رامین وطن خواه

This study is performed to estimate the error of solving governing equations of a dual-cone scanning earth horizon sensor in presence of geometric and environmental parameters. In the process of extracting the equations for determining the sensor’s attitude, firstly, a simplified form of the earth as an sphere without atmosphere is used to model the earth and compared with the governed attitude of simulated satellite on a hypothetical orbit. But in reality, the geometric factor of the earth oblateness and environmental factors such as the sensor's field of view, the effect of the atmosphere and its reflection from the earth's surface cause errors in attitude determination of the satellite. Therefore, by assuming that the sensor is mounted on a satellite, simulating motion in a near earth orbit and modeling the sensor, the sensor’s inlet pulse and the amount of roll and pitch angles in different geometric and environmental conditions are calculated. Then, by comparing the calculated attitude with the simplified case, the effect of each in the occurrence of error are obtained. The simulation is based on a dual-cone scanning earth horizon sensor made in the Institute of Mechanics of Iranian Space Research Center on MicroMAS satellite. According to the simulation results, the atmosphere radiation and surface reflection, earth oblateness and sensor FOV in roll angle and in pitch angle, earth oblateness, atmosphere radiation and surface reflection and sensor FOV are the most effective factor in revealing error respectively.

Vibrations due to backlash and other nonlinear effects is a common problem in industries with power transmission systems with gear. Various dynamic models show chaotic behavior in power transmission systems that use spur gears. The aim of this study is to control the chaotic behavior in spur gear transmission system by transferring the system onto an existing unstable periodic orbit and tracking the trajectory using sliding mode control. The proposed model in this study considers a pair of spur gears with time dependent stiffness, backlash and static translation error. Firstly, the dynamic equations are extracted and the effect of model parameters on system response are indicated by simulation results. Then using Poincare’ map and an efficient algorithm, the unstable periodic orbit is detected. Finally, the sliding mode controller is designed to track the desired trajectory obtained from the unstable periodic orbit. The simulation results show the performance of the proposed controller.

A major problem in design of a controller is that some of the parameters of the governing dynamic equation might be unknown. The purpose of the present study is to provide a method for identification of the unknown parameters of the dynamic equations of the two-axis gimbal system and then applying a suitable controller to it. Among the uncertain parameters which may exist in the dynamic equations of a two-axis gimbal, the components of the inertia matrix, the coriolis matrix, and the friction matrix can be named. In this research, in order to estimate the unknown parameters of the system, the Gauss-Newton method which is a gradient-based inverse technique is used. Regarding the severe sensitivity of inverse problems to measurement errors, by using a proper smoothing technique, this undesirable effect is reduced. In the present work, for the first time, an accurate technique for computation of sensitivity coefficients of the dynamic equations of the gimbal is presented. After identification of the unknown parameters, the control of the two-axis gimbal is also performed by sliding mode control. The applied moments are designed by sliding mode control to stabilize the line of sight. Also, proof of stability is presented for the sliding mode control. Simulation of the laboratory tests in the identification section and also control results are obtained by modeling of the system in MATLAB.

In this article, the sensitivity and resonant frequency of the atomic force microscope made of functionally graded materials is investigated by couple stress theory (MCST). In MCST, the size effect of the system is taking into account by means of the material length scale parameter. is made of a mixture of metal and ceramic with properties varying through the thickness following a simple In this work, due to the kinematic energy and potential energy of , the governing equations of motion and corresponding boundary conditions are derived on the basis of Hamilton principle by considering Euler-Bernoulli beam theory. Based on the results, it is clear that when the contact stiffness increases, the sensitivity of the system decreases, and resonant frequency increases. Moreover, when the thickness comes approximately close to material length scale parameter, the difference between MCST and classical continuum mechanic becomes significant. Furthermore, in low contact stiffness, increasing the power reduces the sensitivity of , while in high contact stiffness, increasing the power  increases the sensitivity of the system. Results also show that at each value of contact stiffness, as ceramic volume fraction increases the resonant frequency will be increased, too.

