SSA-based stochastic subspace identification of structures from output-only vibration measurements

Chin-Hsiung Loh,Yi-Cheng Liu,Yi-Qing Ni 국제구조공학회 2012 Smart Structures and Systems, An International Jou Vol.10 No.4

In this study an output-only system identification technique for civil structures under ambient vibrations is carried out, mainly focused on using the Stochastic Subspace Identification (SSI) based algorithms. A newly developed signal processing technique, called Singular Spectrum Analysis (SSA), capable to smooth a noisy signal, is adopted for preprocessing the measurement data. An SSA-based SSI algorithm with the aim of finding accurate and true modal parameters is developed through stabilization diagram which is constructed by plotting the identified system poles with increasing the size of data matrix. First, comparative study between different approaches, with and without using SSA to pre-process the data, on determining the model order and selecting the true system poles is examined in this study through numerical simulation. Finally, application of the proposed system identification task to the real large scale structure: Canton Tower, a benchmark problem for structural health monitoring of high-rise slender structures, using SSA-based SSI algorithm is carried out to extract the dynamic characteristics of the tower from output-only measurements.

Vibration-based identification of rotating blades using Rodrigues’ rotation formula from a 3-D measurement

Chin-Hsiung Loh,Yu-Ting Huang,Wan-Ying Hsiung,Yuan-Sen Yang,Kenneth J. Loh 한국풍공학회 2015 Wind and Structures, An International Journal (WAS Vol.21 No.6

In this study, the geometrical setup of a turbine blade is tracked. A research-scale rotating turbine blade system is setup with a single 3-axes accelerometer mounted on one of the blades. The turbine system is rotated by a controlled motor. The tilt and rolling angles of the rotating blade under operating conditions are determined from the response measurement of the single accelerometer. Data acquisition is achieved using a prototype wireless sensing system. First, the Rodrigues' rotation formula and an optimization algorithm are used to track the blade rolling angle and pitching angles of the turbine blade system. In addition, the blade flapwise natural frequency is identified by removing the rotation-related response induced by gravity and centrifuge force. To verify the result of calculations, a covariance-driven stochastic subspace identification method (SSI-COV) is applied to the vibration measurements of the blades to determine the system natural frequencies. It is thus proven that by using a single sensor and through a series of coordinate transformations and the Rodrigues' rotation formula, the geometrical setup of the blade can be tracked and the blade flapwise vibration frequency can be determined successfully.

Application of recursive SSA as data pre-processing filter for stochastic subspace identification

Chin-Hsiung Loh,Yi-Cheng Liu 국제구조공학회 2013 Smart Structures and Systems, An International Jou Vol.11 No.1

The objective of this paper is to develop on-line system parameter estimation and damage detection technique from the response measurements through using the Recursive Covariance-Driven Stochastic Subspace identification (RSSI-COV) approach. To reduce the effect of noise on the results of identification, discussion on the pre-processing of data using recursive singular spectrum analysis (rSSA) is presented to remove the noise contaminant measurements so as to enhance the stability of data analysis. Through the application of rSSA-SSI-COV to the vibration measurement of bridge during scouring experiment, the ability of the proposed algorithm was proved to be robust to the noise perturbations and offers a very good online tracking capability. The accuracy and robustness offered by rSSA-SSI-COV provides a key to obtain the evidence of imminent bridge settlement and a very stable modal frequency tracking which makes it possible for early warning. The peak values of the identified 1st mode shape slope ratio has shown to be a good indicator for damage location, meanwhile, the drastic movements of the peak of 2nd mode slope ratio could be used as another feature to indicate imminent pier settlement.

