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This research investigates using an inerter system to control the impact-induced vibration response of a single degree of freedom(SDOF) and two degrees of freedom(TDOF) vibration system. An analytic model of the SDOF system with an inerter is first derived, and simulation is performed to compare the inerter performance in suppressing the maximum acceleration response under shock load. Next, a more complex TDOF vibration model with an inerter is derived, and the effectiveness of the inerter in reducing the large acceleration amplitude is evaluated. The energy analysis is conducted to investigate the energy transfer mechanism during impact. The simulation study shows that one can significantly decrease the maximum acceleration response with an appropriate selection of the inerter parameters. For the SDOF vibration system with an inerter, response reduction is greatly influenced by the system’s natural frequency. In the TDOF vibration system, the maximum acceleration response attenuation is caused by two factors. For a large inerter radius, the acceleration response reduction is mainly influenced by energy transfer between unsprung and inerter mass. However, for a big inerter mass, attenuation of the acceleration response is caused by decreasing the system’s natural frequency. It is observed from the simulation that the maximum acceleration response can be reduced up to 35% by adjusting the inerter radius of gyration. Furthermore, the optimum condition for reducing the acceleration response occurs when the inerter mass is half the unsprung mass ( m i = 0.5 m u). An experimental study is conducted to validate the simulation results.

This article describes the data logging technique for large-scale solar panels system. The input data of the developed data logger can be increased significantly by optimizing the Integrated Circuit (IC) Multiplexer analog input. Multiplexer ICs are suitable for recording parameter data on largescale solar panel systems, which are often called solar panel parks. The data logger system consists of an Arduino microcontroller equipped with a current sensor, a voltage sensor, multiplexer IC, RTC, and an SD card. The obtained data is stored on the SD-card every 5 minutes, in the form of a .txt file with the format of the day, date, time, current value, and the voltage value of each solar panel. The test results show that data acquisition on the solar panel park using a data logger with multiplexer IC has been able to store and display a large number of solar panel data.

In seismic areas, the application of structural dampers becomes compulsory in the design of buildings. There are various types of dampers, such as viscous elastic dampers, viscous fluid dampers, friction dampers, tune mass dampers, yielding/ metallic dampers, and magnetic dampers. All damper systems are designed to protect structural integrities, control damages, prevent injuries by absorbing earthquake energy, and reduce deformation. This paper is a part of research investigating the behaviour of the U-shaped steel damper (as one type of metallic damper) that can be applied to the buildings in seismic areas. The dampers are used as connections between the roof and supporting structure, with the two general purposes. The first is to control the displacement of roof under an earthquake, and the second is to absorb seismic energy through the plasticity of some parts in dampers. If a strong earthquake occurs, the plasticity will absorb the seismic energy; therefore, heavy damage could be avoided from the roof’s mainframes. In this paper, several models of U-shaped steel dampers are introduced. Several parameters, such as elastic stiffness, maximum strength, and energy dissipation, are determined under two conditions. Firstly, static analysis of the proposed damper under variation of U-steel plate configurations, searching the model with more significant energy dissipation. Secondly, static analysis of the unsymmetrical and symmetrical damper under different loading directions. An in-house finite element program that involves both geometrical and material nonlinearities is developed as a problem solver. A quasi-static lateral loading is given to each model until one cycle of the hysteresis curve is reached (in the displacement range between -20 mm to +20 mm). The above parameters are calculated from the hysteresis curve. From the results, the behaviour of the U-steel damper can be described as follows. Firstly, increasing the energy dissipation in the lateral direction can be done by increasing the lateral stiffness of the damper. However, it can reduce the maximum elastic deformation of the damper. Secondly, under the random direction of loading, a symmetrical shape can increase the energy dissipation of the damper.

The aim of this research is to evaluate the performance of impact-induced vibration control using momentum exchange impact damper with pre-straining spring mechanism (PSMEID) based on the energy analysis and verifying the effectiveness of the proposed method experimentally using a simple three-body collision model. It is shown from the simulation study that the fraction of energy absorbed by the primary mass was small if the excitation frequency differs from the primary mass natural frequency. In the case of excitation frequency is lower than the primary mass natural frequency, most of the impact energy is transferred to the damper mass. For excitation frequencies higher than the primary mass natural frequency, a large amount of impact energy is reflected after the collision. The energy absorption ratio is small if the damper mass ratio(M d /M p ) approaches 0.2 and the ratio between pin force (f )and the reference friction force (f ) closest to 1. The optimum condition of the pre-straining spring stiffness increases when the impact damper mass ratio is increased. The experiment was conducted to validate the simulation results. The experimental data has shown that the fref minimum acceleration response is obtained using the pre-straining spring deflection ratio (xps/xpsref= 0.18).

