1.9. Control Systems

A control system reads sensor values and command actuators for a mechatronic device to perform its tasks. In a modern mechatronic system with a microcontroller the control system is implemented in software. Normally this is accomplished by an infinite loop that continuously reads sensor values and performs actions.

There are two broad categories of control systems:

• Open loop - actions are independent from the change in the environment

• Closed loop - actions are dependent on changes in the environment

For example we can compare a toaster and an oven. Turning on a toaster runs the heating elements for a fixed amount of time. Even if the toaster gets too hot or the toast starts to burn the heating elements will remain powered. Therefore a toaster uses open loop control. Whereas an oven is equipped with a temperature sensor and the heating elements are turned on when the temperature is below the target temperature. Therefore an oven uses closed loop control.

Within closed loop control there are many different control schemes, which we will discuss in more detail later.