• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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• pp.763-766
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• 1996

A model helicopter is an unstable, multi-input multi-output nonlinear system exposed to strong disturbances and its system parameters change continually. In this paper, Time Delay Control(TDC) is adopted for these reasons. TDC uses past observation of the system's response and the control input to directly modify the control action rather than adjusting the controller gains leading to a model independent robust controller. TDC can force the plant to follow an appropriate reference model, but the reference model cannot be chosen arbitrarily. In this paper the procedure of choosing a reference model and the performance of the controller are presented.

• Journal of Institute of Control, Robotics and Systems
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• v.5 no.2
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• pp.166-173
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• 1999

Reference models are used in many control algorithms for improvement of transient response characteristics. They provide desired trajectories that the plant should follow Most control systems have bounded control inputs to avoid saturation of the plant. If we design the reference models that do not account for limits of the control inputs, control performance of the system may be deteriorated. In this paper a new approach of avoiding saturation by varying the reference model for TDC(time delay control) based systems subject to step changes in the reference input. In this scheme, the variable reference model is determined based on the information on control inputs and the size of the step changes in the reference inputs. This scheme was verified by application to the BLDC motor position control system in simulations and experiments. The responses of the TDC with the variable reference model showed better tracking performance than that with the fixed reference model.

• Proceedings of the KIPE Conference
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• 2002.07a
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• pp.166-169
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• 2002

The purpose of this paper is to develop systematic analysis and automatic tuning rule of PID controller for industry servo applications. Considering the coupling of inner current control loop and speed loop delay, the target plant fit into second-order plus time delay model. Based on PID controller design for high-order plus known/unknown time delay plant model, some formulars are provided for the control gain calculation and system-based theoretical analysis is developed, and it also allows an automatic controller setup to benefit the inexperienced user. In addition, the proposed design rule gives uniformly satisfactory performance and the motor speed stays on a desired response curve with minimal oscillation and settling time. This approach can be applicable in conjunction with the cascaded control loop which is widely used in practice.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.11a
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• pp.1004-1011
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• 1996

This paper covers the technology developmental stage work for the automatic ammunition loading system mainly focusing on the controller design of the electro-hydranlic type direct drive multi-axis manipulator. Mathematical model of the plant derived and PIDM servo-controller structured. Comparative study between the analytical and experimental work has been carried out to help understand the response property of the direct dine multi-axis robot. In the direct drive robot, non-negligible amount of disturbance and load Induced dynamics variation are transmitted to the drive axis and nonlinearity is highly observed. Thereupon a robust controller Implementing time-delay control law is proposed, and computer simulation confirms the possibility for the time-delay control application against the unpredictable disturbance and load-Induced dynamics variation.

• International Journal of Aeronautical and Space Sciences
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• v.12 no.3
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• pp.266-273
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• 2011

This paper deals with missile autopilot design for agile turn phase in air-to-air engagement scenarios. To attain a fast response, angle-of-attack (AOA) is adopted for an autopilot command structure. Since a high operational AOA is generally required during the agile turn phase, dealing with the aerodynamic uncertainties can be a challenge for autopilot design. As a remedy, a new controller design method based on robust nonlinear control methodology such as time delay control is proposed in this paper. Nonlinear observer is also proposed to estimate the AOA in the presence of the model uncertainties. The performance of the proposed controller with variation of the aerodynamic coefficients is investigated through numerical simulations.

• Proceedings of the KIEE Conference
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• 2000.07b
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• pp.1056-1058
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• 2000

Deadbeat technique has been proposed as a digital controller for an UPS inverter to achieve the fast response to a load variation and to conserve a very low THD under a nonlinear load condition. This scheme contains a fatal drawback, sensitivity against parameter variation and calculation time delay. This paper proposes a second order deadbeat current controller, which fundamentally solves the calculation time delay problem and certainly guarantees the robustness of the parameter's variation. This is shown theoretically and practically through simulation and experiment.

• Smart Structures and Systems
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• v.15 no.3
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• pp.863-879
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• 2015

This paper experimentally investigates the effectiveness and applicability of the time delay control (TDC) algorithm, which is simple and robust to unknown system dynamics and disturbance, for an active mass damper (AMD) system to mitigate the excessive vibration of a building structure. To this end, the theoretical background including the mathematical formulation of the control system is first described; and then, a thorough experimental study using a shaking table system with a small-scale three-story building structural model is conducted. In the experimental tests, the performance of the proposed control system is examined by comparing its structural responses with those of the uncontrolled system in the free vibration and forced vibration cases. It is clearly verified from the test results that the TDC algorithm embedded AMD system can effectively reduce the structural response of the building structure.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39B no.10
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• pp.715-721
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• 2014

In decades, many researchers have studied the time delay estimation (TDE) method for the signals in the two different receivers. The channel estimation based TDE is one of the typical TDE methods. The channel estimation based TDE models the time delay between two receiving signals as an impulse response in a channel between two receivers. In general the impulse response becomes sparse. However, most conventional TDE algorithms cannot have utilized the sparsity. In this paper, we propose a TDE method taking the sparsity into consideration. The performance comparison shows that the proposed algorithm improves the estimation accuracy by 10 dB in the white gaussian source. In addition, even in the colored source, the proposed algorithm doesn't show the estimation threshold effect.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.2298-2303
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• 2003

In this paper, very simple methods based on the exponential analysis are presented by which transfer function models for processes can easily be obtained. These methods employ step responses or impulse responses of the processes. These can also give a more precise transfer function model compared to the well-known graphical methods. Transfer functions are determined based on Prony method, which is one of the oldest and the most representative methods in the exponential analysis. Here, the method is reformed and applied to obtain the so-called low-order transfer function with pure time delay from the data of the step response. The effectiveness of the proposed method is examined through several numerical examples and experiments of the 2-tank level control process.

• The Journal of Korean Society of Virology
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• v.26 no.1
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• pp.1-8
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• 1996

Human cytomegalovirus (HCMV) replication and $Ca^{2+}$ response in human cell lines of neuronal origin were investigated. SK-N-SH (neuroblastoma cells) and A172 cells (glioblastoma cells) were used. SK-N-SH cells were permissive for HCMV multiplication with a delay of one day compared to virus multiplication in human embryo lung (HEL) cells. The delay of HCMV multiplication in SK-N-SH cells appeared to be correlated with a delay in the $Ca^{2+}$ response. The cytoplasmic free $Ca^{2+}$ concentration ($[Ca^{2+}]_i$) began to increase at 12 h p.i. in HCMV-infected SK-N-SH cells, while $[Ca^{2+}]_i$ increase in HCMV-infected HEL cells was observed as early as 3 h p.i. On the whole, the level of the increase in $[Ca^{2+}]_i$ in SK-N-SH cells was about 30% of that in HEL cells. On the other hand, in A172 cells infected with HCMV, neither production of infectious virus nor detectable increase in $[Ca^{2+}]_i$ was observed. Treatment with TPA of HCMV-infected SK-N-SH cells resulted in $[Ca^{2+}]_i$ increase at 6 h p.i. The stimulatory effect of TPA on HCMV- induced $[Ca^{2+}]_i$ increase continued until 12 h p.i., but TPA failed to stimulate the $Ca^{2+}$ response in SK-N-SH cells at 24 h p.i., suggesting that the effect of TPA had disappeared in SK-N-SH cells at that time point. In conclusion, SK-N-SH cells are permissive for HCMV replication and the delay in $Ca^{2+}$ response may be a consequence of the lower responsiveness of SK-N-SH cells than HEL cells to HCMV infection.