Abstract
This paper proposes a disturbance observer-based discrete sliding-mode control scheme with the variable sampling rate control for the marine diesel engine speed control in the presence of system uncertainties and disturbances. Initially, a sliding-mode controller based on the fast power reaching law is employed, which has a good dynamic quality of the arrival stage and can suppress chattering. To satisfy the practical requirements in the digital controller and the crank angle-based fuel injection in engine speed control, the proposed method is discretized under the variable sampling rate condition. A disturbance observer based on the second-order sliding-mode control is designed to compensate the system uncertainties and disturbances, by doing such the requirement of the parameters of the sliding-mode controller to be reduced significantly. In addition, a cylinder-by-cylinder mean value engine model (MVEM) is built by restructuring the combustion torque model, based on which numerical simulations are carried out by comparing the proposed method with PID and the extended state observer (ESO)-based sliding mode controllers. The common operation situations of the marine diesel engines are taken into account, including starting process, acceleration and deceleration, load variation, and varied propulsion system parameters. The results demonstrate that the proposed disturbance observer-based sliding-mode controller has prominent control performance and strong robustness.
Highlights
In the ship domain, diesel engines have been widely used as marine main engines for propulsion [1]. ese engines are usually controlled to work at the specified rotating speed to keep the ship sailing at the appropriate speed, this adds unknown load disturbances to the main engines [2].e speed fluctuation and overshoot will cause harm to the whole propulsion system and even paralyze the entire system
As can be seen from the above simulation results, the steady-state fluctuation is basically the same as the PID controller. e robustness and control effect of the SMDObased discrete sliding-mode controller (DSMC) are better than that of the extended state observer (ESO)-based DSMC, which further indicates that the performance of the designed sliding-mode disturbance observer (SMDO) is better than that of the ESO. erefore, control performance of the marine diesel engine speed system can be further improved by the proposed SMDO-based DSMC
A disturbance observer-based discrete slidingmode control scheme is proposed for the speed control of the marine diesel engine. e system uncertainties and external disturbances are estimated by the designed disturbance observer based on the second-order sliding-mode control
Summary
Diesel engines have been widely used as marine main engines for propulsion [1]. ese engines are usually controlled to work at the specified rotating speed to keep the ship sailing at the appropriate speed, this adds unknown load disturbances to the main engines [2]. Afterwards, multisliding surface control is proposed in his literature [18], and different sliding surfaces are selected in the acceleration and steady-state conditions to achieve better control performance in the various working conditions of the marine diesel engine Both of these methods rely on the accurate model. Ere is another issue should be considered in engine speed control, the output speed of the diesel engine is continuous, its working process is not continuous with inherent event-triggered property [11, 24,25,26], making the output of the controller can only be executed once per cylinder per cycle For this reason, the disturbance observerbased SMC employed in this paper should be discrete. The conclusion about the whole work is summarized, and further research of this paper is discussed
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