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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
681

Magnetic Levitation of Polymeric Photo-thermal Microgrippers

Elbuken, Caglar January 2008 (has links)
Precise manipulation of micro objects became great interest in engineering and science with the advancements in microengineering and microfabrication. In this thesis, a magnetically levitated microgripper is presented for microhandling tasks. The use of magnetic levitation for positioning reveals the problems associated with modeling of complex surface forces and the use of jointed parts or wires. The power required for the levitation of the microgripper is generated by an external drive unit that makes further minimization of the gripper possible. The gripper is made of a biocompatible material and can be activated remotely. These key features make the microgripper a great candidate for manipulation of micro components and biomanipulation. In order to achieve magnetic levitation of microrobots, the magnetic field generated by the magnetic levitation setup is simulated. The magnetic flux density in the air gap region is improved by the integration of permanent magnets and an additional electromagnet to the magnetic loop assembly. The levitation performance is evaluated with millimeter size permanent magnets. An eddy current damping method is implemented and the levitation accuracy is doubled by reducing the positioning error to 20.3 µm. For a MEMS-compatible microrobot design, the electrodeposition of Co-Ni-Mn-P magnetic thin films is demonstrated. Magnetic films are deposited on silicon substrate to form the magnetic portion of the microrobot. The electrodeposited films are extensively characterized. The relationship between the deposition parameters and structural properties is discussed leading to an understanding of the effect of deposition parameters on the magnetic properties. It is shown that both in-plane and out-of-plane magnetized films can be obtained using electrodeposition with slightly differentiated deposition parameters. The levitation of the electrodeposited magnetic samples shows a great promise toward the fabrication of levitating MEMS devices. The end-effector tool of the levitating microrobot is selected as a microgripper that can achieve various manipulation operations such as pulling, pushing, tapping, grasping and repositioning. The microgripper is designed based on a bent-beam actuation technique. The motion of the gripper fingers is achieved by thermal expansion through laser heat absorption. This technique provided non-contact actuation for the levitating microgripper. The analytical model of the displacement of the bent-beam actuator is developed. Different designs of microgripper are fabricated and thoroughly characterized experimentally and numerically. The two microgripper designs that lead to the maximum gripper deflection are adapted for the levitating microrobot. The experimental results show that the levitating microrobot can be positioned in a volume of 3 x 3 x 2 cm^3. The positioning error is measured as 34.3 µm and 13.2 µm when electrodeposited magnets and commercial permanent magnets are used, respectively. The gripper fingers are successfully operated on-the-fly by aligning a visible wavelength laser beam on the gripper. Micromanipulation of 100 µm diameter electrical wire, 125 µm diameter optical fiber and 1 mm diameter cable strip is demonstrated. The microgripper is also positioned in a closed chamber without sacrificing the positioning accuracy.
682

One and Two-Dimensional Mass Spring Computational Model for Phononic Band Gap Analysis

Cao, Zhan John January 2009 (has links)
Computation model is presented for mass spring systems of one and two dimensional phononic band gap crystals and micro-electro-mechanical systems. The computation model is veri ed with existing work, and phononic band gap microelectro- mechanical systems are analyzed. Phononic band gap in the scienti c and industrial community is discussed. The motivation and the recent popular methods are discussed. The computation models are highlighted with their pros and cons and adequate computational applications. The one dimensional mass spring model is developed and the simulator operation is validated through comparison with the published simulation data in the original paper by J.S. Jensen et al.. Additionally, the one dimensional mass spring simulator is validated for a micro-electro-mechanical system band structure. The two dimensional mass spring model is developed, as well, the simulator operation is validated through comparison with the published simulation data in the original paper by J.S. Jensen et al.. The two-dimensional simulator is utilized to analyze solid square-shaped, hollow square-shaped, solid diamond-shaped, and hollow diamond-shaped inclusion micro-electro-mechanical band gap structures. The solid inclusion-based micro-electro-mechanical band gap results are compared with hollow inclusion-based micro-electro-mechanical structures.
683

Integrated Communications and Thermal Management Systems for Microsystem-based Spacecraft : A Multifunctional Microsystem Approach

