Dynamic modeling and simulation of an integral bipropellant propulsion double-valve combined test system

This work was financially supported by the National Natural Science Foundation of China (No. 11101023) and the China Scholarship Council (No. 201203070237)

Development of adaptive transducer based on biological sensory mechanism

textAn adaptive sensor concept and prototype has been developed based on a sensing element which is analogous to and inspired by the arrangement of outer hair cells and inner hair cells between the basilar membrane and tectorial membrane which form the organ of corti in mammalian cochlea. The bio-inspired design was supported by development of a bond graph model of the electromotility (active response) of outer hair cells. Outer hair cells perform like actuators and simulation results using this model are compared with physiological data found in the literature to verify its characteristic response. Insight gained from the model is used to develop a sensor structure analogous to the organ of corti and designed to measure acceleration. A piezoelectric bimorph was selected as the transducer basis, and a bond graph model of the bimorph in an accelerometer configuration was formulated to aid control design and simulation. There is no published data regarding the type of information transmitted among the inner hair cells, outer hair cells, and brain. Consequently, a controller intended to adjust the adaptation process similar to what might exist in the cochlear system has been developed for the sensor and based on a model referenced adaptive control algorithm. Simulations verify that the algorithm can successfully control and enhance performance of the sensor. Practicability of the design is evaluated by a series of experiments on a prototype. This study focused on using a controller structure that was programmed, implemented, and tested using programmable logic based on FPGA technology. The experiments evaluated how well the adaptive sensor could meet a specified performance requirement. Implementation issues that arise, such as the need for differentiators in the adaptive controller or internal propagation of vibration within the sensor structure, hinder the tuning ability. Nevertheless, the trends indicate that the algorithm can meet the desired performance if certain limitations can be overcome. Finally, recommendations have been made for expansion of the research in such fields as an alternative structure for tuning, sensor networking, and reference sensor configuration.Mechanical Engineerin

Failure Diagnosis and Prognosis of Safety Critical Systems: Applications in Aerospace Industries

Many safety-critical systems such as aircraft, space crafts, and large power plants are required to operate in a reliable and efficient working condition without any performance degradation. As a result, fault diagnosis and prognosis (FDP) is a research topic of great interest in these systems. FDP systems attempt to use historical and current data of a system, which are collected from various measurements to detect faults, diagnose the types of possible failures, predict and manage failures in advance. This thesis deals with FDP of safety-critical systems. For this purpose, two critical systems including a multifunctional spoiler (MFS) and hydro-control value system are considered, and some challenging issues from the FDP are investigated. This research work consists of three general directions, i.e., monitoring, failure diagnosis, and prognosis. The proposed FDP methods are based on data-driven and model-based approaches. The main aim of the data-driven methods is to utilize measurement data from the system and forecast the remaining useful life (RUL) of the faulty components accurately and efficiently. In this regard, two dierent methods are developed. A modular FDP method based on a divide and conquer strategy is presented for the MFS system. The modular structure contains three components:1) fault diagnosis unit, 2) failure parameter estimation unit and 3) RUL unit. The fault diagnosis unit identifies types of faults based on an integration of neural network (NN) method and discrete wavelet transform (DWT) technique. Failure parameter estimation unit observes the failure parameter via a distributed neural network. Afterward, the RUL of the system is predicted by an adaptive Bayesian method. In another work, an innovative data-driven FDP method is developed for hydro-control valve systems. The idea is to use redundancy in multi-sensor data information and enhance the performance of the FDP system. Therefore, a combination of a feature selection method and support vector machine (SVM) method is applied to select proper sensors for monitoring of the hydro-valve system and isolate types of fault. Then, adaptive neuro-fuzzy inference systems (ANFIS) method is used to estimate the failure path. Similarly, an online Bayesian algorithm is implemented for forecasting RUL. Model-based methods employ high-delity physics-based model of a system for prognosis task. In this thesis, a novel model-based approach based on an integrated extended Kalman lter (EKF) and Bayesian method is introduced for the MFS system. To monitor the MFS system, a residual estimation method using EKF is performed to capture the progress of the failure. Later, a transformation is utilized to obtain a new measure to estimate the degradation path (DP). Moreover, the recursive Bayesian algorithm is invoked to predict the RUL. Finally, relative accuracy (RA) measure is utilized to assess the performance of the proposed methods