This case study proposes the development of damping technology using intelligent materials as working fluids for the landing gear of Unmanned Aerial Vehicles (UAV) during the landing process. The intelligent materials to be used are magnetorheological fluids (MRF), a liquid that has variable viscosity to magnetic fields. This intelligent material can improve the performance of the damping device by allowing it to have variable damping features through viscosity changing. The proposed UAV magnetorheological (MR) dampers design utilizes a magnetic valve that has an annular flow channel configuration with a 0.5 mm gap size equipped with an electromagnetic coil with adjustable current input. Both gap size and the current input selection affect the performance of the damping device. This study discusses the performance to reduce shock during the landing process. The performance is evaluated by analyzing the pressure drop and damping force produced by the device with changes in the current input variation. The numerical and simulation results show that the damping characteristics of the device could be adjusted by changing the current input to the electromagnet. The obtained results are then adjusted based on the needs of the UAV in landing purposes. The study proved that the device performance is suitable to absorb shock during the landing process of the UAV.

This research proposes a new method for boat impact vibration attenuation using the exchange of momentum principle with a pre-straining spring mechanism. The boat dynamic is modeled using a hinged-supported beam structure. The wave excitation on the boat hull is expressed using one degree of freedom spring-mass system. The simulation study is performed to evaluate the impact damper performance in reducing the boat shock response. Two kinds of momentum exchange impact damper i.e., without and with pre-straining spring mechanism, are evaluated. The simulation results show that the impact damper with pre-straining spring mechanism (PSMEID) is better than the passive momentum exchange impact damper (PMEID) in reducing the boat shock vibration response

The web-based PV system monitoring to measure electrical production and consumption to the load or utility grid is presented in this paper. This monitoring system consists of an Arduino Mega 2560 with two PZEM 004T sensor modules. The monitoring system has been designed to store measurement data of current, voltage, power and energy in the database and display on the webpage in real time and infographics history. The PZEM sensor measurement has been tested with an average power difference 0.29% less than IEC-61724 minimum-accuracy. Realtime data is obtained in the form of one-line data for every 2 seconds, with a data size of 375-byte and 75ms delivery delay. For one day period testing, the electrical energy that can be generated by the PV system is 5,925 kWh, while the power consumed by the load is only 1,272 kWh so the accumulated electrical energy that can be exported is 4.65 kWh. The test results show that the system has been able to measure net energy export or import by the PV system to utility grid.

This study aims to obtain an effective solar panel tracking mechanism using energy-efficient electric actuators. Furthermore, we designed and implemented a semi-active solar tracking system. A tracking system is proposed to control solar panel orientation using a moving mass, a spring system, and an actuator. The weight of the moving mass and the spring constant are optimized to reduce actuator size. A stepper motor was used for this case. This electric drive is not the prime mover of the solar tracker; hence, it works against mass elements lighter than solar panel weight as used in the active solar tracker. Experimental results suggest that the average power required by the stepper motor is 0.21% of the energy generated by the solar tracking system. The results indicate that the proposed solar panel tracker works satisfactorily to control solar panel orientation.

Crack is a problem that frequently found in a structure. Identification of crack is a crucial aspect in decision making about structure condition. Structural Health monitoring has become a solution to detect the crack. Basically, if a crack initiates and propagates in a structure, the natural frequencies of the structure will change because of decreasing stiffness and abrupt curvature of mode shapes will occur. This research is developed from before research and aimed to identify the crack position in a free free cantilever beam experimentally by analytically using finite element model (FEM) and experimental modal analysis (EMA). First, a perfect cantilever beam without any cracks is modeled by FEM and identified by EMA. Then artificial cracks are created to the beam with single and two cracks, and FEA model and EMA identification is developed. The position of the crack then is identified by the change of mode shape curvature using curvature change index that obtained from the difference in mode shape curvature between the damage and the undamaged cases, and mode shape curvature based on curvature sensitifity caused by decreasing stiffness caused by cracks.The result shows that mode shape curvature has better sensitifty to detect the position of cracks, and results of experiment show good corelation with results of finite element analysis.

