要約のみTohoku University槙原幹十朗課

Hara Yushin

Tohoku University博士（工学）博士学位論文 (Thesis(doctor))要約のみthesi

Hara, Yushin

Tohoku University Repository (TOUR) / 東北大学機関リポジトリ

Energy-Saving Structural Identification UsingSemi-Active Control Method著者 Hara Yushin学位授与機関 Tohoku UniversityURL http://hdl.handle.net/10097/00137558  氏       名 研究科，選考の名称 学 位 論 文 題 目   論 文 審 査 委 員  はら ゆうしん  原 勇 心  東北大学大学院工学研究科（博士課程） 航空宇宙工学 専攻  Energy-Saving Structural Identification Using Semi-Active Control Method（セミアクティブ制御手法を用いた省エネルギ構造同定に関する研究）  主査 東北大学教授 槙原 幹十朗 東北大学教授 吉田 和哉     東北大学教授 岡部 朋永  東北大学教授 内一 哲哉 論文内容要約  Next-generation spacecraft will become larger in size and more flexible than present spacecraft. Structural vibration on these spacecraft occurs easily due to their flexibility. To suppress this vibration, a model-based vibration suppression method is required. This method requires an exact structural model of spacecraft to achieve effective vibration suppression. Identification of a structural model is necessary. Furthermore, spacecraft will be more likely to be damaged because of their long operational time. Structural health monitoring through the detection of the parameter change in a structural model of these spacecraft is also necessary. The structural identification of spacecraft under microgravity conditions is referred to as on-orbit identification. Implementation of on-orbit identification has considerable technical constraints compared with on-ground identification. Conventional on-orbit identification mainly used a thruster as an actuator to excite the structural vibration on the spacecraft. However, the thruster consumed fuels that were never replenished in space. The vibration sensors are embedded in the space structure to measure the structural vibration. However, the sensors led to weight gain and the design complexity of the spacecraft. The reduction in energy consumption and the elimination of sensors are two problems of conventional on-orbit identification. On-orbit identification will become more accessible if these two problems related to actuators, energy sources, and sensors are resolved. In this dissertation, a semi-active control method using piezoelectric transducers is adopted to solve the two problems of conventional on-orbit identification. The semi-active control method generates input to excite a structure using quite a small amount of energy. Therefore, the first problem related to an actuator and an energy source is solved. The piezoelectric transducer realizes a self-sensing method. In this method, a single transducer acts in two roles as an actuator and a sensor simultaneously. Therefore, the second problem related to a sensor is solved. To realize the semi-active and self-sensing identification method, this dissertation has three objectives. The first objective is to confirm the feasibility of a structural identification method using a semi-active input. The control of a semi-active input generation circuit follows a control strategy. The first strategy is based on the notion that if the semi-active input imitates a conventionally used input in identification, the identification performance can be the same as the conventional one. However, the semi-active input cannot completely imitate the conventional input due to its generation mechanism. Consequently, a portion of the time domains of the semi-active input is unsuitable for identification. The data calibration method is required to achieve adequate system identification. The second objective is to establish a semi-active identification method that takes into account the semi-active generation mechanism. A process is required to directly optimize the semi-active input to make them suitable for identification. The optimization should consider the semi-active input generation mechanism and should not provide infeasible control instructions. A constraint based on the semi-active input generation mechanism is necessary. Optimization is based on the above constraint and indicators that quantitatively evaluates whether the semi-active inputs are suitable for identification. The third objective is to propose a sensor-less structural identification method to remove vibration sensor devices from semi-active identification. A piezoelectric transducer that generates the semi-active input also generates voltage. This voltage contains both input and output information. If this two-information is separated from the measured voltage, the sensor-less identification will be applicable. However, mathematical model-based separation cannot be used in the identification scenario. The separation method without a mathematical model is necessary. This dissertation is organized as follows: In chapter 1, the introduction of this work including theoretical backgrounds of identification and semi-active control was presented as well as past case studies of on-orbit identification and structural identification. In chapter 2, the problem statement and an outline of a state space subspace identification were presented. Mathematical models of a piezoelectric transducer, an identification target structure, and a semi-active input generation were derived. A semi-active input generation mechanism was also presented. In chapter 3, a novel semi-active control strategy was proposed to generate semi-active inputs suitable for identification. This strategy provided appropriate control instants such that the polarity of the semi-active input would be coincident with a polarity of a maximum-length sequence. The semi-active input generation circuit was sometimes unable to imitate the polarity of the semi-active input due to the generation mechanism. A calibration method to extract adequate time domains of the semi-active input was proposed. The outcomes of the numerical analysis and validation experiments showed that the semi-active method was workable. The semi-active method was proven to perform appropriate system identification. We also verified that the proposed semi-active approach requires 98% less energy to excite the output signal than the active method requires. In chapter 4, another control strategy providing a smaller identification error and variation than the conventional strategy is proposed. This novel strategy prevented the malfunctions of the semi-active input generation circuit during the input generation. This malfunction was referred to as a switching failure. The novel strategy generated an optimal reference input suitable for identification within the feasible range of the input generation circuit. The simulation and experiments proved that the proposed strategy provided a small error and variation in the structural identification results. Compared to the strategy discussed in chapter 3, the proposed strategy provided accurate identification results even in noisy experimental environments. This feature of the proposed strategy offered the possibility of applying the semi-active identification method to structural health monitoring. In chapter 5, a self-sensing method to identify the structural models without vibration sensors was proposed. The voltage of the piezoelectric transducer was a linear summation of the semi-active input and the structural vibration. The proposed self-sensing method used the prior information that the dynamics of the semi-active input generation. The self-sensing method was validated through numerical simulation and experiment. The accurate estimations of both input/outputs were achieved by the proposed method. In chapter 6, the main points of this dissertation were summarized as a conclusion. The proposed strategies and method will be able to assist designers and users in introducing not only on-orbit identification but also energy-saving on-ground infrastructure identification. 

Energy-Saving Structural Identification Using Semi-Active Control Method

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セミアクティブ制御手法を用いた省エネルギ構造同定に関する研究

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