• Structural Engineering and Mechanics
• /
• 제90권4호
• /
• pp.357-370
• /
• 2024

Due to the fact that the mechanism of the effects of temperature and initial geometric imperfection on low-velocity impact problem of axially moving plates is not yet clear, the present paper is to fill the gap. In the present paper, the nonlinear dynamic behavior of axially moving imperfect graphene platelet reinforced metal foams (GPLRMF) plates subjected to lowvelocity impact in thermal environment is analyzed. The equivalent physical parameters of GPLRMF plates are estimated based on the Halpin-Tsai equation and the mixing rule. Combining Kirchhoff plate theory and the modified nonlinear Hertz contact theory, the nonlinear governing equations of GPLRMF plates are derived. Under the condition of simply supported boundary, the nonlinear control equation is discretized with the help of Gallekin method. The correctness of the proposed model is verified by comparison with the existing results. Finally, the time history curves of contact force and transverse center displacement are obtained by using the fourth order Runge-Kutta method. Through detailed parameter research, the effects of graphene platelet (GPL) distribution mode, foam distribution mode, GPL weight fraction, foam coefficient, axial moving speed, prestressing force, temperature changes, damping coefficient, initial geometric defect, radius and initial velocity of the impactor on the nonlinear impact problem are explored. The results indicate that temperature changes and initial geometric imperfections have significant impacts.

• 지질공학
• /
• 제27권3호
• /
• pp.191-205
• /
• 2017

본 연구에서는 불투과형 사방댐과 링네트에 가해지는 충격하중을 평가하기 위해 토석류 모형축소실험을 수행하였다. 실험 결과, 토석류는 유체와 유사한 거동을 함에 따라 불투과형 사방댐 배면에 가해지는 토석류 충격하중은 하부구간이 4.14 kN로 가장 높게 작용하며 중간, 상부구간이 3.66 kN, 1.66 kN 가해지는 것으로 측정되었다. 링네트 실험결과 또한 불투과형 사방댐 결과와 같이 충격하중은 하부구간이 크며 상부로 갈수록 감소하는 경향을 보인다(2.28 kN, 1.95 kN, 1.49 kN). 수치해석 결과를 이용하여 토석류 흐름에 의한 토석류 방지시설 충격하중 흡수메커니즘을 분석한 결과, 불투과형 사방댐은 콘크리트 옹벽과 같이 구조물 자체의 강성을 이용하여 수평력에 저항하므로 실제 구조물에 작용한 수평력은 이론식과 유사한 결과가 제시되는 반면, 링네트는 강연선 탄성늘음과 네트 전면으로의 입자 투과를 이용하므로 충격하중은 사방댐 결과보다 최대 45% 감소하는 결과가 제시되었다.

• 제어로봇시스템학회:학술대회논문집
• /
• 제어로봇시스템학회 2001년도 ICCAS
• /
• pp.139.2-139
• /
• 2001

This paper presents identification and control of a surface mounting system. The mount head of the system is modeled to analyze its dynamic characteristics, which is critical to the placement performance of the mounter. Based on this model, an identification work is carried out to estimate the modeled parameters by using genetic algorithm (GA), which plays a role of minimizing an error between the actual response and the model response. Having obtained the identified parameters, we design a disturbance observer control to compensate the friction. The disturbance observer can estimate the friction force and the uncertainty of the system. From the experimental results, it is found that the proposed disturbance observer plus PID controller show a better performance than PID controller alone. In order to accomplish a stable contact content control for fast mounting a ...

• 한국해양공학회지
• /
• 제7권2호
• /
• pp.37-43
• /
• 1993

The simplest vibrtion absorber is the impact damper which consists of a small mass allowed to impact between two gaps sp that energy is dissipated by conversion into noise and heat. Impact damping is a passive vibration control technique to attenuate the vibrations of lightly damped. It has been investigated to reduce the excessive vibrations of turbin blades, radar antennas, machine tools and tall light poles. In this paper, the efficiency of impact vibration absorber was investigated. A steady state vibration of two equispaced impacts per cycle was assumed. The analysis based on the assumption has been considered and the theory is examined experimentally.

• 연구논문집
• /
• 통권32호
• /
• pp.45-53
• /
• 2002

Hydraulic breaker attached excavator generally used for the destroying and disassembling of buildings, crashing road pavement, breaking rocks at quarry and etc. The developed breaker are determined their own destructive force and number of impact by the input hydraulic flow rate and pressure than the operating conditions, In this study, the characteristics of pressure variation in closed vessel is invested for testing the impact energy of hydraulic breaker. To test the impact energy, the test system is designed as a mechanism consisted with a hydraulic cylinder, main base, pressure sensor, LVDT, data acquisition system and etc.. The developed test system is applied to measure the impact energy for hydraulic breaker. The proposed testing method could be applied for conventional impact test and the control system evaluation for hydraulic breakers.