This paper offers a new method to control solar panel orientation. The technique is applied by varying the position and ratio of the added mass to the total mass of solar panel, m/m p (%). The added mass position is varied from the axis point up to the end point of the solar panel. The solar panel orientation is influenced by the moving mass position. The oscillation in solar panel caused by the moving mass is eliminated by adjusting the equivalent damping torque c τ , and the solar panel maximum orientation is varied by changing the equivalent torsion spring k τ . The simulation results proved that the solar panel orientation changed from 00 to 60,630 for parameter values m/m p = 15%, r/0,5r t = 35%, c τ = 3 Nm/rad/sec and k τ = 1 Nm/rad. The ability of the system to control the orientation and ratio of m/m p dan r/0,5r t is effective to reduce energy consumption of the solar panel orientation controlling system.

The efficiency of solar panels is an interesting study now, due to the limitation of material capabilities used in the manufacture of solar panels. The increasing of the received radiation intensity from the sun is a way to improve the performance of solar panels. In this paper will be exposed increased efficiency of solar panels using the method of tracking the sun. The commonly used sunlight tracking is an active tracker, due to significant efficiency improvements compared to passive trackers. The active tracker consists of a single axis and a double axis, both of which use a motor as a driver. This motor is controlled using a microcontroller or a programmable logic controller (PLC). Furthermore, the automatic tracker based on microcontroller or programmable logic controller (PLC) on single axis or double axis which is implemented and can be tested in real time or periodically.

Unmanned aircraft or UAV (Unmanned Aerial Vehicle) is a future technology that continues to be developing. This research examines the structural vibration acceleration response of the aircraft’s nose landing gear. The landing gear is the part of the aircraft that receives the most significant shock load during landing. This is due to the magnitude of the maximum acceleration of the landing gear vibration when experiencing shock loads. This phenomenon causes the landing gear damaged due to excessive vibration. Therefore, uncontrolled shock loads can damage the landing gear structure and even pierce its frame structure. A momentum transfer method was applied to the landing gear design to reduce the maximum acceleration amplitude of vibration due to experiencing shock loads during landing. The research experiment was carried out using the principle of passive momentum transfer; the test was carried out by dropping the landing gear at a certain height. When the landing gear experiences a shock load, kinetic energy and momentum will be transferred to the PMEID system so that the landing gear remains in a stable condition. The experiment gives an output in the form of the vibration acceleration amplitude of the landing gear measured by the accelerometer sensor on the landing gear’s main mass. The vibration response will then be sent to the voltage amplifier and forwarded to the digital signal processing and displayed on a computer monitor. The test results prove the application of the momentum transfer method in the landing gear design can reduce the maximum amplitude of vibration acceleration when landing.

This study proposes a new method for reducing the shock vibration response of an Unmanned Aerial Vehicle (UAV) during the landing process by means of the momentum exchange principle (MEID). The performance of the impact damper is improved by adding a pre-straining spring to the damper system. This research discusses the theoretical application of the damper to the UAV landing gear system. The UAV dynamics is first modeled as a simple lumped mass translational vibration system. Then we analyze a more complex two-dimensional model of UAV dynamics. This model consists of the main wheel, nose wheel and main body. Three cases of UAV landing gear mechanisms: without damper, with passive MEID (PMEID) and with pre-straining spring MEID (PSMEID) are simulated. The damper performance is evaluated from the maximum acceleration and force transmission to the main body. The energy balance calculation is conducted to investigate the performance of PSMEID. The simulation results show that the proposed PSMEID method is the most effective method for reducing the maximum acceleration and force transmission of UAV during impact landing.

A Combination of dynamic vibration absorbers (DVAs) consist of Tuned Mass Damper (TMD) and Tuned Liquid Column Damper (TLCD) for reducing vibration response of a two-DOF shear structure model is proposed. The absorber parameters are optimized using Genetic Algorithm (GA). The cost function is derived from the ratio between structure response and the excitation signal. The limitation in absorber space and fluid motion are considered during optimization process. The simulation results show that GA optimization procedure is effective to get the optimal absorber parameters in the case of limited absorber size and motion.

