Overview


    Dr. Seethaler has three main areas of research.  His first area of interest is a continuation of a project that he had started when working at the engine research department for his previous employer BMW.  At that point he started to develop electromagnetic valve actuation systems that promise to significantly improve the efficiency of automotive engines.  Today, Dr. Seethaler has developed the most flexible electromagnetic valve system shown in literature.

    Dr. Seethaler’s second area of interest deals with improving the reliability and accuracy of piezo based fuel injectors for hydrogen engines.  This topic is part of a collaborative research effort between Faculty members at UBC, Simon Fraser, and Westport Innovations in Vancouver.  At this point, Dr. Seethaler’s team has developed a novel model to describe the behavior of piezo stack actuators and they are currently using this model in order to design a sensorless control strategy for piezo driven positioning stages.

    A third research area of interest lies within the manufacturing area, where ever smaller parts are being manufactured using novel machining approaches.  Here Dr. Seethaler and Dr. Yellowley in Vancouver are developing models for meso machining processes, where the cut features are of a similar size as the tool cutting edge.  Thus, traditional metal cutting models that are mainly based on shear deformations need to be extended to include grinding of the cutting edge along the work-piece.  This work will help to reduce production costs for parts with very small features, since it helps to select optimal tools and cutting conditions.

    Dr. Seethaler’s fourth area of interest is in the smart materials area.  Here Dr. Seethaler is collaborating with Dr Milani in order to develop models to describe the behavior of Carbon Nanotube reinforced composites.  They have worked on finding the optimum distribution of Carbon Nanotubes in cantilever beams in order to achieve maximum natural frequencies and damping ratios.  It is anticipated that this work will help in the optimum design of MEMS sensors
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Electromagnetic Valve Trains


    The automotive industry has been under continued pressure to improve fuel efficiency because of air pollution, global warming and rising gasoline prices. One technology to address this need is electronic valve timing. It promises to achieve fuel savings of 10%-15% by reducing pumping losses, introducing cylinder deactivation, and enabling new combustion strategies like homogeneous charge compression ignition.  Even though these benefits have been known for many years, no car company has been able to develop a reliable and cost effective electrically driven valve train.

Figure 1.  Electromagnetic valves from Valeo


    In the most widely researched solution to this problem, the valve is held in the middle position by a spring system (see Figure1). Two coils are energized alternately to attract an armature mounted on the valve into either the open or the closed position. A nonlinear relationship between force, position and current occurs when the armature approaches either end.  This makes it very difficult to regulate the valve seating velocity which in turn leads to a very noisy operation. Dr. Seethaler’s team has developed advanced control strategies that are able to reduce the seating velocity to acceptable levels in a lab bench setup.  Engine experiments are currently under way that will show how robust these strategies are under real operating conditions
Another approach to drive valves uses a direct drive (see Figure (2)). In this case, the valves are accelerated and decelerated purely by an electric motor.  Energy generated by braking the valves is not fed into mechanical springs, but into electrical capacitors.  The advantage of such a system is that the control scheme is much simpler, since a standard linear servo controller can be employed.  The main challenge for developing such a system is achieving the required bandwidth while reducing the ohmic energy losses in the motor.  Dr Seethaler’s research team has developed a bench top experimental system that shows promising results for the intake valves of naturally aspirated engines.  Currently, we are looking for an opportunity to test this technology on a real engine.

Figure 2.  Directly driven valvetrain



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Piezoelectric Fuel Injectors for Hydrogen Engines


    The transportation and industrial power generation sectors are the largest CO2 emission sources in Canada. Air pollution caused by transportation and industrial power generation has a direct, negative effect on the health of people and quality of life around the world.  The development of a transportation sector relying on hydrogen and other clean fuel technologies is a long-term answer to reducing harmful emissions and preserving the environment.

Figure 3. Direct Injection Fuel Injectors

    A key element of hydrogen-based clean engine technology is the fuel injector (see figure (3)). It is widely accepted that improved fuel injection strategies are the key to implementing an optimized engine strategy that achieves high efficiency. The main challenges in developing H2 fuel injectors are durability and injection accuracy. Westport Innovation Inc. in Vancouver, the leading Canadian developer of internal combustion engine technology based on clean-burning fuels such as natural gas, or hydrogen has initiated this research with different partners including Dr. Seethaler’s Lab at UBCO.

