Multitechnique Concise Robust Control for the Insulation Containment Space Pressure Control of LNG Carrier

Abstract

In this note, a novel multitechnique concise robust control scheme, based on the mirror mapping technique (MMT), closed-loop gain shaping algorithm (CGSA), Smith predictor (SP), and nonlinear feedback technique (NFT), is proposed for the pressure control of the liquefied natural gas (LNG) carrier insulation containment space. Firstly, a kind of integral unstable time-delay model is obtained by linearizing the nonlinear model of the pressure maintenance system around its equilibrium. By using the MMT and CGSA, one acquires the corresponding stable mirror mapping model of the unstable linear model and the designed controller. And the SP is introduced to tackle the time-delay problem. In addition, for the purpose of energy saving, the NFT is added into the control scheme. Finally, a set of experiments has been employed to illustrate the control effects, and the results show that it can achieve satisfying performance in aspects of disturbance rejection and energy saving.

Nonlinear Feedback-Based Path Following Control for Underactuated Ships via an Improved Compound Line-of-Sight Guidance

“…The NFT is a novel technique used to improve the control performance by employing a nonlinear driven function of error, between the reference signal and the actual system output, as the input of the control law, which can achieve the same control effect with minor control action under the unchanged control law [36][37][38][39][40]. However, the researcher should make prudent use of the NFT when the feedback error is too large, which may cause the instability of the control system [38].…”

“…NFT is a technology that can improve the energy efficiency of the system and achieve the same control effect with minor control action under the unchanged control law. In addition, its effectiveness has been validated through the theoretical analysis and the simulation experiments relating to the ship course keeping control [36]- [40]. Motivated by the above observations, this paper investigates both the path following guidance and the rudder-based yaw controller for the underactuated ship.…”