Terje Rølvåg

Influence of Pole and Slot Combinations on Magnetic Forces and Vibration in Low-Speed PM Wind Generators

In this paper, radial forces and torque ripple characteristics are investigated in permanent magnet (PM) machines having different pole and slot combinations. Using the PM machines with concentrated windings could be beneficial in direct-drive wind generators since it is possible to reduce the size and weight of the generator. The PM machines with concentrated windings having a large number of poles are compared to investigate the effect of pole and slot combinations on force and vibration characteristics in low-speed generators. Cogging torque waveforms and torque ripple are investigated using time-stepping finite-element analysis. Analysis of radial forces is presented, including investigation on radial force density distribution, total forces on teeth, and time-dependent force waveforms on a tooth. Structural analysis and experimental modal analysis are performed on the prototype generator. The main mode of vibration in the prototype machine is observed experimentally and the results are in good agreement with the simulations.

Slot Harmonic Effect on Magnetic Forces and Vibration in Low-Speed Permanent-Magnet Machine With Concentrated Windings

In this paper, the influence of slot harmonics on magnetic forces and vibration is studied in a 120-slot/116-pole low-speed PM machine at no-load. It is shown how the lowest mode of vibration is produced at no-load due to slotting. Comparing the cases of open slots, semi-closed slots and magnetic wedges, the effect of slot closure on radial forces and torque production capability is discussed. Magnetic flux distribution in the airgap is computed using finite element analysis. Spatial harmonics due to slotting are investigated in different cases. Maxwells stress tensor is employed to calculate radial and tangential components of the force density in the airgap. Spatial distribution of the total forces on the teeth and also time-dependent force waveform on one tooth are analyzed and discussed for different cases. It is shown how the magnitude of the lowest mode of vibration is reduced in the case of using semi-closed slots and magnetic wedges. Tangential force density distribution and torque production capability are also discussed. Structural analysis is presented to compute the maximum amplitude of the stator deformations due to the radial forces. Experimental results of the prototype generator are presented verifying the existence of the lowest mode of vibration at no-load because of the slot harmonics.

Lean Systems Engineering (LSE): Hands-on Experiences in Applying LSE to a Student Eco-Car Build Project

Abstract The Systems Engineering (SE) field is moving rapidly into commercial industries. Also, SE has more recently been combined with Lean to make it more suitable for highly competitive applications. This paper seeks to explore the application of LSE in a practical project, including the design, build and test of an ultra energy-efficient vehicle for Shell Eco-marathon–—an annual world-wide student competition. The objective is to identify critical factors for implementation of LSE essentials to teams managing the development of complex products. The environment is suitable for studying LSE implementation in a controlled manner, without many of the disturbing factors in industrial projects. The cyclic nature of the project—with new teams every year working to improve last years systems—simulates common real-world problems such as lack of value due to information lost in handoffs and deficient documentation of knowledge. A lean assessment was applied to identify fields with the greater improvement potential: knowledge management and continuous improvement. It is concluded that Visual Workflow Management provides concurrent focus in both fields, while introducing lean to manage project work. Hence, the team achieved a culture for learning, communication and making knowledge transferable; changing the team culture was essential to make LSE successful.

LEANIFICATION OF THE ENGINEERING PROCESS FOR CUSTOMIZED ROAD SAFETY PRODUCTS

Increasing need for customization and documentation but with deficits in a systematic product configuration strategy can result in repeated problem-solving and non-value added engineering. This is especially challenging for SMEs where resources are limited. To remain competitive, they need to gather efficient ways of providing engineer-to-order products. This paper presents a case study of the implementation of a customizable product platform combined with a web-based interface in an industrial SME for road safety products as an opportunity to increase customer value and reduce waste.

Dynamic test bench for motocross engines

Simulation of engine components enables early design verification and reduced development time while helping racing teams in getting new knowledge. This article presents a multidiscipline dynamic test bench and a benchmark of two different connecting rods for HONDA CRF250R. The test bench embeds mechanical and control system modeling and simulation including electric starters, ignition timing, power control as well as sensors and actuators enabling closed-loop systems. A non-linear finite element program that combines the traditional separate multi-body simulation and finite element modeling and simulation tasks captures all load cases and dynamic effects in one single run. Model reduction techniques are applied to optimize simulation speed and results accuracy. The virtual test bench captures dynamic engine effects and efficiently provides new knowledge about engine performance and integrity.

FE simulation of soft wing impactor for aviation mast frangibility testing – sensitivity to model assumptions

ABSTRACT In 1981, the International Civil Aviation Organization (ICAO) instigated the ‘Frangible Aids Study Group’ (FASG), with the aim to define design requirements and crash test procedures addressing the frangibility of airport navigation aids and their support masts. The FASG group soon stated that a specific wing section model should be used as a standard test impactor. This paper describes an attempt to model and verify a virtual model of a wing impactor based on static and dynamic compression test sensitivity analyses. The motivation is to define a standard FE model that will ultimately reduce the need for physical testing, while providing improved opportunities for understanding mechanisms and design parameters related to frangibility. The sensitivity to finite element (FE) model assumptions is studied to ensure a representative deflection-force characteristic for crash tests. The study shows that strain at a fracture value of 15% combined with a bi-linear hardening model gives the most reliable simulation results. This material combination also seems to give the most correct wing impactor behaviour in high-speed crash simulations. The simulations also prove that 1 kHz low pass filtering of reaction forces efficiently eliminates artificial peak forces not contributing to wing damage.

Using finite element modelling and simulations to test MotoGP race bikes

The primary objective of this study is the development of a robust numerical simulation model that captures the dynamical characteristics of the Ilmor X 3 2007 MotoGP racing bike. This model can be reconfigured to vary the weight distribution, the stiffness and the damping properties that affect wheelies and stoppies. The model includes tyre models, the driveline from the engine to the rear wheel and a steering system to control the bike in ride simulations. Sensitivity simulations are performed to study the effect of different bike configurations on wheelies and stoppies, i.e., the front and rear wheel lifts that occur during maximum acceleration and braking of the bike. Various modifications are made to the FE-based simulation model to investigate the effect of these changes on the ride behaviour.

A method for controller parameter estimation based on perturbations

Simulation and prediction of eigenfrequencies and mode shapes for active flexible multibody systems is an important task in disciplines such as robotics and aerospace engineering. A challenge is to accurately include both controller effects and flexible body dynamics in a multidisciplinary system model appropriate for modal analysis. A method for performing modal analyses of such systems in a finite element environment was recently developed by the authors. On issue is, however, that for engineers working in a finite element environment, the controller properties are not always explicitly available prior to modal analyses. The authors encountered this problem when working with the design of a particular offshore windmill. The controller for the windmill was delivered in the form of a dynamic link library (dll) from a third party provider, and when performing virtual testing of the windmill design, it was of great importance to use the “real” controller in the form of the provided dll, rather than re-model it in for instance Simulink or EASY5. This paper presents a method for estimating the controller parameters of PID-type controllers when solving the closed-loop eigenvalue problem for active flexible multibody systems in a finite element environment. The method is based on applying incremental changes, perturbations, to relevant system variables while recording reactions from other system variables. In this work, the theory of the method is derived and the method is tested through several numerical examples.