Mechanical and Mechatronics Engineering

Permanent URI for this collectionhttps://uwspace.uwaterloo.ca/handle/10012/9912

This is the collection for the University of Waterloo's Department of Mechanical and Mechatronics Engineering.

Research outputs are organized by type (eg. Master Thesis, Article, Conference Paper).

Waterloo faculty, students, and staff can contact us or visit the UWSpace guide to learn more about depositing their research.

Browse

Now showing 1 - 6 of 6

Design, fabrication and characterization of ferroelectret energy harvester
(University of Waterloo, 2019-04-22) Kayaharman, Muhammed; Yavuz, Mustafa; Abdel-Rahman, Eihab
Energy harvesters gained significant interest over the last decade with the reduce in power requirements of today’s electrical devices and with the fast developments in low-power electronics. Limited battery life is one of the weak spots that constrains the potential of possible applications. There are only two options for remote applications when the battery is died. Either charging the battery or replacing the battery with a new one. And both of these solutions are time-consuming and expensive. On the other hand, for some of the remote applications, such as health monitoring for aircrafts, battery replacement or charging may not even be an option because of dangerous or inaccessible area conditions. In this research, a one-layer ferroelectret energy harvester is designed and fabricated. Ferroelectret energy harvester is modeled as a mass-spring-damper under harmonic base excitation. d33 piezoelectric constant of the harvester is measured with laser interferometry method. Natural frequency of the harvester is measured experimentally with a frequency sweep up to 1 kHz. Optimum resistance of the three energy harvesters measured with impedance matching to maximize the transduction from mechanical domain into electrical domain. The effect of constant stress and stress-cycling on the stability of ferroelectret energy harvester is analyzed. According to our experiment results, constant stress significantly increased the d33 piezoelectric charge constant and the natural frequency (wn) of the harvester. Increased d33 constant also increased the the power output of the harvester under constant stress compared to stress-cycling and stress-free. Also output voltage and the capacitance value of the energy harvesters are affected by constant-stress and stresscycling. And last, mathematical model is compared with experimental results to validate the piezoelectricity of ferroelectret energy harvesters.
Design, Fabrication and Characterization of MEMS Gyroscopes Based on Frequency Modulation
(University of Waterloo, 2018-07-24) Effa, Dawit (David); Yavuz, Mustafa; Abdel-Rahman, Eihab
Conventional amplitude modulated (AM) open loop MEMS gyroscopes experience a significant performance trade-off between having a large bandwidth or high sensitivity. It is impossible to improve both metrics at the same time without increasing the mass of the gyroscope or introducing a closed loop (force feedback) system into the device design. Introducing a closed loop system or increasing the proof mass on the other hand will surge power consumption. Consequently, it is difficult to maintain consistently high performance while scaling down the device size. Furthermore, bias stability, bias repeatability, reliability, nonlinearity and other performance metrics remain primary concerns as designers look to expand MEMS gyroscopes into areas like space, military and navigation applications. Industries and academics carried out extensive research to address these limitations in conventional AM MEMS gyroscope design. This research primarily aims to improve MEMS gyroscope performance by integrating a frequency modulated (FM) readout system into the design using a cantilever beam and microplate design. The FM resonance sensing approach has been demonstrated to provide better performance than the traditional AM sensing method in similar applications (e.g., Atomic Force Microscope). The cantilever beam MEMS gyroscope is specifically designed to minimize error sources that corrupt the Coriolis signal such as operating temperature, vibration and packaging stress. Operating temperature imposes enormous challenges to gyroscope design, introducing a thermal noise and drift that degrades device performance. The cantilever beam mass gyroscope system is free on one side and can therefore minimize noise caused by both thermal effects and packaging stress. The cantilever beam design is also robust to vibrations (it can reject vibrations by sensing the orthogonally arranged secondary gyroscope) and minimizes cross-axis sensitivity. By alleviating the negative impacts of operating environment in MEMS gyroscope design, reliable, robust and high-performance angular rate measurements can be realized, leading to a wide range of applications