List of vibration and control subject articles

Open Access Article

1 - Nonlinear Vibration Analysis of FG Nano-Beams in Thermal Environment and Resting on Nonlinear Foundation based on Nonlocal and Strain-Inertia Gradient Theory
Ebrahim Mahmoudpour

In present research, nonlinear vibration of functionally graded nano-beams subjected to uniform temperature rise and resting on nonlinear foundation is comprehensively studied. The elastic center can be defined to remove stretching and bending couplings caused by the FG More

In present research, nonlinear vibration of functionally graded nano-beams subjected to uniform temperature rise and resting on nonlinear foundation is comprehensively studied. The elastic center can be defined to remove stretching and bending couplings caused by the FG material variation. The small-size effect, playing essential role in the dynamical behavior of nano-beams, is considered here applying strain-inertia gradient and non-local elasticity theory. The governing partial differential equations have been derived based on the Euler-Bernoulli beam theory utilizing the von Karman strain-displacement relations. Subsequently, using the Galerkin method, the governing equations is reduced to a nonlinear ordinary differential equation. The closed form analytical solution of the nonlinear natural frequency is then established using the homotopy analysis method. Finally, the effects of different parameters such as length, nonlinear elastic foundation parameter, thermal loading, non-local parameter and gradient parameters are comprehensively investigated on the FG nano-beams vibration using homotopy analysis method. As the main results, it is observed that by increasing the non-local parameter, the frequency ratio for strain-inertia gradient theory has increasing trend while it has decreasing trend for non-local elasticity theory. Also, the nonlinear natural frequencies obtained using strain-inertia gradient theory are greater than the results of non-local elasticity and classical theory. Manuscript profile

Open Access Article

2 - Optimal Swing up of Double Inverted Pendulum using Indirect Method
Maral Salehi Amin Nikoobin Ebrahim Shahab

In this paper, optimal swing up of a double inverted pendulum (DIP) with two underactuated degrees of freedom (DOFs) is solved using the indirect solution of optimal control problem. Unlike the direct method that leads to an approximate solution, the proposed indirect m More

In this paper, optimal swing up of a double inverted pendulum (DIP) with two underactuated degrees of freedom (DOFs) is solved using the indirect solution of optimal control problem. Unlike the direct method that leads to an approximate solution, the proposed indirect method results in an exact solution of the optimal control problem, but suffers from its limited convergence domain which makes it difficult to solve. In order to overcome this problem, an inversion-based method is used to obtain the required initial solution for the indirect method. In the proposed methodology, dynamic equations are derived for a general inverted pendulum using Euler-Lagrange formulation. Then the necessary optimality conditions are derived for a DIP on the cart using the Pontryagin’s maximum principle (PMP). The obtained equations establish a two-point boundary value problem (TPBVP) which solution results in optimal trajectories of the cart and pendulums. In order to demonstrate the applicability of the presented method, a simulation study is performed for a DIP. The simulation results confirm the superiority of the proposed method in terms of reduced effort. Manuscript profile

Open Access Article

3 - Simultaneous use of Acoustic Emission Signals and Statistical Analysis to Distinguish between Lubrication Modes in Rolling Element Bearings
Seyed Ali Niknam

The lack of lubricant in bearing surfaces could be considered as the main cause of wear and faults in bearing surfaces. To avoid unexpected failures, special emphasis on adequate evaluation of lubrication mode (lubricated/dry) on the bearing surfaces is demanded. To tha More

The lack of lubricant in bearing surfaces could be considered as the main cause of wear and faults in bearing surfaces. To avoid unexpected failures, special emphasis on adequate evaluation of lubrication mode (lubricated/dry) on the bearing surfaces is demanded. To that end, the proper use of reliable techniques and tools, including sensory information from acoustic emission (AE) signals is among popular methods when real-time condition monitoring evolves. The current work intends to evaluate the sensitivity of AE parameters to different levels of process parameters on the basis of statistical analysis. In this context, rotational speed and radial load were used as the main experimental parameters. Following that, adequacy of a new AE signal parameter for real-time condition monitoring of rolling element bearing is presented. Experimental and statistical results confirmed the great capability of AE signals to differentiate between two types of bearing modes, in particular, dry and lubricated. Signal processing and statistical analysis conducted in this study exhibited that several time series AE parameters, in particular, Std, Max, Mean, and Variance are sensitive to the variation radial load and rotational speed. It was observed that radial load has insignificant effects on computed values of AE parameters from both bearing modes. The statistical analysis revealed that rotational speed (A) has a significant effect on all computed AE parameters from the dry bearing. Manuscript profile

