers or a computer, or by inputting a desired state which the controller attempts to reach. The controller compiles together sensor data and user data, and determines a set of output data to be written to motors and actuators.

The most important and complex part in these systems is the Controller; the logic, calculations, PID controls, trajectory calculations, etc. that determine the behavior of your system happen in this controller.My next post will explain a simple overview and how to use PID, feed forward, and trajectories.