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A Simplified Approach to Assessment of Mission Success for Helicopter Landing on a Ship
문종기,Jean Charles Domercant,Dimitri Mavris 제어·로봇·시스템학회 2015 International Journal of Control, Automation, and Vol.13 No.3
In this paper, operation of a helicopter near a ship is statistically investigated to provide an estimate of the probability of successfully recovering manned rotorcraft on the deck of a moving ship. To this end, pitch, roll, and heave motion of the ship are calculated according to sea states. In addition, effect on dynamics of the rotorcraft from ship airwake is also considered in a simplified way. By assuming that a helicopter can land on a ship if a pilot maintains relative position and attitude difference within the safe boundary for a given time, the operational limits are probabilistically determined in terms of pilot’s workload for a specified mission. The simulation environment consists of linearized helicopter dynamics, an optimal pilot model, effect of turbulent ship airwake, and ship motion. Control activities of the piloted helicopter for position holding with respect to the moving ship are transformed to generalized workload ratings. Simulation results show the proposed approach can evaluate and predict mission success rates for various operational combinations, allowing implementation into the overall effectiveness assessment of the ship and ship-helicopter combination.
문종기 연세대학교 대학원 1985 원우론집 Vol.13 No.1
A Study on the Nonlinear Analysis of Concrete Subject to Biaxial Loading. Researches on the theoretical analysis of the nonlinear behaviors of concrete structures have been carried out intentsively since 1960, and the recent development of the numerical analytic schemes such as finite element method accelerates the qualitative analysis in the field. This research has it as its purpose to suggest an analysis formula in succinct form which has rational geometric and physical background and also could be easily applied to the practical design of the concrete structures subject to biaxial loadings and to investigate the applicability of the proposed method by comparing with the existing theories and test results. Relating to the nonlinear behavior of concrete, the theoretical frame of the formula is established by transforming the two dimensional elastic equation into nonlinear constitutive equation which is compared of nonlinear variables of stress and strain invariants in combination with empirical factors. Stress ratio for the two orthogonal plane stress is introduced as a parameter in the equation to simplify the calculation and the derivation of the formula Poisson's ratio is being kept constant as 0.2 and the degradation of the elastic moduli due to microcracking is not considered in this research. The overall approach of the proposed theory is based on the total deformation theory of plasticity. To investigate the applicability of the theory analyses are carried out for the tests of concrete by use of the proposed method simulating the volumetric dilatancy and the strain softening phenomena the analysis results are very closely matched with the test results.
Design of Missile Guidance Law via Variable Structure Control
Moon, Jong-Ki,Kim, You-Dan 서울대학교 항공우주신기술연구소 2001 항공우주신기술연구소 연구보고 Vol.2 No.1
The missile guidance law utilizing variable structure control is proposed. The acceleration command input is determined considering the target acceleration as uncertainty. The target and the missile are assumed to be point masses moving in a two-dimensional plane. According to the property of missile acceleration, the proposed guidance law can be classified into the IPN type and the RTPN type. It is also shown that the conventional proportional guidance laws can be derived from the proposed guidance law. To compensate for the effects of the uncertainty in the target acceleration, the perturbed guidance command is introduced. Numerical simulations show that the proposed guidance law yields better performance compared to the conventional proportional guidance laws.
양재근,이수권,문종기,백민창 한국강구조학회 2014 International Journal of Steel Structures Vol.14 No.2
As a partially restrained connection, a double split tee connection has demonstrated various behavioral characteristics basedon the combination of T-stub thickness, high-strength bolt gauge distance, and beam and column stiffness ratio, among othercharacteristics. Accordingly, many researchers have proposed an analysis model that would determine the behavioralcharacteristics, stiffness, and strength of a double split tee connection by selecting T-stub thickness and high-strength bolt gaugedistance as parameters. However, such a model has not yet been proven to be accurate due to complicated stress distribution,contact and bearing phenomena, as well as prying action on high-strength bolts. Therefore, this study proposed an improvedprediction model for the initial rotational stiffness and ultimate plastic moment to implement double split tee connections inthe domestic steel structures market. Toward this end, this study performed the three-dimensional nonlinear finite elementanalysis, and validated the proposed model by comparing and reviewing its test results from the works of other researchers