Open Access Article

4 - Modal Analysis of Complex Structures via a Sub-Structuring Approach
Vahid Heydari Mohammd Ahmadi Balootaki Mohammad Orak Mehdi Salehi

10.30495/admt.2021.1896878.1187

In this paper, the problems arising from determining the modal properties of large and complex structures are investigated. For this purpose, the free interface component mode synthesis method has been used. In the following, Singular-Value Decomposition (SVD) is applie More

In this paper, the problems arising from determining the modal properties of large and complex structures are investigated. For this purpose, the free interface component mode synthesis method has been used. In the following, Singular-Value Decomposition (SVD) is applied as a powerful mathematical tool to determine the appropriate coordinates to participate in the coupling process. Also, the effective error resources including modal shear error and the continuous systems overlapping error and their solution are introduced. Initially, a discrete system has been employed to investigate the free interface component mode synthesis method. Eventually, the studied main samples in this research are beam, plate and cylindrical shell. It is worth noting that the application of this method on the cylindrical shell has not been observed in previous researches. Manuscript profile

Open Access Article

5 - Vibration Suppression of Grass Trimmer Handle using Tunable Vibration Absorber
Sushil Sahebrao Patil

The electrical grass trimmers are widely used for cutting grass along the highways, roadside & general agricultural work. Grass trimming involves the use of motorized cutter spinning at high speed, resulting in hand-arm vibration syndrome among the machine operators More

The electrical grass trimmers are widely used for cutting grass along the highways, roadside & general agricultural work. Grass trimming involves the use of motorized cutter spinning at high speed, resulting in hand-arm vibration syndrome among the machine operators. The purpose of this work is to reduce the handle vibration of grass trimmer using tuned vibration absorber (TVA). The variable stiffness dual mass vibration absorber is designed using Dunkerleys Equation and fabricated for testing. The experimental modal analysis of absorber is conducted to find resonance frequencies of the absorber and to validate the results obtained from equations. The experimental tests are carried on grass trimmer with absorber attached at different location for two cutter head positions to find the absorber attachment location to reduce handle vibrations to minimum level. The results indicated that the vibration attenuation is affected by the location of absorber and cutter head position of grass trimmer. Manuscript profile

Open Access Article

6 - Vibration based Assessment of Tool Wear in Hard Turning using Wavelet Packet Transform and Neural Networks
vahid pourmostaghimi Mohammad Zadshakoyan Morteza Homayon Sadeghi

Demanding high dimensional accuracy of finished work pieces and reducing the scrap and production cost, call for devising reliable tool condition monitoring system in machining processes. In this paper, a tool wear monitoring system for tool state evaluation during hard More

Demanding high dimensional accuracy of finished work pieces and reducing the scrap and production cost, call for devising reliable tool condition monitoring system in machining processes. In this paper, a tool wear monitoring system for tool state evaluation during hard turning of AISI D2 is proposed. The method is based on the use of wavelet packet transform for extracting features from vibration signals, followed by neural network for associating the root mean square values of extracted features with tool flank wear values of the cutting tool. From the result of performed experiments, coefficient of determination and root mean square error for the proposed tool wear monitoring system were found to be 99% and 0.0104 respectively. The experimental results show that wavelet packet transform of vibration signals obtained from the cutting tool has high accuracy in tool wear monitoring. Furthermore, the proposed neural network has the acceptable ability in generalizing the system characteristics by predicting values close to the actual measured ones even for the cutting conditions not encountered in the training stage. Manuscript profile

Open Access Article

7 - Comparison of Vibration Amplitude in Isfahan Subway Due to Track Structure- An Experimental Study
sajjad sattari Mohammad Saadat Sayed Hasan Mirtalaie mahdi salehi ali soleimani

10.30486/admt.2023.1973746.1392

Increasing the stability of structures and reducing the maintenance cost of slab track superstructures compared to ballasted tracks are among the reasons for the tendency to use this category of superstructures in the railway industry. Vibration reduction methods can be More

