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RISS 인기검색어
- 검색키워드
- 저자 : Nariman Sepehri (검색결과 2 건)
- 무료
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- 유료
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Root cause detection of leakage in check valves using multi-scale signal analysis
Chengbiao Tong,Nariman Sepehri,Jiang Zhou 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.1
Check valves are key components required to ensure that fluid flows in one direction. Internal cross-port leakage is a common fault that affects the service performance of check valves. Cross-port leakage occurs due to defects in the valve spool. Early detection of this fault and its root cause is important to prevent downtime and subsequent costs. This research presents a multi-scale signal enhancement method based on spool impact and pressure signal analysis for leakage identification and its root causes. The impact signals obtained by accelerometers attached to the valve body are segmented from the entire vibration signal to capture the variations in the inherent characteristics of the valve. Subsequently, wavelet packet decomposition and reconstruction are performed to extract the energy distribution and energy entropy of signals. The time-frequency domain is used to extract features for leakage identification faults. Correlation analysis was applied to select 45 sensitive features out of 105 features. The performance of the method was verified using the RCYCS-G experimental hydraulic platform, and the recognition rate of four modes was found to be 100 % accurate. The proposed method accurately identifies the root causes of leakage in the check valve, lays a foundation for leakage rate prediction, and has significant engineering application value in predictive maintenance.
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Active Disturbance Rejection Control Applied to High-order Systems with Parametric Uncertainties
Zhengrong Chu,Christine Wu,Nariman Sepehri 제어·로봇·시스템학회 2019 International Journal of Control, Automation, and Vol.17 No.6
Active disturbance rejection control (ADRC) is an emerging control technique known for its simplicity and good disturbance rejection ability. It has been applied to first- and second-order systems in many areas. However, the application of the ADRC to high-order systems is few and also challenging because the existing bandwidth tuning method is unable to determine proper controller parameters to achieve desired system performance. To address this problem, a new method is proposed to tune the ADRC for controlling high-order systems. First, the ADRC is decomposed into a controller and a prefilter in the frequency domain. Second, they are tuned to satisfy prescribed performance specifications. Two applications of the ADRC to high-order hydraulic systems are presented. It is shown that the proposed method greatly improves the performance of the ADRC compared to the bandwidth tuning method.
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