Saeid Bayat, Hosein Nejat Pishkenari, Hasan Salarieh,
Volume 18, Issue 6 (10-2018)
Abstract
Nowadays, nano-precision positioning stages, have a special position and are used in a variety of applications, such as taking pictures and taking particles of the surface. In this paper,some observers for a nano-precision positioning platform are designed based on three different types of neural networks. The simulated platform was designed at Sharif University of Technology and, based on the system's final requirement for the feedback signal for use in the control rule, neural network observers were designed. In previous studies, the comsol model of the positioning system has been obtained. At this step, the neural network has used the Comsol model and the system has been trained for a sum of a number of sinusoidal functions, and its generalizability has been investigated for ramp input. Neural networks used include, respectively, a multi-layer perceptron network, a radial basis function network and a support vector regression network. By performing simulations, it has been seen that the multi-layer perceptron network and the radial basis function network yielded a good response with low error, but the support vector regression network has a relatively high error.
M. Nouri Khajavi, Gh.r. Bayat ,
Volume 19, Issue 1 (1-2019)
Abstract
An accurate estimation of the state of charge is necessary not only for optimal management of the energy in the electric vehicles (EV) and smart grids, but also to protect the battery from going to the deep discharge or overcharge conditions that degrades battery life and may create potentially dangerous situations like explosion. Despite the importance of this parameter, the state of charge cannot be measured directly from the battery terminals. In this research, an electric equivalent circuit model is simulated in the Simulink environment with two RC networks. This model has the advantage of providing a quick test for the extraction of parameters and dynamic characteristics of the battery model, but is not suitable for on-line applications in an EV. This is why algorithms need to be developed to estimate the SOC of the battery pack and the individual cells based on the measured data of each one. In this paper, for the validation of the neural network, a discharge rate of 0.6A and in the adaptive neuro fuzzy inference system (ANFIS) network, the discharge rate of 0.8, 0.1, and 0.45 was used. The comparison of ANFIS method with the neural method in this study showed that the ANFIS method is more accurate in estimating the state of charge and correlates the experimental points and the output of the network , so that ANFIS error in some states of charge is less than 2%.
M.m. Sheikhi, A. Hadi, M. Ghasemi Varzaneh,
Volume 19, Issue 2 (2-2019)
Abstract
Spherical joints are specifically used in many robotic systems, including various industrial and medical applications, especially in non-structured environments. Modular robotic systems are the appropriate solution for use in these environments; So that the configuration of the robots can change quick and easy by link or separate different modules. Flexibility of modules, enough degrees of freedom, capability to stabilize the position of the module and rigidity to maintain strength and stiffness of modular robot during mission are the most important features of a modular robot. Shape memory alloys are suitable actuators for use in robotic modules, which a tiny, lightweight, and without noise system is achieved by using them. In this paper, a mechanism with two degrees of freedom has been created by placing three memory shape alloys springs in the structure of a flexible joint module. Also, with the installation of an electromagnetic system in the joint, it is possible to stabilize its position when necessary. The developed module, in addition to its high flexibility, can maintain its position when needed and increase the strength of the robotic arm. In this research, the design of the module has been presented and kinematic and force analysis has been investigated.
S.h. Heidary, J. Farhat, B. Beigzadeh,
Volume 19, Issue 2 (2-2019)
Abstract
New users such as pedestrians are added to navigation systems with developing lightweight, portable, low-cost technologies. The pedestrian navigation systems are currently applied in miscellaneous fields including medicine, sport, military services, animation, robotics, etc. This amount of use has attracted the attention of many scholars over the last few decades. In this paper, the paths of a firefighter, as a pedestrian, was estimated approximately by the help of an inertial measurement unit (IMU) and acceleration sensors. To reduce the measured errors and noises by the sensor, zero velocity update (ZUPT) method and Kalman filter are exploited in a pedestrian navigation system. Due to the fact that the error in blind navigation is divergent over time if the filter is not used, the use of conventional accelerometer sensors cannot produce a satisfactory result.
using the combined module of an inertial measurement sensor that includes accelerometer and gyroscope, it is possible to track the person’s position at any moment while the sensor is tracked on the shoe. The ability of ZUPT in navigation system has been discussed and interpreted by measuring a path using a sensor installed on a person’s shoe and comparing the results with the desired predetermined path.
