Thesis (M.S.)--Brigham Young University. Dept. of Mechanical Engineering, 2006. / Includes bibliographical references (p. 81-82).

The in-cylinder pressure is an important signal that gives information about the combustion process. To further improve engine performance, this information can be used as a feedback signal in a control system. Usually a pressure sensor is mounted in the cylinder to extract this information. A drawback with pressure sensors is that they are expensive and have issues with aging. This master’s thesis investigates the possibility to create a virtual sensor to estimate in-cylinder pressure based on crank angle degree sensor (CAD-sensor) data and physical models of the heavy-duty engine. Instead of using the standard mounted CAD-sensor an optical high-precision sensor measures the elapsed time between equidistant angles. Based on this signal the instantaneous angular acceleration was estimated. Together with the inertia of the crankshaft, connecting rods and pistons, an estimation of the engine torque was calculated. To be able to extract in-cylinder pressure from the estimated torque, knowledge about how the in-cylinder pressure signal propagates in the drivetrain to accelerate the flywheel needs to be known. Two engine models based on the torque balance on the crankshaft are presented. The fundamental difference between them is how the crankshaft is modeled, rigid body or spring-mass-damper system. The latter captures torsional effects of the crankshaft. Comparisons between the estimated torque from sensor data and the two engine models are presented. It is found that torsional effects of the crankshaft is present at normal engine speeds and has a significant influence on the flywheel torque. A separation of the gas torque contribution from one cylinder is done with CAD-sensor data together with the rigid body engine model. The in-cylinder pressure is then estimated by using the inverse crank-slider function and a Kalman filter estimator. The estimated pressure captures part of the compression and most of the expansion at engine speeds below 1200 RPM. Due to the crank-slider geometry the pressure signal disappears at TDC. The torsional effects perturb the estimated pressure during the gas exchange cycle. Further development must be made if this method is to be used on heavy-duty applications in the future.

Orientador: Idomeo Bonetti Filho / Banca: Mário Tanomaru Filho / Banca: Giulio Gavini / Resumo: O objetivo deste estudo foi avaliar a resistência à fratura de instrumentos rotatórios de níquel-titânio por meio de ensaio de torção. Foram avaliados os sistemas Profile 0,04/0,06 (Dentsply/Maillefer) e K3 (Kerr), perfazendo um total de 300 limas, as quais foram divididas em 5 grupos: Grupo A (Profile 0,04), Grupo B (Profile 0,06), Grupo C (K3 0,04), Grupo D (K3 0,06), Grupo E (Protaper). Os instrumentos foram submetidos a ensaio de torção por meio de um dispositivo acoplado à uma máquina de ensaios mecânicos MTS (Material Test System). Esta máquina era conectada à um microcomputador onde foram registrados os valores de carga máxima aplicada a cada lima. Tais valores foram, posteriormente aos testes, convertidos em torque (em N.cm), seguindo a fórmula: torque = carga máxima x raio. Os valores de torque máximo para fratura foram analisados estatisticamente pelo teste t de Student. Os resultados mostraram que instrumentos de maiores conicidades (Grupo B e D) são mais resistentes à fratura do que os de conicidades menores (Grupo A e C). Os instrumentos K3 0,06 necessitam de maiores valores de torque máximo para fratura em relação aos Protaper. Observamos ainda que os instrumentos do sistema K3 foram significativamente mais resistentes à fratura torcional do que os instrumentos do sistema Profile. Porém, os resultados mostraram não haver diferenças significativas na resistência à fratura entre os sistemas Profile 0,04, Profile 0,06 e K3 0,04 quando comparados ao sistema Protaper, da mesma forma que quando comparamos os sitemas Profile 0,04 com o K3 0,04. Porém, quando a comparação foi feita entre instrumentos Profile 0,06 e K3 0,06, os últimos mostraram-se mais resistentes à fratura que os primeiros. / Abstract: The aim of this study was to evaluate the resistance of different nickel-titanium rotary instruments to the fracture by means of torsion test. Profile 0,04/0,06 (Dentsply/Maillefer), Protaper (Dentsply/Maillefer) and K3 ENDO (Kerr) systems were evaluated, resulting in 300 files which were divided in 5 groups: Group A (Profile 0,04), Group B(Profile 0,06), Group C (K3 0,04), Group D (K3 0,06), Group E (Protaper). The instruments were subjected to torsion test by means of an appliance coupled to a mechanical test machine MTS (Material Test System). This machine was connected to a microcomputer in which was registered the values of maximum load applied to each file. Such values were, after the tests, converted to torque (in N.cm), following the formula: torque=maximum load x radius. Maximum torque values for fracture were analyzed statistically by the Student's t. The results showed that more taper instruments (Groups B and D) are more resistant to fracture than the less taper ones (Groups A and C). The K3 0,06 instruments need higher values of maximum torque to fracture with relation to Protaper's ones. We also noticed that the instruments from K3 system were significantly more resistant to the torsion fracture than the Profile system instruments. However, the results showed that there are not significant differences in the resistance to the fracture among the systems Profile 0,04, Profile 0,06 and K3 0,04 when they were compared to Protaper system, as the same way when we compare Profile 0,04 systems to K3 0,04. / Mestre