Increasing the stability of structures and reducing the maintenance cost of slab track superstructures compared to ballasted tracks are among the reasons for the tendency to use this category of superstructures in the railway industry. Vibration reduction methods can be divided into three categories, source, propagation path, and receiver. In general, the slab track structures in Iran are divided into three categories: direct fixation track (DFT), floating slab track (FST), and high resilient fastener (HRF). Although railway tracks are a safe, economical and fast transportation system and can lead to the strengthening of the tourism industry, in the long term, vibrations can damage many historical structures in the city of Isfahan. FST and HRF systems are used in the structure of Isfahan subway track. In this paper, the accelerations (longitudinal, lateral, and vertical) of the Isfahan subway vehicle were measured in 30 stations (15 go stations and 15 return stations). The results showed that the HRF system compared to the FST has a significant effect in reducing the range of vibrations and ultimately the safety of the train and the ride comfort. For example, in the area between Si-O-Se-Pol and Imam Hossein Square, due to the track structure type (HRF), the maximum acceleration and RMS acceleration are in the range of 1.5 and 0.3 m/s2, respectively, while in other stations these values were extracted up to 4 and 0.7 m/s2, respectively. Manuscript profile

Open Access Article

8 - Designing an Impedance Control Algorithm for a Teleoperation System for Orthopedic Surgery
Abolghasem Mokhtari sayedali mousavi

Surgeries, such as orthopedic surgeries, are always performed with the use of a free hand with the aid of a fluoroscopic device to drill and place the screw in the bone position. However, such surgeries are of high risk and radioactive contamination, and have long surge More

Surgeries, such as orthopedic surgeries, are always performed with the use of a free hand with the aid of a fluoroscopic device to drill and place the screw in the bone position. However, such surgeries are of high risk and radioactive contamination, and have long surgery duration. Since the drilling process is very important and usually depends on the skill of the surgeon, a teleoperation system is provided to perform this task. In order to gain better control over the patient's body by the surgeon, an impedance control algorithm that incorporates the robot's position and velocity signal along with the surgeon's hand force and bone response force is provided in order for the surgeon to have proper control over the surgical process. Finally, drilling operation is performed on a cow bone to evaluate the teleoperation system presented. The results of the teleoperation system show that the desired system is acceptable under the proposed control algorithm. The results show that the drilling tool on the cow bone correctly follows the surgeon's hand position and the surgeon correctly feels the force applied to the tool by the cow bone. Manuscript profile

Open Access Article

9 - Effect of using a Dynamic Absorber On Vibrations of an Opposed-Piston Ultralight Aircraft Engine
Mohammad Reza Najafi Saied Mahjoub Moghadas Mojtaba Moradi

10.30495/admt.2021.1907260.1212

In this paper, vibrations reduction of piston engine of ultralight aircrafts was studied with considering a combination of experimental, analytical and numerical methods. Analytical equations of dynamic absorber were obtained. Afterward, experimental test was used to de More

In this paper, vibrations reduction of piston engine of ultralight aircrafts was studied with considering a combination of experimental, analytical and numerical methods. Analytical equations of dynamic absorber were obtained. Afterward, experimental test was used to determine the system torque. Due to the difficulty of obtaining experimental data, the amount of angular acceleration and then velocity and angular displacement were calculated numerically using MATLAB software and verified with experimental results with a difference of less than 2%. Different components of the system were designed with reverse engineering method using SolidWorks software. After data transmission to Adams software, vibrational analysis of the system was performed and validated with analytical results with a difference of less than 1.91%. A suitable dynamic absorber was selected. The results showed that engine vibrations is reduced up to 40%. Manuscript profile

Open Access Article

10 - Investigation of the Stability of the Ball and Beam by the PID Controller
Mojtaba Hadipour Ali Hosseinzadeh Mohsen Sadidi

10.30495/admt.2021.1897179.1189

The purpose of this research is to construct and investigate the stability of the ball and beam control system with PID coefficients derived from the simulation and compare them. In this research, by first obtaining the mathematical model of the mechanical system and it More

The purpose of this research is to construct and investigate the stability of the ball and beam control system with PID coefficients derived from the simulation and compare them. In this research, by first obtaining the mathematical model of the mechanical system and its simulation, the best PID coefficients are selected for it to minimize the settling time and the error. Then, to create this system, the types of mechanisms provided for the ball and beam control system are examined. Depending on the equipment and facilities available, the best design is chosen and built. The best design is the use of the four_bar mechanism using the servo motor and the ultrasonic sensor. The appropriate design is first developed in SolidWorks software to provide accurate measurements for the production of components. Laser cutting and 3D printers are used to produce system components. After the control system is built, the simulation coefficients in the MATLAB software are inserted into the system microcontroller program to check the system responses to the various control coefficients obtained. So doing multiple experiments indicated that the best PID coefficients for this system are PD coefficient. The difference between the experimental graph and the simulation graph is their overshoot. They also have different settling times. One of the reasons for this difference is the use of some approximations as well as disregarding friction. Manuscript profile