Figure 4.  Piezo stack actuator test bed

    Dr. Seethaler’s team aims to improve the injection accuracy of fuel injectors for hydrogen engines.  Today, the performance of piezo driven fuel injectors changes with temperature and age.  However, there is no direct needle position sensor available to measure the injection accuracy of the injector.  Instead, emission measurements in the exhaust stream are utilized to calibrate the injectors.  This process reacts to emission problems after they have occurred.  In the long run, it is necessary to ensure that injection accuracy does not deteriorate to the point where harmful emissions are produced.  To achieve this, advanced injector monitoring and strategies are being developed that utilize the current signature through the injector in addition to the driving voltage to determine the health of the actuator as well as the needle position.  Figure 4 shows the experimental testbed that is used for this study.  Currently, Mohammad Islam, a PhD student in Dr. Seethaler’s Lab is refining a sensorless control strategy, that provides a ten times improvement in positioning accuracy over the traditional voltage feed-forward technique used in injectors today.


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Modelling of Milling Processes


    Today, many different metal removal techniques are available to transform raw pieces of material into finished products.  One of the most common machining operations used in the aerospace, automobile and die-mold industries is milling.  This operation removes material by feeding a workpiece past a rotating single or multiple teeth cutter; the process is versatile and allows large amounts of material to be removed quickly

Figure 5. Milling Geometry

    In order to apply this operation efficiently to different manufacturing scenarios, an accurate model linking material parameters to cutting geometry and cost is required.  Unfortunately, defining the traditional constitutive equations for the milling process is a considerable challenge due to the severe deformation process.  As a result, many of today’s models are empirical in nature and are applicable over a very narrow range of operating conditions.  Dr. Seethaler is interested defining cutting models that are physically based, but do not rely on an intricate constitutive model.  To achieve this, he uses upper bound models and simple slip line field models in order to describe the cutting process.

    An second area of interest in milling arises due to the increasing interest in using traditional machining processes to manufacture micro-electromechanical systems. As a result, the milling process is being used to manufacture ever smaller parts.  This requires that smaller cutting tools are used.  However, due to manufacturing constraints, the sharpness of a tool cannot be scaled indefinitely.  Thus, as the tools become smaller, the radii of the cutting edge stay constant.

Figure 6. Tool edge radius, re, and cutting depth, h0.

    In traditional machining models it is assumed that the cutting edge radius is small compared to the cutting feature.  It is then assumed that most of the deformation work takes place in a shear zone in front of the tool between the chip and the workpiece.  When the edge radius is the same order of magnitude as the cutting depth, this approximation is no longer valid, since there is considerable work expanded by the tool through frictional and shear fork underneath the tool.  In fact when the cutting depth is too small, then the tool ploughs across the workpiece without cutting.  Much of the metal removal with small cutting depths is then performed in an operation with significant ploughing and cutting.  Guiping Zou, a former student of Dr. Seethaler and Dr. Yellowley developed models that can be used for cutting, ploughing, and any combination of these two mechanisms.

Figure 7. The difference between ploughing and cutting


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Optimum Design of Carbon Reinforced Composites


    The superior mechanical properties of carbon nanotubes (CNTs) have prompted high interest in the production of CNT-reinforced composite materials for structural applications. However, due to their toxicity and high cost, CNTs need to be optimally distributed within composite structures so as to achieve mechanical or electrical properties of interest. As the first step in this direction, Hossein Rokni, a former student of Dr. Milani and Dr. Seethaler, optimized the vibration behavior of multi-walled carbon nanotube (MWCNT)-reinforced polymer composite micro-beams by an appropriate distribution of the CNT reinforcement within the beams.

Figure 8. Multi walled carbon Nanotube.

    Hossein Rokni performed analytical and experimental investigations to find the optimum distributions of carbon nanotubes both in the axial and the transverse direction of a cantilever beam.

Figure 9.  Axial distribution of Carbon Nanotubes

Figure 10. Transverse Distribution of Carbon Nanotubes

    He found that the transverse distribution is most effective in increasing the natural frequency of the beams.  However, a 2D optimum dispersion of MWCNTs within the polymer micro-beam resulted in the highest improvement in the fundamental frequency value.  Mr. Rokni performed his analytical work at UBC on the Okanagan campus and he was able to validate the analytical findings using experiments performed at the Industrial Materials Institute with the National Research Council Canada.


Figure 11.  2D optimum distribution of Carbon Nanotubes in a Clamped-Free Canitlever Beam



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Last updated December 27, 2011