Dynamical Sliding Mode Control for Robust Dynamic Positioning Systems of FPSO Vessels

The conventional proportional derivative (PD) control algorithm with appropriate gain scheduling is generally applied to a dynamic positioning (DP) system. However, finding appropriate gains through gain scheduling makes the DP system more complicated. A sliding-mode control algorithm controls an arbitrary point, such as the turret system on a floating production storage and offloading (FPSO) vessel. This algorithm was developed for DP and can be applied to FPSO vessels considering the uncertainty of the vessel dynamics, unknown time-varying environmental disturbances, and transient performance. To control an arbitrary point on the FPSO vessel using a DP controller, the Jacobian matrix in the kinematic equation is modified to present the arbitrary point in the control. The Lyapunov stability theory is applied in the design of the SM control algorithm to provide robustness to the control system. A time-domain simulation tool was developed to verify the effectiveness of the proposed SM control algorithm. The performance of the control algorithm was evaluated numerically to address its efficacy. The results were compared with those obtained using the conventional PD control algorithm

Effect of iridium oxide as an additive on catalysts with different Pt contents in cell reversal conditions of polymer electrolyte membrane fuel cells

© 2021 Hydrogen Energy Publications LLCCell reversal is observed when a current load is applied to the polymer electrolyte membrane fuel cell under fuel starvation conditions. Cell reversal causes severe corrosion (or oxidation) of the carbon support in the anode, which leads to a decrease in overall fuel cell performance. To suppress the corrosion reaction of carbon under cell reversal conditions and to increase the durability of fuel cells, studies on anode additives are being conducted. However, studies on the effect of additives on catalysts with different platinum contents have not been conducted. In this study, 20 wt%, 40 wt%, 60 wt% commercial Pt/C catalyst was applied to the anode, and 50 cycles of cell reversal were performed. Furthermore, the performance change with and without IrO2 as an additive was observed and its effect was assessed. Changes in the morphologies of the electrodes before and after cell reversal tests were also observed using a transmission electron microscope and a scanning electron microscope. The higher the platinum content of the catalyst, the more resistant to cell reversal. In addition, the addition of IrO2 to the anode effectively prevents performance degradation due to cell reversal.11Nsciescopu

Development of an Autonomous Underwater Vehicle ISiMI6000 for Deep-sea Observation

1034-1041The Korea Institute of Ocean Science and Technology (KIOST) has developed AUVs for survey on the swallow sea, and is under developing a deep-sea AUV based on the former experience. Since 2010, the AUV named ISiMI6000 was designed to explore the deep-seabed topography and hydrothermal vent up to 6,000 m depth. ISiMI6000 was designed witha cylindrical shape having Myringform to minimize fluid resistance. It has one main thruster and four control planes, of which the maximum speed is 4 knots and has over 1.5 knots in up/down direction. It equips with an underwater navigation system composed of Ultra Short Baseline (USBL), Doppler Velocity Log (DVL), Attitude and Heading Reference System (AHRS), Inertial Measurement Unit (IMU), Obstacle Avoid System (OAS), and Global Positioning System (GPS). Its communication tools are Acoustic Telemetry Modem (ATM) under the sea and Radio Frequency (RF) modem at surface. Oceanographic sensors were equipped for precise survey on the deep-sea floor, such as Conductivity Temperature Depth (CTD), Side Scan Sonar (SSS), methane sensor, and sub-bottom profiler (SBP) in optional. A HD Camera and LED light was installed for monitoring the sea floor, and an emergency managing device was designed with a weight drop system, a radio beacon and a xenon flash. This paper introduces the system design and configuration of ISiMI6000 and describes the operating software system in brief. This paper also describes a tank tests and field tests to evaluate the operation process and navigation performance at the Southern Sea