Open Access Article

11 - Mass and Stiffness Matrices and Frequencies of Simple Beam Elements Based on Real Shape Functions
Pedram Abouzari Karen Khanlari Reza Esmaeilabadi

10.30486/admt.2022.1949656.1336

In this research, we investigate and compare the natural frequencies of simple beams and their mass and stiffness matrices of the two methods: classic shape functions and real shape functions. To this end, we solve the beam motion Equation and apply boundary conditions. More

In this research, we investigate and compare the natural frequencies of simple beams and their mass and stiffness matrices of the two methods: classic shape functions and real shape functions. To this end, we solve the beam motion Equation and apply boundary conditions. This article shows that the coefficients of the real shape functions, and consequently, the real shape functions, become harmonic and hyperbolic and also, they are dependent on the natural frequency value of the element. As a result, the real mass and the real stiffness matrix of each element are also dependent on the element frequency. The frequency values obtained from these two methods are compared with the exact frequency values of two simple beam types with different support conditions. In this way, we determine which method leads to more accurate and acceptable frequencies for these beams. Based on the obtained results, the percentage of frequency error obtained by the classical method is relatively high in the sample beams. Hence, the natural frequency value of the beams studied using exact shape functions shows a small error compared to the classical method in terms of the exact frequency value of these beams. It is of note that the frequency error obtained from the classical method is greater in the elements with a higher natural frequency. Overall, obtaining the exact natural frequency of an element will result in accurate dynamic responses and more appropriate analyses and designs. Manuscript profile

Open Access Article

12 - Design an Adaptive Sliding Mode Controller for a Class of Underactuated Systems
Hossein Moeinkhah Mohammad Ahmadi Balootaki

10.30495/admt.2021.1898210.1194

The majority of underactuated systems are nonholonomic, due to non-integrable differential constraints. Therefore, controlling an underactuated system is considered as a challenging problem. In this study, an adaptive controller based on super-twisting sliding mode cont More

The majority of underactuated systems are nonholonomic, due to non-integrable differential constraints. Therefore, controlling an underactuated system is considered as a challenging problem. In this study, an adaptive controller based on super-twisting sliding mode controller is proposed for a class of robust underactuated systems subjected to uncertainties and external disturbances. The adaptive compensator was designed so that there would be no need to the upper bound of the external disturbance. The controller parameters of adaptive sliding mode control are tuned based on a multi-objective non-dominated sorting of genetic optimization algorithm. The results of simulation and the demonstration of the effectiveness and applicability of the proposed scheme are presented. Manuscript profile

Open Access Article

13 - Modeling and Simulation of 6DOF Robot Manipulators with Tactile Position-Force Control
Mohammad Reza Najafi Ahmad Khoogar Hadi Darabi

10.30486/admt.2021.1918232.1235

In this paper, a joint position-force controller is used to control a 6R general-purpose robot manipulator. The manipulator comes into interaction with a spherical object in a numerically simulated environment. A controller has been implemented using the MATLAB Simulink More

In this paper, a joint position-force controller is used to control a 6R general-purpose robot manipulator. The manipulator comes into interaction with a spherical object in a numerically simulated environment. A controller has been implemented using the MATLAB Simulink software which uses the Simmechanics second-generation toolbox. A useful numerical contact model is used for modelling the interaction between the manipulator’s end-effector and the environment which generates the interaction feedback forces. The control algorithm presented in this paper is developed in the Cartesian space and the original control algorithm was modified to satisfy the desired input position in the base coordinate frame. The control algorithm was verified using a virtual environment, before hardware implementation. The novelty of the controller is determining the input tactile forces for the robot without actually causing a collision between the end-effector and the object in the environment which can lead to fracture and damage to the environment or the manipulator. The modeling process of interaction with the spherical environment was investigated using Simmechanics to model precise mechanical characteristics of manipulator that are unknown to the designers and provide a great advantage in the simulation for them. The considered position and tactile force were tracked successfully with good accuracy. The results show that the proposed manipulator system controls the position and force with more than 95% accuracy and the accuracy of desired tracing trajectory is 99%. Manuscript profile

Open Access Article

14 - Modelling and Control of Mutation Dynamics of the Cancer Cells Employing Chemotherapy
Hami Tourajizadeh zahra zarandi zakie farbodi ehsan sadeghi

10.30486/admt.2021.1920220.1240

In this paper, the analytic model of the mutation dynamics related to the cancer cells which is under the control of chemotherapy is developed and its corresponding metastasis is controlled using chemotherapy method. The progress of a cancer tumours is contributed to tw More

