Robust Liquid Level Control of Quadruple Tank System: A Nonlinear Model-Free Approach

Abstract: In this paper, two new versions of modified active disturbance rejection control (MADRC)
are proposed to stabilize a nonlinear quadruple tank system and control the water levels of the
lower two tanks in the presence of exogenous disturbances, parameter uncertainties, and parallel
varying input set-points. The first proposed scheme is configured from the combination of a modified
tracking differentiator (TD), modified super twisting sliding mode (STC-SM), and modified nonlinear
extended state observer (NLESO), while the second proposed scheme is obtained by aggregating
another modified TD, a modified nonlinear state error feedback (MNLSEF), and a fal-function-based
ESO. The MADRC schemes with a nonlinear quadruple tank system are investigated by running
simulations in the MATLAB/SIMULINK environment and several comparison experiments are
conducted to validate the effectiveness of the proposed control schemes. Furthermore, the genetic
algorithm (GA) is used as a tuning algorithm to parametrize the proposed MADRC schemes with the
integral time absolute error (ITAE), integral square of the control signal (ISU), and integral absolute
of the control signal (IAU) as an output performance index (OPI). Finally, the simulation results show
the robustness of the proposed schemes with a noticeable reduction in the OPI.
Keywords: four-tank system; modified active disturbance rejection control (MADRC); water level control

https://doi.org/10.3390/act12030119