• 한국추진공학회지
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• 제3권1호
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• pp.86-94
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• 1999

충격파가 초음속 수소-공기 제트화염의 화염 안정한계에 미치는 영향을 충격파의 강도와 위치를 변화시키면서 연구하였다. 이러한 목적으로 마하수 2.5의 초음속 연소기 벽면에 쐐기를 부착시켜 경사 충격파를 발생시켰다. 본 실험은 충격파가 초음속 화염에 미치는 영향을 연구한 최초의 실험연구이다. 쉬릴렌 가시화 사진과 벽면 정압, 화염 안정 한계를 측정하였으며 충격파가 없는 경우와 비교하였다. 보염 재순환 영역에 충격파를 적절히 간섭시킴으로써 화염 안정 한계가 대폭 개선되었다. 화염 안정한계가 대폭 향상된 이유는 충격파에 의해 발생한 역압력구배로 화염안정화에 중요한 아음속 재순환 영역의 크기가 증대된 때문으로 여겨진다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 학술대회 논문집 정보 및 제어부문
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• pp.675-677
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• 2004

This paper presents a nonlinear controller design for optical disk drive systems to improve anti-shock performance. The nonlinear anti-shock controller is added parallel to the original linear servo control loop. In the previous work, dead-zone nonlinear element is used for nonlinear controller and PID control method is used for linear controller. Although this strategy improves anti-shock performance, it has a narrow stability bound. In this paper, we propose dead-zone with saturation nonlinear element for the nonlinear controller. Since this nonlinear element improves stability margin, we can use higher gain of dead-zone than the controller with dead-zone only. In the linear controller design, we show that lead-lag control has improved stability margin over PID control. Numerical simulation results show that the proposed method can get better performance to the external shock than previously proposed method.

• 한국안전학회지
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• 제21권2호
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• pp.107-113
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• 2006

Earthquake motion is one of the most significant influence factors on the slope stability. In this paper, an effective stress analysis with the elasto-plastic model was carried out to investigate the behavior of the slope stability subjected to the successive two strong earthquake motions, fore and main shock. The major influence of fore shock to the slope stability was considered as the existence of the residual excess pore water pressure. The paper presents the influence of the existence of the fore shock to slope stability using the numerical analyses. In conclusion, the excess pore pressure by the fore shock was not dissipated during the 7hrs of consolidation. By this residual excess pore water pressure, the factor of safety at the sliding face showed the minimum values, and the deformations of slope was large when compared with the case that considered the main shock only. Furthermore, the minimum of the factor of safety came out after the end of the earthquake motion.

• 한국자동차공학회논문집
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• 제16권3호
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• pp.118-126
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• 2008

The levitation stability of a Maglev vehicle utilizing electromagnetic suspension is primarily influenced by the deformation, roughness, and vibration of the guideway. Optimum design for both the vehicle and the guideway is desirable in order to reduce guideway construction cost, while meeting requirements for stability and ride quality. This paper presents an analysis of the levitation stability of the UTM-01, an urban Maglev vehicle, using a numerical simulation. The ODYN/Maglev, a dynamics analysis program, is used to simulate dynamics to evaluate the stability. A running test of the UTM-01 is also carried out to verify the results of the simulation. Using the simulation results, the levitation stability of the UTM-01 can be numerically analyzed at a variety of vehicle speeds.

• 한국자동차공학회논문집
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• 제6권4호
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• pp.1-8
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• 1998

In order to solve the conflict problem between the ride comfort and the road holding, the optimal design of shock absorber that minimizes the r.m.s. of sprung mass vertical acceleration and pitch rate with the understeer characteristics constraints in the high speed stability is proposed. The design of experiments and the nonlinear optimization algorithm are used together to obtain the optimal design of shock absorber. The second order regression models of the input variables(front and rear damping coefficients) and the output variables (ride comfort index and road holding one) are obtained by the central composite design in the design of experiments. Then the optimal design of shock absorber can be systematically adjusted with applying the nonlinear optimization algorithm to the obtained second order regression model. The frequency response analysis of sprung mass acceleration and pitch rate shows the effectiveness of the proposed optimal design of shock absorber in the sprung mass resonance range with the understeer characteristics constraints.