Penelitian ini membahas tentang analisis respon dinamik pada landing gear pesawat tanpa awak saat mendarat. Penelitian diawali dengan pemodelan mekanisme landing gear untuk mendapatkan harga kekakuan dan redaman ekivalen. Penurunan persamaan gerak dilakukan dengan asumsi sistem getaran satu derajat kebebasan. Respon sistem dihitung dari persamaan gerak secara analitik. Simulasi numerik dilakukan untuk mendapatkan grafik respon simpangan dan percepatan. Evaluasi respon sistem dilakukan untuk sejumlah variasi dimensi batang dan kekakuan pegas pada mekanisme landing gear. Dari hasil simulasi ditunjukkan bahwa harga maksimum amplitudo respon percepatan berbanding terbalik dengan harga maksimum amplitudo respon simpangan. Disamping itu, peningkatan harga kekakuan pegas k s menyebabkan meningkatnya harga maksimum respon percepatan dan mengurangi amplitudo respon simpangan pada landing gear.

This research proposes a novel landing gear system using a four-bar linkage mechanism. The mathematical model of the landing gear system is calculated analytically. A simulation study is performed to investigate the landing gear performance in reducing the impact vibration response of the main system. It is found from the simulation study that nonlinear characteristic of the landing gear stiffness improves its impact vibration response. The simulation results show that rebound displacement and acceleration response of the main system using the proposed technique is smaller than that of using a conventional landing gear system.

This research proposes a technique for reducing the seismic response of a vibration system using TMD and TLD absorbers. Application of the proposed method to the dynamic model of a two DOF shear structure is evaluated. The equation of motion of the system is calculated by considering the nonlinear behavior of the fluid motion inside the TLD container. The nonlinear characteristic of the TLD absorber is modeled using a nonlinear stiffness and dashpot. Robust optimum design of the absorber parameters using Genetic Algorithm (GA) is conducted base on the mean value and the variance of the performance function, which calculated from the ratio between the system response and its excitation signal. The simulation results shown that a combination of TMD and TLD absorbers can effectively reduce the seismic response of a two DOF vibration systems.

A Tuned Liquid column Damper (TLCD) performance depends on the TLCD natural frequency and damping ratio. Theoretically, the TLCD natural frequency is determined by its dimension and the length of fluid inside TLCD column. The damping ratio of TLCD is influenced by several factors such as friction between the fluid and TLCD column, TLCD junction angle and a built-in orifice plate with a small opening. In this research, the effect of TLCD junction angle to its performance in reducing the structural response is evaluated by varying the TLCD angle from 30° to 90°. An experimental model of two DOF shear structure with TLCD is governed to evaluate the TLCD performance. The experimental results show that a TLCD with junction angle 60° filled with 325 ml water is better than others in reducing the vibration response of a two DOF shear structure.

This paper investigates one type of metallic dampers used in many large buildings in seismic areas. The previous studies have shown a possibility of the introduced damper to act as a damper as well as energy absorber through yielding on some parts of the damper. However, the occurred yielding caused a plastic deformation after unloading. The study aims to substitute the previous critical area to another part which is considerably uncritical during loading. Therefore, an additional part in the form of a slender column is inserted into the damper. The bottom part of the column is clamped to the base plate of the damper. There is a restoring moment acting on the column which was able to restore a large displacement of the damper to at least a small residual plastic displacement after unloading. A stiffness, strength and energy dissipation of the modified damper is determined by a nonlinear finite element technique which involves both geometrically and materially nonlinearities. The model was subjected by a monotonic increasing load which is applied horizontally through the method of displacement control until one cycle of hysteresis is formed. The final result is in a term of comparison of hysteresis curves between a full model of hysteresis damper with and without a slender column.

Tuned Liquid Column Damper (TLCD) has become an alternative solution for reducing low frequency vibration response of machines and structures. This is not surprisingly that the damper has simply structure and low maintenance cost. The main disadvantage of using TLCD is the complexity in controlling TLCD damping factor experimentally. Theoretically, damping factor can be controlled by adjusting the orifice dimension. However, this method is time consuming and not appropriate conducted in the real application. A more simply method for adjusting TLCD damping factor is by varying the fluid viscosity. This research is aimed to evaluate the effect of fluid viscosity to the damper performance. Two DOF shear structure with TLCD is used as the experimental model. Several TLCD fluids with different viscosity are evaluated. Evaluation of TLCD damping factor due to variation of the fluid viscosity is conducted by comparing the Frequency Response Function (FRF) obtained from the experimental data.

