Showing 13 results for Mems
Ehsan Davoodi, Mhadi Rezaei,
Volume 14, Issue 3 (6-2014)
Abstract
This paper presents the inverted PID control of a quadrotor based on the experimentally measured sensors and actuators’ specifications. The main goal is the control and closed loop simulation of a quadrotor using inverted PID algorithm. First, a nonlinear model of quadrotor is derived using Newton-Euler equations. To have a more realistic simulation a setup were designed and developed to measure the sensors noise performance as well as the actuators’ dynamics. The setup involves a platform that two brushless motors mounted at the ends and rotates on a shaft. The platform attitude is measured using the MEMS sensors attached to it. A Kalman filter was used to reduce the sensors noises effect. Results demonstrate good performance for Kalman filter and the controller.
Amir R. Askari, Masoud Tahani,
Volume 14, Issue 8 (11-2014)
Abstract
Rrectangular plates-based resonant micro-sensors utilize the resonance frequency of electrically pre-deformed clamped micro-plates for sensing. Free vibration analysis of such systems in order to find their resonance frequency is the objective of present paper. For this aim, the modified couple stress theory (MCST) together with the Kirchhoff plate model is considered and the size-dependent equation of motion which accounts for the effect of axial residual stresses as well as the non-linear and distributed electrostatic force is derived using the Hamilton's principle. The lowest frequency of the system as the resonance frequency of these micro-plates is extracted using a single mode Galerkin based reduced order model (ROM). It is found that the fundamental frequency of the system is decreased with an increase of applied voltage and becomes zero when the input voltage reaches the pull-in voltage of the system. The findings of present paper are compared and validated by available results in the literature and an excellent agreement between them is observed. Also it is found that using the MCST in pull-in analysis of clamped rectangular micro-plates can remove the existing gap between the results of classical theory (CT) and available empirical observations. Furthermore, it is observed that accounting for the size-effect on free vibration analysis of electrostatically pre-deformed micro-plates is more essential than flat ones.
Mina Ghanbari, Siamak Hossainpour, Ghader Rezazadeh,
Volume 14, Issue 10 (1-2015)
Abstract
In this paper, squeeze film damping in a micro-beam resonator based on micro-polar fluid theory has been investigated. The proposed model for this study consists of a clamped-clamped micro-beam suspended between two fixed stratums. The gap between the micro-beam and stratums is filled with air. Equation of motion governing the transverse deflection of the micro-beam based on strain gradient theory and also non-linear Reynolds equation of the fluid field based on micro-polar theory have been non-dimensionalized, linearized and solved simultaneously to calculate the quality factor of the squeeze film damping. The effect of non-dimensional length scale parameter of the air and micro-beam for different values of micro-polar coupling parameter has been investigated. It has been shown that applying micro-polar theory underestimates and also applying strain gradient theory overestimates the values of quality factor that are obtained in the case of classic theory. The quality factor of the squeeze film damping for different values of non-dimensional length of the beam, squeeze number and non-dimensional pressure have been calculated and compared to the obtained values of quality factor based on classic theory.
Mahdi Rezaei, Meghdad Babaei,
Volume 14, Issue 14 (3-2015)
Abstract
The Stewart platform with six degree of freedom (three translational and three rotational motions) consists of two rigid bodies, lower plate (base) and upper one (mobile). These two bodies are connected together by six extensible legs between three pairs of joints on each of the bodies. This platform can be used to isolate the top plate of the platform and its payload from the applied motions to the base. Since the passive isolation methods are not effective in elimination of the high amplitude (and usually) low frequency motions, this paper practically investigates the possibility of using the 6DOF Stewart platform as an active vibration isolator. In this study, a Stewart platform was designed and constructed based on electric actuators (servo-motors). And then it was practically utilized to isolate its top plate from the applied pitch and roll rotations to the base plate. MEMS sensors including two accelerometers and one rate gyro along with Kalman filter and kinematic relations were utilized for measuring the pitch and roll motions. A PI controller was implemented to keep the top plate at level position using the MEMS sensors installed on the bottom plate. The experimental results indicated that the platform can effectively isolate the pitch and roll motions while the frequency of these motions is in the working speed range of the electric actuators.
Navid Seyedkazem Viliani, Mehdi Hashemi, Hadi Vadizadeh, Hassan Pourrostami, Seyed Mohsen Mostafavi, Faramand Hashemizadeh,
Volume 14, Issue 16 (3-2015)
Abstract
This article presents analytical and empirical studies of a micro-electromechanical package. This micro-electro-mechanical (MEMS) pressure sensor package contains of a printed circuit board (PCB), the capacitance LCD. First of all, mathematical modeling and computer simulation using software COMSOL software which is based on finite element method are presented to compute the sensitivity of the MEMS pressure sensor and output voltage output. It is worth noting that an Xducer resistor type is adopted to measure the diaphragm deflection. In addition to static and modal analyses of the sensor, the effects of geometric parameters on the voltage has also been studied. Simulation results show that by changing the size and position of the resistor and also the size and thickness of the diaphragm, sensor sensitivity can be changed. Then, with the construction and placement of components on printed circuit boards, the package has been prepared and tested in a laboratory. The experimental results of the package show that the error of the devised system in measuring the pressure is less than 0.5 percent. This pressure sensor package is capable of accurately measuring the pressure up to 6 bar in which all the empirical results are presented at the end of the study. The package can be designed according to the requirements of the petrochemical industry in measuring gas pressure of storage tanks and drums in FANAVARN petrochemical company.