• 제어로봇시스템학회논문지
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• 제11권9호
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• pp.741-749
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• 2005

This paper presents a nonlinear controller design for optical disk drive systems to improve anti-shock performance. The nonlinear anti-shock controller is added parallel to the original linear servo control loop. In the previous work, a dead-zone nonlinear element is used for the nonlinear controller and a PID control method is used for the linear controller. Although this parallel structure of the controller improves anti-shock performance, it has a narrow stability bound. In this paper, the dead-zone with saturation nonlinear element is proposed for the nonlinear controller. Since this nonlinear element improves stability margin, we can use higher slope gain of dead-zone than that of nonlinear controller using dead-zone only. In the linear controller design, it is shown that the lead-lag control has an improved stability margin over PID control. Numerical simulation results and experimental results show that the proposed method can get better performance to the external shock than previously proposed methods.

• 한국정밀공학회지
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• 제28권1호
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• pp.31-39
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• 2011

This paper presents design and control of a quarter-vehicle magneto-rheological (MR) suspension system for ECS (electronic control suspension). In order to achieve this goal, MR shock absorber is designed and manufactured based on the optimized damping force levels and mechanical dimensions required for a commercial mid-sized passenger vehicle. After experimentally evaluating dynamic characteristics of the manufactured MR shock absorber, the quarter-vehicle MR suspension system consisting of sprung mass, spring, tire and the MR shock absorber is constructed in order to investigate the ride comfort and driving stability. After deriving the equations of the motion for the proposed quarter-vehicle MR suspension system, the skyhook controller is then implemented for the realization of quarter-vehicle MR suspension system. In order to present control performance of MR shock absorber for ECS, ride comfort and driving stability characteristics such as vertical acceleration of sprung mass and tire deflection are experimentally evaluated under various road conditions and presented in both time and frequency domain.

• 한국운동역학회지
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• 제25권1호
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• pp.29-37
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• 2015

Objective : The purpose of this study was to investigate the biomechanical properties of shock absorption strategy and postural stability during the drop landing for each types. Methods : The motions were captured with Vicon Motion Capture System, with the fourteen infra-red cameras (100Hz) and synchronized with GRF(ground reaction force) data(1000Hz). Ten male soccer players performed a drop landing with single-leg and bi-legs on the 30cm height box. Dependent variables were the CoM trajectory and the Joint Moment. Statistical computations were performed using the paired t-test and ANOVA with Turkey HSD as post-hoc. Results : The dominant leg was confirmed to show a significant difference between the left leg and right leg as the inverted pendulum model during Drop Landing(Phase 1 & Phase 2). One-leg drop landing type had the higher CoM displacement, the peak of joint moment with the shock absorption than Bi-leg landing type. As a lower extremity joint kinetics analysis, the knee joint showed a function of shock absorption in the anterior-posterior, and the hip joint showed a function of the stability and shock absorption in the medial-lateral directions. Conclusion : These findings indicate that the instant equilibrium of posture balance(phase 1) was assessed by the passive phase as Class 1 leverage on the effect of the stability of shock absorption(phase 2) assessed by the active phase on the effect of Class 2 leverage. Application : This study shows that the cause of musculo-skeletal injuries estimated to be focused on the passive phase of landing and this findings could help the prevention of lower damage from loads involving landing related to the game of sports.

• 한국소음진동공학회논문집
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• 제20권5호
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• pp.444-452
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• 2010

This paper presents design and performance evaluation of electro-rheological(ER) shock absorber for electronic control suspension(ECS). In order to achieve this goal, a cylindrical ER shock absorber that satisfies design specifications for a mid-sized commercial passenger vehicle is designed and manufactured to construct ER suspension system for ECS. After experimentally evaluating dynamic characteristics of the manufactured ER shock absorber, the quarter-vehicle ER suspension system consisting of sprung mass, spring, tire and the ER shock absorber is constructed in order to investigate the ride comfort and driving stability. After deriving the equations of the motion for the proposed quarter-vehicle ER suspension system, the skyhook controller is implemented for the realization of quarter-vehicle ER suspension system. In order to present control performance of ER shock absorber for ECS, ride comfort and driving stability characteristics such as vertical acceleration and tire deflection are experimentally evaluated under various road conditions and presented in both time and frequency domain.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2001년도 춘계 학술대회논문집
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• pp.99-104
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• 2001

This paper deals with the development of shock stable scheme that is free from shock instability. Roe's FDS is known to preserve good accuracy but to suffer from shock instability, i.e. the carbuncle phenomenon. As the first step toward the shock stable scheme, Roe's FDS is compared with HLLE scheme to identify the source of shock instability. Then control function f is introduced into the pressure term in Roe's FDS to cure shock instability. Various numerical tests concerned with shock instability are performed to demonstrate the shock stability of the proposed scheme.