• Title/Summary/Keyword: External Load

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Upwind Finite Element Model for Suspended Sediment Transport

  • Noh, Joon-Woo
    • Journal of Wetlands Research
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    • v.5 no.1
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    • pp.67-78
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    • 2003
  • The unsteady 2D convection and diffusion equation is solved numerically for the real-time simulation of suspended load propagation. The streamlined upwind scheme efficiently reduces numerical oscillations due to the high Peclet number in the convection dominant flow. By using the mixed boundary condition to express the external source terms or externally induced suspended load as a function of time in the algorithm, the model is capable of handling not only continuous load cases but also non-continuous suspended load influx. The suspended load transport modelwas verified using a case study for which an analytical exact solution is available and was applied to the real-time simulation of a suspended load influx case on the Mississippi River. The model algorithm can provide a framework upon which water quality as well as contaminant transport models can be built.

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Load Position and Residual Vibration Control of an Offshore Crane System Based on Input-Output Linearization Theory

  • Le, Nhat-Binh;Lee, Kwon-Soon;Kim, Young-Bok
    • Journal of Navigation and Port Research
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    • v.41 no.5
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    • pp.337-344
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    • 2017
  • In the offshore crane system, the requirements on the operating safety are extremely high due to many external factors. Rope extension is one of the factors producing vertical vibration of load. In this study, the load is carried by the motor-winch actuator control and the rope is modeled as a mass-damper-spring system. To control the load position and suppress the vertical vibration of the load, a control system based on input-output linearization method is proposed. By the simulation and experiment results with pilot crane model, the effectiveness of proposed control method is evaluated and verified.

Disturbance observer-based robust backstepping load-following control for MHTGRs with actuator saturation and disturbances

  • Hui, Jiuwu;Yuan, Jingqi
    • Nuclear Engineering and Technology
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    • v.53 no.11
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    • pp.3685-3693
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    • 2021
  • This paper presents a disturbance observer-based robust backstepping load-following control (DO-RBLFC) scheme for modular high-temperature gas-cooled reactors (MHTGRs) in the presence of actuator saturation and disturbances. Based on reactor kinetics and temperature reactivity feedback, the mathematical model of the MHTGR is first established. After that, a DO is constructed to estimate the unknown compound disturbances including model uncertainties, external disturbances, and unmeasured states. Besides, the actuator saturation is compensated by employing an auxiliary function in this paper. With the help of the DO, a robust load-following controller is developed via the backstepping technique to improve the load-following performance of the MHTGR subject to disturbances. At last, simulation and comparison results verify that the proposed DO-RBLFC scheme offers higher load-following accuracy, better disturbances rejection capability, and lower control rod speed than a PID controller, a conventional backstepping controller, and a disturbance observer-based adaptive sliding mode controller.

A STUDY OF THE ANTI-ROTATING INNER POST SCREW SYSTEM AS A MEANS OF PREVENTING ABUTMENT SCREW LOOSENING (회전 방지용 Post Screw 시스템의 임플랜트 지대나사풀림 방지효과에 관한 연구)

  • Kim Jong-Hui;Lim Ju-Hwan;Cho In-Ho;Lee Joon-Seok
    • The Journal of Korean Academy of Prosthodontics
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    • v.43 no.5
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    • pp.671-683
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    • 2005
  • Statement of problem: The most commonly reported problem associated with dental implant restoration is the loosening of the screws. Purpose: This study compared the efficacy of an implant system incorporating an anti-rotational locking sleeve(Anti-Rotating Inner Post Screw System(ARIPS-system)) with other, traditional implant systems as a means of minimizing vibration loosening. Materials and methods: Three implant systems were examined; the conventional external hex type, the ARIPS-system, and the internal taper type implant system 30 specimens(10 samples per group)were fabricated and each abutment screw was secured to the implant future with 32Ncm of torque force and loosening torque was measured using a Torque Gauge. The procedure was repeated 3 times, recording initial loosening torque each time. The re-tightened abutment screw was subjected to a cyclic load having a maximum forte of 200N and minimum of 20N at 2Hz over a period of 12,600 cycles. after which the loosening torque was measured. Measured values were calaulated for statistical analysis. Analysis of measured value was performed by 3 methods: (i) as a percentage average of the initial 3 loosening-torque values(initial loosening value) to the tightening torque of 32Ncm, (ii) as a percentage of the loosening torque value after a load of 200N(experimental value) to the initial loosening value, and (iii) as a percentage of the experimental value to the 32Ncm of tightening torque. The analyses shows the amount of initial loosening at the screw, loosening by repetitive load and the the final loosening value. Results: The results of this study were as follows (1) Percentage of initial loosening value to tightening-torque was increased in order of external hex, ARIPS-system and internal taper and all values between each groups showed statistical significance (p<0.05). (2) Percentage of experimental value to initial loosening value was increased in order of external hex, ARIPS-system and internal taper. Value of internal taper showed significant difference with those of external hex and ARIPS-system (p<0.05). (3) Percentage of experimental value to tightening torque was increased in order of external hex, ARIPS-system and internal taper and all values between each groups showed statistical significance (p<0.05). Conclusion: The results of the analysis of the final loosening level value, which are closely correlated to clinical use, show that the ARIPS-system can be a useful means of minimizing abutment screw loosening when compared to the external hex type system. Although further clinical studies need to be made, the ARIPS-system should be considered to maximize the long-term success of the implant prosthesis.

