臺灣博碩士論文加值系統

本研究主要發展出一種新型系統鑑別方法以獲知結構系統參數，應用範圍可從結構系統設計階段時作為鑑別系統參數之校準及驗證外，亦可用於評估系統結構之耐用性及安全性之損耗監測，此方法更進一步廣泛應用於無損檢測（NDT）。
首先本研究利用能量損耗的觀念發展出穩態響應調變之傅立葉係數(Fourier Coefficient Ratio method, FCR)法做結構阻尼比量測，並實驗用於直昇機旋翼葉片之結構阻尼比參數鑑別，再以現有傳統理論之對數衰減法(Logarithmic decrement)與半能量點法(Half power point method)的量測方法相互驗證比較，以驗證FCR法的準確性。同時以FCR法的能量損耗觀念為基礎，對旋翼葉片結構的損壞進行量測以獲得旋翼葉片結構損壞之指標與趨勢。
最後本研究進一步發展多自由系統鑑別方法，同樣使用新近發展的穩態響應調變法將偶合系統利用模態對角化關係得到非耦合系統矩陣。接著求取該調變後訊號之傅立葉係數，研製出一種新的系統辨識方法，應用於鑑別AFM（Atomic Force Microscope）探針系統參數驗證。藉由本研究之鑑別系統方法，無論應用在單自由度或多自由度之系統上，皆可精準鑑別出系統之參數值，此外實驗證明當環境阻尼改變亦可準確的鑑別出系統參數。

The main objective of the report is to present a new identification method has been derived for Two-Degree of Freedom (TDOF) base excited systems. Firstly has developed a common and simple procedure to measure the structure damping of rotor blades. The latest developed Fourier Coefficient Ratio method (FCR) is applied to proceed on our measurement of rotor blades structure damping. In this study, we not only apply the method of FCR to identify the damping ratio of rotor blade but also introduce two traditional methods, “Logarithmic decrement” and “Half power point method” to ensure that damping ratio measured by FCR is relatively correct. In the meantime, based on the FCR method to predict the potential damage of the blade can be predicted so that the vehicle design and safety are assured. The proposed procedure can also be applied to other airplane critical components, such as the frame structure, turbine blade, etc.
Although there are many studies in the area of system parameter identification, unfortunately none of them can be applied to calibrate the probes of atomic force microscopes (AFM). The author has derived a Single-Degree of Freedom (SDOF) identification method that had been proven reliable. However, the original patented SDOF method is found not accurate enough in some cases when applying to an AFM. The main objective of the study is to generalize the one for SDOF systems to multi-DOF ones. Before doing that, the present report focused at structural systems that have TDOF.
Unlike the currently using method, the present method can be applied in situ or when the AFM probe is well installed inside the probe clip. In order to improve the precision of the method, a TDOF model is adopted for observing the dynamic responses. Meanwhile, the TDOF system is decomposed into two SDOF in the principal coordinates by using their mode shapes. It is well-known that by means of mode superposition, one is able to superimpose the responses of the two modal responses into the system ones. Thus, the present identification method starts with giving a wide band excitation and acquires the responses that were used to lock the damped natural frequency. From which, the excitation frequency is thus changed to find the location where the phase lag is 90ﾟ. As a result, one is able to compute the system dissipative energy under that condition. Once the energy is obtained, the system damping is readily found and followed by the other system parameters.
The present identification method is numerically substantiated by using the Simulink toolbox of MATLAB. The numerical results clearly showed the good consistency with very small error. However, one also found that the system quality factor tended to enlarge identification errors when systems under slightly larger damping. Nevertheless, the new method is demonstrated its capability to identify structural parameters for TDOF systems with viscous damping. In addition to the numerical verification, the method is also experimentally validated. The procedures were followed exactly as those wound be done for an AFM, except the model is a cantilever beam instead of an AFM probe. The system parameters could be successfully identified even under different damping which were mimicked by air, water as well as #40 lubricant. The experimental results further showed the validity of the present identification method.

Table of Contents
ABSTRACT I
ACKNOWLEGEMENTS III
Table of Contents IV
List of Figures VI
List of Table VIII
Chapter 1 1
Introduction 1
1.1 Background 1
1.2 Literature Review 2
1.2.1 Detection of Structural Damage 3
1.2.2 Parameter Identification of Structural Systems 4
1.2.3 Research motivation and purpose 6
1.3 Research Methods and procedures 7
Chapter 2 10
Derivation of the method 10
2.1 Parameter Identification method of dissipative energy system 10
2.2 Identification of Two-DOF systems 15
2.3 Introduction damping material 17
Chapter 3 19
Application of damping measurement and damage indicators 19
3.1 Helicopter Rotor Blade Research 19
3.2 Applications of AFM Probe Parameter 22
Chapter 4 24
Experimental Design 24
4.1 Rotor Blade Test Equipment 24
4.2 AFM probe test equipment and Planning 26
4.2.1 Numerical simulations 27
4.2.2 Laboratory equipment 29
Chapter 5 36
EXPERIMENTS AND MEASUREMENTS 36
5.2 Structural Damping Rotor Blade Measurement and Damage Indicators 36
5.1.1 Half-point method 37
5.1.2 Logarithmic Decrement Method 38
5.1.3 FCR Method 38
5.1.4 Damping ratio of Experimental Discussion 39
5.1.5 Discussion of the Rotor Blade Damage Indicators 39
5.2 Parameter Identification of AFM Probes 41
5.2.1 Numerical Simulations Result 41
5.2.1.1 Simulation of Linearism System 41
5.2.1.2 Identification of the dissipative energy of two degrees of freedom system 44
5.2.1.3 Identification of the parameter of two degrees of freedom 47
5.2.2 CAE Simulation 54
5.2.3 Experimental Static Deformation 55
5.2.4 Energy Dissipative and Identification the Parameters of System 57
Chapter 6 62
CONSLUSIONS AND SUGGESTIONS 62
Reference 65

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