Mohammad Durali
Sharif University of Technology, Mechanical Engineering, Faculty Member
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In this paper, a 4-DOF robotic arm for tool handling in laparoscopic surgery is introduced. The robot provides sufficient force to handle endoscopic tools used for large organ manipulation and is capable of measuring the tool-tissue... more
In this paper, a 4-DOF robotic arm for tool handling in laparoscopic surgery is introduced. The robot provides sufficient force to handle endoscopic tools used for large organ manipulation and is capable of measuring the tool-tissue forces. The RCM constraint is achieved using a spherical mechanism and roll and insertion motions are provided using time pulley and spindle-drive, respectively. The forward and inverse kinematics of the robot was solved and the dimensions of its links were determined, using particle swarm optimization method, so that the maximum kinematic and dynamic performance could be achieved.
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A nonlinear comprehensive model has been developed in this paper to study the train derailment and hunting in severe braking conditions. The train consists of cars each having 40 dof, connected to each other by couplers and buffers. The... more
A nonlinear comprehensive model has been developed in this paper to study the train derailment and hunting in severe braking conditions. The train consists of cars each having 40 dof, connected to each other by couplers and buffers. The car model is nonlinear and three-dimensional and includes nonlinear springs and dampers of primary and secondary suspensions, dry friction between different parts such as car body and side bearers, center-plate parts, wheelset bearings and bogie frames, and also clearances and mechanical stops. Nonlinearities of wheel and rail profiles, pressure build-up delay in brake circuit, and nonlinearities of connecting parts have also been included in the model. A complete set of equations has been derived for the train. The equations are solved numerically for different car weight configurations when severe brake is applied. Derailment coefficient is determined for several train make-ups and tendency of the wheels towards derailment is investigated. Optimum configuration of cars in a light-heavy set, and critical derailment velocity can be determined to minimize the tendency of train derailment. The results are in excellent agreement with the field experience.
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ABSTRACT Laser Powder Deposition (LPD) process is an advanced material processing technique which has many applications. Despite this fact, reliable and accurate control schemes have not yet fully developed for the process. In this paper,... more
ABSTRACT Laser Powder Deposition (LPD) process is an advanced material processing technique which has many applications. Despite this fact, reliable and accurate control schemes have not yet fully developed for the process. In this paper, the problem of controlling the clad height in the LPD process is studied. Due to a faster response of the process to change in scanning velocity over the laser power, the scanning velocity is selected as the input control variable. Since the governing equations of the LPD process are complex for designing a controller, an identified nonlinear dynamic model is used. The model is a Hammerstein model with a linear dynamic and a nonlinear memoryless block. The model parameters are identified offline using experimental data. The controller has a proportional-integral-derivation (PID) architecture. The controller was implemented on the real plant to asses its performance in the fabrication of several metallic parts composed of stainless steel.
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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.... more
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 vehicle. The proposed method in this paper does not need to disassemble the powertrain from the chassis. The procedure shows a good ability of vibration path ranking in a vehicle and is an effective tool to diagnose the vibration problem inside the vehicle. The simulated vibration spectrums in di...
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In this investigation, the Flexible String Algorithm (FSA), used before for 2D subsonic ducts inverse design, is developed and applied to inverse design of supersonic ducts with and without normal shock wave. In this method, the duct wall... more
In this investigation, the Flexible String Algorithm (FSA), used before for 2D subsonic ducts inverse design, is developed and applied to inverse design of supersonic ducts with and without normal shock wave. In this method, the duct wall shape is changed under an algorithm based on deformation of a virtual flexible string in a flow. The deformation of the string due to the local flow conditions resulting from changes in wall geometry is performed until the target shape satisfying the prescribed walls pressure distribution is achieved. The flow field at each step is analyzed using Euler equations solutions by the AUSM method. Some validation test cases and design examples in subsonic and supersonic regimes are presented here which show the robustness and flexibility of the method in handling the complex geometries in various flow regimes. In the case of unsymmetrical ducts with two unknown walls, the FSA has been modified to increase the convergence rate significantly. Also, effect ...
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ABSTRACT Laser Powder Deposition (LPD) process is an advanced material processing technique which has many applications. Despite this fact, reliable and accurate control schemes have not yet fully developed for the process. In this paper,... more
ABSTRACT Laser Powder Deposition (LPD) process is an advanced material processing technique which has many applications. Despite this fact, reliable and accurate control schemes have not yet fully developed for the process. In this paper, the problem of controlling the clad height in the LPD process is studied. Due to a faster response of the process to change in scanning velocity over the laser power, the scanning velocity is selected as the input control variable. Since the governing equations of the LPD process are complex for designing a controller, an identified nonlinear dynamic model is used. The model is a Hammerstein model with a linear dynamic and a nonlinear memoryless block. The model parameters are identified offline using experimental data. The controller has a proportional-integral-derivation (PID) architecture. The controller was implemented on the real plant to asses its performance in the fabrication of several metallic parts composed of stainless steel.
