Multi-level fine pointing test-bed for space applications

For space applications that need high accuracy pointing of the payload, fine pointing system is an indispensable tool. To reach high level of high accuracy pointing and tracking, proper synchronization between the attitude of the satellite and each stage of the pointing module should be considered. This study focuses on developing and demonstrating staging control for fine pointing system. Currently, an experimental model for multi-stage control has been built in the laboratory to be used as a testbed and a teaching tool to validate the control strategies. This paper gives a brief introduction of the study, experimental model design criteria and staging control strategy. An example of a controller synthesis for multi-stage actuators based on Hinfinity is also presented

Design and Analysis of MEMS-based Microballoon Actuators for Aerodynamic Control of Flight Vehicles

The development of microelectromechanical systems (MEMS) technology and the suitability and compatibility of sizes of microactuators with the boundary layer thickness fueled the active flow separation control to gain the air flow momentum for the last few years. The present paper deals with the development of a robust, largedeflection, and large-force MEMS-based microballoon actuator for aerodynamic control of flight vehicles such as projectiles, micro air vehicles, aircrafts, etc. Experiments were carried out on the scaled-up models for different input pressure conditions to study the response of microballoon actuator. To evaluate the performance of the microballoon actuators, simulation studies on MEMS scale models were conducted in the CoventorWare environment. Simulation studies involving static and dynamic analyses have been carried-out on the microballoon actuator models. Various geometric and input parameters influencing the behaviour of the microballoon actuator were investigated. It has been observed that a maximum deflection of 1.2 mm to 1.5 mm can be achieved using microballoon actuators and the maximum operational frequency of 60 Hz to 80 Hz can be used for the operation of microballoon actuators. Also, the sizes of the microballoon actuators designed are compatible and suitable tobe used in turbulent boundary layer of aerodynamic flight vehicles.Defence Science Journal, 2009, 59(6), pp.642-649, DOI:http://dx.doi.org/10.14429/dsj.59.157

Dynamic modelling for thermal micro-actuators using thermal networks.

International audienceThermal actuators are extensively used in microelectromechanical systems (MEMS). Heat transfer through and around these microstructures are very complex. Knowing and controlling them in order to improve the performance of the micro-actuator, is currently a great challenge. This paper deals with this topic and proposes a dynamic thermal modelling of thermal micro-actuators. Thermal problems may be modelled using electrical analogy. However, current equivalent electrical models (thermal networks) are generally obtained considering only heat transfers through the thickness of structures having considerable height and length in relation to width (walls). These models cannot be directly applied to micro-actuators. In fact, microactuator congurations are based on 3D beam structures, and heat transfers occur through and around length. New dynamic and static thermal networks are then proposed in this paper. The validities of both types of thermal networks have been studied. They are successfully validated by comparison with nite elements simulation and analytical calculations

A reconfigurable tactile display based on polymer MEMS technology

This research focuses on the development of polymer microfabrication technologies for the realization of two major components of a pneumatic tactile display: a microactuator array and a complementary microvalve (control) array. The concept, fabrication, and characterization of a kinematically-stabilized polymeric microbubble actuator (¡°endoskeletal microbubble actuator¡±) were presented. A systematic design and modeling procedure was carried out to generate an optimized geometry of the corrugated diaphragm to satisfy membrane deflection, force, and stability requirements set forth by the tactile display goals. A refreshable Braille cell as a tactile display prototype has been developed based on a 2x3 endoskeletal microbubble array and an array of commercial valves. The prototype can provide both a static display (which meets the displacement and force requirement of a Braille display) and vibratory tactile sensations. Along with the above capabilities, the device was designed to meet the criteria of lightness and compactness to permit portable operation. The design is scalable with respect to the number of tactile actuators while still being simple to fabricate. In order to further reduce the size and cost of the tactile display, a microvalve array can be integrated into the tactile display system to control the pneumatic fluid that actuates the microbubble actuator. A piezoelectrically-driven and hydraulically-amplified polymer microvalve has been designed, fabricated, and tested. An incompressible elastomer was used as a solid hydraulic medium to convert the small axial displacement of a piezoelectric actuator into a large valve head stroke while maintaining a large blocking force. The function of the microvalve as an on-off switch for a pneumatic microbubble tactile actuator was demonstrated. To further reduce the cost of the microvalve, a laterally-stacked multilayer PZT actuator has been fabricated using diced PZT multilayer, high aspect ratio SU-8 photolithography, and molding of electrically conductive polymer composite electrodes.Ph.D.Committee Chair: Allen,Mark; Committee Member: Bucknall,David; Committee Member: Book,Wayne; Committee Member: Griffin,Anselm; Committee Member: Yao,Donggan