Ehsan Poloei, Mahdi Zamanian, Seyed Ali Asghar Hosseini,
Volume 15, Issue 5 (7-2015)
Abstract
In this study, the static deflection and natural frequency of an electrostatically excited patch-coated microcantilever beam are analyzed. The proposed model is considered as the main element of many microsensors and microswitches. Firstly, the nonlinear motion equation is extracted by means of Hamilton principle, assuming shortening effect. Secondly, differential equations, governing the static deflection and free vibration equation around the stability point, are solved using Galerkin method and the three mode shapes of a uniform microbeam are employed as the comparison function. By assuming that the volume of deposited layer is constant, the variation of natural frequency and static deflection are examined in three different cases. In any cases, it is presumed that the second layer is initially deposited on the entire length of microbeam. In the first case, one end of coated layer is considered fix at the clamped side of microcantilever, and then its length is decreased from other side, where its thickness is increased. In the second case, one end of coated layer is perceived fix at the free side of microcantilever, and then its length is decreased from other side, where its thickness is escalated. In the third case, the length of second layer is decreased from both of left and right ends, where its thickness is expanded. In addition, the effect due to the change of the second layer position is considered on mechanical behavior of the system.
Ali Khanchehgardan, Ahad Amiri, Ghader Rezazadeh,
Volume 15, Issue 9 (11-2015)
Abstract
In this work effect of mass diffusion on the damping ratio in micro-beam resonators is investigated based on modified couple stress theory and the Euler-Bernoulli beam assumptions. The couple stress theory is a non-classical elasticity theory which is capable to capture size effects in small-scale structures. The governing equation of a micro-beam deflection is obtained using Hamilton’s principle and also the governing equations of thermo-diffusive elastic damping are established using two dimensional non-Fourier heat conduction and non-Fickian mass diffusion models. Free vibration of the micro-beam resonators is analyzed using Galerkin reduced order model formulation for the first mode of vibration. A clamped-clamped micro-beam with isothermal boundary conditions at both ends is studied. The obtained results are compared with the results of a model in which the mass diffusion effect is ignored. Furthermore the mass diffusion effects on the damping ratio are studied for the various micro-beam thicknesses, ambient temperature and length scales parameters. The results show that in the valid region based on Euler-Bernoulli beam theory and before the critical thickness there is no difference between the results of mass diffusion and thermo-elastic damping and also the results indicate that by increasing the length scale parameter damping ratio decreases.
Ehsan Davoodi, Mahmood Mazare, Pedram Safarpour,
Volume 16, Issue 10 (1-2017)
Abstract
This paper presents the control of a quadrotor using nonlinear approaches based on the experimentally measured sensors data. The main goal is the control and closed loop simulation of a quadrotor using feedback linearization and sliding mode algorithms. First, a nonlinear model of quadrotor is derived using Newton-Euler equations. To have a more realistic simulation the sensors noise performance were measured using a setup. sensors data was measured under on engines. Since the experimental data for sensor had error and noise, a Kalman filter was used to reduce sensors noise effect. Results demonstrate good performance for Kalman filter and controllers. Results showed that feedback linearization and sliding mode controllers performance was good but angles changes were smoother on feedback linearization controller. With increasing uncertainty, feedback linearization performance was away desired mode from this aspect The time to reach the goal situation while increasing uncertainty was no significant impact on the performance of sliding mode controller.Thus feedback linearization controller added PID is Appropriate to Maintain the quadrotor attitude while sliding mode controller has better performance to angles change and transient situations.
Masoud Nourimotlagh, Pedram Safarpour, Mehdi Pourgholi,
Volume 16, Issue 12 (2-2017)
Abstract
The purpose of this article is dynamic modeling of a quadrotor and control of its Roll and Pitch angles based on the experimentally measured sensors data. So, after driving nonlinear model of quadrotor equations, the control of the quadrotor’s angular situation was simulated using PID and feedback linearization algorithms. Due to the widespread application of MEMS sensors in measuring the status of various systems and to have a more realistic simulation, sensors data was measured and used in simulation of controllers. Due to errors of MEMS sensors, vibration of motors and airframe, being noise on outputs, Kalman filter was used for estimation of angular situation. As one of the purposes of this paper was the use of its results in actual control of a quadrotor, motor model was used to determine PWM control signals. The results obtained from simulation in Simulink showed good performance of both controllers in controlling roll and pitch angles.