Kratz, Henrik January 2006 (has links)
This thesis explores the potential of multifunctional silicon-based microsystems for advanced integrated nanospacecraft (AIN). Especially, multifunctional microsystems with the coexistant functions of communications and thermal management implemented in multilayer silicon stacks are approached with systems study. Host vehicles, composed of microsystems, including micro/nano-spacecraft and spherical rovers are contemplated with respect to future performance and implications, system level design, and breadboard realizations. A module of great importance, named the "integrated communications and thermal management system for advanced integrated spacecraft" or ICTM, symbolizes the achievements within the field of self-contained microsystems and is a prioritized entity throughout the thesis. The ICTM is natively placable onboard all types of highly miniaturized craft. The single AIN spacecraft and future clusters of these are investigated with respect to future full scale implementation of space systems designed and implemented with the distributed reconfigurable nanospacecraft cluster (DRNC) concept. Here, a true entanglement of microsystems technology (MST) and miniaturized spacecraft technology can revolutionize the applications, cost, and span of conceivable space missions. An intended communications scenario supporting a data rate of 1 Mbps, for the transmitter, is achieved during 6 minutes with a maximum continuous power dissipation of 10 W. Thermal simulations support the expectation, of a thermally biased ICTM, that the module is capable of supporting this energy burst, by using the mechanisms of heat storage and heat switches, and still fulfilling the requirements imposed by AIN type of spacecraft. In addition, multiple functional surfaces for the ICTM are evaluated with respect to equilibrium temperature and process compatibility. The tailored surfaces provide temperature control using micromachining methods. A design of a micromachined Ka-band front end with several MST enabled features is presented including e.g. vias, phase-shifters, and antennas. Similar antennas have been manufactured resulting in an evaluation of ring- and slot-antennas on silicon substrate. Based on a primitive version of the ICTM, a S-band patch antenna has been successfully implemented and characterized. Included in the thesis is a microthruster, an enabling technology for DRNC.
684

Fluidic Microsystems for Micropropulsion Applications in Space

Bejhed, Johan January 2006 (has links)
Spacecraft on interplanetary missions or advanced satellites orbiting the Earth all require propulsion systems to complete their missions. Introducing microelectromechanical systems technology to the space industry will not only reduce size and weight of the propulsion system, but can also increase the performance of the mission. Fluid handling systems are used in chemical and electric propulsion. Some components incorporated in a fluidic handling system are presented and evaluated in this work. Microsystems are very sensitive to contamination. Reliable, robust, and easily integrated filters were modeled, manufactured, and experimentally verified. A fluid connector, designed to withstand large temperature variations and aggressive propellants was manufactured and characterized. Similar designs was also be used as a thermally activated minute valve. The feasibility of a cold gas system for precise attitude control has been demonstrated. Steps towards improving the performance (from specific im-pulse 45 s) have been taken, by the integration of suspended heater elements. For electric propulsion, two thermally regulated flow restrictors have been characterized. These devices can fine-tune the propellant flow to e.g. an ion engine. A single-use valve using a soldered seal has also been successfully dem-onstrated within a pressure range of 5 to 100 bar. The microsystem-based propulsion systems of tomorrow’s spacecraft need to be demonstrated in space, in order to gain necessary credibility.
685

Användning av accelerometrar för detektering av rörelse i Husqvarna ABs gräsklippare Automower / Use of accelerometers for detection of movement in Husqvarna’s lawnmower Automower

Ivanic, Boris January 2008 (has links)
In order to detect movements and vibrations on different appliance, especially robots and self-going devices are used different sensors. One of the most used movement sensors are accelerometers. They are three different types of accelerometers one-axes, two-axes and three-axes. They can be analogue or digital. Husqvarna AB uses an accelerometer to detect movements of their self-going lawnmower Automower. Since it begins to turn up others sensors on the market and the sensor which today uses in Husqvarna’s lawnmower don’t fulfils all functions there is a need to find other solutions. What sensors can be found on a market and which new has come? How can they be used best and which difference is between them? How can they use to detect movements in x, y and z direction and how can they read different movements to detect collision, inclination and lift? Sensor analysis will be done to find out how they can be used in this matter and an big analysis will be done to find out how a sensor witch already is in a lawnmower can be use on the better ways? / För att kunna detektera rörelse och vibrationer på olika anordningar och framförallt robotar och självgående maskiner används olika sensorer. En av de mest använda rörelsesensorer är accelerometer. Det finns en uppsjö av olika utföringar som kan vara med en axel, två axlar eller tre axlar. Accelerometrar finns som digitala eller analoga. Husqvarna AB använder en sådan sensor för att detektera rörelse på sin självgående gräsklippare Automower. Eftersom det börjar dyka upp andra sensorer på marknaden och den sensor som används idag uppfyller inte alla funktioner finns det behov av att lägga tid på att se vad kan åstadkommas med en sådan sensor. Vilka sensorer kan hittas på marknaden och vilka nya har dykt upp? Hur kan de användas på bästa sätt och vad skiljer de åt? Hur kan de användas för att detektera rörelse i x, y, z-led och hur kan de läsa av olika rörelse för att detektera krock, lutning och lyft? Det skall göras analys för att se hur olika sensorer reagerar och hur kan de användas på bästa sätt. Det skall utforskas hur den sensor som redan sitter kan användas på ett bättre sätt.
686

