• The Transactions of the Korean Institute of Electrical Engineers P
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• v.50 no.3
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• pp.130-137
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• 2001

In this paper, we propose a new Active Noise Filter Control System which operate as a control performance when a adaptive filter fault. In this system, half-fixed filter which is new filter, connected to parallel with adaptive filter. An adaptive filler use to continuous parameter estimating, but adaptive filter is fault, half-fixed filter update newly data which is continuous estimating date each during sampling period. We simulate and apply the proposed active noise filter system to in the cylinder type duct. Experimental results show that proposed Active Noise Filter Control System has better control performance than existing filter which Eriksson's or Parallel Filter System in term of noise reduction.

• Journal of Positioning, Navigation, and Timing
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• v.9 no.2
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• pp.99-115
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• 2020

Since GNSS is easily affected by jamming and/or spoofing, alternative navigation systems can be operated as backup system to prepare for outage of GNSS. Alternative navigation systems are being researched over the world, and a multi-radio integrated navigation system using alternative navigation systems such as KNSS, eLoran, Loran-C, DME, VOR has been researched in Korea. Least Square or Kalman filter can be used to estimate navigation parameters in the navigation system. A large number of measurements of the Kalman filter may lead to heavy computational load. The decentralized Kalman filter and the federated Kalman filter were proposed to handle this problem. In this paper, the decentralized Kalman filter and the federated Kalman filter are designed for the multi-radio integrated navigation system and the performance evaluation result are presented. The decentralized Kalman filter and the federated Kalman filter consists of local filters and a master filter. The navigation parameter is estimated by local filters and master filter compensates navigation parameter from the local filters. Characteristics of three Kalman filters for a linear system and nonlinear system are investigated, and the performance evaluation results of the three Kalman filters for multi-radio integrated navigation system are compared.

• Journal of Institute of Control, Robotics and Systems
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• v.19 no.5
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• pp.481-487
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• 2013

This paper presents an FIR (Finite Impulse Response) fixed-interval smoothing filter for fast and exact estimating state variables of a discrete nonlinear system with modeling uncertainty. Conventional IIR (Infinite Impulse Response) filter and smoothing filter can estimate state variables of a system with an exact model when the system is observable. When there is an uncertainty in the system model, however, conventional IIR filter and smoothing filter may cause large errors because the filters cannot estimate the state variables corresponding to the uncertain model exactly. To solve this problem, FIR filters that have fast estimation properties and have robustness to the modeling uncertainty have been developed. However, there is time-delay estimation phenomenon in the FIR filter. The FIR smoothing filter proposed in this paper makes up for the drawbacks of the IIR filter, IIR smoothing filter, and FIR filter. Therefore, the FIR smoothing filter has good estimation performance irrespective of modeling uncertainty. The proposed FIR smoothing filter is applied to the integrated navigation system composed of a magnetic compass based DR (Dead Reckoning) and a GPS (Global Positioning System) receiver. Even when the magnetic compass error that changes largely as the surrounding magnetic field is modeled as a random constant, it is shown that the FIR smoothing filter can estimate the varying magnetic compass error fast and exactly with simulation results.

• Journal of the Korean Society of Industry Convergence
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• v.26 no.6_2
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• pp.1163-1169
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• 2023

In this study, the flow characteristics of the filter system were analyzed due to the effect of the density of the filter in the triple filter system. Flow analysis was performed as a flow passing through a porous medium. The flow characteristics of each filter system were analyzed by arranging filters with different densities in the forward flow flow and the reverse flow. The arrangement order of the triple filters was excellent in the case of forward fluid flow and in the case of higher density from the inside to the outside filter. In the reverse flow filter system, the performance of the system was the best in the case of reverse order filter arrangement. As a result of the analysis, Case II, which showed a pressure drop rate of 5.65% for forward flow, was the best in the reverse direction with a pressure drop rate of 14.25%. Considering reverse and forward flows, it was found that the optimal filter arrangement was most effective when the intermediate filter was the densest, and the inner or outer filter was less dense.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.1
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• pp.349-354
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• 2006

For robust INS/GPS navigation system, an efficient multi-filter fusion technique is proposed. In the filtering for nonlinear systems, the representative filter - EKF, and the alternative filters - RHKF filter, SPKF, etc. have individual advantages and weak points. The key concept of the multi-filter fusion is the mergence of the strong points of the filters. This paper fuses the IIR type filter - EKF and the FIR type filter - RHKF filter using the adaptive strategy. The result of the fusion has several advantages over the EKF, and the RHKF filter. The advantages include the robustness to the system uncertainty, temporary unknown bias, and so on. The multi-filter fusion technique is applied to the tightly coupled INS/GPS navigation system and the performance is verified by simulation.