Different strategies are studied to control chemotherapy delivery in cancerous tumors. The main aim of control is to reduce cancer cells immediately and, at the same time, it is the least harm to the healthy tissue of the body. Besides, at the end of treatment, the amount of drug remaining in the patient's body should be as low as possible. Various control algorithms are applied dynamic models with different orders. In this paper, a model for cancer with five ordinary differential equations by considering normal, endothelial and cancer cells, and the amount of two chemotherapy drugs and anti-angiogenic residues in the body as state space variables and the rate of injection of as a control After discussing the mathematical model of the system, the system is controlled by defining the rules along with and by one of the control signals (rate of chemotherapy drug). This means that the rate of normal and cancerous counts as the input of the fuzzy controller and the amount of chemotherapy drug signal is the output. The simulation results show that in the last days of treatment, cancer cells have a downward trend, and normal and endothelial cells also tend to the healthy state. The solutions of the fuzzy controller are compared with the uncontrolled mode as well as the available experimental data. The results indicate that the system has met the permissible limits, which indicates the validity of the answer from the fuzzy controller.

Dynamic behavior of continuous systems, such as beams and plates under the application of moving concentrated loads, is an important issue in engineering. In this study, a meshfree method is presented for the analysis of the dynamic response of thick plates under the influence of concentrated moving loads. The displacement field is based on the third-order shear deformation theory. In this numerical method, the field variables are interpolated only by using nodes distributed purposively in the computational domain. Since there is no conectivity between the nodes, it is possible to add nodes in the areas of application of the force. Another feature of the proposed method is the use of the radial point interpolation method (RPIM) shape functions which possess the Kronecker delta function property and therefore satisfies the essential boundary conditions easily. Also, due to the high density of nodal points in the vicinity of the point of application of the load, the background decomposition method (BDM) is used in order to achieve a high accuracy with appropriate speed. In this paper, nodes are re-arranged in the path of the moving load adaptively which leads to high accuracy and speed of the final solution. To validate the proposed method, the obtained results are compared with the analytical solutions.

In this study, nonlinear behavior of an atomic force microscopes (AFM) immersed in acetone, water, carbon tetrachloride (CCl4), and 1-butanol is investigated using non-classical strain gradient theory. In this theory, the size effect of system is taking into account by means of material length scale parameter. The nonlinear behavior of the AFM is due to the nonlinearity of the AFM tip–sample interaction caused by the Van der Waals attraction/repulsion force. Behavior of micro beam immersed in liquid is completely different with its behavior in air and vacuum due to the existence of hydrodynamic force. The Resonant frequencies, mode shapes, governing nonlinear partial and ordinary differential equations (PDE and ODE) of motion, stability analysis, boundary conditions, potential function and phase-plane of the system are obtained analytically in the present study. Furthermore, the results are compared with the one obtained by the modified couple stress theory. For this purpose, the AFM and the probe at the free end of micro beam are modeled as a lumped mass. The fixed end of micro beam is excited by piezoelectric element. The nonlinear PDE of motion is derived based on Euler-Bernoulli theory by employing the Hamilton principle. The Galerkin method is utilized to gain the governing nonlinear ODE of motion and the obtained ODE is analytically solved by means of perturbation techniques.

In this syudy, a size-dependent modeling of micro plate with piezoelectric layers based on classical plate theory using modified couple stress theory is developed in this paper. Introducing only one material length scale parameter in modified couple stress theory to take into account the size effect of the system is one of the main advantage of this theory over other nonclassical continuum mechanics theories. Also, this theory is able to predict and interpret the size-dependent static and dynamic behavior of micro-scale structures with more accuracy and precision in comparison to classical continuum mechanics theory. The piezoelectric layers are modeled according to linear piezoelectricity theory and due to small thickness, the electric field is assumed to be constant over the layers. The equation of motion and its corresponding boundary conditions are derived using Hamilton principle. The equation of motion is solved numerically using finite element method and the effect of material length scale parameter and piezoelectric layers on free vibration and static deflection of micro-plate are investigated.

High blood glucose levels in the body named diabetes can increase damage in kidneys, eyes, heart and etc. In this investigation, a novel TS fuzzy static output feedback control structure is proposed to regulate the blood glucose level in the pre-defined desired values for type 1 diabetes using exogenous intra-venous insulin delivery rate. To this end, a nonlinear delay differential equation framework is considered to model the blood glucose/insulin endocrine metabolic regulatory system. The governing equations of the blood glucose/insulin model are approximated by a TS fuzzy model and then the proposed static output feedback controller is designed for this TS model.