• Smart Structures and Systems
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• 제5권6호
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• pp.663-679
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• 2009

The use of Micro-Electro-Mechanical Systems (MEMS) accelerometers in geotechnical instrumentation is relatively new but on the rise. This paper describes a new MEMS-based system for in situ deformation and vibration monitoring. The system has been developed in an effort to combine recent advances in the miniaturization of sensors and electronics with an established wireless infrastructure for on-line geotechnical monitoring. The concept is based on triaxial MEMS accelerometer measurements of static acceleration (angles relative to gravity) and dynamic accelerations. The dynamic acceleration sensitivity range provides signals proportional to vibration during earthquakes or construction activities. This MEMS-based in-place inclinometer system utilizes the measurements to obtain three-dimensional (3D) ground acceleration and permanent deformation profiles up to a depth of one hundred meters. Each sensor array or group of arrays can be connected to a wireless earth station to enable real-time monitoring as well as remote sensor configuration. This paper provides a technical assessment of MEMS-based in-place inclinometer systems for geotechnical instrumentation applications by reviewing the sensor characteristics and providing small- and full-scale laboratory calibration tests. A description and validation of recorded field data from an instrumented unstable slope in California is also presented.

• 자동차안전학회지
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• 제13권1호
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• pp.14-25
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• 2021

This paper presents a RLS based adaptive sliding mode observer (A-SMO) for unknown fault reconstruction in longitudinal autonomous driving. Securing the functional safety of autonomous vehicles from unexpected faults of sensors is essential for avoidance of fatal accidents. Because the magnitude and type of the faults cannot be known exactly, the RLS based A-SMO for unknown acceleration fault reconstruction has been designed with relationship function in this study. It is assumed that longitudinal acceleration of preceding vehicle can be obtained by using the V2V (Vehicle to Vehicle) communication. The kinematic model that represents relative relation between subject and preceding vehicles has been used for fault reconstruction. In order to reconstruct fault signal in acceleration, the magnitude of the injection term has been adjusted by adaptation rule designed based on MIT rule. The proposed A-SMO in this study was developed in Matlab/Simulink environment. Performance evaluation has been conducted using the commercial software (CarMaker) with car-following scenario and evaluation results show that maximum reconstruction error ratios exist within range of ±10%.

• Geomechanics and Engineering
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• 제36권2호
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• pp.167-181
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• 2024

The soil-structure relative stiffness is a key factor affecting the seismic response of underground structures. It is of great significance to study the soil-structure relative stiffness for the soil-structure interaction and the seismic disaster reduction of subway stations. In this paper, the dynamic shear modulus ratio and damping ratio of an inhomogeneous soft soil site under different buried depths which were obtained by a one-dimensional equivalent linearization site response analysis were used as the input parameters in a 2D finite element model. A visco-elasto-plastic constitutive model based on the Mohr-Coulomb shear failure criterion combined with stiffness degradation was used to describe the plastic behavior of soil. The damage plasticity model was used to simulate the plastic behavior of concrete. The horizontal and vertical relative stiffness ratios of soil and structure were defined to study the influence of relative stiffness on the seismic response of subway stations in inhomogeneous soft soil. It is found that the compression damage to the middle columns of a subway station with a higher relative stiffness ratio is more serious while the tensile damage is slighter under the same earthquake motion. The relative stiffness has a significant influence on ground surface deformation, ground acceleration, and station structure deformation. However, the effect of the relative stiffness on the deformation of the bottom slab of the subway station is small. The research results can provide a reference for seismic fortification of subway stations in the soft soil area.

• 한국신뢰성학회지:신뢰성응용연구
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• 제12권3호
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• pp.165-176
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• 2012

Hydrostatic bearing improves performance and life time of a product by avoiding solid friction and reducing viscosity friction with the help of creating pressure equilibrium between two faces doing relative motion. This study suggests failure analysis and test evaluation for a ball joint that adopts the hydrostatic bearing and introduces the entire process to improve reliability of the product by design improvement. A typical failure is growth of friction torque by solid friction, and its failure cause is determined and the improvement is proposed. Finally, reliability improvement is established by analysis of the results of before and after acceleration test.