Modeling of Magnetoelectric Microresonator Using Numerical Method and Simulated Annealing Algorithm

A comprehensive understanding of the linear/nonlinear dynamic behavior of wireless microresonators is essential for micro-electromechanical systems (MEMS) design optimization. This study investigates the dynamic behaviour of a magnetoelectric (ME) microresonator, using a finite element method (FEM) and machine learning algorithm. First, the linear/nonlinear behaviour of a fabricated thin-film ME microactuator is assessed in both the time domain and frequency spectrum. Next, a data driven system identification (DDSI) procedure and simulated annealing (SA) method are implemented to reconstruct differential equations from measured datasets. The Duffing equation is employed to replicate the dynamic behavior of the ME microactuator. The Duffing coefficients such as mass, stiffness, damping, force amplitude, and excitation frequency are considered as input parameters. Meanwhile, the microactuator displacement is taken as the output parameter, which is measured experimentally via a laser Doppler vibrometer (LDV) device. To determine the optimal range and step size for input parameters, the sensitivity analysis is conducted using Latin hypercube sampling (LHS). The peak index matching (PIM) and correlation coefficient (CC) are considered assessment criteria for the objective function. The vibration measurements reveal that as excitation levels increase, hysteresis variations become more noticeable, which may result in a higher prediction error in the Duffing array model. The verification test indicates that the first bending mode reconstructs reasonably with a prediction accuracy of about 92 percent. This proof-of-concept study demonstrates that the simulated annealing approach is a promising tool for modeling the dynamic behavior of MEMS systems, making it a strong candidate for real-world applications

Towards smart self-clearing glaucoma drainage device.

For patients who are unresponsive to pharmacological treatments of glaucoma, an implantable glaucoma drainage devices (GDD) are often used to manage the intraocular pressure. However, the microscale channel that removes excess aqueous humor from the anterior chamber often gets obstructed due to biofouling, which necessitates additional surgical intervention. Here we demonstrate the proof-of-concept for smart self-clearing GDD by integrating magnetic microactuators inside the drainage tube of GDD. The magnetic microactuators can be controlled using externally applied magnetic fields to mechanically clear biofouling-based obstruction, thereby eliminating the need for surgical intervention. In this work, our prototype magnetic microactuators were fabricated using low-cost maskless photolithography to expedite design iteration. The fabricated devices were evaluated for their static and dynamic mechanical responses. Using transient numerical analysis, the fluid–structure interaction of our microactuator inside a microtube was characterized to better understand the amount of shear force generated by the device motion. Finally, the anti-biofouling performance of our device was evaluated using fluorescein isothiocyanate labeled bovine serum albumin. The microactuators were effective in removing proteinaceous film deposited on device surface as well as on the inner surface of the microchannel, which supports our hypothesis that a smart self-clearing GDD may be possible by integrating microfabricated magnetic actuators in chronically implanted microtubes

Steady-state and transient analysis of electro-thermal microactuators using finite element methods

