Advanced Materials Research Vols. 403-408

Abstract: Metcognitive learning has been developed to 1) enhance students to have awareness for conducting self study, 2) verify metacognitive knowledge and 3) provide proper lessons for each student. The test of metacognitive knowledge was implemented, and at least two out of three metacognitive knowledges; knowledge of self, knowledge of task, and knowledge of strategy, should be presented so that students’ metacognitive regulation can be proved. Therefore classification techniques were proposed to classify metacognitive knowledge of students via accuracy comparison of four classification techniques: Bayesian classifier, Decision Tree, Rule Based, and General Classification as 92.04%, 91.22%, 86.56%, and 92.87% respectively. Nonetheless, Bayesian Classifier is selected to be algorithm for metacognitive learning environment.

Abstract: This paper introduces three methods to increase the output power of the vibration based electrostatic MEMS energy converters. This will be done by taking the effect of the parallel capacitance of the converter in the output power equation. In addition the output power of the converter will be increased by two other ways: Firstly, by depositing dielectric materials on the sidewalls of the converter fingers, secondly, by increasing the converter thickness. In addition the output power will be increased to an optimum value by combining the effect of increasing the device thickness and depositing dielectric materials on the sidewalls of the converter fingers.

Abstract: This paper introduces the design of the power conditioning circuit for electrostatic MEMS energy converters and how it is effective in decreasing the dissipated power to be suitable for energy scavenging systems. This will be done firstly by explaining the need for the power conditioning circuit. Then the use of each of its element and how to design it will be introduced. Finally the dissipated power in the power conditioning circuit due to the non – ideality of its elements will be calculated.

Abstract: This paper introduces the steps for fabricating an electrostatic MEMS converter found in energy scavenging systems. The fabrication carried out at Rensselaer Polytechnic Institute (RPI) clean room, Troy, New York, USA. The testing results for the fabricated converter are presented. The main objective of fabricating and testing the electrostatic MEMS converter is to verify the new idea of enhancing its output power by including the effect of its parallel capacitance in the output power equation.

Abstract: In recent years, assembling and packaging methods of Micro Electro Mechanical System (MEMS) components have been profoundly studied. The focus of this paper is presenting a novel alignment technique in wafer-level packaging. In conventional wafer-level strategies, either an Alignment Template (AT) must have special receptor sites according to the microchip geometry and its material, or the microcomponents should be additionally featured by circular and cross pegs for shape recognition stage. In this article, we have developed electrothermal microclamps (ETMCs) to hold and locate six microchips of 360×360×20 micrometers in a microfixturing cell. This is to provide accurate preliminary positioning for final flip-chip bonding process of wafer-level packaging on a main assembly board (MAB). The new approach enjoys the advantages of omitting special AT with receptor sites and using identical ETMCs for diverse assembly configurations. Being applicable for different types of microcomponent materials, it does necessitate no surface treatment on microcomponents such as Semidry uniquely orienting self-organizing parallel assembly (Semi-DUO-SPASS) technique. Comparing nickel and polysilicon as fabrication materials, corresponding values of input voltage to reach 3 micrometers displacement of the ETMC arm are estimated via finite element analysis to ascertain positioning and holding of microchips. Nickel showed to be a better choice for fabrication due to requiring lower input voltage and lower maximum resulting temperature. The simulation results are verified with published experimental measurements.

Abstract: This paper presents a novel procedure to calibrate the strap-down 3-axis MEMS accelerometers for UAV navigat-ion. Firstly, we establish an explicit calibration model with the measurement values of accelerometers, where the calibration is realized via geometric transformations. Secondly, the transfor-mation parameters are calculated through particle swarm optimization (PSO). For the problem of slower convergence rates near the global optimum, the classical PSO algorithm is improved. Based on the numerical optimization idea, the steepest descent method is introduced to PSO. The parameters are searched in the rough by adopting PSO and the precision ones are found by using steepest descent method. Then, the optimal transformation is achieved by the minimum distance function based on this improved PSO(IPSO) algorithm. Finally, the calibration procedure is tested by comparing the attitude produced by the 3-axis accelerometers with that measured by a turntable. The results show that the IPSO algorithm can significantly improve the performance of the classical PSO algorithm, and the maximum attitude error is reduced to 6% of that before calibration. In addition, the proposed procedure does not rely on prior knowledge of the accelerometers and any equipment. So, it is suitable for calibration in field. Such a method is especially useful in UAV applications.

Abstract: Squeeze film damping effect of MEMS parallel plate structure was analyzed based on thin film and Reynolds Equation in ANSYS under the different Knudsen numbers. Perforation effect of parallel plate with certain size and operating frequency was achieved under the different Knudsen numbers, the simulation results of two methods are very close. For unperforated plate, when Knudsen number is below 0.01, the discrepancy of two simulations is nonsignificant, and it grows up with Knudsen number. But gas rarefaction effects related with Knudsen number was considered in heat transfer analogy theory and used viscosity modification according to Veijola model, two simulations get the same result. For perforated plate, the simulation discrepancy of two methods will be great because of channel flow's effect and also grow up with Knudsen number, it can't be avoided even if the channel flow's effect and viscosity modification were concerned in heat transfer analogy theory.

Abstract: ANSYS thin film analysis was adopted to simulate the effects of squeeze film damping. The relation of damping effects versus operating frequency, velocity, material accommodation factor was analyzed, and the gas squeeze film damping and pressure distribution was simulated by steady-state analysis or harmonic analysis. Moreover, pressure distribution of damping effect in plate gap both with perforated holes and without holes, were determined and compared. Simulation results show that operating frequency and the structure of microstructures are the main influencing factors to air damping and perforated holes in plate gap can control stiffness coefficients of squeezed film damping.

Abstract: In order to realize the miniaturization of fuze safety mechanism, a novel MEMS safe and arm is proposed through concept, analysis, design and initial prototyping. A microscale inertial mechanical logic for mechanical safe and arm functions in the form of sliders, springs, and locks that interact on a planar substrate in response to setback acceleration and centrifugal force to thereby arm the fuze, and the bulk fabrication process were analyzed. The safety criteria, design principles, modeling and simulation methods for arming slider, setback lock, and arming lock are introduced. Air gun testing demonstrates the feasibility of MEMS safe and arm device and the validity of the design method.

Abstract: MEMS devices, Micro Electro-Mechanical Systems, are electrical and mechanical systems with characteristic dimensions on the order of microns. Since these systems have moving mechanical parts, characterization of their dynamics, including their modal parameters, is highly desirable. This paper describes the validation of an existing implementation of the Stochastic Subspace Identification (SSI) algorithm, called MACEC, for experimental modal analysis of a micro-cantilever switch. A white noise signal applied to the built-in electrostatic actuator in the switches excited a response measured using microscanning Laser Doppler Vibrometry (LDV). The modal parameters found using MACEC matched well those predicted by theory, thus validating this combination for experimental modal analysis of MEMS structures.