Thesis MTech(Electrical Engineering))--Cape Peninsula University of Technology, 2006 / Reluctance Synchronous Machines (RSM) have, due to their rotor geometry, an inherently high torque ripple. This torque ripple is defined as the deviation of the minimum and maximum torque from the average value. It is unwanted as it indicates uneven pull on the rotor causing deformation of it and hence different air-gaps along the rotor circumference as well as acoustic noise. In applications such as power steering, robotics and radar positioning systems where high precision movement is vital, oscillating torque will lead to the malfunction of these devices and therefore suppressed the use and development of RSMs. Unlike the Induction machine (IM), the RSM has no copper losses in the rotor, which reduces the operating temperature significantly. With the development of electronic drives the quality of the output torque could be improved by means of accurate current- and flux space phasor control methods with much success and made the RSM a possible replacement for the IM. However, reducing torque ripple by means of purely geometrical changes is still a challenge to the machine designer. This thesis will focus on the reduction of torque ripple while leaving the average torque relatively unchanged by changing the rotor geometry. The rotor changes will take place by means of flux barriers and cut-outs while the stator has either semi-closed slots or magnetic wedges. In this work rotor structures with equal harmonic magnitudes but their angles 1800 apart. will be combined to form one machine and identify how torque harmonics respond. The change in average torque and power factor will be evaluated with all geometrical changes made to these machines throughout this work.

This thesis presents a theory of multi-scale, curvature and torsion based shape representation for planar and space curves. The theory presented has been developed to satisfy various criteria considered useful for evaluating shape representation methods in computer vision. The criteria are: invariance, uniqueness, stability, efficiency, ease of implementation and computation of shape properties. The regular representation for planar curves is referred to as the curvature scale space image and the regular representation for space curves is referred to as the torsion scale space image. Two variants of the regular representations, referred to as the renormalized and resampled curvature and torsion scale space images, have also been proposed. A number of experiments have been carried out on the representations which show that they are very stable under severe noise conditions and very useful for tasks which call for recognition of a noisy curve of arbitrary shape at an arbitrary scale or orientation. Planar or space curves are described at varying levels of detail by convolving their parametric representations with Gaussian functions of varying standard deviations. The curvature or torsion of each such curve is then computed using mathematical equations which express curvature and torsion in terms of the convolutions of derivatives of Gaussian functions and parametric representations of the input curves. Curvature or torsion zero-crossing points of those curves are then located and combined to form one of the representations mentioned above. The process of describing a curve at increasing levels of abstraction is referred to as the evolution or arc length evolution of that curve. This thesis contains a number of theorems about evolution and arc length evolution of planar and space curves along with their proofs. Some of these theorems demonstrate that evolution and arc length evolution do not change the physical interpretation of curves as object boundaries and others are in fact statements on the global properties of planar and space curves during evolution and arc length evolution and their representations. Other theoretical results shed light on the local behavior of planar and space curves just before and just after the formation of a cusp point during evolution and arc length evolution. Together these results provide a sound theoretical foundation for the representation methods proposed in this thesis. / Science, Faculty of / Computer Science, Department of / Graduate

The Master’s thesis deals with the design of unconventional tractor cab suspension. It contains overview of current conceptions, mensions description of single components, takes closer look at torsion bar calculations and strength analysis. Subsequently, there is dynamic analysis of suspension in the thesis, performed with use of Adams View software aimed at ride over bump. Last section describes strength analysis of whole construction according to OECD methodics with use of numerical simulations in ANSYS Workbench software. Part of the thesis is also complete drawing documentation.