• Tribology and Lubricants
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• 제14권1호
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• pp.14-22
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• 1998

This paper describes the effects of exciting frequency on the stiffness and damping coefticients of a 5-pad tilting pad journal bearing, LOP (load on pad) type. The stiffness and damping coefficients are investigated experimentally under the different values of exciting frequency, bearing load and shaft speed. These coefficients are estimated by measuring the response of the relative displacement between the bearing and the shaft and acceleration of the bearing due to the known exciting loads acting on the bearing. In order to analysis the response of exciting load, displacement and acceleration, a FFT analyzer is used. It is shown that the variation of exciting frequency has a little effect on both the stiffness and damping coefficients. Both the stiffness and damping coefficients in the loading direction are decreased by the increase of shaft speed but increased by the increase of bearing load.

• International Journal of Aeronautical and Space Sciences
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• 제15권3호
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• pp.281-292
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• 2014

We propose a novel cooperative guidance law design method based on the finite time disturbance observer (FTDO) for multiple near space interceptors (NSIs) with impact time control. Initially, we construct a cooperative guidance model with head pursuit, and employ the FTDO to estimate the system disturbance caused by target maneuvering. We subsequently separate the cooperative guidance process into two stages, and develop the normal acceleration command based on the super-twisting algorithm (STA) and disturbance estimated value, to ensure the convergence of the relative distance. Then, we also design the acceleration command along the line-of-sight (LOS), based on the nonsingular fast terminal sliding mode (NFTSM) control, to ensure that all the NSIs simultaneously hit the target. Furthermore, we prove the stability of the closed-loop guidance system, based on the Lyapunov theory. Finally, our simulation results of a three-to-one interception scenario show that the proposed cooperative guidance scheme makes all the NSIs hit the target at the same time.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2001년도 ICCAS
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• pp.178.4-178
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• 2001

In this paper a self-tuning gain-scheduled skyhook control for semi-active suspension systems is investigated. The dynamic characteristics of a continuously variable damper including electro-hydraulic pressure control valves is analyzed. A 2-d.o.f. time-varying quarter-car model that permits variations in sprung mass and suspension spring coefficient is considered. The self-tuning skyhook control algorithm proposed in this paper requires only the measurement of body acceleration. The absolute velocity of the sprung mass and the relative velocity of the suspension deflection are estimated by using integral filters. The skyhook gains are gain-scheduled in such a way that the body acceleration and the dynamic tire force are optimized. An ECU prototype ...

• 천문학회지
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• 제1권1호
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• pp.37-50
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• 1968

By comparison and analysis of the optical data of the two galactic clusters of Pleiades and h and x Persei and the radio data of the HI gas clouds which are related with those two clusters, the relative motions of those gas clouds with retpect to the two clusters were obtained. The three theories on the acceleration of HI gas cloud surrounding a star cluster by Blaauw. Oort and Spitzer, and Kahn were examined with the above obtained kinetic data of the Pleiades and the h and x Penei clouds. And it was shown that Blaauw's theory is applicable to the h and x Persoi clouds but not to the Pleiades, that Dart and Spitzer's theory can explain the motions of both clouds, and that Kahn's theory needs more improvement to be a complete one.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2000년도 제15차 학술회의논문집
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• pp.113-113
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• 2000

A robust adaptive technique for the longitudinal control of a platoon of automated vehicles is presented. A nonlinear model is used to represent the vehicle dynamics of each vehicle within the platoon. The external disturbance such as wind gust and a disturbance term due to engine transmission variations and so on are considered. The state observer is used to avoid direct measurement of the relative velocity or acceleration between the controlled and leading vehicles or the controlled vehicle's acceleration. It is shown that platoon stability can be recovered in operation even if a speed dependent spacing policy is adopted, which incorporates a constant time headway in addition to the constant distance. The simulation results demonstrate excellent tracking even in the presence of disturbances.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2000년도 제15차 학술회의논문집
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• pp.114-114
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• 2000

In this paper a self-tuning modified skyhook control for the semi-active suspension systems is investigated. The damping force generation mechanism is modeled We consider a 2 DOF time-varying quarter car model that permits parameter variations of the sprung mass and suspension spring coefficient. The modified skyhook control algorithm proposed in this paper requires only the measurement of body acceleration. The absolute velocity of the sprung mass and the relative velocity of the suspension deflection are estimated by using integral filters, according to parameter variations. The skyhook gains are designed in such a way that the body acceleration and the dynamic tire force are optimized. An ECU prototype will be discussed