including dynamic vehicle control, navigation/guidance systems, and IOT applications. The FM sensing approach was also investigated using a traditional crab-leg design. Tested under the same conditions, the crab-leg design provided a direct point of comparison for assessing the performance of the cantilever beam gyroscope. To verify the feasibility of the FM detection method, these gyroscopes were fabricated using commercially available MIDIS™ process (Teledyne Dalsa Inc.), which provides 2 μm capacitive gaps and 30 μm structural layer thickness. The process employs 12 masks and hermetically sealed (10mTorr) packaging to ensure a higher quality factor. The cantilever beam gyroscope is designed such that the driving and sensing mode resonant frequency is 40.8 KHz with 0.01% mismatch. Experimental results demonstrated that the natural frequency of the first two modes shift linearly with the angular speed and demonstrate high transducer sensitivity. Both the cantilever beam and crab-leg gyroscopes showed a linear dynamic range up to 1500 deg/s, which was limited by the experimental test setup. However, we also noted that the cantilever beam design has several advantages over traditional crab-leg devices, including simpler dynamics and control, bias stability and bias repeatability. Furthermore, the single-port sensing method implemented in this research improves the electronic performance and therefore enhances sensitivity by eliminating the need to measure vibrations via a secondary mode. The single-port detection mechanism could also simplify the IC architecture. Rate table characterization at both high (110 oC) and low (22 oC) temperatures showed minimal changes in sensitivity performance even in the absence of temperature compensation mechanism and active control, verifying the improved robustness of the design concept. Due to significant die area reduction, the cantilever design can feasibly address high-volume consumer market demand for low cost, and high-volume production using a silicon wafer for the structural part. The results of this work introduce and demonstrate a new paradigm in MEMS gyroscope design, where thermal and vibration rejection capability is achieved solely by the mechanical system, negating the need for active control and compensation strategies.
Electromagnetic Vibrational Energy Harvesters and Power Management
(University of Waterloo, 2016-01-14) Tunkar, Bassam; Yavuz, Mustafa; Abdel-Rahman, Eihab
The interest in scavenging various energy sources from the environment is rapidly increasing. Thanks to the advances in developing effective energy harvesters researches. Kinetic energy is a renewable source and it can be found numerously in the environment. One of the most popular class of the kinetic energy harvesters in this field is vibration energy harvesters (VEH). It is an electrical source that converts the vibrational energy into usable electrical energy to power up low-power portable or unreachable devices. The harvesting system can be self-powered as stand-alone or as alternative power source depending on the application. In this thesis, we have studied and developed two architectures for electromagnetic VEHs: a baseline VEH and a springless VEH. We introduced and studied power management circuits consisting of a full-wave bridge rectifier and a smoothing capacitor. Moreover, electromechanical model was developed and validated by the comparison to the experimental data. The basic electromagnetic VEH uses a mechanical mass-damper-spring oscillator to capture kinetic energy from vibrations. It has an electrical transducer using induction between a moving coil and a fixed magnets. It uses a cantilever suspension and operates at a frequency range of 57-59 Hz. We re-designed it using 80 turns coil-chip instead of 30-turns. The springless VEH works in a frequency range of 13-18 Hz. It was redesigned to carry 60-turns coil-chip. The re-design of the VEHs successfully increased the output voltage and power. The maximum power experimentally measured were 14.3mW and 12.27mW at optimal loads RL of 40 ohm and 3 ohm, respectively. The power management circuits introduced is consist of a MOSFET-based full-wave bridge rectifier and a smoothing capacitor to convert the VEH AC output waveform into a DC signal. We found that this rectifier can effectively convert the VEHs output with high voltage and power efficiencies > 93 %. The smoothing capacitor trades-in the signal ripples for lower voltage and power e efficiencies > 79 %. We identified the model parameters for the cantilever VEH, namely the natural frequency, mechanical Qm and total Qt quality factors, and effective average magnetic field density B. We solved the model equations numerically and analytically to find the eigenvalues, frequency response, output voltage and power. The model results agree with the obtained experimental results.