Hassan Abdollahi,
Volume 17, Issue 5 (7-2017)
Abstract
We know, cantilevers are based for the most of the MEMS components, in this paper, the fabrication process of SiO2 micro cantilever array based on bulk micromachining technology is introduced. The results of which can be used to fabricate of SiO2 micro cantilever sensors. The micro-cantilever fabrication process is implemented in the 13th stage with two glass and talcous masks and it is also suspend by wet release technique. The main advantages of the proposed method can be expressed no need for advanced deposition equipment, design with minimum mask, fast and simplicity in implementation of the micro cantilever, avoid of complexity release from sacrificial layer, release the micro cantilever at environment temperature, low cost price and finally possible to implement in microelectronics research laboratories with limited equipment. The SiO2 micro cantilevers fabricate with 1and 2µm thickness, 50, 100, 150, 200, 250, 300, 350 and 400μm lengths, and 20 and 40µm widths. The resonant frequency and the spring constant values are also calculated for different materials (Si3N4, Si, Au, SiO2, Al and SU8) with various sizes. The SEM images results show that the lithographic process is correctly done on the roughness of the backside substrate, the fabrication process and Si etching operations controls are performed suitable, and micro-cantilevers are suspended with negligible stress.
Mohammad Reza Salehi Kolahi, Hossein Moeinkhah,
Volume 17, Issue 12 (2-2018)
Abstract
In this research, the dynamic behavior and nonlinear vibration of a clamped-clamped initially curved microbeam under electrostatic step actuation is investigated. The initially curved microbeams under transverse loading may exhibit two different stable states and this is the basis of the emergence of bi-stable micro electro mechanical systems (MEMS). The equation of motion is derived based on energy method and Hamiltonian principle, and re-written in non-dimensional form by using appropriate non-dimensional parameters. The resultant equation of motion in non-dimensional form is discretized and converts to a system of nonlinear ordinary differential equations by using a reduced order model based on the Galerkin procedure. Runge-kutta method of order four is employed to solve the resulting system of nonlinear ordinary differential equations. COMSOL Multiphysics software is used for finite element simulation. Then, the effect of various parameters including voltage parameter, damping, initial midpoint elevation and gap length is investigated. It is concluded that the critical voltage of pull-in is decreased by increasing of the initial midpoint elevation. Also The results depict that by increasing of the damping parameter, the possibility of transition between two stable stats is eliminated.
E. Akrami Nia, H. Ekhteraei Toussi,
Volume 19, Issue 10 (10-2019)
Abstract
Microbeams are one of the most important members of microelectromechanical systems (MEMS) which contrast of electrical and mechanical forces in them cause pull-in instability. One of the proposed mechanisms for controlling this instability and enlarging the stable range of system are initially curved microbeams. Despite studying various pull-in instability in straight elastic or viscoelastic microbeams, the instability of curved microbeams has been investigated only within the range of elastic behavior. Therefore in the present study, assuming a clamped-clamped viscoelastic initially curved microbeam, the effect of viscoelastic behavior on the instabilities called snap-through and pull-in, was investigated. The viscoelastic behavior was simulated by the standard anelastic linear solid model. The governing differential equation was obtained based on the modified couple stress theory and by use of Hamilton’s pull-in instability principle. By using the Galerkin method, the governing equation was converted to a nonlinear ordinary differential equation and solved by MATLAB sofware. The structure behaviors are compared in two extreme situations before and after the viscoelastic relaxation by drawing diagrams. The results show when the time of structure relaxation increases, viscoelastic behavior causes more decreasing in instabilities voltage, but its effect on the position of instability will depend on the axial load. In this way, in the presence of tensile load, viscoelastic behavior increases the snap-through position and decreases the pull-in position, but in the presence of compressive load, snap-through occurs at smaller deflections and pull-in occurs at larger deflections.
Hamed Kavand, Javad Koohsorkhi, Reza Askari Moghaddam,
Volume 23, Issue 1 (12-2022)
Abstract
The electrical properties of nanostructured piezoelectric materials have attracted the attention of many researchers in the last decade. These features are used in piezoelectric micro-sensors. Mechanical propulsion is usually the result of contact between a piezoelectric surface and a foreign object. In this paper, the effect of mechanical propulsion using an air wave (sound) or vacuum on a silicon diaphragm is investigated. The local stresses created on the diaphragm due to the impact of an air wave have a significant effect on the peak-to-peak voltage of the piezoelectric sensor, which can be measured by measuring changes in this parameter. To investigate this, a micromachined diaphragm of silicon was examined and it was found that fabricating a piezoelectric sensor on a thin and patterned diaphragm could increase the peak-to-peak voltage by about 1.3 times. Detection of these stresses using piezoelectric material layered on the thin and formable diaphragm can act as a piezoelectric microphone or a barometer that the presence of microstructures on the diaphragm will increase their sensitivity.