Optical measuring system using a camera and laser fan-out for narrow mounting on a miniaturized submarine

Berglund, Martin January 2009 (has links)
The aim was to develop, manufacture and evaluate diffractive lenses, or diffractive optical elements (DOE), for use in correlation with a camera to add perspective in pictures. The application is a miniaturized submarine developed in order to perform distant exploration and analysis in harsh and narrow environments. The idea is to project a laser pattern upon the observed structure and thereby add geometrical information to pictures acquired with an onboard CMOS camera. The design of the DOE-structures was simulated using the optimal rotational angle method (ORA). A set of prototype DOEs were realized using a series of microelectromechanical system (MEMS) processes, including photolithography, deposition and deep reactive-ion etching (DRIE). The projected patterns produced by the manufactured DOEs were found to agree with the simulated patterns except for the case where the DOE feature size was too small for the available process technology to handle. A post-processing software solution was developed to extract information from the pictures, called Laser Camera Measurement (LCM). The software returns the x, y and z coordinate of each laser spot in a picture and provides the ability to measure a live video stream from the camera. The accuracy of the measurement is dependent of the distance to the object. Some of the patterns showed very promising results, giving a 3-D resolution of ~0.6 cm, in each dot, at a distance of 1 m from the camera. Lengths can be resolved up til 3 m distance from the submarine. / Tillämpningen finns i en miniatyriserad ubåt framtagen för utforskning och analys av svåråtkomliga och trånga håligheter. Målet var att designa, tillverka och utvärdera en diffraktiv lins (DOE) för användning tillsammans med en kamera för att skapa perspektiv i bilder. Idén var att projicera ett lasermönster på objektet och därmed lägga till geometrisk information till bilderna tagna med CMOS kameran. Utformningen av DOE-strukturerna simulerades med the optimal rotational angle method (ORA). En uppsättning av prototyp DOE-linser tillverkades med hjälp av en serie mikrostrukturteknikprocesser, bland annat fotolitografi, deponering och plasmaetsning. Mönster projicerade med de tillverkade DOE-linserna stämde väl överens med önskade mönster, med undantag för de DOEs där strukturstorleken underskred processens begränsningar. En programvara, kallad Laser Camera Measurement (LCM), utvecklades för att extrahera information från bilderna. Programvaran returnerar x, y, och z koordinaterna för varje laserpunkt i en bild och ger möjlighet att mäta i en kontinuerlig videoström från kameran.  Mätosäkerheten är beroende av avståndet till objektet. Vissa mönster gav mycket lovande resultat, med en 3-D upplösning på ~0.6 cm, i varje punkt, på ett avstånd av 1 m från kameran. Längder kan upplösas upp till 3 m från kameran där ett så kallat far-field uppstår. / DADU
687