• Journal of Institute of Control, Robotics and Systems
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• v.13 no.12
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• pp.1230-1242
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• 2007

This paper describes an IIR/FIR fusion filter for a nonlinear system, and analyzes the stability of the fusion filter. The fusion filter is applied to INS/GPS integrated system, and the performance is verified by simulation and experiment. In the fusion filter, an IIR-type filter (SPKF) and FIR-type filter (MRHKF filter) are processed independently, then the two filters are merged using the mixing probability calculated using the residuals and residual covariance information of the two filters. The merits of the SPKF and the MRHKF filter are embossed and the demerits of the filters are diminished via the filter fusion. Consequently, the proposed fusion filter has robustness against to model uncertainty, temporary disturbing noise, large initial estimation error, etc. The stability of the fusion filter is verified by showing the closeness of the states of the two sub filters in the mixing/redistribution process and the upper bound of the error covariance matrices. This fusion filter is applied into INS/GPS integrated system, and important factors for filter processing are presented. The performance of the INS/GPS integrated system designed using the fusion filter is verified by simulation under various error environments and is confirmed by experiment.

• Journal of the Korean Society of Industry Convergence
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• v.26 no.4_2
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• pp.615-621
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• 2023

In this study, flow analysis of single, double, and triple filter systems of cylindrical structures was performed to analyze the flow characteristics of each filter. As a result of the flow analysis of the filter system, the number of filters and the pressure drop rate tend to be proportional to each other. It was found that the area passing through the inside of the filter had almost the same pressure. The maximum pressure drop rate of the triple filter system was about 14.9% for the forward-flow and about 12.4% for the reverse-flow. It was determined that the performance of the filter was stable within 20% of the allowable pressure drop rate of the filter system, which is the standard presented to the Korea Water Technology Certification Institute(KWTCI). In the future, a study on the decompression characteristics of the filter system according to the effect of the arrangement interval and filter density of the triple filter will be conducted.

• Journal of Institute of Control, Robotics and Systems
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• v.13 no.7
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• pp.688-693
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• 2007

The INS/GPS integration system is designed by employing an adaptive filter that can estimate the measurement noise variance using the residual of the filter. To verify the efficiency of the proposed loosely-coupled INS/GPS integration system, simulation is performed by assuming that GPS information has large position errors. Simulation results show that the proposed integration system with the adaptive filter is more effective in estimating the position and attitude errors than those with the Extended Kalman Filter.

• The Transactions of the Korean Institute of Power Electronics
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• v.26 no.5
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• pp.307-314
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• 2021

Even though the LCL filters have superior harmonic attenuation ability to L filters, stability has always been an issue. The system could be unstable because of the resonance phenomenon, especially when digital controller is used. Adding a notch filter to the compensator is one approach to solve the problem. Resonance phenomenon can be inhibited by aligning notch frequency to system resonance frequency. However, resonance frequency variation can be obtained because the actual system has a nonstationary characteristic. Therefore, the system could be unstable, where the system parameters are changed when the conventional notch filter is used. An adaptive digital notch filter that stabilizes the system even system parameters are changed. Simulation and experiment results are provided to verify the validity of the proposed adaptive filter.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.5
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• pp.892-897
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• 2007

This paper presents the output filter design and the output characteristic analysis by cut-off frequency set up of the LCR filter on NPC multi-level inverter with trap-filter. The single-phase NPC three-level inverter operates at low switching frequency. The proposed LC trap filter is comprised of a conventional LCR output filter, by using LC trap filter the need for high damping resistor and low LC cut-off frequency is eliminated. Also. low damping resistor is increased the output filter system. The multilevel inverter system used NPC type inverter in proper system for high power application and controller is used DSP(TMS320C31). The effectiveness of proposed system confirmed the validity through SPICE simulation and experimental results.