• Journal of Mechanical Science and Technology
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• v.14 no.10
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• pp.1061-1071
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• 2000

Linear cyclic systems (LCS's) are a class of systems whose dynamic behavior changes periodically. Such a cyclic behavior is ubiquitous in systems with fundamentally repetitive motion. Yet, the knowledge of the noise and vibration transmission paths in LCS's is quite limited due to the time-varying nature of their dynamics. The first part of this two-part paper derives a generic expression that describes how the noise and/or vibration are transmitted between two (or multiple) points in the LCS's. In Part II, experimental validation of the theoretical development of Part I is provided. The noise and vibration transmission paths of the scroll and rotary compressors (two typical LCS's) are examined to show that the LCS's indeed generate a series of amplitude modulated input signals at the output, where the carrier frequencies are harmonic multiples of the LCS' fundamental frequency. The criterion proposed in Part I to determine how well a given LCS can be approximated as a linear time-invariant systems (LTIS) is applied to the noise and vibration transmission paths of the two compressors. Furthermore, the implications of the experimental validations/applications are discussed in order to assess the applicability of the noise/vibration source and transmission path identification techniques based on the assumption that the system under consideration is linear and time-invariant.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.1 no.1
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• pp.123-132
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• 2002

In this study, the static and dynamic characteristics of endmilling process was modelled and the analytic realization of chatter mechanism was discussed. In this regard, We have discussed on the comparative assessment of recursive time series modeling algorithms that can represent the machining process and detect the abnormal machining behaviors in precision endmilling operation. In this study, simulation and experimental work were performed to show the malfunctional behaviors. For this purpose, new recursive least square method (RLSM) were adopted for the on-line system identification and monitoring of a machining process, we can apply these new algorithms in real process for detection of abnormal chatter. Also, The stability lobe of chatter was analysed by varying parameter of cutting dynamices in regenerative chatter mechanics.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1993.10a
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• pp.321-327
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• 1993

In order to maintain the cutting force at a desired level during peripheral end milling processes in spite of variation of the depth of cut and other machining conditions, a feedrate override. Apaptive Control Constraint (ACC) system are developed. Feedrate override was accomplished by a developed MMC board and PMC interface techniques. Nonlinear model of the cutting process was linearized as an adaptive model with time varying paramrters. Integral type estimators were introduced for on-line identification of cutting and control parameters in peripheral and milling processes. Zero Order Jold (ZOH) type degital control methodology which uses pole-placement concepts was applied for the ACC system. Performance of the developed ACC system was confirmed on the vertical machining center equipped with FANUC OMC for a large amount of experiment

• Journal of KSNVE
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• v.5 no.3
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• pp.385-394
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• 1995

Recently, since robot manipulator becomes faster and lighter, its link is no longer regarded as rigid body, and robot controller which only controls robot position cannot reduce vibration of the flexible link. Therefore vibration control is needed in robot manipulator control in addition to position control. In the case that tip mass changes when robot manipulator in working, it is clear that the efficiency of the vibration/position controller designed for the fixed system goes down. In this paper, the system with time varying parameters, adaptive control theory is adopted which estimates parameters changed by the variation of the tip mass and re-calculates the gain of the controller. Validify of the proposed adaptive controller and capability of the estimator are evaluated by computer simulations and experiments. Comparison results of the optimal controller for the fixed system and proposed adaptive controller and carried out.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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• pp.427-431
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• 1996

The MRAS proposed by Schauder [8] is modified to improve robustness to the change of load torque and/or the variation of the stator resistance. The difference between the voltage and the current model is fed into the current model via proportional and integral gains. In order to generalize the MRAS, supposing that the rotor speed is time varying, we add a compensating term to the current model. It does not alter the Popov's integral inequality condition. Also, the asymptotic stability of the modified MRAS (MMRAS) is shown with the stability proof technique as in the original paper. By the simulation works, it is verified that the MMRAS obtains improved performance than the original MRAS.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.971-974
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• 2001

In this study, the static and dynamic characteristics of endmilling process was modelled and the analytic realization of chatter mechanism was discussed. In this regard, We have discussed on the comparative assessment of recursive time series modeling algorithms that can represent the machining process and detect the abnormal machining behaviors in precision endmilling operation. In this study, simulation and experimental work were performed to show the malfunctional behaviors. For this purpose, new recursive(RLSM) were adopted for the on-line system identification and monitoring of a machining process, we can apply these new algorithms in real process for detection of abnormal chatter. Also, the stability lobe of chatter was analysed by varying parameter of cutting dynamices in regenerative chatter mechanics.

• Proceedings of the KIEE Conference
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• 2000.07d
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• pp.2681-2683
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• 2000

This paper considers the problem of identifying the time-varying parameters of the bilinear systems. The Parameters, in this paper, are identified by using the EBPOMs (Extended Block Pulse Operational Matrices) which can reduce the burden of operation and the volume of error caused by matrices multiplication

• Proceedings of the KIEE Conference
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• 1996.07b
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• pp.1037-1041
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• 1996

Input-output linearization technique in nonlinear control does not guarantee the robustness in the presence of parameter uncertainty or unmodeled dynamics, etc. However, it has been used as an important preliminary step in achieving additional control objectives, for instance, robustness to parameter uncertainty and disturbance attenuation. An indirect adaptive control scheme based on input-output linearization is proposed in this paper. The scheme consists of a Hopfield network for process parameter identification and an adaptive sliding mode controller based on input-output linearization, which steers the system response into a desired configuration. A numerical example is presented for the trajectory tracking of uncertain nonlinear dynamic systems with slowly time-varying parameters.

• Proceedings of the KIEE Conference
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• 2001.07d
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• pp.2311-2313
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• 2001

This paper considers the problem of identifying the time-varying parameters of the bilinear systems. The Parameters, in this paper, are identified by using the EBPOMs(Extended Block Pulse Operational Matrices) which can reduce the burden of operation and the volume of error caused by matrices multiplication.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.11
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• pp.151-157
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• 2000

The MRAC theory has proved to be one of the most popular algorithms in the field of adaptive control, particularly for practical application to devices such as an hydraulic servosystem of which parameters are unknown or varying during operation. For small sampling period, the discrete time system becomes a nonminimal phase system. The $\delta$-MRAC was introduced to obtain the control performance of nonminimal phase system, because the z-MRAC can not control the plant for small sampling period. In this paper, $\delta$-MRAC is applied to the control of an hydraulic servosystem which is composed of servovalve, hydraulic cylinder and inertia load.