A Guidance and Control Law Design for Precision Automatic Take-off and Landing of Fixed-Wing UAVs

This paper presents an automatic take-off and landing control system (ATOLS) for fixed-wing UAVs. We propose a guidance and control system to satisfy the requirement for high-precision landing using arresting wires. For trajectory tracking, Line-of-Sight (LOS)-based longitudinal and lateral guidance laws are derived. For the design of inner loop controllers, linear models are identified directly from the flight data. In order to maintain the consistency of the control performance in the presence of flight regime changes during take-off and landing, the linear baseline controller is augmented with a compensator designed using L 1 adaptive control theory, which eliminates the need for conventional gain scheduling. The proposed control system is implemented on a scale Cessna UAV with an arresting hook for validation. The proposed take-off and landing system demonstrated a consistent performance in a series of test flight on a full-scale carrier model

Seasonal Sea Surface Temperature Asymmetry in the Northwestern Pacific Marginal Seas

Sea surface temperature (SST) is an important component of climate and weather systems at various time scales. Asymmetric seasonal SST variations in the Northwestern Pacific Marginal Seas (NWPMS) are investigated in this study using observation data and numerical model results. The asymmetry in SST seasonal variation is estimated quantitatively and compared with heat advection and surface net heat flux using SST data and atmospheric variables from the European Centre for Medium-Range Weather Forecast (ECMWF). The SST increases faster than it decreases, whereas air temperature increases slowly. Heat advection and surface heat flux were estimated using numerically modeled SST and ocean currents, which contribute to the asymmetry of seasonal SST variations. Heat advection shows good correlation with the SST seasonal variation asymmetry. Model results without currents along the boundary show more symmetrical SST variations. This suggests that heat advection is a prominent cause of asymmetry in the seasonal variation

Predicting Typhoon Induced Storm Surges Using the Operational Ocean Forecast System

This study was performed to compare storm surges simulated by the operational storm surges/tide forecast system (STORM : Storm surges/Tide Operational Model) of the Korea Meteorological Administration (KMA) with observations from 30 coastal tidal stations during nine typhoons that occurred between 2005 and 2007. The results (bias) showed that for cases of overestimation (or underestimation), storm surges tended to be overestimated (as well as underestimated) at all coastal stations. The maximum positive bias was approximately 6.92 cm for Typhoon Ewiniar (2006), while the maximum negative bias was approximately -12.06 cm for Typhoon Khanun (2005). The maximum and minimum root mean square errors (RMSEs) were 14.61 and 6.78 cm, which occurred for Typhoons Khanun (2005) and Usagi (2007), respectively. For all nine typhoons, total averaged RMSE was approximately 10.2 cm. Large differences between modeled and observed storm surges occurred in two cases. In the first, a very weak typhoon, such as Typhoon Khanun (2005), caused low storm surges. In the other, exemplified by Typhoon Nari (2007), there were errors in the predicted typhoon strength used as input data for the storm surge model

Modeling and Verification of the Subsurface Current Core of the Ryukyu Current

In recent years, several observations based on direct current measurements and model simulations have been successful in detecting a north east ward under current, _ Ryukyu _ along the Pacific side of the Ryukyu Is lands with a unique _ north east ward current _ structure. The volume transport (20 - 25 Sv) of the Ryukyu current completes the volume transport budget (45 - 50 Sv) of the Kuroshio system. A Pacific Ocean circulation model based on the RIAM Ocean Model (RIAMOM) with _ resolution success fully reproduced the observed structures of the north east ward Ryukyu Current with a subsurface core at 500 - 600 m. A three-layer model simulation shows the existence of the Ryukyu Current and explains the mechanism of subsurface current maximum through blocking effect of bottom topography around the Ryukyu Islands