Flexible Wheel/Rail Contact Model for Railway Vehicle Dynamics Without Pre-Calculation. [ASME Conference Proceedings 2007, 87 (2007)]. Mohammad Durali, S. Hassan Salehi, Mohammad Mehdi Jalili. Abstract. An advanced ...
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In this article a train model is developed for studying train derailment in passing through bends. The model is three dimensional, nonlinear, and considers 43 degrees of freedom for each wagon. All nonlinear characteristics of suspension... more
In this article a train model is developed for studying train derailment in passing through bends. The model is three dimensional, nonlinear, and considers 43 degrees of freedom for each wagon. All nonlinear characteristics of suspension elements as well as flexibilities of wagon body and bogie frame, and the effect of coupler forces are included in the model. The equations
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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... more
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 parameters method. The influence of angular velocity on transition curves and stability zones is examined. Finally, stable and unstable zones are determined and the existence of periodic solutions on transition curves is verified by numerical analysis.
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Investigation on Dynamic Interaction Between Wagon and Randomly Irregular Rail Track. [ASME Conference Proceedings 2005, 1825 (2005)]. Mohammad Durali, Mohammad Mahdi Jalili. Abstract. Rail profile irregularities are ...
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Research Interests: Simulation and Trains
Shape optimization of a submarine for minimized noise emission has been the objective of this work. Boundary element method and finite element methods have been employed to determine the acoustic field around the object. A combined neural... more
Shape optimization of a submarine for minimized noise emission has been the objective of this work. Boundary element method and finite element methods have been employed to determine the acoustic field around the object. A combined neural network and genetic algorithm scheme is developed to find the optimum external geometric ratios of the submarine for a minimized emitted acoustic energy
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Page 1. 1633 The effect of three-dimensional crack growth on the force distribution and meshing stiffness of a spur gear: ideal and misaligned contacts MG Saryazdi∗ and M Durali Mechanical Engineering Department, Sharif University of... more
Page 1. 1633 The effect of three-dimensional crack growth on the force distribution and meshing stiffness of a spur gear: ideal and misaligned contacts MG Saryazdi∗ and M Durali Mechanical Engineering Department, Sharif University of Technology, Tehran, Iran ...
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In this paper, a 4-DOF robotic arm for tool handling in laparoscopic surgery is introduced. The robot provides sufficient force to handle endoscopic tools used for large organ manipulation and is capable of measuring the tool-tissue... more
In this paper, a 4-DOF robotic arm for tool handling in laparoscopic surgery is introduced. The robot provides sufficient force to handle endoscopic tools used for large organ manipulation and is capable of measuring the tool-tissue forces. The RCM constraint is achieved using a spherical mechanism and roll and insertion motions are provided using time pulley and spindle-drive, respectively. The forward and inverse kinematics of the robot was solved and the dimensions of its links were determined, using particle swarm optimization method, so that the maximum kinematic and dynamic performance could be achieved.
Research Interests:
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Recent research has been extending the applications of small satellites called microsatellites, nanosatellites, or picosatellites. To further improve capability of those satellites, a lightweight, active attitude-control mechanism is... more
Recent research has been extending the applications of small satellites called microsatellites, nanosatellites, or picosatellites. To further improve capability of those satellites, a lightweight, active attitude-control mechanism is needed. This paper proposes a concept of inertial orientation control, an attitude control method using movable solar arrays. This method is made suitable for nanosatellites by the use of shape memory alloy
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... Simple control strategies, mechanical decoupling of engine from driven wheels, maximumefficiency of engine ... series HEV lead the research group to select this configuration as their first attempt in designing the conceptual Hybrid... more
... Simple control strategies, mechanical decoupling of engine from driven wheels, maximumefficiency of engine ... series HEV lead the research group to select this configuration as their first attempt in designing the conceptual Hybrid pneumatic vehicle (HPV) power train. ...
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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... more
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.
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ABSTRACT Summary 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... more
ABSTRACT Summary 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 global optimization technique is used to find the magnitude of the adjusting parameters to minimize objective functions in low and high frequency excitations. The results indicate significant improvement over conventional hydraulic mounts. It is further shown that when the upper compliance is used as the adjusting parameter, a simple on-off control which is triggered by the engine revolution and vehicle speed is sufficient for tuning the adaptive mount.