Application of recursive SSA as data pre-processing filter for stochastic subspace identification

Loh, Chin-Hsiung,Liu, Yi-Cheng Techno-Press 2013 Smart Structures and Systems, An International Jou Vol.11 No.1

The objective of this paper is to develop on-line system parameter estimation and damage detection technique from the response measurements through using the Recursive Covariance-Driven Stochastic Subspace identification (RSSI-COV) approach. To reduce the effect of noise on the results of identification, discussion on the pre-processing of data using recursive singular spectrum analysis (rSSA) is presented to remove the noise contaminant measurements so as to enhance the stability of data analysis. Through the application of rSSA-SSI-COV to the vibration measurement of bridge during scouring experiment, the ability of the proposed algorithm was proved to be robust to the noise perturbations and offers a very good online tracking capability. The accuracy and robustness offered by rSSA-SSI-COV provides a key to obtain the evidence of imminent bridge settlement and a very stable modal frequency tracking which makes it possible for early warning. The peak values of the identified $1^{st}$ mode shape slope ratio has shown to be a good indicator for damage location, meanwhile, the drastic movements of the peak of $2^{nd}$ mode slope ratio could be used as another feature to indicate imminent pier settlement.

SSA-based stochastic subspace identification of structures from output-only vibration measurements

Loh, Chin-Hsiung,Liu, Yi-Cheng,Ni, Yi-Qing Techno-Press 2012 Smart Structures and Systems, An International Jou Vol.10 No.4

In this study an output-only system identification technique for civil structures under ambient vibrations is carried out, mainly focused on using the Stochastic Subspace Identification (SSI) based algorithms. A newly developed signal processing technique, called Singular Spectrum Analysis (SSA), capable to smooth a noisy signal, is adopted for preprocessing the measurement data. An SSA-based SSI algorithm with the aim of finding accurate and true modal parameters is developed through stabilization diagram which is constructed by plotting the identified system poles with increasing the size of data matrix. First, comparative study between different approaches, with and without using SSA to pre-process the data, on determining the model order and selecting the true system poles is examined in this study through numerical simulation. Finally, application of the proposed system identification task to the real large scale structure: Canton Tower, a benchmark problem for structural health monitoring of high-rise slender structures, using SSA-based SSI algorithm is carried out to extract the dynamic characteristics of the tower from output-only measurements.

Researches Related to Seismic Hazard Mitigation in Taiwan

Loh Chin Hsiung,Yeh Chin Hsun 한국지진공학회 1998 한국지진공학회논문집 Vol.2 No.3

In view of the rapid development of economics and technology, perilous meteorological and geological conditions often cause natural disasters and result in severe loss of lives and properties in Taiwan. To promote multi-hazard mitigation strategies in an integrated a, pp.oach, the National Science Council established a National Science and Technology Program for Disaster Mitigation in January 1998. This program emphasizes on the implementation of research results in the National Disaster Management System. This paper describes the earthquake loss estimation methodology that is currently developed in Taiwan. Topics of potential earth science hazards (PESH) and building vulnerability analysis are described in detail.

Vibration-based identification of rotating blades using Rodrigues' rotation formula from a 3-D measurement

Loh, Chin-Hsiung,Huang, Yu-Ting,Hsiung, Wan-Ying,Yang, Yuan-Sen,Loh, Kenneth J. Techno-Press 2015 Wind and Structures, An International Journal (WAS Vol.21 No.6

In this study, the geometrical setup of a turbine blade is tracked. A research-scale rotating turbine blade system is setup with a single 3-axes accelerometer mounted on one of the blades. The turbine system is rotated by a controlled motor. The tilt and rolling angles of the rotating blade under operating conditions are determined from the response measurement of the single accelerometer. Data acquisition is achieved using a prototype wireless sensing system. First, the Rodrigues' rotation formula and an optimization algorithm are used to track the blade rolling angle and pitching angles of the turbine blade system. In addition, the blade flapwise natural frequency is identified by removing the rotation-related response induced by gravity and centrifuge force. To verify the result of calculations, a covariance-driven stochastic subspace identification method (SSI-COV) is applied to the vibration measurements of the blades to determine the system natural frequencies. It is thus proven that by using a single sensor and through a series of coordinate transformations and the Rodrigues' rotation formula, the geometrical setup of the blade can be tracked and the blade flapwise vibration frequency can be determined successfully.