This research is aimed to design and analyze the performance of double dynamic vibration absorber (DVA) using a pendulum and a spring-mass type absorber for reducing vibration of two-DOF vibration system. The conventional fixed-points method and genetics algorithm (GA) optimization procedure are utilized in designing the optimal parameter of DVA. The frequency and damping ratio are optimized to determine the optimal absorber parameters. The simulation results show that GA optimization procedure is more effective in designing the double DVA in comparison to the fixed-points method. The experimental study is conducted to verify the numerical result.

One of the important consideration in designing an unmanned aerial vehicle (UAV) is the dynamics characteristic of UAV structure. The dynamics characteristic of UAV structure can be evaluated from its dynamic parameters such as : natural frequencies and mode shape. These parameters play an important role in determining the system’s dynamic response. In general, a low stiffness structure is more sensitive to the dynamic load in comparison with a high stiffness structure. In this research, modification UAV structural stiffness is conducted by varying rib and spar number and configuration on UAV wing. Evaluation of rib and spar number and configuration effect to the natural frequency and mode shape of UAV structure is conducted numerically and experimentally. The simulation results show that the natural frequencies increases with increasing of the number of spar and decreases with decreasing of the number of rib.

Device that can convert sunlight into electrical energy is called solar modules. The solar modules are available in the market only for a static condition, while the light intensity always changes based on the incidence angle of the sun. To make the solar modules more optimal, it is always perpendicular to the direction of the sun so it is needed to use solar tracker device. Solar tracker device is commercially sold at relatively high prices. To solve this problem, it will be designed a relatively lower price one. The design is also made to overcome the obstacles of previous studies and fulfill the wishes of prospective consumers. After the design is done, it is obtained solar tracker for solar modules with a control system microcontroller arduino uno ATMega 328. In this research, the testing parameters consist of; the angle of solar modules, solar radiation intensity, the output voltage of the solar modules and battery charging voltage when the load is given. From the research having been done, solar modules with solar tracker have about 0.99% angle deviation of the ideal angle value, can increase about 65.68 W/m 2 solar intensity and about 0.22 Volts battery voltage with a fixed load.

Tuned liquid column damper (TLCD) is a simple technique used to increase the structure resistance to the external load. This type of damper can effectively decrease the structure response when the TLCD parameters such as the natural frequency and damping factor are well selected. Even though several TLCD models have been proposed and many algorithms to optimize the TLCD parameters have been developed. However, it is very little research has been conducted to evaluate the TLCD damping factor experimentally. A simple method for adjusting the TLCD damping factor empirically is by varying the orifice blocking ratio. In this research, 5 types of blocking ratio were trialled in the TLCD. They were without orifice and with 2, 4, 6 and 8 18 mm diameter orifices. The TLCD is positioned at the second floor of a Two-DOF shear structure. A frequency response function showing the ratio between the response magnitude and the excitation force on the structure in the frequency domain was recorded for each trial. The results show that the TLCDs with orifices damped vibrations more effectively than the one without orifice. The larger the blocking ratio, the larger the TLCD damping factor. Two 18 mm orifices were insufficient to damp the vibration as the blocking ratio is too large and TLCD is less responsive to the vibrations. The optimum condition of a U-Shaped TLCD blocking ratio was found to be 70.77% which corresponded to 4 holes of 18 mm orifice diameter. This type of TLCD dampened up to 80.04% of the vibration magnitude.

This paper is a part of research in searching an appropriate damper for space structures constructed in seismic areas. The study investigates a stiffness, strength and energy dissipation of the damper under loading. For this purpose, a U-shaped hysteresis steel damper is modeled and analyzed by a nonlinear finite element technique which involves both geometrical and material nonlinearities. The model is subjected to a monotonic increasing load which is applied horizontally until one cycle of hysteresis is formed. The stiffness, strength, and energy dissipation of the damper is directly determined from the graph of load–displacement. Feasibility of the hysteresis damper is investigated further for application on building construction. The damper is placed on the roof and supporting structure of the building. A 2-DOF spring-mass model, as a simple modelling of the building is introduced with damper’s properties are taken from the results of the first study. A seismic load is applied to see the response of the model. The static numerical analysis showed that the properties of the introduced damper, such as stiffness, strength and energy dissipation, are depending on the geometry of the damper. The results show that reducing the length of lower plate or height of the damper will increase stiffness, strength and energy absorption. In contrary, reducing the width of the damper will decrease all properties. Moreover, the results of the dynamic analysis show the feasibility of damper to reduce to reduce the amplitudes of the response of the roof under seismic load.