Optimal Material Selection for Transducers
(University of Waterloo, 2018-02-15) Seviora, Gregory; Yavuz, Mustafa; Abdel-Rahman, Eihab
When selecting an active material for an application, it is tempting to rely upon prior knowledge or commercial products that fit the design criteria. While this method is time effective, it does not provide an optimal selection. The optimal material selection requires an understanding of the limitations of the active material, understanding of the function, constraints and objectives of the device, and rigorous decision making method to ensure rational and clear material selection can be performed. Therefore, this work looks into the three most researched active materials (piezoelectrics, magnetostrictives and shape memory alloys) and looks at how they work and their difficulties. The field of piezoelectrics is vast and contains ceramics, plastics and cellular structures that couple the mechanical and electrical domain. The difficulty with piezoelectric ceramics is their small strains and the dependence of their coefficients on the ferroelectric domains. Giant magnetostrictives materials couple the mechanical and magnetic domains. They are generally better suited for low-frequency operations since they properties deteriorate rapidly with heat. Shape memory alloys are materials that couple thermal and mechanical domains. They have large strain but are limited in their force output, fatigue life and cycle frequency. Optimal material selection requires a formalized material selection method. In mechanical material selection, the formal material selection method uses function, constraints and objectives of the designer to limit the parameter space and allow better decisions. Unfortunately, active materials figures of merit are domain dependent and therefore the mechanical material selection method needs to be adapted. A review of device selection of actuators, sensors and energy harvesters indicates a list of functions, constrains and objectives that the designer can use. Through the analysis of these devices figures of merit, it is realized that the issue is that the simplification that the figures of merit perform does not assist in decision making process. It is better to use decision making methods that have been developed in the field of operational research which assists complex comparative decision making. Finally, the decision making methods are applied to two applications: a resonant cantilever energy harvester and an ultrasound transducer. In both these cases, a review of selection methods of other designers provides guidance of important figures of merit. With these selection methods in consideration, figures of merit are selected and used to find the optimal material based upon the designer preference.
Power Module Packaging in Automotive Applications
(University of Waterloo, 2016-05-02) Atelge, Muhammed Rasit; Yavuz, Mustafa; Abdel-Rahman, Eihab
In this study, nano silver paste was used as die attach material with the aim of increasing reliability of joints in power modules in automotive applications. Prior to joining, nano silver paste was spread on the interface between silver coated copper substrates and dummy chips by screen printing method. 5 groups of samples were produced using three different joining techniques based on different combinations of ultrasonic force and persistent pressure in air and vacuum atmospheres. The bonding quality of the interface region was evaluated by microstructural examination and quasi-static shear tests. On the other hand, electrical properties of sintered nano silver particles within the joints were characterized through resistivity measurements. Sintered nano silver regions in all samples exhibited two types of porosity, namely, macro and micro porosity. Macro pores formed during the evaporation and removal of organics present in the starting paste, while micro pores were left in the structure because of insufficient sintering of silver nano powders. Although the sintered silver interface in samples produced using 5 MPa persistent pressure in air displayed a minimum amount of porosity, pores as large as 5 m in diameter were observed in joints produced in air by a preload of 0.01 MPa with or without ultrasonic force. In addition, vacuum sintering yielded relatively porous interfaces compared to samples manufactured in air even though the same compaction pressure was applied during sintering. Accordingly, in the samples produced either in air by the application of low preloads of 0.01 MPa or in vacuum at 5MPa, additional microcracks were formed, particularly in the interface region between silver coating and sintered nano silver particles. Stress-strain curves of the joints exhibited linear elastic, small strain hardening and fracture regions similar to wrought alloys. The strengths of the joints increased proportionally to the degree of sintering