S. Nezamivand Chegini, A. Bagheri , F. Najafi ,
Volume 19, Issue 4 (4-2019)
Abstract
In this paper, a new hybrid intelligent method is presented for detecting the bearing faults in the various rotating speeds. The vibration signals are collected in four conditions, including the normal state, the faulty inner race, the faulty outer race, and the faulty bearing element. Firstly, twenty-two statistical features in the time domain and four frequency features, three Wavelet packet decomposition (WPD), and the first five intrinsic mode functions obtained by the empirical mode decomposition (EMD) are extracted from the original signal; finally, the feature vector for each signal sample has 424 features. However, in the high dimensional feature matrix, there may exist the insensitive features to the presence of defects. Therefore, in this study, the compensation distance evaluation technique (CDET) is used to select the optimal features. Then, the selected features are used as the inputs of the support vector machine (SVM) classifier to diagnose the bearing conditions. In the CDET method, there is a threshold indicator that plays a decisive role in choosing the desired attributes. Also, the SVM method has some parameters that need to be set during the fault detection process. Therefore, the particle swarm optimization (PSO) algorithm is used to determine the optimal threshold in the CDET method and the optimal SVM parameters, so that the prediction error of the bearing conditions and the number of the selected features are minimized. The obtained results demonstrate that the selected features are well able to differentiate between different bearing conditions at various speeds. Comparing the results of this paper with other fault detection methods indicates the ability of the proposed method.
H. Ghafarirad, S.m. Rezaei, M. Zareinejad,
Volume 19, Issue 5 (5-2019)
Abstract
Piezoelectric bending actuators have been extensively utilized in recent years. Two major modeling methods, lumped and continuous, have been generally proposed in previous researches for these actuators. The lumped method can only express the transverse vibration of one specified point on the actuator. In addition, the effect of higher vibrational modes has been ignored. Hence, continuous dynamic models have been proposed to rectify the mentioned drawbacks. In this method, linear constitutive equations for low voltage applications are usually applied. But, the main challenge in continuous modeling of piezoelectric actuators is the hysteresis nonlinear phenomenon caused by excitation voltages. In this paper, piezoelectric nonlinear constitutive equations have been employed to carry out the continuous dynamic model for two general types of bending actuators i.e. Series and Parallel. In addition, zero dynamic analysis for nonlinear systems has been applied to clarify the effect of higher vibrational modes the actuator dynamic behavior based on the location of Experimental results show the maximum error 1.44 and 1.2% in the identification of first and second modes, respectively, and the maximum error 2.89% in the modeling of actuator nonlinear behavior by two modes. These results validate the efficiency of the proposed dynamic model to express the actuator nonlinear behavior, dynamic analysis, and its superiority over conventional models with one mode.
M. Mousazadeh, K. Jahani, M. Abdollahi,
Volume 19, Issue 5 (5-2019)
Abstract
The aim of this paper is identifying the parameters of for a double-ended magnetorheological damper with different sizes of iron- powders suspended in magnetorheological fluid. There is not any published work in literature about identification of parameters of spherical iron particles with different particle diameters in magnetorheological fluids. Hence, in at first, two different magnetorheological fluids with different diameters of iron particle and same volume percentage are prepared. Then, using a double-ended magnetorheological damper, dynamic displacement tests with harmonic excitation in different frequencies and using different electric currents are conducted. The parametric Spencer model is selected for modeling the damper and identifying its parameters. 10 parameters of this model are identified, using nonlinear least square solver and implementing for damper, using two different magnetorheological fluids in different frequencies and different electric currents. The appropriate polynomials are extracted for parameters that have systematic trends with increasing electric current. experimental hysteresis curves in different electric currents, excitation frequencies and different fluids, it is to assess the capability of Spencer model in regenerating the experimental counterparts. The comparisons of the hysteresis curves obtained from with identified parameters by the experimentally achieved counterparts show that this model has adequate compatibility with experiments in predicting force-velocity hysteresis curves. However, the implemented model has not enough success in predicting the force-displacement hysteresis curves, especially in sharp ends of the curves and force delaying regions.
B. Sharifi, S.h. Hashemabadi,
Volume 19, Issue 6 (6-2019)
Abstract
In the present study, CFD simulation of Transit-time ultrasonic flowmeter with the PZT-5J piezoelectric sensor was modeled for light, heavy, and medium crude oil by the wave equation in the acoustic wave propagation path and finite element solving method in the unsteady state and it was implemented, using COMSOL Multiphysics 5.3 software. Different samples of light, heavy, and medium crude oil at different temperatures were modeled and simulated under constant pressure, using CFD tools. voltage and speed of sound in were calculated by the proposed model. To evaluate the accuracy of the proposed model, the simulation results were compared with the empirical data obtained from the experimental work of the researchers. The average values of the maximum voltage of signals for an ultrasonic containing light, heavy, and medium light crude oil samples are 0.9491, 1.0115, and 0.943 v, respectively. The difference between the simulation results and the experimental data for the speed of sound in the light, heavy, and medium crude oil samples was at most about 0.2336%, 0.4339%, and 0.1378%, respectively. Therefore, the high costs of designing and optimizing the transit-time ultrasonic flowmeter for crude oil can be reduced, using the proposed model.
T. Falahati Nodeh, M. Mirzaei , E. Babazadeh Mehrababni, M.j. Khosrowjerdi,
Volume 19, Issue 7 (7-2019)
Abstract
In this paper, the effect of different sensors on the observer performance of vehicle suspension system is investigated. For this purpose, the concept of observable degree analysis is used to quantitatively measure the observability for different sensor choices. A new method, for determining the observable degree of linear time invariant (LTI) systems has been developed on the basis of distance of system from set of similar unobservable systems. A long distance is equivalent to a strong observability and a short distance is equivalent to a weak observability. The zero distance means that the system is unobservable. Since the distance to different unobservable modes can be determined separately, a comprehensive investigation of system observability and the effect of different sensor choices on the observer performance can be provided. In the following, the observable analysis of the suspension system was performed based on the proposed method and the effect of different outputs on the observer performance has been investigated. The results show that when the observable degree is increased for a specific sensor, the observer gain is decreased and consequently the sensitivity of observer relative to the noise and measurement errors is decreased. The increased accuracy of observer demonstrates a good conformity between observable degree analysis and observer performance. Also, a comparative study showed that, contrary to previous criteria that only considered a certain aspect of observability, the proposed method is more comprehensive and realistic, and the results obtained from the previous criteria can easily be achieved through the proposed method.
M. Ebrahimi Dehshalie , M.b. Menhaj , M. Karrari,
Volume 19, Issue 7 (7-2019)
Abstract
In this paper, the optimal control algorithm design is proposed for droplet generation.
In the proposed algorithm, the redundancy in the microfluidic channel network for droplet generation is used to the optimization setting in order to determine
volume flow rate of fluid for each input channel; an optimization problem is proposed for minimizing the volume flow rate of fluid such that the droplet formed in the outlet channel
is produced at the desired size. Also, due to the importance of estimating the system state, the design of the Luenberger observer (reduced order observer) has been developed. Then, the proposed scheme is robust against output feedback delay with respect to the optimal LQR control structure for tracking the desired value. While designing for the observer and controller sections, the delays in the measurement of the output feedback are considered, and the sustainability analysis for each of the sections has been performed due to the fixed delay in the output feedback. Output feedback is a measurable variable of the input volume flow of each channel. Finally, the optimal control algorithm of droplet generation for a microfluidic structure with a T shape has been stimulated.
S.a. Sajjady, S. Amini,
Volume 19, Issue 8 (8-2019)
Abstract
Since the invention of ultrasonic vibration assisted turning, this process has been widely considered and investigated. The reason for this consideration is the unique features of this process, which include reducing machining forces, reducing wear, and friction, increasing the tool life, creating periodic cutting conditions, increasing the machinability of difficult-to-cut material, increasing the surface quality, creating a hierarchical structure (micro-nano textures) on the surface and so on. Different methods have hitherto been used to apply ultrasonic vibration to the tip of the tool during the turning process. In this research, a unique horn has been designed and constructed to convert linear vibrations of piezoelectrics to three-dimensional vibrations (longitudinal vibrations along the z axis, bending vibrations around the x axis, and bending vibrations around the y axis). The advantage of this ultrasonic machining tool compared with other similar tools is that in most other tools, it is only possible to apply one-dimensional (linear) and two-dimensional (elliptical) vibrations, while this tool can create three-dimensional vibrations. Additionally, since the nature of the designed horn can lead to the creation of three-dimensional vibrations, there is no need for piezoelectric half-rings (which are stimulated by 180 phase difference) to create bending vibrations around the x and y axes. The reduction of costs as well as simplicity of applying three-dimensional vibrations in this new method can play an important role in industrializing the process of three-dimensional ultrasonic vibration assisted turning.
K. Kianfar , A. Ranjbar Noiey , B. Rezaie,
Volume 19, Issue 8 (8-2019)
Abstract
In recent years, scientific advances in navigation systems and technological development of low-power consumption and high-precision in magnetic sensors have made researchers to realize that earth’s magnetic field can be applied for locating purposes. Earth’s magnetic field is applied in the navigation method where the required data from earth’s magnetic field can be read from high accuracy magnetic sensors. It is possible to determine the location by comparing the data with the reference maps through adaption of algorithms and/or filtering. Generally, in this method of locating, the inertia system is used to determine the velocity and condition, and the magnetic navigation system represents navigational assistance. In the first step toward obtaining a magnetic locating system, a reference magnetic map must be created; so, it is required to carefully analyze the earth’s magnetic field, the quantity, and quality of the field variations over different time and places. In this paper, the possibility of obtaining the geographical location of an observatory by extracting available data of a magnetic observatory has been investigated and, then, the effect of the displacement of geographical location on the magnitude of the earth's magnetic field has been examined by an experimental test. The results of simulation and data collection confirm the fact that geographic location for a variety of vehicles can be attainable just using earth's magnetic field data and there is no need to use any other navigation sensors.
M. Fallah, B. Moetakef-Imani,
Volume 19, Issue 8 (8-2019)
Abstract
In this paper, a novel dynamic model is proposed for an actively damped boring bar equipped with electromagnetic actuator. The dynamic models of actuator and boring bar are obtained by using the suggested systematic identification approach, which is based upon the fundamental tools and techniques of system identification theory. The electro-mechanical system or the forward path is consisted of 3 basic components, i.e. linear power amplifier, electrodynamic shaker, and boring bar structure. In this paper, the dynamic models of forward path’s sub-systems are simultaneously identified. The component-based identification approach has led to a remarkable finding about the source of nonlinearity in the dynamic model of forward path. According to the presented experimental observations, it has been concluded that electromagnetic actuator can be modeled as a linear dynamic system, while the boring bar structure exhibits nonlinear behavior, since the prediction accuracy of boring bar dynamic model is drastically reduced by changing the amplitude of excitation. As a result, a new parameter varying dynamic model is presented for describing the dynamic behavior of forward path in terms of both frequency and excitation level. The proposed dynamic model has a predefined representation with the least possible mathematical order. It can anticipate the time domain response of forward path due to chirp excitation with 88% accuracy. In addition, during the validation stage, the proposed model forecasts the dynamic response of system due to Gaussian white noise excitation with remarkable accuracy. Moreover, the dynamic model of electromagnetic actuator can predict the dynamic force signature of actuator with 85% accuracy.
H. Fada, A. Soleimani, H. