Sharif Digital Repository

The powering requirement of a land yacht is one of the most important aspects of its design. In this respect the wind tunnel testing is an effective design tool. In fact, changing the parameters of the vehicle and testing the changes in the wind tunnel will give us a better understanding of the most efficient vehicle, and yet it is time consuming, expensive, and has inherent scaling errors. Another set of design tools are Computational Fluid Dynamics and parametric prediction. Computational Fluid Dynamics (CFD) codes are not yet wholly proven in its accuracy. Parametric prediction is the starting point for most engineering studies. It will be used to calculate the land yacht's performance... 

It is important to understand the flow characteristics and performance of wings for designers who want to have an efficient thrust in a land yacht. In this paper, a comparison of aerodynamic forces obtained by testing the land yacht model in a wind tunnel and by the Velocity Prediction Program (VPP) is presented. The wind tunnel testing of a land yacht is an effective design tool, but at present it is mainly used for VPP validation, which allows for a faster and more efficient design process. The rigid wing land yacht model, which is a radio controlled model, is tested in the national open jet wind tunnel of the Malek Ashtar University of Technology in Iran. The wing data, which is obtained... 

To study of vibration effect on fluidization behaviour of high moisture materials, a laboratory vibro-fluidized bed dryer was designed and fabricated. The blower was selected based on transferring velocity of particles and pressure drop caused by airflow through the bedplate and the channels. It was centrifugal type with backward blades, static pressure of 3.5 kPa, flow rate of 0.4 m 3/s and impeller diameter of 0.4 m. The dryer was constructed with 4.9 kW electrical heater capacity, bed plate with holes diameter of I mm and 140626 holes/m 2. The dryer chamber was made of Plexiglass with 0.16×0.16 m square section and 0.5 m height The bedplate was vibrated mechanically, which was adjustable... 

Underground pipelines are important infrastructure for transporting energy resources, particularly water and oil. Due to the high risk of damage and possible consequences, close monitoring of pipelines is a serious challenge for researchers and decision makers. Piezoelectric sensors/actuators are being used to monitor the physical characteristics of pipelines, including corrosion and crack. Piezoelectric ceramics as transmitters and/or receivers are connected to data concentrators in order to monitor the defects in pipelines. The performance and accuracy of this system highly depends on the accurate interpretation of the received electrical signals due to changing mechanical fields. However,... 

This paper will first describe the Linear-Quadratic-Gaussian (LQG) and Lead-Compensator when the Proportional-Integral-Derivative (PID) controllers are inactive for procedures that have large delay time (LDT) in transfer stage. Therefore in those states, LQG and Lead Compensator perform better than the PID controllers. The constrained LQG is optimal and stabilizing. The solution algorithm is guaranteed to terminate in finite time with a computational cost that has a reasonable upper bound compared to the minimal cost for computing the optimal solution. In this work all actual working area condition for instance noises and disturbances are considered. Eventually, LQG and Lead Compensator have... 

Gaining insight into possible vibratory responses of dynamical systems around their stable equilibria is an essential step, which must be taken before their design and application. The results of such a study can significantly help prevent instability in closed-loop stabilized systems by avoiding the excitation of the system in the neighborhood of its resonance. This paper investigates nonlinear oscillations of a rotary inverted pendulum (RIP) with a full-state feedback controller. Lagrange’s equations are employed to derive an accurate 2-DoF mathematical model, whose parameter values are extracted by both the measurement and 3D modeling of the real system components. Although the governing... 

Hexapod robots gives us the ability to study walking robots without facing problems such as stability in many aspects. It has a great deal of flexibility in movement even if a leg becomes malfunctioned. Radially symmetric (hexagonal) hexapods have more flexibility in movement than rectangular leg alignments. Because of symmetry they can move in any direction and time efficiently. Inverse kinematic problem of this kind of hexapods is solved through a modular mobile view considering six degrees of freedom for the trunk. Then typical tripod and wave gaits are analyzed and simulated through the presented formulation. In Reinforcement Learning algorithm for walking it is important how to make... 

Magneto-rheological (MR) fluids consist of magnetic particles in carrying fluid. One of the drawbacks in using MR dampers in laboratory work is their price. At present, there is a compelling need for the production of the laboratory scale of MR fluids to lower their production cost. In this study, to show that the MR fluid is an applicable prototyped laboratory scale of single ended and mono-tube, MR dampers with a prototyped MR fluid are presented. The main features of produced MR fluid and dampers are simplifying in constructing and their low cost. These dampers are useful for laboratory research work. To illustrate the validity of the MR fluids, using this fluid, four MR dampers are made... 

The objective of this work is to design electrostatic actuators for a CMOS-MEMS nano-newton capacitive force sensor to suppress vertical vibrations disturbances. Electrostatic actuators are selected because the movable part of this force sensor is anchored to the fixed parts. In the first step, we propose a framework for simulation of the force sensor based on finite element method. The proposed model is modified utilizing comparison between the simulation and experimental models to improve the performance of the model. Then, 14 pairs of electrostatic actuators are designed for applying the control algorithm and their pull-in voltage is calculated. In next step, Modal Analysis is applied to... 

The vibration suppression of semi-actively controlled jacket-type offshore platforms using Magnetorheological (MR) dampers is studied. The main goal of using MR damper system is to reduce vibration caused by wave hydrodynamic forces. A fixed jacket-type offshore platform affected by wave-induced hydrodynamic forces and controlled by MR dampers is modelled as a semi-active controlled system with 30 DOFs. In comparison with earlier studies, an improvement in problem modelling is made. Based on the wave theory and Morison equation, an exosystem is designed to simulate regular wave forces. The necessary input voltage to MR dampers to generate desired damping force is derived by clipped optimal... 

Considerable attention has been devoted recently to vibration control using intelligent materials as sensor/actuator. An intelligent control technique using a neural network is proposed for vibration control of micro-cantilever beam with bonded piezoelectric sensor and actuator. Structure modal characteristic analysis is done to determine the optimal configuration of piezoelectric sensor and actuator. With the piezoelectric elements are surface-bonded near the same position to the fixed end of micro-cantilever beam, an optimal controller, linear quadratic Gaussian (LQG), and an intelligent strategy based on neural network are investigated. Finally, the simulation results are given to...