In the authors’ previous study, we proposed a novel shock vibration control method using the active momentum exchange impact damper (AMEID). By using this method, the shock vibration of the vibratory system is greatly reduced by transferring part of its momentum to the damper mass. This feature is effective for suppressing the first large peak value of the acceleration response due to a shock load. However, the validity of AMEID for actual implementations has not yet been investigated. In this paper, the active control of shock vibration using AMEID under real conditions is evaluated by simulation and experiment. A one-degree-of-freedom vibratory system is used as the controlled object. The controller is designed using the linear quadratic regulator optimal control theory. Reductions in the acceleration response and transmitted force to the base are investigated using simulations. Experiments are carried out to verify the simulation results.

Impact vibration such as a floor vibration caused by jumping of children or vibration of a press machine is very important engineering problem. The momentum exchange impact damper has been proposed to solve these problems. The basic principle of this damper is based on the energy transfer on collision of three body systems. However energy or momentum transfer at the impact is not explained theoretically. This paper considers the energy transfer incurred during collisions in three body systems. The three body systems considered herein consists of an impact mass, a main body and an absorber mass. When the impact mass collides with the main body, part of its kinetic energy is transferred to the main body. When the main body simultaneously collides with the absorber mass, part of the kinetic energy of the main body is transferred to the absorber mass. Consequently, the main body receives a small amount of shock and it is possible to keep the main body nearly stationary. In this study, the influence of contact frequency and natural frequency of the system on the energy transfer during collision is analyzed. A theoretical model is developed to analyze the effect of various system parameters. It is shown that the maximum transfer of energy that can be obtained occurs when the contact frequencies are the same. The theoretical analysis is validated with experimental results., Special Issue on The Twelfth Asia Pacific Vibration Conference (APVC2007)

This paper proposes an active control type of momentum exchange impact damper (AMEID) and its application to reducing shock vibration of the floor. The floor is modeled as a one-degree-of-freedom system. The active component of AMEID is realized by using a linear motor. The controller design of AMEID is based on the LQR optimal control theory. The simulation results show that the performance of AMEID is not affected by the mass ratio. In addition, the performance of AMEID is compared with the conventional passive momentum exchange impact damper (PMEID), the active mass damper (AMD) and the conventional active control method in reducing the floor shock vibration. It is shown that the shock reduction performance obtained by AMEID is larger than that obtained by PMEID. The power consumption and the stroke of the actuator for AMEID are lower than those of AMD. Furthermore, the transmitted force obtained by AMEID is smaller than that of the conventional active control.

This paper deals with reducing floor impact vibration and sound by using a momentum exchange impact damper. The impact damper consists of a spring and a mass that is contact with the floor. When a falling object collides with the floor, the floor interacts with the damper mass, and the momentum of the falling object is transferred to the damper. In this works a computational model is formulated to simulate dynamic floor vibration induced by impact. The floor vibration is simulated for various sized damper masses. A proof-of-concept experimental apparatus was fabricated to represent a floor with an impact damper. This example system consists of an acrylic plate, a ball for falling object, and an impact damper. A comparison between simulated and experimental results were in good agreement in suggesting that the proposed impact damper is effective at reducing floor impact vibration and sound by 25% and 63%, respectively.

This research discusses the static analysis of the kiln girth gear at Indarung cement Factory V PTSP due to replacement of the oldest girth gear with the newest one. The newest version of girth gear system has a smaller number of supporting spring (spring plate) in comparison with the previous one. Therefore, it is necessary to analyze the effect of the spring plate number to the strength and stiffness of the girth gear system to assure the kiln can work properly. In this research the effect of the spring plate number to the linear and torsional stiffness of the girth gear is evaluated. Based on the simulation results, decreasing of the spring plate number from 16 to 12, significantly affect the total stiffness of the supporting spring. Furthermore, it was found from the simulation that the total stiffness of the supporting spring much affected by the axial stiffness of the spring plate comparing to its lateral stiffness.