In this paper, the analytic model of the mutation dynamics related to the cancer cells which is under the control of chemotherapy is developed and its corresponding metastasis is controlled using chemotherapy method. The progress of a cancer tumours is contributed to two main factors including metastasis and mutation. It is observed that controlling the metastasis dynamic without considering the mutation phenomenon is doomed to fail. In this paper, the mathematical model of the cancer dynamic is improved considering the mutation of the stem cells and the effect of chemotherapy injection as the corresponding controlling signal is investigated in the extracted state space. Controlling the cancer growth and its mutation process is accomplished here using PID controller and State Feedback Control (SVFC) method. It is shown that by the aid of the proposed model of this paper, not only the number of the cancer cells can be converted to zero, but also the mutation process can be blocked since the feedback of the mutated cells are also engaged in the state space of the system. Verification of the model is conducted by the aid of simulation in the MATLAB and comparing the results with previous studies. Manuscript profile

Open Access Article

15 - Attitude Tracking Control of Autonomous Helicopter using Polytopic-LPV Modeling and PCA-Parameter Set Mapping
Reza Tarighi Amir Hooshang Mazinan Mohammad Hosein Kazemi

10.30495/admt.2021.1910292.1219

This paper presents a new method for modeling and Attitude Control of Autonomous Helicopters (A.H.) based on a polytopic linear parameter varying approach using parameter set mapping with the Principal Component Analysis (PCA). The polytopic LPV model is extracted based More

This paper presents a new method for modeling and Attitude Control of Autonomous Helicopters (A.H.) based on a polytopic linear parameter varying approach using parameter set mapping with the Principal Component Analysis (PCA). The polytopic LPV model is extracted based on angular velocities and Euler angles, that is influenced by flopping angles, by generating a set of data over the different trim points. Because of the high volume of trim data, parameter set mapping based on (PCA) is used to reduce the parameter set dimension. State feedback control law is proposed to stabilize the system by introducing a Linear Matrix Inequality (LMI) set over the vertices models. The proposed controller is performed for an Autonomous Helicopter in different scenarios. All the scenarios are investigated with the PCA algorithm as a technique for reducing the computational volume and increasing the speed of solving the LMI set. The simulation results of implementing the planned controller on the nonlinear model of an autonomous helicopter in different scenarios show the effectiveness of the proposed scheme. Manuscript profile

Open Access Article

16 - Increasing the Fundamental Frequency of the Cantilever Rotating Beam by Placing the Intermediate Elastic Support with Minimum Stiffness at the Optimum Point Based on the Courant’s Maximum–Minimum Theorem using Finite-Element Analysis Software
Mehdi Asgarikia Farshad Kakavand Hasan Seidi

10.30495/admt.2021.1917477.1232

: In this paper, the effect of the optimal position and minimum stiffness of the elastic middle support on increasing the fundamental frequency of a rotating cantilever beam is investigated based on the Courant’s maximum–minimum theorem using ABAQUS finite e More

: In this paper, the effect of the optimal position and minimum stiffness of the elastic middle support on increasing the fundamental frequency of a rotating cantilever beam is investigated based on the Courant’s maximum–minimum theorem using ABAQUS finite element software. First, the software analysis results are compared with the numerical analysis results for a non-rotating cantilever beam to confirm the accuracy of the software model. Next, by placing the middle elastic support at the optimal point selected based on the Courant theorem, the minimum stiffness of the elastic intermediate support for the maximum fundamental frequency of the rotating console beam was obtained. The results of this study prove that the Courant’s maximum–minimum theorem is completely valid for rotating cantilever beams and can be used to improve the vibrational behavior of rotating engineering components. Finally, the minimum diameter of damping wire for the turbomachine blade is calculated as a practical application of the minimum stiffness of the intermediate elastic support for the rotating beam. Manuscript profile

Open Access Article

17 - A New Design for Active Isolation of Patient's Compartment from Ambulance Body using the Adaptive Control Method
Aliasghar Meraji Saied Mahjoub Moghadas

10.30486/admt.2022.1942823.1319

Vertical vibrations in the ambulance patient compartment due to road disturbances can cause serious injury to patients. In the present study, after extracting the vibrations entering an ambulance with passive suspension system, the use of a new active vibration isolatio More

