Drehmomentregelung eines hochdrehenden Switched Reluctance Starter-Generators (SR S/G) für die Anwendung in Flugzeugen

Die vorliegende Dissertation behandelt die Drehmomentregelung eines hochdrehenden Switched Reluctance Starter-Generators (SR S/G) für die Anwendung in Flugzeugen. Das Starter-Generatorsystem ist für ein konstantes Drehmoment von 15 Nm bis zur Drehzahl von 27.000 min -1 im Starterbetrieb und für eine konstante Leistung von 30 kW bis zur Drehzahl von 50.000 min -1 im Generatorbetrieb sowie eine Bordnetzspannung von 270 V spezifiziert. Im ersten Kapitel wird ein Überblick über die Literatur gegeben Darauf folgt eine Motivation aufgrund offener Forschungsfragen, die insbesondere eine optimierte Regelung unter Berücksichtigung der nichtlinearen magnetischen Eigenschaften von SRM betreffen. Im zweiten Kapitel wird ein 2D-FEA Modell vorgestellt, mit dem die Flussverkettung und das innere Drehmoment der SRM berechnet werden können. Diese Simulationen werden durch experimentelle Ergebnisse unter Berücksichtigung der Ummagnetisierungsverluste ergänzt. In Kapitel 3 werden Methoden zur Bestimmung der Ummagnetisierungsverluste und zur thermischen Analyse der SRM vorgestellt. Erstere ergeben sich durch Simulation auf Basis der Flussdichten in Stator und Rotor. Im nächsten Teil wird ein thermische Analyse auf Basis von Näherungsformeln und CFD-Simulation durchgeführt. Kapitel 4 behandelt eine Regelungsstrategie zur Maximierung des Drehmoments. Die rechnerisch optimierten Schaltwinkel werden in einer Look-Up-Tabelle für im experimentellen Aufbau gespeichert. Die Evaluation erfolgt auf Basis eines speziell für hochdrehende Antriebe geeigneten Drehmomentmessverfahrens, welches auf Beschleunigungsmessungen basiert. Die Leistung im Generatorbetrieb ergibt sich analog durch einen Abbremsversuch. Kapitel 5 fasst nochmals die wesentlichen Ergebnisse der Arbeit zusammen.The maximum torque control has an important role in improving the torque performances of a high speed Switched Reluctance Starter/Generator (SR S/G) drive system. Especially for high speed switched reluctance drives, optimal torque control is a big challenge due to the non-linear magnetization characteristics of the flux and electromagnetic torque with the current and rotor position. To realize the maximum torque control strategy, some improved measurement techniques were used to characterize performance and optimized control parameters were applied to maximize the starting torque by an experimental setup. Many electronics and mechanical design ideas have been implemented to set up the test bench. The SR S/G performances have been obtained in starting and generating modes within a wide speed range of up to 47,000 rpm. High speed machines engineering spans multiple different high technologies. Some problems have occurred due to mechanical and electromagnetic structures, rotor bearings, power electronics and control methods, which will be treated in the appropriate chapters. The main contributions of this thesis are pointed out as follows: 1. The flux linkage and electromagnetic torque characteristics have been calculated by a FEA simulation method. The results have been validated by experiments with adequate measurement techniques which can remove iron loss current to improve the accuracy of the measurement method. 2. The iron losses calculation method for the high speed and flux density of the SRMs have been investigated by simulation and experiment. Based on the iron loss density of the SRM rotor and stator parts, the iron losses of the different components can be determined in both simulation and experimental models. Afterward, a thermal model of the SRM stator directly cooled the forced water system has been developed and verified experimentally. 3. The maximization of the average torque has been implemented by optimizing the turn-on and turn-off angles, torque and current controllers. The torque performance was validated by an indirect torque measurement based on the acceleration method. The torque performance was proven by the acceleration test and the results meet the requirements of the SR S/G performance. 4. The electric power of the switched reluctance generator has been measured by the deceleration test. The optimal turn-on and turn-off angles vs current and speed have been investigated to maximize the output power experimentally. 5. The acoustic noise frequency spectrum and the sound level have been measured at different speeds. The experimental results have been compared with the natural frequency of the SRM stator. Critical speeds have been identified by analyzing the resonant frequencies of the SRM