Mechanically Tunable RF/Microwave Filters: from a MEMS Perspective

Yan, Dong 22 June 2007 (has links)
RF/microwave tunable filters are widely employed in radar systems, measurement instruments, and communication systems. By using tunable filters, the frequency bandwidth is utilized effectively and the system cost and complexity is reduced. In the literature, various tuning techniques have been developed to construct tunable filters. Mechanical tuning, magnetic tuning, and electrical tuning are the most common. In terms of quality factor, power handling capability, and linearity, mechanical tuning is superior to the other two tuning techniques. Unfortunately, due to their bulky size, heavy weight, and low tuning speed, mechanically tunable filters have limited applications. MicroElectroMechanical Systems (MEMS) technology has the potential to produce highly miniaturized tunable filters; however, most of the MEMS tunable filters reported so far have a relatively low quality factor. The objective of the research described in this thesis is to investigate the feasibility of using MEMS technology to develop tunable filters with a high quality factor. The integration of MEMS tuning elements with a wide range of filter configurations is explored, from micromachined filters to traditional dielectric resonator filters, from planar filters to cavity filters. Both hybrid integration and monolithic integration approaches are carried out. To achieve tunability, MEMS tuning elements are embedded within RF and microwave filters. Tuning is accomplished by disturbing the electromagnetic fields of resonators with nearby MEMS tuning elements, which in turn change the resonant frequency of the resonators. First, the proposed tuning concept is experimentally demonstrated by integrating a surface micromachined planar filter with MEMS thermal actuators as the tuning elements. Then, a novel micromachined ridge waveguide filter embedded with similar MEMS tuning elements is proposed and constructed by using the EFAB^{TM} micromachining technique. A power handling analysis is performed for the newly devised 3D micromachined filter, and potential failure mechanisms such as air breakdown are identified. For the first time, a tunable dielectric resonator bandpass filter, incorporating vertical long-throw MEMS thermal actuators as tuning elements, is developed to achieve a wide tuning range, high quality factor, and large power handling capability. Several prototype tunable filter units are fabricated and tested. The experimental results reveal that the tunable filters maintain a relatively high quality factor value over a wide tuning range. In addition to the hybrid integration approach, a monolithic integration approach is investigated. A novel surface micromachining process is developed to allow monolithic integration of MEMS tuning elements into micromachined filters. Due to a stress mismatch, MEMS actuators fabricated by this process obtain a vertical deflection of several hundred microns, resulting in a wide tuning range. Various latching mechanisms are created, based on the micromachining processes that are used to fabricate the MEMS tuning elements. These out-of-plane latching mechanisms with multi-stable states have the potential to be adopted not only for tunable filter applications but also for switches and phase shifters.
688

Micro-electro-thermo-magnetic Actuators for MEMS Applications

Forouzanfar, Sepehr 22 November 2006 (has links)
This research focuses on developing new techniques and designs for highly con- trollable microactuating systems with large force-stroke outputs. A fixed-fixed mi- crobeam is the actuating element in the introduced techniques. Either buckling of a microbridge by thermal stress, lateral deflection of a microbridge by electro- magnetic force, or combined effects of both can be employed for microactuation. The proposed method here is MicroElectroThermoMagnetic Actuation (METMA), which uses the combined techniques of electrical or electro-thermal driving of a mi- crobridge in the presence of a magnetic field. The electrically controllable magnetic field actuates and controls the electrically or electrothermally driven microstruc- tures. METMA provides control with two electrical inputs, the currents driving the microbridge and the current driving the external magnetic field. This method enables a more controllable actuating system. Different designs of microactuators have been implemented by using MEMS Pro as the design software and MUMPs as the standard MEMS fabrication technology. In these designs, a variety of out-of- plane buckling or displacement of fixed-fixed microbeams have been developed and employed as the actuating elements. This paper also introduces a novel actuating technique for larger displacements that uses a two-layer buckling microbridge actu- ated by METMA. Heat transfer principles are applied to investigate temperature distribution in a microbeam, electrothermal heating, and the resulting thermoelas- tic effects. Furthermore, a method for driving microactuators by applying powerful electrical pulses is proposed. The integrated electromagnetic and electrothermal microactuation technique is also studied. A clamped-clamped microbeam carry- ing electrical current has been modeled and simulated in ANSYS. The simulations include electrothermal, thermoelastic, electromagnetic, and electrothermomagnetic effects. The contributions are highlighted, the results are discussed, the research and design limitations are reported, and future works are proposed.
689

Novel MEMS Tunable Capacitors with Linear Capacitance-Voltage Response Considering Fabrication Uncertainties

