On-off Control

This kind of control is based on the comparison of two different signals: one is the variable we want to control Ts and the other is the setpoint we want to obtain Ti. It is evaluated the difference between them and in function of the value of this error is calculated the output. If it is in stop state, the output is not set to 1 until is reached a value of the difference higher than ATa. If it’s running and the error begins to decrease, it does not stop till this error reaches a value ATp. With this kind of control, is possible to reduce the number of oscillations of the system.

Control by means of PI (Proportional-Integral).

Once they have been established the conditions to start up the installation, using any of the previous strategies, the setpoint value can be sent to the pump, in which case there can be an on-off control system or on the other hand there can be a controller which receives the start signal and that varies the pump flow in order to maintain the temperature setpoints.

Although there are a huge amount of theories about the adjust of the parameters of the controller, note that the fine-tuning has been made in this case by means of trial and error, and so the values introduced on the system are the best of all obtained.

The PI controller has been used for the variable flow regulation of the pumps as well as for the three way valve if necessary (depends on the case).