Road and rail vehicles and aircraft rely mainly or solely on friction brakes. These brakes pose several problems, especially in hybrid vehicles: significant wear, fading, complex and slow actuation, lack of fail-safe features, increased fuel consumption due to power assistance, and requirement for anti-lock controls. To solve these problems, a contactless magnetic brake has been developed. This concept includes a novel flux-shunting structure to control the excitation flux generated by permanent magnets. This brake is wear-free, less-sensitive to temperature than friction brakes, has fast and simple actuation, and has a reduced sensitivity to wheel-lock. The present dissertation includes an introduction to friction braking, a theory of eddy-current braking, analytical and numerical models of the eddy-current brake, its excitation and power generation, record of experimental validation, investigation and simulation of the integration of the brake in conventional and hybrid vehicles.

Road and rail vehicles and aircraft rely mainly or solely on friction brakes. These brakes pose several problems, especially in hybrid vehicles: significant wear, fading, complex and slow actuation, lack of fail-safe features, increased fuel consumption due to power assistance, and requirement for anti-lock controls. To solve these problems, a contactless magnetic brake has been developed. This concept includes a novel flux-shunting structure to control the excitation flux generated by permanent magnets. This brake is wear-free, less-sensitive to temperature than friction brakes, has fast and simple actuation, and has a reduced sensitivity to wheel-lock. The present dissertation includes an introduction to friction braking, a theory of eddy-current braking, analytical and numerical models of the eddy-current brake, its excitation and power generation, record of experimental validation, investigation and simulation of the integration of the brake in conventional and hybrid vehicles.

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Práce se zabývá problematikou měření momentu u velmi vysokootáčkových strojů. Z důvodů vysokých rychlostí jsou tradiční metody měření momentu nepoužitelné, z tohoto důvodu je nutno vyvinout novou bezkontaktní metodu. Pro měření je zvolena metoda zatěžování vířivou brzdou, pro kterou je proveden analytický výpočet jejích vlastností pomocí Maxwellových rovnic a je vytvořen model vířivé brzdy v programu FEMM a Ansys/Maxwell 2D. Na závěr jsou výsledky simulací a výpočtů porovnány s měřením na prototypech brzdy.

A novel electromechanical brake (EMB) based on the eddy current principle is proposed for application in electrical vehicles. The proposed solution is a feasible replacement for the current conventional hydraulic brake (CHB) systems. Unlike CHBs eddy current brakes (ECBs) use eddy currents and their interaction with an externally applied magnetic field to generate braking torque. Due to their pure electrically controllable and contact free nature, ECBs have multiple advantages over the current CHB systems, such as faster response, reduced weight and number of components, ease of implementing various controllers (e.g., anti-lock braking), and reduced noise levels. However, the torque generated by a typical ECB at low speeds is insufficient to effectively and completely stop a moving vehicle. Therefore, an ECB is commonly used as an assistive brake to the CHB system in heavy vehicles, i.e. trains and trucks In order to overcome this shortcoming, the use of AC magnetic fields is proposed to realize a stand-alone ECB system in which sufficient braking torque can be generated at low speeds. To this end, eddy currents are modeled analytically using the governing Maxwell’s equations with the consideration of time varying field application. The analytical model was validated using finite element analysis. Results show that the braking torque increases with the application of a time varying field. Various forms of time varying fields have been studied. It was found that the frequency-modulated applied field in triangular waveform results in the highest braking torque. Next, the design was optimized to maximize the braking torque and an optimum configuration was obtained using multiple pole projection areas (PPAs). Optimization results show that the braking torque significantly increases with the introduction of additional PPAs to the configuration, and the braking torque generation for an optimum four-PPA ECB configuration exceeds the braking requirements for current passenger vehicles. For control purposes, a dynamic model for a novel stand-alone ECB system using AC fields for automotive applications has been successfully designed and evaluated. Also, a model-based predictive controller has been developed for the optimum ECB configuration. Finally an experimental test-bed has been designed for experimentation of both DC and AC field application on ECB. / Graduate

The present master thesis deals with the technologies for gas liquefaction focused on helium. The first part of the thesis contains a description of the history of liquefaction, production and usage of liquid helium, as well as the principles of liquefaction and cooling cycles. In the following part of the thesis is a detailed model of the liquefaction cycle for which radial-axial turbine wheels were designed. The last part of the thesis contains financial analysis of the suitability of using the expander with eddy current brake and the expander with an electric generator.

This master’s thesis deals with the design of equipment for testing differentials. The aim of the thesis is therefore the design of a special device that will be able to measure the steady and transient characteristics of differentials. Master’s thesis is divided into four chapters. The first chapter points out the disadvantages of fully open and closed differentials, the second deals with a basic overview of the structures and design of self-locking differentials. The third chapter deals with research of existing devices that test and measure the characteristics of differentials. The fourth chapter then discusses the possible drives of the tested unit. The fifth chapter focuses on the actual construction design of the test equipment. The subsequent sixth chapter then solves the strength calculations of the chosen structural elements of this device.