Shavezipur, Mohammad January 2008 (has links)
Electrostatically actuated parallel-plate MEMS tunable capacitors are desired elements for different applications including sensing, actuating and communications and RF (radio frequency) engineering for their superior characteristics such as quick response, high Q-factor and small size. However, due to the nature of their coupled electrostatic-structural physics, they suffer from low tuning range of 50% and have nonlinear capacitance-voltage (C-V) responses which are very sensitive to the voltage change near pull-in voltage. Numerous studies in the literature introduce new designs with high tunability ranging from 100% to over 1500%, but improvement of the nonlinearity and high sensitivity of the capacitor response have not received enough attention. In this thesis, novel highly tunable capacitors with high linearity are proposed to reduce sensitivity to the voltage changes near pull-in. The characteristic equations of a perfectly linear capacitor are first derived for two- and three-plate capacitors to obtain insight for developing linear capacitance-voltage responses. The devices proposed in this research may be classified into three categories: designs with nonlinear structural rigidities, geometric modifications and flexible moving electrodes. The concept of nonlinear supporting beams is exploited to develop parallel-plate capacitors with partially linear C-V curves. Novel electrodes with triangular, trapezoidal, butterfly, zigzag and fishbone shapes and structural/geometric nonlinearities are used to increase the linearity and tuning ratio of the response. To investigate the capacitors' behavior, an analytical approximate model is developed which can drastically decrease the computation time. The model is ideal for early design and optimization stages. Using this model, design variables are optimized for maximum linearity of the C-V responses. The results of the proposed modeling approach are verified by ANSYS FEM simulations and/or experimental data. When the fabrication process has dimensional limitations, design modifications and geometric enhancements are implemented to improve the linearity of the C-V response. The design techniques proposed in this thesis can provide tunabilities ranging from 80% to over 350% with highly linear regions in resulting C-V curves. Due to the low sensitivity of the capacitance to voltage changes in new designs, the entire tuning range is usable. Furthermore, the effect of fabrication uncertainties on parallel-plate capacitors performance is studied and a sensitivity analysis is performed to find the design variables with maximum impact on the C-V curves. An optimization method is then introduced to immunize the design against fabrication uncertainties and to maximize the production yield for MEMS tunable capacitors. The method approximates the feasible region and the probability distribution functions of the design variables to directly maximize the yield. Numerical examples with two different sets of design variables demonstrate significant increase in the yield. The presented optimization method can be advantageously utilized in design stage to improve the yield without increasing the fabrication cost or complexity.
690

Magnetic Levitation of Polymeric Photo-thermal Microgrippers

Elbuken, Caglar January 2008 (has links)
Precise manipulation of micro objects became great interest in engineering and science with the advancements in microengineering and microfabrication. In this thesis, a magnetically levitated microgripper is presented for microhandling tasks. The use of magnetic levitation for positioning reveals the problems associated with modeling of complex surface forces and the use of jointed parts or wires. The power required for the levitation of the microgripper is generated by an external drive unit that makes further minimization of the gripper possible. The gripper is made of a biocompatible material and can be activated remotely. These key features make the microgripper a great candidate for manipulation of micro components and biomanipulation. In order to achieve magnetic levitation of microrobots, the magnetic field generated by the magnetic levitation setup is simulated. The magnetic flux density in the air gap region is improved by the integration of permanent magnets and an additional electromagnet to the magnetic loop assembly. The levitation performance is evaluated with millimeter size permanent magnets. An eddy current damping method is implemented and the levitation accuracy is doubled by reducing the positioning error to 20.3 µm. For a MEMS-compatible microrobot design, the electrodeposition of Co-Ni-Mn-P magnetic thin films is demonstrated. Magnetic films are deposited on silicon substrate to form the magnetic portion of the microrobot. The electrodeposited films are extensively characterized. The relationship between the deposition parameters and structural properties is discussed leading to an understanding of the effect of deposition parameters on the magnetic properties. It is shown that both in-plane and out-of-plane magnetized films can be obtained using electrodeposition with slightly differentiated deposition parameters. The levitation of the electrodeposited magnetic samples shows a great promise toward the fabrication of levitating MEMS devices. The end-effector tool of the levitating microrobot is selected as a microgripper that can achieve various manipulation operations such as pulling, pushing, tapping, grasping and repositioning. The microgripper is designed based on a bent-beam actuation technique. The motion of the gripper fingers is achieved by thermal expansion through laser heat absorption. This technique provided non-contact actuation for the levitating microgripper. The analytical model of the displacement of the bent-beam actuator is developed. Different designs of microgripper are fabricated and thoroughly characterized experimentally and numerically. The two microgripper designs that lead to the maximum gripper deflection are adapted for the levitating microrobot. The experimental results show that the levitating microrobot can be positioned in a volume of 3 x 3 x 2 cm^3. The positioning error is measured as 34.3 µm and 13.2 µm when electrodeposited magnets and commercial permanent magnets are used, respectively. The gripper fingers are successfully operated on-the-fly by aligning a visible wavelength laser beam on the gripper. Micromanipulation of 100 µm diameter electrical wire, 125 µm diameter optical fiber and 1 mm diameter cable strip is demonstrated. The microgripper is also positioned in a closed chamber without sacrificing the positioning accuracy.

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