THREE-DIMENSIONAL STEADY STATE AND TRANSIENT EDDY CURRENT MODELING

Maglev transportation using electrodynamic wheels is a promising new technology aimed at providing a low cost, high-speed and environmental friendly mode of transportation. In this technology, Halbach permanent magnet rotors, termed electrodynamic wheels, are simultaneously rotated and translationally moved above a conductive non-magnetic guideway. The time-changing magnetic field created in the airgap between the rotors and guideway induces eddy currents in the guideway which in turn interact with the magnetic rotor field to produce suspension and propulsion or braking forces which are required for maglev transportation. This technology offers an integrated suspension and propulsion system. In this dissertation the eddy current distribution in the conductive guideway has been modeled in three-dimension. An approach for the computation of the static magnetic fields due to the Halbach rotor has been presented using novel magnetic charge sheet concept. Finite element models have been developed to study the steady state and transient eddy current field distribution. Three analytic models have been developed to compute the electromagnetic forces and torque acting on the rotor as well as joule loss in the guideway. The models include the heave, translational and rotational motion of the magnetic rotor for dynamic simulation. The developed analytic and finite element models are highly generic and thus can be applied to any magnetic source. The developed finite element models have been validated by comparing it with commercial finite element software and previously developed boundary coupled steady state finite element model. Commercial finite element software and two experimental setups have been used to verify the developed analytic models. Computational efficiency of the presented models has been compared with the previously developed finite element model and commercial software. Good performance of the developed models has been achieved

Machine generated vertical vibration in elevators

Vertical vibration deteriorates passenger comfort during an elevator travel. The drive system is a source of vertical vibration as well as the source of energy of the system. This report presents the results of a study of car vertical vibrations generated at the drive system in elevator installations. The elevator system can be considered as a translating assembly of inertia elements coupled and constrained by one-dimensional slender continua. The inertia elements are the car assembly, the counterweight, the traction sheave and other rotating components of the system. According to the roping arrangement and to the ratio of the tangential velocity of the traction sheave to the velocity of the car, the traction elevators can be classified as roped 1:1 or multiple reeving systems: the types examined in the present work are 1:1 and 2:1 traction elevators. Distributed- and lumped-parameter models (DPM and LPM respectively) are developed to calculate the natural frequencies and mode shapes of stationary elevator systems and their results compared. A non-stationary model of a 1:1 roping configuration elevator is developed as well to simulate the elevator acceleration response. The model accommodates the drive system dynamics: it includes the electric motor and the torque and velocity controllers, which ensure that the car follows a prescribed kinematic profile, so that good ride quality of the elevator is achieved. The machine parameters are computed by means of the Finite Element Method simulation software FLUX. With respect to the carcounterweight-sheave-ropes assembly, a LPM and a novel DPM are developed. The elevator dynamics represented by the DPM is described by a partial differential equation set that is discretised by expanding the vertical displacements in terms of the linear stationary mode shapes of a system composed of three masses constrained by the suspension rope. The models are implemented in the MATLAB/Simulink computational environment and the system response is determined through numerical simulation. It is shown that the LPM forms a good approximation of the DPM. Experimental tests are carried out on laboratory models. The elasticity modulus of the rope and the friction coefficients at the guide rail contact and at the machine are estimated. The acceleration response at the suspended masses and at the drive machine, the machine shaft velocity and the three phase current intensities supplied to the machine are measured during several travels. The machine torque is estimated from the current intensities. The computed and measured accelerations are compared either in time or frequency domain and it is demonstrated that the elevator car vibrates at frequencies generated at the machine, especially when they are close to the system natural frequencies. The proposed simulation models can be used as design and analysis tools in the development of high-performance elevator systems

Minimum-lap-time optimisation and simulation

The paper begins with a survey of advances in state-of-the-art minimum-time simulation for road vehicles. The techniques covered include both quasi-steady-state and transient vehicle models, which are combined with trajectories that are either pre-assigned or free to be optimised. The fundamentals of nonlinear optimal control are summarised. These fundamentals are the basis of most of the vehicular optimal control methodologies and solution procedures reported in the literature. The key features of three-dimensional road modelling, vehicle positioning and vehicle modelling are also summarised with a focus on recent developments. Both cars and motorcycles are considered

Structural Dynamic Modeling and Simulation of Acoustic Sound Emissions of Electric Traction Motors

The acoustic behavior of electric drive systems is one of the main comfort criteria of electromobility. Due to its high-pitched sound emissions, the electric motor plays an important role. The corresponding noise is predominantly determined by the vibrational behavior of the electric machine given by the structural transfer function. The early phase consideration of the vibrational behavior of electric machine structures becomes even more relevant if one takes into account the strong requirements towards lightweight design and spatial restrictions inside vehicle applications. One of the most important tools inside the early stage development is the structural dynamic simulation. In order to be able to sustainably predict the vibrational behavior of an electric machine, the corresponding simulation model needs to sufficiently represents all acoustically relevant structural effects and at the same time remain practical and numerically solvable in a reasonable amount of time. This conflict is dealt with in this dissertation. The acoustic behavior of electric machines is strongly coupled to the vibrational behavior of the electric machine stator. The microscopic representation of the strongly heterogeneous stator structure is elaborate and requires a large computational effort. Therefore, so-called homogenized substitutional materials are typically employed in structural dynamical simulations of electric motors. The homogenized materials intend to represent the effective stiffness and damping properties of the underlying heterogeneous structure by an anisotropic substitutional material. Typically, the corresponding effective stiffness and damping properties of the homogeneous material are reversely obtained from experimental investigations on the particular structure. However, this approach presumes the physical existence of prototypes that can be tested. In this thesis, different so-called homogenization techniques will be investigated that allow the identification of homogenized material properties based micromechanical models of the underlying heterogeneous structure. Therefore, various numerical and analytic approaches will be investigated. The resulting modeling approaches will be validated based on different experimental analyses on an exemplary stator structure and subsequently be employed in a comprehensive acoustic simulation of an entire electric drive train. However, the simulation and optimization of the mostly broadband acoustic behavior of electric motors remains time-consuming. In order to efficiently predict the acoustic behavior of electric machines the use of model order reduction methods can be advantageous. Model order reduction methods typically involve mathematical algorithms that yield the effective reduction of the model’s degrees-of-freedom. In this thesis, different model order reduction techniques will be applied and evaluated regarding their usability in the area of vibrational simulations of electric machines. A particularly efficient model order reduction could be achieved by using so-called Krylovsubspaces. By employing the Krylov-subspace method the solution time for particular operation points of the electric machine could be reduced to less than 10% of the original solution time. The integrated modeling procedure, presented in this thesis, yields the sustainable and efficient representation of the vibrational behavior of electric machines. It allows the early phase evaluation and optimization of the acoustic behavior of different electric machine designs. This thesis differs from similar research so far that a generic approach was used to make the representation of the global dynamic behavior of the electric machine possible. The process includes micromechanical models which add a unique robustness and sustainability to the approach