Integral Sliding Mode Control and Gain-Scheduled Modified Utkin Observer for an Underground Coal Gasification Energy Conversion Process

One of the challenging control problems of an underground coal gasification (UCG) process involves maintaining a desired heating value from the extracted product gases. In this paper, a model-based control and state estimation of UCG process is described. For the purpose of control and state estimation, a sophisticated model of the UCG process using partial differential equations is approximated by a gain-scheduled nonlinear control-oriented model. Based on this approximated plant model, a robust integral sliding mode control is designed to track a desired trajectory of the heating value. Furthermore, for the estimation of unknown states of the system, a gain-scheduled modified Utkin observer is designed as well. The robustness of the nonlinear control and estimation techniques is assessed by introducing parametric uncertainties in the UCG plant. The simulation results highlight the effectiveness of the proposed nonlinear control and estimation techniques in comparison to a conventional PI controller.