Vai trò của nhóm nghiên cứu đối với việc công bố quốc tế trong lĩnh vực khoa học tự nhiên và kỹ thuật

Công bố khoa học được xem là một trong những thước đo trình độ phát triển khoa học công nghệ và sức cạnh tranh của mỗi một quốc gia do đó nó luôn là chủ đề gây chú ý đối với toàn xã hội trong những năm gần đây. Nâng cao số lượng và chất lượng nghiên cứu khoa học, công bố quốc tế được xem là một trong những yếu tố quan trọng quyết định đến sự hình thành và phát triển của các nhóm nghiên cứu cũng như quyết định cho sự thành công của các hoạt động khoa học công nghệ của bất kỳ cơ quan tổ chức nghiên cứu, giáo dục nào. Nghiên cứu này được thực hiện nhằm đánh giá vai trò của các nhóm nghiên cứu đối với việc công bố quốc tế riêng trong lĩnh vực khoa học tự nhiên và kỹ thuật

The Finite Element Method Applied to the Magnetostatic and Magnetodynamic Problems

Modelling of realistic electromagnetic problems is presented by partial differential equations (FDEs) that link the magnetic and electric fields and their sources. Thus, the direct application of the analytic method to realistic electromagnetic problems is challenging, especially when modeling structures with complex geometry and/or magnetic parts. In order to overcome this drawback, there are a lot of numerical techniques available (e.g. the finite element method or the finite difference method) for the resolution of these PDEs. Amongst these methods, the finite element method has become the most common technique for magnetostatic and magnetodynamic problems

Neural network based patient recovery estimation of a PAM-based rehabilitation robot

Rehabilitation robots have shown a promise in aiding patient recovery by supporting them in repetitive, systematic training sessions. A critical factor in the success of such training is the patient’s recovery progress, which can guide suitable treatment plans and reduce recovery time. In this study, a neural network-based approach is proposed to estimate the patient’s recovery, which can aid in the development of an assist-as-needed training strategy for the gait training system. Experimental results show that the proposed method can accurately estimate the external torques generated by the patient to determine their recovery. The estimated patient recovery is used for an impedance control of a 2-DOF robotic orthosis powered by pneumatic artificial muscles, which improves the robot joint compliance coefficients and makes the patient more comfortable and confident during rehabilitation exercises

Optimal control and real-time simulation of hybrid marine power plants

With significantly increasing concerns about greenhouse effects and sustainable economy, the marine industry presents great potential for reducing its environmental impact. Recent developments in power electronics and hybridisation technologies create new opportunities for innovative marine power plants which utilize both traditional diesel generators and energy storage like batteries and/or supercapacitors as the power sources. However, power management of such complex systems in order to achieve the best efficiency becomes one of the major challenges. Acknowledging this importance, this research aims to develop an optimal control strategy (OCS) for hybrid marine power plants. First, architecture of the researched marine power plant is briefly discussed and a simple plant model is presented. The generator can be used to charge the batteries when the ship works with low power demands. Conversely, this battery energy can be used as an additional power source to drive the propulsion or assist the generators when necessary. In addition, energy losses through braking can be recuperated and stored in the battery for later use. Second, the OCS is developed based on equivalent fuel consumption minimisation (EFCM) approach to manage efficiently the power flow between the power sources. This helps the generators to work at the optimal operating conditions, conserving fuel and lowering emissions. In principle, the EFCM is based on the simple concept that discharging the battery at present is equivalent to a fuel burn in the future and vice-versa and, is suitable for real-time implementation. However, instantaneously regulating the power sources’ demands could affect the system stability as well as the lifetime of the components. To overcome this drawback and to achieve smooth energy management, the OCS is designed with a number of penalty factors by considering carefully the system states, such as generators’ fuel consumption and dynamics (stop/start and cranking behaviour), battery state of charge and power demands. Moreover, adaptive energy conversion factors are designed using artificial intelligence and integrated in the OCS design to improve the management performance. The system therefore is capable of operating in the highest fuel economy zone and without sacrificing the overall performance. Furthermore, a real-time simulation platform has been developed for the future investigation of the control logic. The effectiveness of the proposed OCS is then verified through numerical simulations with a number of test cases

