• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.228-228
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• 2000

To deal with non-linearities and time-varying characteristics of hydraulic systems, in this paper, the neuro-fuzzy controller has been introduced. This controller does not require an accurate mathematical model for the nonlinear factor. In order to solve general fuzzy inference problems, the input membership function and fuzzy reasoning rules are used for determining the controller Parameters. These parameters are determined by using the learning algorithm. The control performance of the neuro-fuzzy controller is obtained through a series of experiments for the various types of input while applying disturbances to the cylinder. .and performance of this controller was compared with that of PID, PD controller. As a experimental result, it can be proven that the position tracking performance of the neuro-fuzzy is better than that of PID and PD controller.

• Tribology and Lubricants
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• v.18 no.1
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• pp.68-74
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• 2002

In this study, the dynamic characteristics of the spool type counter balance valve are studied. The nonlinear governing differential eguations are derived. Routh-Hurwitz criterion is used to characterize the linearized eguations. Static and dynamic experiments are carried out for the determination of parameters that are necessary for the analysis and the stability of the system.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2011.04a
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• pp.409-414
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• 2011

The drivers of commercial vehicle easily feel tired because of a long time driving and bad road condition. Therefore it is very important to make the driver seat comfortable. This paper introduces the suspension system of driver's seat using magnetic force. The combination of linear spring and magnetic force can make nonlinear spring which has optimal stiffness for minimal vibration transmissibility. The vibrations of driver's seat floor are measured in various road condition. And the numerical simulations and experiments are performed to define the optimal parameter of magnetic suspension system.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1994.10a
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• pp.577-583
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• 1994

The purpose of this paper is to study the force control law which can be implemented on a non-modified robot system. The external force control algorithm proposed in this paper can be designed by means of a classical and modern control law. We showed the validation and the possibility of muti-dimensional force control idea through the simulation and experiments. Also, the Iterative learning control is studied for compensating errors due to thr disturbances and nonlinear effects. The previous information(control input, error) was used to determine the control input of next trial. The experimental result show the vaidity of this algorithm.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.14 no.10
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• pp.1029-1034
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• 2004

Linear motion ( LM) guides having rolling elements have been used to position precision machines accurately. For ultra-accurate Positioning control of Precision machines, the understanding of the dynamic behavior of the LM guide at the macro and/or micro scales is most critical, but the research on this subject is rare. The objective of the present research is to investigate the vibration phenomena of the LM guide where balls are used as the rolling elements. Several experiments show the nonlinear characteristics of the LM guide such as hysteresis behavior and force-dependent natural frequencies phenomena.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.6 no.3
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• pp.794-814
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• 2012

We propose a novel method for improving Wi-Fi positioning accuracy while reducing the energy consumption of mobile devices. Our method presents three contributions. First, we jointly and intelligently select the optimal subset of access points for positioning via maximum mutual information criterion. Second, we further propose local discriminant embedding algorithm for nonlinear discriminative feature extraction, a process that cannot be effectively handled by existing linear techniques. Third, to reduce complexity and make input signal space more compact, we incorporate clustering analysis to localize the positioning model. Experiments in realistic environments demonstrate that the proposed method can lower energy consumption while achieving higher accuracy compared with previous methods. The improvement can be attributed to the capability of our method to extract the most discriminative features for positioning as well as require smaller computation cost and shorter sensing time.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.24 no.12
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• pp.943-947
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• 2014

Recently, a new method for reconstructing a forced nonlinear dynamic system has been proposed; specifically, the simultaneous reconstruction of its excitation as well as restoring characteristics of the system. The reconstruction was just theoretically shown to be possible by measuring the system's responses, based on newly introduced notions, a J-function and a zero-crossing time. However, numerically in the current paper, we are to reconstruct a linear system, i.e., we focus on numerical experiments to reconstruct both the excitation and the linear restoring characteristic of a linear forced oscillating system by using response data, based on the J-function and the zero-crossing time.

• Journal of KSNVE
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• v.7 no.2
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• pp.239-246
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• 1997

This paper presents an active suspension control algorithm to improve the suspension performance trade-offs between riding comfort and handling stability. In this paper, a hybrid control scheme is proposed, the idea of which is that sliding mode control is used for nonlinear hydraulic system and the skyhook control is applied to control the vehicle behavior. The parameter variations in hydraulic system are considered for the robust controller design. The performance of the proposed control method is evaluated by simulation and experiments based on a half car roll model which can reveal both heave and roll behavior.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.10a
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• pp.382-387
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• 2012

A virtual prototype (VP) model of the rotor-to-stator rub of the rotor system is established to study the nonlinear vibration characteristics. The non-linear bearing stiffness is considered to approximate to an actual system in the model. In order to validate the effectiveness of the proposed approach, a special structure of stator is designed to simulate different kinds of rub condition. The results of experiment are well consistent with the results of simulation by VP. The vibration characteristics of rub-impact are well observed by VP model under different conditions. Based on the validated model, the torsional vibration of rub-impact is discussed. The contribution of this paper is to provide one new approach to study rub-impact problem. Based on the validated VP model, the more research can be done for incident fault identification.

• Transactions of the Korean Society of Automotive Engineers
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• v.4 no.1
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• pp.110-122
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• 1996

The objective of this study is to understand the dynamic characterictics of OHV type valve trains and to design and optimal cam profile which will improve engine performance. A numerical model for valve train dynamics is presented, which aims at both accuracy and computational efficiency. The lumped mass model and distributed parameter model were used to describe the valve train dynamics. Nonlinear characterictics in the valve spring behavior were included in the model. Comprehensive experiments were carried out concerning the valve train dynamics, and the model was tuned based on the test results. The dynamic model was used in designing an optimal cam profile. Because the objective function has many local minima, a conventional local optimizer cannot be used to find an optimal solution. A modified adaptive random search method is successfully employed to solve the problem. Cam lobe area could be increased up to 7.3% without any penalties in kinematic and dynamic behaviors of the valve train.