• Journal of the Korean Society of Manufacturing Process Engineers
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• v.11 no.4
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• pp.72-81
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• 2012

This study investigates structural, fatigue and modal analyses at bicycle suspension seat post. When weight is applied to the saddle, models 1 and 2 have the weakest strength at the part connected with saddle. And model 2 is greater total deformation and equivalent stress than model 1. Among the cases of nonuniform fatigue loads at models 1 and 2, 'SAE bracket history' with the severest change of load becomes most unstable but 'Sample history' becomes most stable. In case of 'Sample history' with the average stress of 0 to $-10^4MPa$ and the amplitude stress of 0 to $10^4MPa$, the possibility of maximum damage becomes 4%. This stress state can be shown with 5 to 7times more than the damage possibility of 'SAE bracket history' or 'SAE transmission'. Model 1 has better impulse relaxation and passenger sensitivity than model 2. The structural result of this study can be effectively utilized with the design of bicycle suspension seat post by investigating prevention and durability against its damage.

• Wind and Structures
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• v.18 no.1
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• pp.1-20
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• 2014

Modern design of long suspension bridges must satisfy at the same time spanning very long distances and limiting their response against several external loads, even if of high intensity. Structural Control, with the solutions it provides, can offer a reliable contribution to limit internal forces and deformations in structural elements when extreme events occur. This positive aspect is very interesting when the dimensions of the structure are large. Herein, an updated numerical model of an existing suspension bridge is developed in a commercial finite element work frame, starting from original data. This model is used to reevaluate an optimization procedure for a passive control strategy, already proven effective with a simplified model of the buffeting wind forces. Such optimization procedure, previously implemented with a quasi-steady model of the buffeting excitation, is here reevaluated adopting a more refined version of the wind-structure interaction forces in which wind actions are applied on the towers and the cables considering drag forces only. For the deck a more refined formulation, based on the use of indicial functions, is adopted to reflect coupling with the bridge orientation and motion. It is shown that there is no variation of the previously identified optimal passive configuration.

• Wind and Structures
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• v.10 no.6
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• pp.543-554
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• 2007

The suspension bridge is situated in an area of complex topography with both open sea and overland turbulence characteristics, and it is subject to frequent typhoon occurrences. This paper investigates experimentally the possible vortex shedding events of the structure under high wind and typhoon conditions. A single-degree-of-freedom model for the vibration of a unit bridge deck section is adopted to determine the amplitude of vibration and to estimate the parameters related to the lifting force in a vortex shedding event. The results of the studies are presented in a companion paper (Law, et al. 2007). In this paper, statistical analysis on the measured responses of the bridge deck shows that the vibration response at the first torsional mode of the structure has a significant increase at and beyond the critical wind speed for vortex shedding as noted in the wind tunnel tests on a section model of the structure.

• Proceedings of the KSME Conference
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• 2001.06c
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• pp.339-344
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• 2001

In recent engineering, the designer has become more and more dependent on the computer simulations such as FEM (Finite Element Method) and BEM (Boundary Element Method). In order to optimize such implicit models more efficiently and reliably, the meta-modeling technique has been developed for solving such a complex problems combined with the DACE (Design and Analysis of Computer Experiments). It is widely used for exploring the engineer's design space and for building meta-models in order to facilitate an effective solution of multi-objective and multi-disciplinary optimization problems. Optimization of a train suspension is performed according to the minimization of forty-six responses that represent ten ride comforts, twelve derailment quotients, twelve unloading ratios, and twelve stabilities by using the Kriging meta-model of a train suspension. After each Kriging meta-model is constructed, multi-objective optimal solutions are achieved by using a nonlinear programming method called SQP (Sequential Quadratic Programming).

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.1583-1588
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• 2000

The dynamic characteristics of a HDD suspension system are investigated by finite element analysis and experimental modal analysis. A finite element model of the suspension Type850 was developed for unloaded case. The calculated vibration modes were compared with measurements and agree well in shape and frequency except some local modes. Local thickness and Young's modulus of the finite element model are updated by modal tuning method to develop the precise FE model. A sensitivity matrix of the natural frequencies for some design variables was calculated using finite difference method. Most natural frequencies calculated by the tuned FE model coincide with the measurements and the errors between them are less than 2%.

• Transactions on Control, Automation and Systems Engineering
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• v.2 no.1
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• pp.1-6
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• 2000

This paper presents a control of active suspension for quarter car model with two degree of freedom by using H$\infty$ method. Absolute velocity of car body is measured for feedback. The system parameter variations are treated with multiplicative uncertainty model. Simulation results show that the H$\infty$ control provides good trade-off between ride quality, suspension packaging and road holding constraints. The experiment with a front wheel suspension system was done to verify the simulation results.

• Journal of international Conference on Electrical Machines and Systems
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• v.1 no.4
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• pp.509-516
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• 2012

This paper describes the testing and experimental characterization of a linear permanent magnet actuator, which is designed and developed for active vehicle suspension, under both static and dynamic conditions. Since the active suspension unit operates over a wide force-velocity range with varying duty ratios, it is essential to establish an effective thermal model which can be used for assessing temperature rise of the actuator under various operating conditions. The temperature rise of the actuator is measured and the results are compared with the prediction by the derived transient thermal model. It is shown that the measured actuator parameters and characteristics are closed to their predicted values. The linear actuator is controlled by a dSPACE system via a three phase inverter and its velocity tracking performance is presented.

• Transactions of the Korean Society of Automotive Engineers
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• v.5 no.5
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• pp.132-139
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• 1997

It is difficult for most of passenger cars to attach various types of suspensions. The modular experimental vehicle, which is designed to exchange suspension systems, has been developed to evaluate the effect of design changes of a suspension upon ride and handling characteristics of a vehicle. In order to enable the assemblage between modules, the experimental vehicle design is based on a space frame construction through finite element analysis. Moreover, module frames and brackets are designed using three-dimensional solid modeler to check the interference between each part of a vehicle. Steady-state and transient road tests were performed. Multibody dynamic model and simplified linear vehicle model are made to compare with the tests. The results of simulations and tests show the performance and validity of this experimental vehicle.

• Journal of Biosystems Engineering
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• v.23 no.4
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• pp.327-334
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• 1998

This work was intended to determine the optimum values of the cab suspension parameters by a simulation method in order to minimize the seat accelerations of agricultural tractors in the frequencies lower than 50Hz. A dynamic model of cab motions was developed and verified using a tractor excited over half-sine bumps on a concrete test road. A simulation program based on the model was also developed. A method was proposed to determine the optimum values of the suspension parameters. It was found that the natural frequencies of the cab and seat suspensions must be apart as far as possible until the sum of seat and cab accelerations is minimized, which also reduces the seat accelerations maximally.

• Journal of Institute of Control, Robotics and Systems
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• v.9 no.9
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• pp.669-678
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• 2003

A road-adaptive LQG control for the semi-active Macpherson strut suspension system of hydraulic type is investigated. A new control-oriented model, which incorporates the rotational motion of the unsprung mass, is used for control system design. First, based on the extended least squares estimation algorithm, a LQG controller adapting to the estimated road characteristics is designed. With computer simulations, the performance of the proposed LQC-controlled semi-active suspension is compared with that of a non-adaptive one. The results show better control performance of the proposed system over the compared one.