Optimal Design of V-Shaped Fin Heat Sink for Active Antenna Unit of 5G Base Station

The active antenna unit (AAU) is one of the main parts of the 5G base station, which has a large size and a high density of chipsets, and operates at a significantly high temperature. This systematic study presents an optimal design for the heat sink of an AAU with a V-shaped fin arrangement. First, a simulation of the heat dissipation was conducted on two designs of the heat sink – in-line and V-shaped fins – which was validated by experimental results. The result shows that the heat sink with V-shaped fins performed better compared to conventional models such as heat sinks with in-line fins. Secondly, computational fluid dynamics (CFD) and the Lagrange interpolation method were applied to find out an optimal set of design parameters for the heat sink. It is worth noting that the optimal parameters of the orientation angle and fin spacing considerably affected the heat sink’s performance.  

Optimal Design of V-Shaped Fin Heat Sink for Active Antenna Unit of 5G Base Station

The active antenna unit (AAU) is one of the main parts of the 5G base station, which has a large size and a high density of chipsets, and operates at a significantly high temperature. This systematic study presents an optimal design for the heat sink of an AAU with a V-shaped fin arrangement. First, a simulation of the heat dissipation was conducted on two designs of the heat sink – in-line and V-shaped fins – which was validated by experimental results. The result shows that the heat sink with V-shaped fins performed better compared to conventional models such as heat sinks with in-line fins. Secondly, computational fluid dynamics (CFD) and the Lagrange interpolation method were applied to find out an optimal set of design parameters for the heat sink. It is worth noting that the optimal parameters of the orientation angle and fin spacing considerably affected the heat sink’s performance.  

A Vietnamese Handwritten Text Recognition Pipeline for Tetanus Medical Records

Machine learning techniques are successful for optical character recognition tasks, especially in recognizing handwriting. However, recognizing Vietnamese handwriting is challenging with the presence of extra six distinctive tonal symbols and vowels. Such a challenge is amplified given the handwriting of health workers in an emergency care setting, where staff is under constant pressure to record the well-being of patients. In this study, we aim to digitize the handwriting of Vietnamese health workers. We develop a complete handwritten text recognition pipeline that receives scanned documents, detects, and enhances the handwriting text areas of interest, transcribes the images into computer text, and finally auto-corrects invalid words and terms to achieve high accuracy. From experiments with medical documents written by 30 doctors and nurses from the Tetanus Emergency Care unit at the Hospital for Tropical Diseases, we obtain promising results of 2% and 12% for Character Error Rate and Word Error Rate, respectively

On the solutions of universal differential equation by noncommutative Picard-Vessiot theory

Basing on Picard-Vessiot theory of noncommutative differential equations and algebraic combinatorics on noncommutative formal series with holomorphic coefficients, various recursive constructions of sequences of grouplike series converging to solutions of universal differential equation are proposed. Basing on monoidal factorizations, these constructions intensively use diagonal series and various pairs of bases in duality, in concatenation-shuffle bialgebra and in a Loday's generalized bialgebra. As applications, the unique solution, satisfying asymptotic conditions, of Knizhnik-Zamolodchikov equations is provided by d\'evissage

Families of eulerian functions involved in regularization of divergent polyzetas

Extending the Eulerian functions, we study their relationship with zeta function of several variables. In particular, starting with Weierstrass factorization theorem (and Newton-Girard identity) for the complex Gamma function, we are interested in the ratios of $\zeta(2k)/\pi^{2k}$ and their multiindexed generalization, we will obtain an analogue situation and draw some consequences about a structure of the algebra of polyzetas values, by means of some combinatorics of noncommutative rational series. The same combinatorial frameworks also allow to study the independence of a family of eulerian functions.Comment: preprin