Investigation of Control Systems of FOPDT Plants with Dynamics Asymmetry

This work investigates feedback control systems with first order plus dead time (FOPDT) plants, which are characterized by asymmetric dynamics. The term asymmetric dynamics is understood to mean that the dynamics of the response of the controlled parameter of the plant to the rise and fall of the plant control signal are different. The novelty of the current work is that it analyzes a case where the asymmetry is introduced by both dynamic parameters of the FOPDT plant: by the asymmetry of the time constant and by the asymmetry of the response delay. Another novelty is that in the proposed asymmetrical PI (aPI) controller, the change in the plant control signal time derivative sign is used to determine the moments for the switching of controller parameters. The use of an aPI controller instead of a conventional PI controller allows us to improve the quality of the control of plants with asymmetric dynamics. It is also important that the problem is solved using a PI type controller, which automation engineers are well aware of and know how to tune its parameters to the dynamics of the plant. Therefore, an aPI controller can be attractive in practical applications. All investigations were performed using Matlab/Simulink software (version R2021b).