Clinical and Urodynamic Predictors of the Q-Tip Test in Women With Lower Urinary Tract Symptoms

Chin-Jui Wu,Wan-Hua Ting,Ho-Hsiung Lin,Sheng-Mou Hsiao 대한배뇨장애요실금학회 2020 International Neurourology Journal Vol.24 No.1

Purpose: The Q-tip test is used to measure urethral hypermobility and can predict surgical outcomes. However, certain factors may affect the reliability of this test. Our aim was to identify independent clinical and urodynamic predictors of the results of the Q-tip test. Methods: Between January 2014 and June 2019, 176 consecutive women with lower urinary tract symptoms who underwent the Q-tip test and urodynamic studies were included in this retrospective study. Results: Multivariable regression analysis revealed that age (regression coefficient, -0.55), point Ba (regression coefficient, 4.1), urodynamic stress incontinence (regression coefficient, 9.9), maximum flow rate (Qmax) (regression coefficient, 0.13), pressure transmission ratio (PTR) at maximum urethral pressure (MUP) (regression coefficient, -0.14), and the score on the fifth question of the Incontinence Impact Questionnaire (IIQQ5; “Has urine leakage affected your participation in social activities outside your home?”; regression coefficient, -4.1) were independent predictors of the Q-tip angle, with a constant of 87.0. The following Spearman rank correlation coefficients were found between the Q-tip angle and the following variables: age, -0.38; point Ba, 0.34; urodynamic stress incontinence, 0.32; Qmax, 0.28; PTR at MUP, -0.28; and IIQQ5, -0.23. A receiver operating characteristic curve (ROC) analysis for the prediction of urodynamic stress incontinence found that the optimum cutoff for PTR at MUP was <81%, with an area under the ROC curve of 0.70. Conclusions: Age, point Ba, urodynamic stress incontinence, Qmax, PTR at MUP, and IIQQ5 were independent predictors of the Q-tip angle. However, none of these could be used as effective surrogates for the Q-tip test due to their lack of a sufficient correlation.

The Mentors’Mentoring Model on Teaching Reflection and Professional Growth Process of Health and Physical Education Student Teachers

Yuh-Chih Chen,Yu-Hsiung Cheng,Keh Nyit Chin 한국스포츠교육학회 2011 한국스포츠교육학회 국제학술대회 자료집 Vol.2011 No.12

Adjuvant Trastuzumab for 6 Months is Effective in Patients with HER2-positive Stage II or III Breast Cancer

Tai, Cheng-Jeng,Pan, Chin-Kwun,Chen, Ching-Shyang,Hung, Chin-Sheng,Wu, Chih-Hsiung,Chiou, Hung-Yi Asian Pacific Journal of Cancer Prevention 2013 Asian Pacific journal of cancer prevention Vol.14 No.3

Objective: The optimal duration of adjuvant trastuzumab treatment in patients with HER2-positive breast cancer is not known. The aim of this study was to evaluate the efficacy of 6 months of adjuvant trastuzumab treatment in patients with stage II or III HER2-positive breast cancer. Methods: The records of patients with HER2-positive stage II or III breast cancer who were admitted to the Breast Center of Taipei Medical University Hospital and Yuan's General Hospital between 2000 and 2008 were reviewed. All patients received adjuvant trastuzumab at an initial dose of 4 mg/kg followed by a maintenance dose of 2 mg/kg/week for 22 weeks in combination with chemotherapy. Results: A total of 51 patients were included with a mean age of 46.9 years. Approximately 55% of the patients had stage III disease. The mean follow-up time from initiation of treatment was 45.2 months (range, 0.9 to 85 months). During follow-up, 46 patients (90.2%) did not experience tumor recurrence. The mean estimated disease free survival was 80.2 months. The estimated 1-, 2-, 5-, and 7-year survival rates were 97.9%, 93.1%, 93.1%, and 93.1%, respectively. The most common adverse effects were gastrointestinal symptoms (21.6%), chills (17.6%), dizziness (9.8%), and bone pain (7.8%). No cardiac or hematologic adverse events occurred. Conclusion: Adjuvant therapy with trastuzumab for 6 months resulted in a clinical benefit in patients with HER2-positive breast cancer.