Liquid level tracking for a coupled tank system using quasi–lpv control

This article proposes a gain-scheduling procedure based on quasi-LPV modeling for a nonlinear coupled tank system to track the liquid level with zero steady-state error. The nonlinearities are directly represented by a parameter vector that varies within a bounded set constrained by the physical limits of the tank system levels. This approach enables accurate nonlinear system modeling using a linear parameter-varying model. State-feedback linear controllers are designed at the extreme vertices of the bounded set. The global controller is derived as the weighted average of local controller contributions, with the weighting determined by the instantaneous values of the parameter vector. Two interpolation mechanisms are proposed to implement this weighted averaging of the linear controllers. The results confirm the effectiveness of the proposed method in achieving accurate liquid level tracking.