Robust control of valves in ship diesel engines with the use of the Derivative-free nonlinear Kalman filter

Abstract

This article studies robust nonlinear control for gas exchange valves in ship diesel engines, with the use of the derivative-free nonlinear Kalman filter. Robust control of gas exchange valves is important for improving the efficiency in the operation of diesel engines. Due to the relatively wide range of typical internal combustion engine operating conditions imposed on a variable valve timing actuator, the control scheme must compensate for model uncertainties, parametric variations and rapid external disturbances. By applying differential flatness theory, the initial nonlinear model of the system is transformed into the linear canonical (Brunovsky) form. For the latter model, it is possible to design a state feedback controller that enables accurate tracking of the valve’s reference setpoints. To estimate the non-measurable state variables of the model and the unknown external disturbances, the derivative-free nonlinear Kalman filter is used as a disturbance observer. The derivative-free nonlinear Kalman filter consists of the standard Kalman filter recursion on the linearized equivalent model of the valve and of computation of state and disturbance estimates using the diffeomorphism (relations about state variables’ transformation) provided by differential flatness theory. Evaluation tests are performed for assessing the performance of the proposed control scheme.