Investigation of Nonlinear Control Systems for Steam Boiler Pressure and Water Level

Based on the control principle of the steam pressure and water level of marine boilers, a set of differential equations to describe steam pressure and water level was derived. By fitting equation coefficients together with the use of a quadratic polynomial, a dual-input coupling mathematical model was derived, in which steam pressure and water level were set as the state variables, while the degree of opening of the fuel solenoid valve and the degree of opening of the feed valve were adopted as input variables. The model was treated as a type of affine nonlinear system for further analysis. Using the sliding-mode variable structure control method, the sliding-mode variable structure controller was solved to realize decoupling of the nonlinear coupling system. By performing a simulation of the boiler steam pressure and water level using the MATLAB environment, it was found that sliding-mode variable structure control based on a nonlinear mathematical model exhibits a series of advantages, including favorable system stability and a strong self-balancing capability.