Analysis of Indeterminate Truss Structures by Element-Focused Network Approach (요소 중심의 네트워크 접근법을 이용한 부정정 트러스 구조 해석)

  • Han, Yicheol
    • Journal of The Korean Society of Agricultural Engineers
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    • v.58 no.3
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    • pp.13-19
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    • 2016
  • Element-focused network analysis method for truss structure is proposed. The propagation process of loads from external loads to connected other elements is similar to that of connections between nodes in accordance with attachment rule in a network. Here nodes indicate elements in a truss structure and edges represent propagated loads. Therefore, the flows of loads in a truss structure can be calculated using the network analysis method, and consequently the structure can also be analyzed. As a first step to analyze a truss structure as a network, we propose a local load transfer rule in accordance with the topology of elements, and then analyze the loads of the truss elements. Application of this method reveal that the internal loads and reactions caused by external loads can be accurately estimated. Consequently, truss structures can be considered as networks and network analysis method can be applied to further complex truss structures.

Dynamic Characteristics Analysis of Linear BLOC motor using Finite Element Method Coupling with External Circuit Model (외부회로가 결합된 선형 BLDC 전동기의 유한요소법을 이용한 동특성 해석)

  • Chung, Koon-Seok;Kim, Mi-Jung;Moon, Ji-Woo;Cho, Yun-Hyun
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.56 no.7
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    • pp.1231-1235
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    • 2007
  • This paper presents the dynamic characteristics of a linear brushless dc (BLDC) motor with permanent magnet excitation for the precision conveyor according to the load condition. Dynamic performance of the linear BLDC motor driven with 6 step inverter such as thrust force and speed is simulated by finite element method coupling with external circuit and measured for the prototype motor. The results of finite element analysis are compared to the experimental results and verify reliability.

A PID learning controller for DC motors (DC 전동기를 위한 PID 학습제어기)

  • 백승민;이동훈;국태용
    • 제어로봇시스템학회:학술대회논문집
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    • 1996.10b
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    • pp.347-350
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    • 1996
  • With only the classical PID controller applied to control of a DC motor, a good (target) performance characteristic of the controller can be obtained, if all the model parameters of DC motor and operating conditions such as external load torque, disturbance, etc. are exactly known. However, in case when some of system parameters or operating conditions are uncertain or unknown, the fixed PID controller does not guarantee the good performance which is assumed with precisely known system parameters and operating conditions. In view of this and robustness enhancement of DC motor control system, we propose a PID learning controller which consists of a set of learning rules for PID gain tuning and learning of an auxiliary input. The proposed PID learning controller is shown to drive the state of uncertain DC motor system with unknown system parameters and external load torque to the desired one globally asymptotically. Computer simulation results are given to demonstrate the effectiveness of the proposed PID learning controller, thereby showing whose superiority to the conventional fixed PID controller.

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One-dimensional consolidation analysis of clayey soils based on elasto-viscous liquid model (탄점성압밀방정식을 이용한 점성토의 일차원 압밀 해석에 관한 연구)

  • 염혜선;김지용;정승용;김수삼
    • Proceedings of the Korean Geotechical Society Conference
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    • 2000.11a
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    • pp.689-694
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    • 2000
  • The traditional concept after Terzaghi was that consolidation was the dissipation process of pore water pressure compatible to external loading which was generated immediately after the loading. However, a theory of one-dimensional consolidation based on elasto-viscous liquid model proposed by Yoshikuni(1994) explained that the process of primary and secondary consolidation was considered to be not a simple process of dissipation of pore water pressure but a simultaneous process of dissipation and generation by external loading. This study attempts to demonstrate general consolidation behaviour of clayey soils including effects of consolidation history, load increment and thickness of cohesive layer by one-dimensional Finite Difference Method(F.D.M) analysis from the viewpoint of elasto-viscous consolidation theory.

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Retrofitting of Reinforced Concrete Wall to Increase Axial Load Capacity (벽체의 축력 증진 방안 연구)

  • 신영수;홍기섭;최완철;홍영균;김상준
    • Proceedings of the Korea Concrete Institute Conference
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    • 1997.10a
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    • pp.673-678
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    • 1997
  • The main structural system of domestic apartments is the wall-slab system. In such structures, the lack of material strength of wall affects severely on the safety of structures. It is fond frequently that the wall in the apartment structures has lower strength in concrete than the specified. This paper presents the retrofitting method of the reinforced concrete wall with low concrete strength. The tests are performed to investigate the structural behavior and the effects of external reinforcing and thickness increasing on the axial load capacity of walls. Six specimens are tested. As the test results, the external reinforcing method is less effective than thickness increasing method.

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Sub-surface Stress Analysis beneath the Contact Surface of Spur Gear Teeth (스퍼 기어 접촉 치면의 내부응력 해석)

  • Kwang-Jin, Lee;Hyung-Ja, Kim
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.3 no.3
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    • pp.64-70
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    • 2004
  • The sub-surface stress field beneath the spur gear's contact surface in lubricated condition has been analysed. The surface pressure was obtained by the elasto-hydrodynamic lubrication analysis using the accurate geometric clearances around the contact region of the teeth. The sub-surface stress field was calculated by using the Love's rectangular patch solution. The analysis results show that the sub-surface stress distribution is quite dependent on the surface pressure distribution. The pattern of sub-surface stress field is similar to that of the external load. The depth where the maximum effective stress occurs is not proportional to the intensity of the external load.

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