Accident which is occurred due to the harmful gas always found in the mining location. One example of harmful gas is the explosive methane gas. One of attempt to overcome this problem is by using a methane gas detector robot that can detect the gas early before the mining process is conducted. This kind of robot can be control autonomously from a place which is located far away from the mining area. Therefore, the mining workers can work safely. This research is aimed to design and manufacturing a mobile robot for detecting a methane gas in the mining area. The research is conducted step by step by making the mechanical components of robot, manufacturing the electronic circuits and programming the Arduino microcontroller using the Arduino IDE software. Mechanical design of the robot is targeted for operating the robot in the off-road environments. The main control center of the robot arm uses an Arduino UNO microcontroller. Robot control system has a methane gas detector to sense the methane gas. The command signal is applied autonomously by using Android based smart phone, which move the robot to the desired area. The signal sent by gas sensor MQ-04 will ring the buzzer and turn on the LED of the robot whenever the robot detects a methane gas. The experimental results shows that the robot can detect the methane gas and robot maneuvering can be conducted successfully.

In recent research it was found that squeal noise caused by friction-induced vibration can result in mode coupling instability. Presently, there is no method that can be reliably used to eliminate this kind of noise. This paper is focused on the use of dynamic vibration absorbers (DVAs) to suppress the generation of squeal noise. The performance of the DVA is investigated numerically for two simple cases, i.e. a simple two-degree of freedom model, and an L-shape space frame. It is found that the DVA can be applied to shifting or reducing the unstable region of mode coupling, by which the unstable region is removed from the operating condition. Particularly, the addition of the DVA in horizontal direction on the near-point-of-friction can possibly avoid unstable mode coupling. However, the addition in vertical direction will increase the possibility of squeal noise incident. Moreover, a high frequency DVA in horizontal direction at the near-point-of-friction shifts the unstable region into higher normal contact stiffness and higher friction coefficient. Consequently, addition of a mass with very stiff spring or a rigid mass in the horizontal direction can prevent the occurrence of unstable mode coupling, as long as it is not coupled with the vertical direction. If the added mass affects the dynamic behaviors in both vertical and horizontal directions, squeal noise in the original normal contact stiffness can still occur.

The authors' previous study proposed a novel shock vibration control using the active momentum exchange impact damper (AMEID) in simulations. By using this method, the shock vibration of the vibratory system is greatly reduced by transferring a part of its momentum to the damper mass. This feature is effective for suppressing the first large peak value of the acceleration response due to a shock load. In this paper, the active control of shock vibration using AMEID in actual conditions is evaluated by experiments. A one-degree-of-freedom vibratory system is used as the controlled object. The controller is designed by using the discrete-time LQR optimal control theory. The effectiveness of the AMEID approach is verified experimentally.

Nowadays, a passive vibration control technique using dynamic vibration absorbers (DVA) has drawn many researchers’ attention in the structural dynamic field. The reason is that this technique is simple and it can work effectively in reducing the vibration response when its parameters are optimally designed. The DVA fundamental concept is the addition of a new vibration system to the primary system. This new system addition causes reduction of the vibration response of the primary system during excited by a dynamic load. One simple technique to realize the DVA for structural application is by using water vibration. This research is aimed to develop one type of dynamic vibration absorber using the water vibration system in a U-shaped container for a two-story building structure model. Besides being used as the dynamic absorber, this U-shaped container is also functioned as the water storage tank in the building. Regarding reduce the first bending mode response of the structure in x-z and y-z plane, two U-shaped water storage tanks are placed on the upper floor of the building. The dimensions of the water storage tanks are designed so that the natural frequency of moving water in the tank is the same as the natural frequency of the first bending mode of the structure in x-z and y-z plane. The performance of dynamic absorber is evaluated by applying the impulsive and seismic loads on the building. The simulation results show that the U-shaped water storage tank placed on the upper floor of the building can reduce the response amplitude of the structure under impulsive loads. Meanwhile, for the seismic load case, the performance of dynamic absorber is clearly seen when the excitation frequency is close to the natural frequency of the building structure.