CHAIR OF

COMPUTATIONAL

MECHANICS

The project is dedicated to the development of an efficient calculation method for solving three-dimensional vibroacoustic problems using porous insulation materials. The aim is to resolve the microstructure of the insulation material in order to overcome the current limitations of Biot's theory, which is often used and seems particularly unsuitable for modeling closed-cell foams. In order to enable the extremely complex geometry-resolved modeling we are aiming for, fictitious domain methods with higher-order approach functions are to be used. On the one hand, these can be applied very advantageously to voxel data and, on the other hand, a high efficiency for wave propagation problems can be expected.

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Robotics has developed by leaps and bounds over the last few decades and many of the challenges of medium to large scale robotics have found suitable solutions. However, at the mesoscale, on the order of a millimeter to centimeters, few of these challenges have been addressed, chief among them, fabrication and actuation. Due to favourable scaling characteristics, piezoelectric actuation becomes more appropriate than electromagnetic actuation at small scales. Piezoelectric materials provide an actuation as they are materials that generate strain when a voltage is applied to them. They also generate a voltage when strained, which gives them the capability to operate as sensors or actuators, or both simultaneously. Due to their small total displacement, large bandwidth, and lack of friction, they have the ability to generate fast and precise movements.

The overall goal is to optimize a new class of piezoelectric motors based on a series of unimorph (a piezoelectric material bonded to a substrate) arms. The Canadian partner, Assistant Prof. Dr. Ryan Orszulik, has recently designed and fabricated a series of prototypes of a piezoelectric motor which has a planar rotor diameter of 9 mm, stator diameter of 8 mm, a total integrated motor thickness of 0.8 mm, weighs approximately 200 milligrams, and is capable of producing bidirectional motion with relatively low rotational speeds but high torque. However, a number of challenges remain, the most important of which is optimizing the torque density of the motor. For this purpose a numerical optimization will be used, which considers the mass and volume limitations, in order to achieve much higher torques without compromising structural integrity. This multi-objective optimization is a very challenging task, especially on such small scales. For mesoscale robotic applications, it is the torque that is of the greatest interest as it mitigates the need for a gearbox, which is very difficult to manufacture and integrate at these small scales. The unimorph based piezoelectric motor that is the focus of this project is simpler to construct, as it relies on non-standard planar fabrication techniques, and requires only a single drive source at a lower frequency to produce a high torque. In this research program, the goal is to leverage new fabrication techniques to create and miniaturize these piezoelectric motors, test them, and optimize them via analytical and finite element techniques. By employing the developed design, modeling, and fabrication techniques, a number of applications will be pursued including miniature autonomous vehicles and surgical instruments. The most promising possible application, which would create further opportunities for collaboration with the satellite design laboratory at York University, is to use these motors as the actuator for single gimbal control moment gyroscopes in pico to femto class satellites.

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This project is a cooperation between the Chair of Multibody Dynamics and the Chair of Computational Mechanics with one research assistant from each partner. The core objective of the project is the development of a practical simulation methodology for calculating the noise emissions of engines and their psychoacoustic evaluation. This makes it possible to directly trace the effects of structural modifications (stiffness, mass distribution) and tribological system parameters (bearing clearances, viscosity, deaxialization and filling level) back to the excitation mechanisms and the internal structure-borne sound paths and to preventively combat them in terms of acoustic optimization through design and tribological measures. This purely virtual engineering approach is intended to do entirely without real prototypes and thus enable an acoustic evaluation early on in the engine development process. In this way, design measures to improve acoustic quality can be implemented in coordination with the development groups of adjacent subject areas without negatively influencing other important design criteria such as performance, pollutant emissions or total mass.
In contrast, passive measures to combat noise emissions through insulation, for example, are generally cost-intensive, as they require additional material as well as additional assembly steps and therefore have an impact on the production process. At the same time, this runs counter to the idea of lightweight construction, reduced consumption and environmental friendliness and leads to additional installation space being required, which is usually a very scarce resource in the development of modern engines and automobiles. The fundamental problem with these insulation measures, which are being used more and more frequently these days, is their symptomatic approach, which combats the effect but ignores the causes of the acoustic disturbance.
The holistic methodology that is the focus of this project, on the other hand, makes it possible to directly analyze and combat the cause of the disruptive noise emissions. In addition, the psychoacoustic evaluation of the sound emission allows it to be categorized into disturbing and less disturbing sound emissions. In this way, the design can be specifically modified so that the resulting noise is classified as more pleasant by people; after all, a quiet noise can still be perceived as more disturbing than a loud one.
This text was translated with DeepL

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