When a body vibrates in a fluid, some of the fluid is carried with it and the mass loading lowers its resonant frequency. Similarly, when compression of the fluid occurs, there is an added stiffness which by design can be made to predominate. In addition, there is an energy dissipation arising from viscous losses and acoustic radiation. The starting point of this research was a tuning fork with flat rectangular tines, designed to trap a narrow laminar of gas which is forced to pump in and out as the tines vibrate. The increase in kinetic energy, contributed by this high velocity' gas, gives the device a relatively large sensi ti vi ty as a gas density transducer. The change in frequency between vacuum and atmospheric pressure is typically a few percent, during which period the mechanical "Q" remains high enough to keep the fork sharply resonant. A high stability oscillator incorporating the transducer as the frequency controlling element was built. Small piezoelectric Cp2t) elements were used to drive the transducer and pick up the vibrations. A typical stability, equivalent to a pressure change of 0. 05 mBar was achieved. The supporting equipment re qui red for the work centred around a vacuum system with facilities for introducing a range of gases at precise rates. Computer control enabled the transducer's temperature, frequency, and "Q" factor to be measured and stored as the gas pressure was increased from vacuum. Extensive experiments were carried out on a range of tuning fork transducers, including a circular one in which a pair of disks clamped at the center acted as the tines and gave a simple radial gas displacement. Common to all these transducers is, the linearity of 1/f 2 with gas density for pressures above about 50 mBar; a departure from. linearity below this pressure; and below 10 mBar an overriding stiffness effect, where from vacuum to a few mBar the frequency paradoxically increases. The resultant calibration to this non-linear response, while exhibiting high stablility, is unattractive for general use. It has however applications over limited ranges as for example, those of a barometer or altimeter. Insight gained from experience with the double disk resonator, led to a new geometry which has resulted in an extremely viable transducer, without calibration anomalies, and capable of operating in a pressure or dehsity mode. Here, the gas is confined in two cylindrical cavities above and below a thin circular diaphragm, clamped at the periphery and again made to vibrate using p2t elements. In the fundamental mode, the alternating change in cavity volume due to compression and rarefaction of the gas, adds stiffness to the diaphragm. In the next mode, there is no net volume change, but the gas is pumped across the cavities adding inertial loading. No anomalies were experienced in the empirical calibrations obtained for each mode- the fundamental being linear with pressure Cf 2 proportional to Pl, and the first overtone linear with density (1/f 2 proportional to pl. A simple theory, which is sufficiently accurate for general design purposes, has been developed. Future work, which is of a straightforward development nature, is proposed. The high degree of stability achieved for these vibrating structures was later realised in a different geometry. In this, a long rod was excited into a torsional mode so as to produce two nodes a quarter wavelength from. either end. By securing the rod at these points and immersing the lower length in a liquid, a sensitive, robust, viscometer was produced. Driving the rod with a burst of oscillations, shears the liquid in contact with it. By removing this drive and measuring the rate of vibrational decay under the action of viscous dissipatiop, an indication of the viscosity can be obtained. The features of a pure shearing force, and the real-time, on-line nature of the device, makes it attractive for the characterisation of both thick and thin liquids and automatic process control.

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La déformation de torsion que subit un profil aérodynamique a une importance capitale car elle a une influence directe sur la valeur des incidences locales et donc sur la valeur locale des densités de portance et de traînée. L'amélioration des performances aérodynamiques passe donc par la connaissance et la maîtrise de ce vrillage. Cette thèse se propose d'y contribuer. Une des méthodes développées actuellement par de nombreux auteurs consiste à munir le profil d'actionneurs permettant de le déformer en torsion de manière à compenser tout ou partie, voire même contrer, la déformation " naturelle " de la structure. Cette méthode, dite de contrôle actif, est certes très efficace, mais elle présente des limitations car elle nécessite l'introduction d'une quantité d'énergie qui peut être importante. La méthode que nous proposons ici pour maîtriser le vrillage du profil consiste à modifier ses conditions d'équilibre interne. En solidarisant ou en désolidarisant des cloisons à l'intérieur du profil, il est possible de déplacer le centre de torsion des sections du profil sans modifier sa forme extérieure. Ces modifications internes induisent donc une modulation du moment de torsion et donc une modulation du vrillage. Ce processus ne demande que très peu d'énergie. A partir d'un profil simple, des simulations ont permis de montrer le potentiel théorique du système proposé. Trois démonstrateurs, de complexité croissante, ont également été réalisés pour évaluer les capacités du contrôle " réactif " de la torsion. La technique a été validée par la deuxième démonstration. Malheureusement, le troisième démonstrateur, beaucoup plus complexe, n'a pas permis, à l'heure actuelle, d'obtenir la validation finale.