as expected. The shear strength reached to 32 MPa in samples sintered in air at 5 MPa constant pressure, whereas shear strength decreased to 4 MPa in highly porous joints produced by ultrasonic force and preloading with 0.01 MPa. All samples revealed shear-type dimples in the direction of mechanical testing indicating ductile behavior of joints. The electrical resistivity of the sintered nano silver layer showed the same trend as the mechanical properties. The weakest or most porous joint had the highest electrical resistivity of approximately 125.5 μΩ-cm). On the other hand, the least porous silver joint, manufactured at 5 MPa constant pressure in air exhibited the lowest electrical resistivity (7.8 μΩ-cm); however, it was five times higher than that of bulk silver. The results have presented that the nano silver paste is the most promising die attach material to replace conventional solder and conductive epoxies.
Resonant Adaptive Mirrors
(University of Waterloo, 2020-05-28) Kamel, Amr; Yavuz, Mustafa; Abdel-Rahman, Eihab
Deformable mirrors (DMs) are integrated into adaptive optical (AO) systems to compensate for wavefront aberrations. These aberrations degrade the image resolution of telescopes, microscopes, ophthalmoscopes, and optical coherent tomographs. The objective of the DM in these applications is to compensate for wavefront aberrations. Continuous and segmented DMs utilize a variety of mechanisms such as electrostatic, piezoelectric, and electromagnetic actuation. Micro-electromechanical systems (MEMS) DMs have the advantages of low cost, low power consumption, and high electrode density. As the electrode count increases, the possibility of the desired modes corresponding to the Zernike modes appearing increases. However, the complexity of the static actuation also increases. In ophthalmology, fth order Zernike modes are used to categorize the aberrations induced by the human eye. These aberrations would degrade the image resolution of the retina during laser scanning. Therefore, a dynamically continuous DMs were developed and actuated at a natural frequency corresponding to the desired Zernike mode. The actuations would drive the mirror plate to deform into the shape of the desired mode. Multiple modes corresponding to low- and high-order Zernike modes were obtained. Resonant DMs exploit the dynamic ampli cation available at natural frequency's in order to reduce voltage and power requirements. This will also reduce the requirements for spatial control of individual electrodes' voltage. However, the use of circular mirror plates to create the electromechanical modes has led to the appearance of degenerate modes (pairs of almost identical modes with closely spaced frequencies). Electrostatic elds were designed to separate those modes and help break coupling between them. The elds employ selectively, actuating some of the electrodes under the DM while grounding the rest. An AC voltage was applied to selective scheme of electrodes in order to induced mode shapes that are corresponding to the Zernike modes. This design relies on a new technique which uses pulsed laser scanning instead of continuous laser scanning. The proposed DM was designed and fabricated using a Micra-GEM fabrication process. Simulations using the nite element method (FEM) software COMSOL were used in order to determine the natural frequencies and mode shapes, and to separate degenerate modes natural frequencies by applying electrostatic elds that increase the di erence between them. Characterization of the DM was conducted using laser Doppler vibrometer to identify the mode shapes and its natural frequencies experimentally. The stroke measurements of the target DM were shown as a function of frequency and amplitude. In addition, RMS error measurements were used as a comparison between DM modes and there corresponding Zernike mode. The aim of this research was to over come the in uence function due to mechanical coupling in the continuous DMs. In uence function requires di erent voltages that apply to electrode scheme. Therefore, static actuation of the DMs rely on a complex driving circuits. Resonant DMs eliminate the e ect of the in uence function by triggering the mirror via its natural frequencies. They reduce the number of red electrode scheme by applying single voltage to the electrodes. As a result, they reduce the complexity of the driving circuits that require to control its shape. This research requires a new technique of using a pulsed laser instead of a continuous laser for the proposed DM. This may lead to manipulation of the optical laser signal using the mirror as a part of the signaling process. This should be completed by synchronizing the frequencies of both the DM and the laser to produce a high resolution image of the retina.

Browse

Browsing Mechanical and Mechatronics Engineering by Author "Abdel-Rahman, Eihab"