Control structure design for an 18O isotope separation column

This paper presents the design of a control structure that ensures a constant isotopic concentration at the output of the 18O isotope cascade separation column, with an overshoot as small as possible. This paper focuses on obtaining a PID type controller, using the relay method as tuning method, due to the nonlinear behavior of the plant. The controller parameters are adjusted in order to achieve a suitable step response through computer simulation, using the plant fractional - order model. Further, a fractional - order PID controller is tuned in order to improve the control signal, so as to fit within the range of unified current's variation, 0 to 16 mA.