Nowadays the majority of the regulators used in industry are of the PID type. A plant may have hundreds of regulators which would be rather time-consuming to manually tune and the access to units could be physically cumbersome. This has motivated the development of self-tuning regulators.
There are several self-tuning algorithms available, which are able to autonomously determine the control parameters based on the input or output of the plant. One such algorithm is the relay feedback method, in which a relay is connected to the control loop parallel to the PID controller. In the initial tuning mode the control signal of the plant is provided by the relay which forces the output signal to oscillate by changing between two values. We can deduce the parameters of the PID controller from the amplitude and the period time of the oscillations.
The aim of this paper is to describe and implement the relay feedback method in the Matlab/Simulink environment and to test it on a real linear, one-input and one-output linear plant. The real-time testing is done by using a Quanser hardware.