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Buoyancy Control of a Scientific Submersible Using Variable Ballast System
Mojiz Abbas Trimzi,Young-Bog Ham,Byeung-Cheol An,Gi-Tae Lee,Jung-Ho Park,So-Nam Yun 유공압건설기계학회 2015 유공압건설기계학회 학술대회논문집 Vol.2015 No.10
The magnitude of buoyant force always equals the weight of liquid displaced. On basis of this principle the buoyancy of submersible has been calculated by using variable ballast tank. When the seawater is pumped into variable ballast tank the density of submersible is increased, as a result submersible dives deep into water. When water is pumped out from ballast tank and air replaces that volume, the submersible dives out towards surface because of decreased density. In this paper using sea water hydraulics, a trajectory profile showing position of deep-diving and rising submersible is produced. It is proposed that air to water ratio in variable ballast tank can effectively control the buoyancy of a submersible making it useful for deep sea exploration.
Versatile LED Drivers for Various Electronic Ballasts by Variable Switched Capacitor
Lee, Eun S.,Choi, Bo H.,Duy Tan Nguyen,Jang, Gi C.,Rim, Chun T. IEEE 2016 IEEE TRANSACTIONS ON POWER ELECTRONICS - Vol.31 No.2
<P>An LED driver compatible with various electronic ballasts that are currently commercially used is newly proposed, which adopts a variable switched capacitor by controlling the switching duty cycle for LED power regulation. The resonant frequency of an LC resonant tank of electronic ballasts can be changed, which makes the proposed LED driver versatile for electronic ballasts for various switching frequencies. In this way, the fluorescent lamp is replaced with an LED lamp, where the electronic ballast in the lighting infrastructure remains unchanged. The zero voltage switching is applied for the variable switched capacitor in the electronic ballast, operating at a frequency of 30-60 kHz. Neither an inductor nor a transformer is introduced in the proposed LED driver, which leads to compact size and high efficiency. Furthermore, no electrolytic capacitor is used, which is beneficial for the long lifetime of LED drivers. A prototype LED driver of 16 W was implemented and verified for the three types of electronic ballasts that are most popular in markets. The LED power was well regulated for a wide range of the source voltage variations between 180 and 270 V, and the power efficiencies of the proposed LED driver were 95.8%, 96.1%, and 94.1% for the instant start, rapid start, and programmed start types of the electronic ballasts, respectively.</P>
Kim, Tae Ho,Yang, Kyong Uk,Hwang, Kyu Serk,Jang, Duck Jong,Hur, Jung Gyu Elsevier 2011 Aquacultural engineering Vol.45 No.2
<P><B>Highlights</B></P><P>► We conducted model experiments on automatic submersible fish cage system by air control. ► The algorithm and program required to control the submersible fish cage system were developed. ► The cage was automatically submerged to the target water level and surfaced to the original location. ► The algorithm and controller was useful to the auto submerging and surfacing of the cage.</P> <P><B>Abstract</B></P><P>An automatic, submersible fish cage system using air control was developed and a set of model experiments were conducted to examine the automatic submerging characteristics of the cage. The components of the fish cage consist of a rigid frame assembly with 6 variable ballast tanks and 6 fixed ballast tanks. The variable ballast tanks were used to change the buoyancy characteristics of the system by air control so that the fish cage can either be placed at the surface or submerged. The cage is free to move vertically within a water column by adjusting the weight and the buoyancy with an air control system. The model of this system, with dimensions of 2.20m in diameter and length and 1.04m in net cage depth, was constructed to be 1/10 the size of the full-scale system. In the model experiments, the submerging and surfacing characteristics of the cage were regulated with measurements from a water-pressure gauge and a gyroscope incorporated into the automatic control system. Model tests were performed in a still water tank and a large wave tank to develop the algorithm required to control the cage system and to verify the ability of the automatic submersion mechanism to function. The control system was designed so that when the variable ballast tanks were flooded with water, the model descended. To raise the system, compressed air is injected into the tanks by opening the main evacuation valve on the manifold. After the required amount of compressed air is supplied, the main evacuation valves can be shut and as a result, the fish cage becomes buoyant. Measured performance results in a still water tank are then compared with calculations from a previously developed numerical technique. The submerging and surfacing characteristics of the fish cage were relatively similar to the measurements obtained with the physical model experiments using air control. The cage was submerged to a target depth when incidence wave heights were higher than the critical wave height and raised when little wave actions were detected in a wave tank. On the other hand, the cage was placed at the surface when incidence wave heights were the same as the critical wave height or lower.</P>
이건호 ( Gun Ho Lee ),차봉진 ( Bong Jin Cha ),정성재 ( Seong Jae Jeong ) 한국어업기술학회 2012 수산해양기술연구 Vol.48 No.1
This study aims to analyze the performance of a submersible fish cage which was designed for developing an economical cage system can be applied in korean aquaculture environment easily. To analyze the performance of the designed cage a model test was carried out. In the test, inclination changes of the upper frame and mooring tensions of model cage were measured during the submerging and surfacing motion in still water and wave condition (period: 2s, wave height: 0.1, 0.2, 0.3m). As a result, in the still water condition the model cage kept horizontal balance and inclination degree of the upper frame was about 1。. In the wave condition, the model cage showed bilateral symmetric up-and-down motion but the average inclination degree of the upper frame was about 0 。. When the model cage reached at a depth of 1m, the upand- down motion of the cage was decreased by 12% compared with that of at the surface (period 2s, height 0.3m). In the same wave condition, the maximum and average line tension under the bottom position were about 8% and 11% respectively compared with that of at surface.