Vertical vibrations in the ambulance patient compartment due to road disturbances can cause serious injury to patients. In the present study, after extracting the vibrations entering an ambulance with passive suspension system, the use of a new active vibration isolation system between the patient's Compartment and the ambulance body is proposed. This isolation system includes an air spring, a linear shaft motor and a suitable active controller, which is abbreviated as AVI system. In this paper, instead of using one AVI system to control the vibrations of the stretcher, four AVI systems are used to control the vibrations of the patient's Compartment. The accurate modelling for ambulance with passive suspension system in both types non-isolated and active isolated patient's Compartment has been done by SOLIDWORKS software. Then by extracting the mathematical model, differential equations and state space model, the comparison of both types was done using MATLAB-SIMULINK software and finally the results were optimized using the Model Reference Adaptive Control (MRAC). In this control method, the functional parameters automatically adapt themselves by changing the position of the centre of gravity. The results obtained according to the IS02631 standard, show that with the present method, vertical vibrations are reduced by more than 80%. Manuscript profile

Open Access Article

18 - Stability Enhancement of In-Wheel Motor Drive Electric Vehicle Using Adaptive Sliding Mode Control
Majid Majidi Aria noori Asiabar

10.30486/admt.2022.1938721.1311

A multi-layer controller of direct yaw moment for electric vehicles is developed in this study. In the upper layer, the yaw moment are obtained using Adaptive Sliding Mode Control (ASMC) with adaptation gain to track the desired vehicle yaw rate. The corrective yaw mome More

A multi-layer controller of direct yaw moment for electric vehicles is developed in this study. In the upper layer, the yaw moment are obtained using Adaptive Sliding Mode Control (ASMC) with adaptation gain to track the desired vehicle yaw rate. The corrective yaw moments are applied by four in-wheel electric motors. The lower layer controller consists of a torque distribution algorithm and in-wheel motor torque controllers as well. The proposed torque distribution algorithm is intended to distribute the reference torques of each in-wheel motor controller appropriately based on both total longitudinal force and corrective yaw moment. To elucidate the effectiveness and robustness of the above control method, the simulation under various manoeuvres was carried out. A 7-DOF non-linear vehicle model is used for simulations and their results signify that the proposed control algorithm accomplishes a proper distribution of longitudinal force among four individual wheels, in turn, enhancing the yaw stability of the vehicle. Manuscript profile

Open Access Article

19 - Optimization of Location and Stiffness of an Intermediate Support to Maximize the First Natural Frequency of a Beam with Tip Mass-With Application
Hossein Ebrahimi Farshad Kakavand Hassan Seidi

10.30486/admt.2022.1933790.1291

The optimal position and minimum stiffness of an intermediate support is implemented to maximize the fundamental natural frequency of a vibrating cantilever Euler-Bernoulli beam with tip mass. According to Courant’s maximum-minimum theorem, maximum value of the fi More

The optimal position and minimum stiffness of an intermediate support is implemented to maximize the fundamental natural frequency of a vibrating cantilever Euler-Bernoulli beam with tip mass. According to Courant’s maximum-minimum theorem, maximum value of the first natural frequency of a beam with a single additional rigid internal support, is equal to the second natural frequency of the unsupported beam. In literature, for a cantilever beam without tip mass, the optimum position of intermediate support was reported as 0.7834L and minimum dimensionless stuffiness as 266.9. In this paper, the effect of tip mass ratio on optimum location and minimum stiffness is investigated. The Finite element method is employed. Cross sectional area is uniform and material is homogeneous and isotropic. Numerical results demonstrate that as tip mass ratio increases the optimal position moves toward the tip mass and minimum stiffness increases. For instance, for tip mass ratio 0.5, optimal position is 0.92L and minimum dimensionless stiffness is 284. Optimal position and minimum stiffness are presented for various range of mass ratio. In many applications, it is not possible to place intermediate support at optimal position; therefore, the minimum stiffness does not exist. In these cases, a tolerances zone is considered and related design curves are proposed. As a practical example, an agitator shaft is considered and end impeller is modeled as tip mass. The effectiveness of the proposed design curves in order to maximize natural frequency is shown. A design of an intermediate support is presented; in this example the fundamental frequency has increased as much as 300 percent without any change in shaft diameter. Manuscript profile

Open Access Article

20 - Effect of Adding a Styrene-Butadiene Rubber Damper to A Sled Sample and Extraction of Its Equivalent Stiffness and Damping
Mohammad Reza Najafi Saied Mahjoub Moghadas

10.30486/admt.2022.1939798.1313

Protection of sled systems from destructive vibrations is inevitably under attraction due to the importance of sled testing in the aerospace industry. A pair of SBR dampers were used between the slipper and the sled body to reduce vertical vibrations, so a design of the More

Protection of sled systems from destructive vibrations is inevitably under attraction due to the importance of sled testing in the aerospace industry. A pair of SBR dampers were used between the slipper and the sled body to reduce vertical vibrations, so a design of the sled model was studied. Both equivalent stiffness and equivalent damping of the sled system were obtained to reduce the transmission of vibrations from slippers to the body. A combination of analytical, numerical and experimental test methods was utilized and the results were validated. The stiffness values of 370500 and 391000 N&frasl;m were obtained from numerical and experimental measurements, respectively. Finally, by designing the sled model, first and second natural frequencies of 12.49 and 19.56 Hz and mode shapes of the sled system were obtained. The results show that the dampers used in the sled have an important role in reducing the transmission of vibrations to the sled body by withstanding the tension and pressure on the slippers. Manuscript profile

Open Access Article

21 - Vibration Analysis of an Imperfect Single-Layer Graphene Sheet using Quasi-3d Theory and Isogeometric Approach
Heidar Fazeli Armen Adamian Ahmad Hosseini-Sianaki

10.30486/admt.2022.1951472.1338

In this study, the size-dependent free vibration analysis of a geometrically imperfect single-layer graphene sheet (SLGS) is studied by an isogeometric approach along with the quasi-3D shear and normal deformation theory. Initial geometric imperfections alter the natura More

In this study, the size-dependent free vibration analysis of a geometrically imperfect single-layer graphene sheet (SLGS) is studied by an isogeometric approach along with the quasi-3D shear and normal deformation theory. Initial geometric imperfections alter the natural frequencies of the graphene sheets that may exist inherently or purposely created by researchers. The initial curvature is modelled by an analytical function in the governing Equations of the plate. A 4-variable quasi-3D theory with a seventh-order distribution function is used to include both shear deformation and thickness stretching influences. A weak form of a nonlocal plate for free vibration analysis is derived that requires the first-order continuity of the displacement fields. Inherent high-order continuity of non-uniform rational B-spline (NURBS) basis functions in isogeometric analysis can meet this condition. A comparison between the present study and other published works reveals the efficiency and accuracy of the proposed method in imperfect SLGS. The results of the present study show a significant effect of initial geometric imperfection on the natural frequency of single-layer graphene sheets. Manuscript profile

Open Access Article

22 - Analysis and Control of Chaos in Nonlinear Gear System using Predictive Sliding Mode Control
Nima Valadbeigi Seyed Mahdi Abtahi

10.30486/admt.2022.1949735.1333

This paper presents a control system for elimination of chaotic behaviors in spur gear system. To this end, at first different aspects of chaos are investigated by means of numerical tools including time series response, phase plane trajectories, bifurcation diagram, Po More

This paper presents a control system for elimination of chaotic behaviors in spur gear system. To this end, at first different aspects of chaos are investigated by means of numerical tools including time series response, phase plane trajectories, bifurcation diagram, Poincare’ section, Lyapunov exponent and power spectrum density. The nonlinear dynamic model encompasses constant mesh stiffness and damping along the line of action, static transmission error and backlash. In order to suppress the chaotic oscillations, a novel controller on the basis of the Predictive Sliding Mode Control (PSMC) is proposed in which the sliding surface is predicted by the use of model predictive control theory and the control input is obtained. Consequently, the control system takes advantage of the both approaches in developing a robust controller. The simulation results of the feedback system depict the effectiveness of the controller in elimination of the chaotic vibrations along with reduction of settling time, overshoots, and energy consumption. Furthermore, stability and robustness of the system are guaranteed. Manuscript profile

Open Access Article

23 - Investigation of the Effects of Dimensional Inaccuracies on the First Natural Frequency of Cellular Lattice Structures
Amir Hosein Samimi Mohammad Reza Karamooz-Ravari Reza Dehghani

10.30486/admt.2022.1946219.1324

Lattice structures have attracted a great deal of attention for being used in different industries due to unique properties such as high strength-to-weight ratio and high damping coefficient. These metamaterials might suffer from dimensional inaccuracies, i.e., variable More

Lattice structures have attracted a great deal of attention for being used in different industries due to unique properties such as high strength-to-weight ratio and high damping coefficient. These metamaterials might suffer from dimensional inaccuracies, i.e., variable strut’s diameter, wavy struts, micropores, and deviation from the designed cross-sectional area, which arise from the fabrication process. These inaccuracies can drastically affect their mechanical response. In this paper, the effects of different dimensional inaccuracies, including variable struts’ diameter, wavy struts, and material concentration at nodes, on the frequency response of different cellular lattice structures are studied. To do so, a finite element model is constructed using Timoshenko beam elements, and the natural frequencies are obtained for four different lattices. The obtained results show that, by increasing the average diameter, the natural frequency increases drastically, whereas by increasing the amount of variation in the struts’ diameter and waviness the natural frequency decreases by a small amount. It is also observed that the lattice structures whose main deformation mechanism is axial loading are more sensitive to the change of average struts’ diameter. In addition, the natural frequency increases as the concentration of material in the vicinity of the nodes increases. The effect of material concentration inaccuracy is more pronounced for the first lattice for which the number of struts meeting at one node is the smallest. Manuscript profile

Open Access Article

24 - Investigation of Pressure Distribution on Slippers of a Monorail Sled with Vibration Damper
Mohammad Reza Najafi Saied Mahjoub Moghadas

10.30495/admt.2022.1949929.1334

In this paper, the pressure distribution on the slippers of a mono-rail sled with vibration damping is investigated. Due to the many applications of sled testing in the aerospace industry, the study of system vibrations is highly noticeable. In this research, first, by More

In this paper, the pressure distribution on the slippers of a mono-rail sled with vibration damping is investigated. Due to the many applications of sled testing in the aerospace industry, the study of system vibrations is highly noticeable. In this research, first, by mathematical modelling of the sled, the governing Equations are extracted and natural frequencies and vibration modes are obtained from the analytical method using the mass and stiffness matrix of the system. Then, using numerical simulation and validation methods with experimental results performed in wind tunnels, the modal analysis of the designed sled sample is performed. A difference of less than eight percent in both numerical and analytical methods proves the accuracy of the results. The results show that the role of the slipper in the vibrations created in the sled is very important due to the large torsional and transverse oscillations in different positions, and the highest static pressure occurs in the inner layer of the slipper. Manuscript profile

Open Access Article

25 - Active Control of Shimmy Vibration in Aircraft Nose Landing Gear using Fuzzy and NARMA-L2 Controllers
Milad Yazdanpanah Alireza Nateghi hassan Zare

10.30486/admt.2023.1965079.1373

In this paper, control of shimmy vibration of aircraft nose landing gear is presented. In this regard, the NARMA-L2 neural controller and a robust controller using a fuzzy method are designed and compared. The efficiency of these controllers was measured by comparing th More

In this paper, control of shimmy vibration of aircraft nose landing gear is presented. In this regard, the NARMA-L2 neural controller and a robust controller using a fuzzy method are designed and compared. The efficiency of these controllers was measured by comparing the results obtained from CTM and PID controllers. Using the NARMA-L2 neural controller, maximum effort and settling time are improved whereas using fuzzy controller overshoot of the vibration response improvement in the closed-loop system was observed. According to these results, a large part of the design requirements can be solved by the implemented controllers. Manuscript profile

Open Access Article

26 - Improvement Analysis of Response Between Jacket Platforms and Sea Waves using the Vibration Dampers
Latif Pendarian Alireza Fiouz Abbas Gasemi

10.30486/admt.2023.1961890.1359

Offshore fixed metal platforms have unique characteristics in specific location such as shallow waters, and oil platform may be physically connected to seabed. Offshore platforms in the sea are affected by complex and destructive forces caused by wind, waves, marine cur More

Offshore fixed metal platforms have unique characteristics in specific location such as shallow waters, and oil platform may be physically connected to seabed. Offshore platforms in the sea are affected by complex and destructive forces caused by wind, waves, marine currents, earthquakes and even large displacement vortex forces. The purpose of refurbishing metal fixed platforms is to somehow equalize the capacity of the structure with its seismic requirements. In some cases, they increase the capacity of the structure to meet seismic requirements. In this research, dynamic vibration absorbers or dampers, such as passive dampers, fluid system adjusted for damping vibrations and reduced structural response against wave and earthquake hydrodynamic loads will be used as an efficient control method. The purpose of this research is to improve the performance of the liquid platform vibration damping of the metal platform. The results show that equipping offshore platforms with liquid damping systems has a good performance on the safety and dynamic behaviour of the platforms and has a significant effect on the displacement response and acceleration of the platform under study at its highest deck level. Also, as the water depth in the tank increases, the damping value for the rectangular and cylindrical tanks decreases and the rectangular tank creates more control and damping force than the cylindrical tank. Manuscript profile

List of articles (by subject) vibration and control