• 드라이브 ㆍ 컨트롤
• /
• 제16권2호
• /
• pp.1-7
• /
• 2019

Jaw crusher is a device that breaks rock collected from mines or quarries to produce aggregates of the size desired by user. A representative method for measuring load is to measure them by attaching force sensors directly to the part where the load is generated. However, the direct method has many limitations such as high-impact loads generation in equipment or space constraints, sensor capacities and costs. Therefore, Transfer Path Analysis (TPA) was used to indirectly measure impact loads by attaching acceleration sensors. In this study, both direct and TPA methods were used to measure the impact load of Jaw crusher. This study finally quantifies the impact of the load generated by the Jaw crusher using direct method and TPA method, and comparing the impact load measured calculated the derive the error rate.

• 연구논문집
• /
• 통권32호
• /
• pp.15-22
• /
• 2002

In offset or intaglio printing machine, it's operated with combination of blanket cylinder and impression cylinder. The blanket cylinder has some number of grooves to attach the blanket on surface. In case of operating the printing machine, it has generate mechanical impact noise when the two cylinders encounter with the grooves. So, in this study, we developed a printing pressure control algorithm with hydraulic servo control system. We also proposed simulation model of experimental device to analysis the throw on force response of hydraulic servo actuator. Finally, we have reduced the mechanical impact noise and improved printing quality with a groove detecting signal and PI control of hydraulic servo actuator.

• 전자공학회논문지B
• /
• 제32B권7호
• /
• pp.1010-1024
• /
• 1995

An intelligent trajectory control method that controls a direction and a average velocity for a prosthetic arm by force and direction estimations using EMG signals is proposed. 3 stage linear filters are used as a real time joint trajectory planner to minimize the impact to human body induced by arm motions and to reduce muscle fatigues. We use combination of MLP and fuzzy filter for a limb direction estimation and a time model of force for determining a cartesian trajectory control parameter. EMG signals are acquired by using a amputation simulator and 2 dimensional joystick motion. Simulation results of the proposed method show that the arm is effectively followed the desired trajectory by estimated foreces and directions. This method reduces the number of electrodes and attatched sites compared with the method using Hogan's impedance control.

• 한국운동역학회지
• /
• 제17권1호
• /
• pp.91-97
• /
• 2007

The purpose of this study was to investigate the changes of various balls velocity under the different surface conditions after impact. For this study, four different balls were used which are golf ball, tang-tang ball, table tennis ball, and iron ball. And two different types of ground conditions were used which are artificial grass green and glass green. Movements of putter head and ball were recorded with 2 HD video cameras(60 Hz, 1/500s shutter speed). Small size control object($18.5cm{\times}18.5cm{\times}78.5cm$) was used in this study. To transfer the same amount of kinetic energy to the ball, pendulum putting machine was used. Analyzing the process of impact and the ball movement, a putter was digitized the whole movement but the ball was digizited within the 50cm movement. Velocities were calculated by the first central difference method(Hamill & Knutzen, 1995). Putter head velocities were about 112.2cm/s-116.2cm/s at impact. Maximum ball velocities were appeared 0.08s-0.10s after impact no matter what the ground conditions are. Table tennis ball recorded higher ball velocities than the other ball velocities and iron ball recorded the lowest ball velocity in this group. But Table tennis ball was influenced with the frictional force and immediately was decreased at the artificial grass green condition. If an object is received the kinetic energy under the static condition(v=0cm/s), the object recorded the maximum velocity shortly after the impact and then decreased the velocity because of the frictional force. The ball distance from the start position to the peak velocity position is about 6cm-10cm under the 112.2cm/s-116.2cm/s putting velocity with putter. 0.25 seconds later after impact balls were placed 40cm distance from the original position except iron ball. In this study, ball moving distances were too short therefore it was not possible to investigate the reactions after the translational force is disappeared. Rotational force would play a major role at the end of the ball movement. Future study must accept two things. One is long distance movement of ball and the other is balanced ground. Three-piece ball is a good item to investigate the golf ball movement on the different surface conditions.

• 대한기계학회논문집
• /
• 제17권12호
• /
• pp.3045-3054
• /
• 1993

The mechanics related with piston-slap induced vibration has been studied in terms of non-dimensionalized dynamic equation of motion, various non-dimensional parameters such as non-dimensional side-thrust force and non-dimensional impact velocity throughout the numerical simulation. Experimental verification on the suggested prediction method has been also performed by using single cylinder engine which was carefully designed and manufactured to wisely control the engine parameters, especially clearance and the mass of piston. The predicted and experimentally observed vibration signature confirm that the proposed method is practically useful.