Recent techniques in radar and communication systems favor the development of phased arrays. The major problems to such systems are size and cost due to the large number of individual transmit/receive modules required. Photonic systems implemented in MEMS technology have reduced bulk optical systems to microscale proportions. This reduction in scale is particularly important to phased arrays since it allows flexibility in deployment. This thesis aims to understand the steady state and transient characteristics of an electrically heated, thermally driven, surface micromachined MEMS polysilicon beam flexure actuator to be employed for the rotation of an r-f phase shifter utilized in phased array systems. The characteristics of the thermal actuator are examined through finite element analysis by investigating the relative importance of the temperature dependencies of the material properties of MUMPs polysilicon. The comprehensive finite element model of the thermal actuator developed using ANSYS 5.6, a commercial finite element package, has the ability to include full temperature dependencies of all parameters and also has the capacity to impose all heat transfer modes, which are beyond the capabilities of current analytical models. Steady-state thermal profiles of the thermal actuator are presented for the thermal actuator in an environment of air and vacuum. The model is validated indirectly by comparing the steady-state deflections with measured data of six thermal actuators of different geometries. The finite element simulations are also validated with a previous analytical model to compare model accuracy. The dynamic behavior of the thermal actuator is examined in both air and vacuum, which gives an insight into power and energy consumption of the thermal actuator. Initial results show a limited power and energy savings for the thermal actuator operated in vacuum over that operated in air. Design optimization of the thermal actuator is investigated using the ANSYS Parametric Design Language (APDL) with the Subproblem Approximation Method for maintaining low power consumption. An indirect method is employed by maximizing the steady-state deflection for unloaded actuators and minimizing the steady-state deflection for loaded actuators for the same applied voltage. A significant reduction in power consumption with an increase in the maximum steady-state deflection has been observed for unloaded actuators. For loaded actuators the available force output is increased slightly, the steady-state deflection decreased slightly and the power consumption increased slightly

Microelectromechanical Systems and Devices

The advances of microelectromechanical systems (MEMS) and devices have been instrumental in the demonstration of new devices and applications, and even in the creation of new fields of research and development: bioMEMS, actuators, microfluidic devices, RF and optical MEMS. Experience indicates a need for MEMS book covering these materials as well as the most important process steps in bulk micro-machining and modeling. We are very pleased to present this book that contains 18 chapters, written by the experts in the field of MEMS. These chapters are groups into four broad sections of BioMEMS Devices, MEMS characterization and micromachining, RF and Optical MEMS, and MEMS based Actuators. The book starts with the emerging field of bioMEMS, including MEMS coil for retinal prostheses, DNA extraction by micro/bio-fluidics devices and acoustic biosensors. MEMS characterization, micromachining, macromodels, RF and Optical MEMS switches are discussed in next sections. The book concludes with the emphasis on MEMS based actuators

Optical packaging of microlens over UV-LED array

Abstract unavailable please refer to PD

Design, modeling, fabrication, and testing of a multistage micro gas compressor with piezoelectric unimorph diaphragm and passive microvalves for microcooling applications

This dissertation investigates the development of a multistage micro gas compressor utilizing multiple pump stages cascaded in series to increase the pressure rise with passive microvalves and piezoelectric unimorph diaphragms. This research was conducted through modeling, simulation, design, and fabrication of the microcompressor and its components. A single-stage and a two-stage microcompressor were developed to demonstrate and compare the performance and effectiveness of using a cascaded multistage design. Steady fluid flow through static microvalves structure was studied to gain insight on its gas flow dynamics and characteristics. Transient analysis combined with the structure\u27s interaction was investigated with an analytical model and FEM model. The static analysis and transient analysis enabled lumped model parameter extraction for modeling and simulations. The transient FEM solution of the microvalve fluid-structure interaction (FSI) allows for extraction of the damping ratio for the lumped model. The microvalves were fabricated with MEMS microfabrication methods and integrated into a machined microcompressor housing. Study from the simulation of the microvalve fluid-structure dynamics in Simulink showed the frequency of the microvalves, at which frequency the mierovalve is more prone to leakage. Simulation indicated that the reverse leakage from the sealing of the microvalve can have a significant impact on the pressure rise performance of the compressor. A model of the single- and the two-stage microcompressor were developed with Simulink to observe the dynamics and performance of the multistage microcompressor. The simulation shows the dead volume between the two chambers to decrease in the overall pressure rise of the multistage microcompressor. Operating scenarios with different frequency and in phase and out of phase actuation between stages were simulated to understand the dynamics and performance of the multistage design. The fabricated single- and two-stage microcompressor produced a maximum pressure rise of 10 kPa and 18 kPa, respectively, and a maximum flow rate of 32 sccm for both. To obtain these maximum pressure rises, the microcompressors were operated at high frequency at the resonance of the piezoelectric diaphragm. This dissertation investigated the feasibility and operation of a multistage gas microcompressor with passive microvalves, allowing the exploration of its miniaturization