Smart Hydraulic Controller

Neste projecto é apresentado uma modelação de um aquecedor de água a gás com sistema bypass. Na modelação, é feita com base na realidade, para o modelo ser mais perfeito possível, tendo em conta também a hidráulica, perdas de carga nas tubagens, e o controlo da válvula bypass através do caudal de entrada, pressão e temperatura

A preliminary study on passive and active flutter suppression concepts for aeronautical components

The scope of this work is to study computationally both passive and active flutter suppression characteristics of a cantilever cork agglomerate core sandwich with CFRP facings and an aluminum plate, the latter through the application of piezoelectric patches, respectively. Recently, cork agglomerates have been gaining an increasing interest from the aerospace industry due to their good thermal and acoustic insulation capabilities. In addition, cork based materials intrinsically have excellent vibration suppression properties, which suggest that the combination of cork with high performance composites (such as CFRPs) may lead to high specific strength materials with improved damping characteristics suitable for flutter prevention. Sandwich specimens were modeled using commercially available software ANSYS® and a demo version of ZAERO® software for the determination of the flutter speed and related frequencies. ANSYS® piezoelectric modeling and transient analysis capabilities were used for the active vibration study. Specimen aspect ratio and thickness were chosen as a function of wind tunnel maximum speed for further experimental tests. Results were compared with conventional CFRP and aluminum plates. It was demonstrated that a cork agglomerate core sandwich with CFRP facings can act as a natural flutter suppresser which allows the reduction of the wing weight for a given flight envelope and that the application of piezoelectric actuators is a valuable aeroelastic control concept. An increase of about 20% in flutter speed was achieved using actuated piezoelectric devices. The main goal remains in investigating higher strain smart materials and control strategies, since these improvements are only possible in small structures.O objectivo deste trabalho é o estudo computacional de soluções de supressão de flutter, passiva e activa, através de uma sandwich com núcleo de aglomerado de cortiça e faces de carbonoepoxy e de uma placa de alumínio, esta última através de actuadores piezoeléctricos, respectivamente. Recentemente, os aglomerados de cortiça têm ganho um interesse crescente por parte da indústria aeronáutica devido às suas propriedades de isolamento térmico e acústico. Além disso, os materiais à base de cortiça têm intrinsecamente excelentes propriedades antivibráticas, o que sugere que a sua combinação com materiais de alto desempenho (como o carbono-epoxy) pode levar a materiais de resistência específica elevada e com características de amortecimento melhoradas, adequados à prevenção do flutter. A sandwich foi modelada usando o software de elementos finitos ANSYS® e uma versão de demonstração do ZAERO® para a determinação da velocidade de flutter e respectiva frequência. Por sua vez, as capacidades de modelação piezoeléctrica e transiente do ANSYS® foram usadas para o estudo do controlo de vibração activa. A razão de aspecto das placas foi escolhida em função da velocidade máxima do túnel de vento, para posteriores testes experimentais. Os resultados foram comparados com placas de alumínio e carbono-epoxy convencionais. Foi demonstrado que a sandwich com núcleo de aglomerado de cortiça pode actuar como um supressor natural de flutter que permite uma redução do peso da estrutura para um dado envelope de voo. No que concerne ao controlo activo, a aplicação de actuadores piezoeléctricos é um conceito de controlo aeroelástico valioso que permitiu, neste estudo, um aumento de 20% na velocidade de flutter. No entanto, o principal objectivo permanece em investigar estratégias de controlo e materiais de características piezoeléctricas com capacidade de induzir maiores extensões a custo de uma menor potência

Advanced Control and Estimation Concepts, and New Hardware Topologies for Future Mobility

According to the National Research Council, the use of embedded systems throughout society could well overtake previous milestones in the information revolution. Mechatronics is the synergistic combination of electronic, mechanical engineering, controls, software and systems engineering in the design of processes and products. Mechatronic systems put “intelligence” into physical systems. Embedded sensors/actuators/processors are integral parts of mechatronic systems. The implementation of mechatronic systems is consistently on the rise. However, manufacturers are working hard to reduce the implementation cost of these systems while trying avoid compromising product quality. One way of addressing these conflicting objectives is through new automatic control methods, virtual sensing/estimation, and new innovative hardware topologies