Sharif Digital Repository

By new advancements in vehicle manufacturing, evaluation of vehicle quality assurance has got a more critical issue. Today noise and vibration generated inside and outside the vehicles are more important factors for customers than before. So far several researchers have focused on interior noise transfer path analysis and the results have been published in related papers but each method has its own limitations. In present work, the vibration transfer path analysis and vibration path ranking of a car interior have been performed. As interior vibration is a source of structural borne noise problem, thus, the results of this research can be used to present the structural borne noise state in a... 

This paper describes a new quasi-3D design method for centrifugal compressor impeller. The method links up a novel inverse design algorithm, called Ball-Spine Algorithm (BSA), and a quasi-3D analysis. Euler equation is solved on the impeller meridional plane. The unknown boundaries (hub and shroud) of numerical domain are iteratively modified by BSA until a target pressure distribution in flow passage is reached. To validate the quasi-3D analysis code, existing compressor impeller is investigated experimentally. Comparison between the quasi-3D analysis and the experimental results shows good agreement. Also, a full 3D Navier-Stokes code is used to analyze the existing and designed compressor... 

The meshless element-free Galerkin method was generalized and an algorithm was developed for 3D dynamic modeling of deformable bodies in real time. The efficacy of the algorithm was investigated in a 3D linear viscoelastic model of human spleen subjected to a time-varying compressive force exerted by a surgical grasper. The model remained stable in spite of the considerably large deformations occurred. There was a good agreement between the results and those of an equivalent finite element model. The computational cost, however, was much lower, enabling the proposed algorithm to be effectively used in real-time applications  

The need for service passenger cars, like taxies and governmental vehicles, to work in central Tehran that can produce less emission has been the main drive behind this research. A series hybrid pneumatic vehicle based on Iran manufactured Samand Passenger car was developed using commercially available components. The idea is to use as much standard parts as possible to reduce the development and manufacturing costs of the developed hybrid car. The vehicle space and weight limitations and the fixed geometry have been the main constraint in adoption of the components. The calculations show that the designed vehicle succeeds to satisfy the requirements set by driving cycle, but requires... 

Development of hybrid cars is the most popular subject among automotive engineers both in production and research. The need for service passenger cars, like taxies and governmental vehicles, to work in central Tehran that produce less emission has been the main drive behind this paper. A parallel hybrid pneumatic vehicle based on Iran manufactured Samand passenger car was developed using commercially available components. The idea is to use as many standard components as possible to reduce development and manufacturing costs. The vehicle space and weight limitations and fixed geometry have been the main constraint in adoption of the components. In this design the 75 kW engine of the Samand... 

One of the main subjects under consideration of automotive companies seeking for higher efficiency and lower atmospheric pollution is the usage of hybrid vehicles instead of usual internal combustion engine driven cars. Developing a service car for commutation in the city centers that can produce less emission has been the main idea behind this research. The preliminary design of a series Hybrid-Pneumatic vehicle based on Samand platform satisfying the requirements of ECE-15 driving cycle is presented in this paper. One of the main goals is to use as much standard parts as possible to reduce the development and manufacturing costs. The vehicle space, fix geometry and weight limitations have... 

High center of mass vehicles are likely to rollover in extreme maneuvers. Available works present control strategies to prevent rollover. In these works, however, other important parameters such as path trajectory tracking are not a main concern. In this paper conflicts between rollover prevention and trajectory tracking is investigated. Model predictive control (MPC) is adopted to predict and avoid rollover while tracking desired trajectory. For this regard a model based future error estimation is introduced. The control framework predicts both rollover and trajectory error simultaneously. It avoids rollover while tries to track the trajectory. Simulation results for two controllers with... 

In this paper vehicle path-following in the presence of rollover risk is investigated. Vehicles with high centre of mass are prone to roll instability. Untripped rollover risk is increased in high centre of gravity vehicles and high-friction road condition. Researches introduce strategies to handle the short-duration rollover condition. In these researches, however, trajectory tracking is affected and not thoroughly investigated. This paper puts stress on tracking error from rollover prevention. A lower level model predictive front steering controller is adopted to deal with rollover and tracking error as a priority sequence. A brake control is included in lower level controller which... 

This paper presents a new design process of a low-cost swirler employed in axial micro-turbines. The swirler is simple in design, inexpensive and easy to produce and has good adaptability to different potential conditions without major changes. The blades are shaped from trapezoid-shaped steel sheets curved to a certain radius to form a tin airfoil with suitable outlet angle distribution from hub to tip. The formed blades are then welded between two concentric rings to form a round cascade. Correction from flow to blade angles, namely induced incidence and trailing edge deviation angles, were calculated by CFD analysis and considered in blade shape design. The manufactured prototype made on... 

This article presents a routine for prediction of the crack growth path in gears. Crack simulation helps in determining failure modes and crack detecting by vibration monitoring. To simulate crack propagation an effective method is developed by which the meshing force is calculated based on the compliance of meshing teeth in every stage of crack growth. In this method the compliance matrix of the tooth is calculated using three-dimensional boundary element analysis without the need for simultaneously modelling two meshing gears. The force distribution on the contact area is then calculated using Hertz theory and compliance matrices of meshing teeth. The method is used in prediction of the... 

A general modeling framework is presented for the development of the frequency equation of a microgyroscope, which is modeled as a suspended cantilever beam with a tip mass under general base excitation. Specifically, the beam is considered to vibrate in all the three directions, while subjected to a base rotational motion around its longitudinal direction. This is a common configuration utilized in many vibrating beam gyroscopes and well drilling systems. The governing equations are derived by using the Extended Hamilton's Principle with a general 6-dof base motion. The natural frequency equation is then extracted in a closed-form for the case where the beam support undergoes longitudinal... 

This paper discusses the determination of the transition curves for a pair of spur gear with coulomb friction. Transition curves are the loci of periodic response of parametrically excited systems and separate the stable and unstable solutions. A discrete model of a pair of spur gear is developed and the friction forces are calculated base on instantaneous dynamic force between gear teeth. The dynamic equation of the system is a linear ordinary differential equation with periodic coefficients. Periodic friction torque, as the parametric excitation is represented by Fourier series. The loci of periodic solutions are determined in μ - Γ plane (coefficient of friction-contact ratio) by strained... 

In this paper, a method for overtaking stationary and moving obstacles will be introduced. The method consists of designing a desired trajectory for lateral motion of the vehicle and then using a lateral motion controller for tracking this desired trajectory. The desired trajectory is a sigmoid exponential function of relative distance between the vehicle and the obstacle and guarantees overtaking the obstacle, if tracked exactly, despite of lateral and longitudinal motions of the obstacle. Lateral acceleration of the vehicle should not exceed safety limits during tracking desired trajectory. This matter has been used as a decision criterion for determining feasible and unfeasible desired... 

This paper discusses the effects of substrate motions on the performance of microgyroscopes modeled as ring structures. Using the Extended Hamiltonian Principle, the equations of motion of a ring micro-gyroscope are derived, and the natural frequency equation and response characteristics are extracted in closed form for the case where the substrate undergoes normal rotation. The Galerkin approximation is then used to arrive at the ordinary differential equations of motion for the ring. In these equations, the effects of angular, centripetal and Coriolis accelerations are all apparent. The response of the system to different inputs is studied and the system sensitivity to variation in input... 

This paper discusses the effects of substrate motions on the performance of a microgyroscope modeled as a ring structure. Using Extended Hamilton's Principle, the equations of motion are derived. The natural frequency equation and response of gyroscope are then extracted in closed-form for the case where substrate undergoes normal rotation. The Galerkin approximation is used for discretizing the partial differential equations of motion into ordinary differential equations. In these equations, the effects of angular accelerations, centripetal and coriolis accelerations are well apparent. The response of the system to different inputs is studied and the system sensitivity to input parameter... 

This paper discusses the effects of substrate motions on the performance of microgyroscopes modeled as suspended beams with a tip mass. The substrate movements can be motions along as well as rotations around the three axes. Using Extended Hamiltonian Principle and Galerkin approximation, the equations of the motion of the beam are analytically derived. In these equations, the effects of beam distributed mass, tip mass, angular accelerations, centripetal and coriolis accelerations are clearly apparent. The effect of electrostatic forces inducing the excitation vibrations are considered as linear functions of beam displacement. The response of the system to different inputs is studied and the... 

This paper presents the modeling steps towards development of frequency equations for a cantilever beam with a tip mass under general base excitations. More specifically, the beam is considered to vibrate in all the three directions, while subjected to a base rotational motion around its longitudinal direction. This is a common configuration utilized in many vibrating beam gyroscopes and well drilling systems. The governing equations are derived using Extended Hamilton's Principle with general 6-DOF base motion. The natural frequency equations are then extracted in closed-form for the case where the base undergoes longitudinal rotation. For validation purposes, the resulting natural... 

In this paper, we introduce a new high-performance adaptive hydraulic engine mount. The mount is tuned to road and engine conditions by changing the length of the inertia track and effective decoupler area in low-frequency road and high-frequency engine excitations. A single actuator is used to tune the mount in both low-frequency and high-frequency regimes. Sensitivity analysis is used to show that changing the length of the inertia track and decoupler area is the most effective way to tune an adaptive mount. Numerical simulations indicate that the proposed design can significantly improve the performance of a passive hydraulic mount  

In this paper an experimental/numerical technique is developed for engine mount optimization. The method is general and can be applied to optimize active and passive vibration isolators or absorbers in any mechanical systems or civil structures. Engine mount optimization techniques mostly rely on an accurate mathematical model of the whole vehicle, which in most cases is not available or is too difficult to develop. As a result, the current approach for selecting engine mounts for a vehicle is based upon trial and error which is very time-consuming and expensive. The proposed technique counts upon experimental data for optimization and does not require any mathematical model of the vehicle... 

In this paper, the sensitivity analysis is applied to the development of high performance adaptive hydraulic mounts. The analysis allows us to select the most effective design parameters for tuning an adaptive mount to different road and engine conditions. It is shown that in the low frequency road excitation, the upper chamber compliance and inertia of the fluid column in the inertia track are the most influential properties in changing the dynamic stiffness of the hydraulic mount. These properties for the high frequency engine excitations are the upper compliance and the inertia of the fluid column of the decoupler. For tuning the adaptive mount to different road and engine excitation, a...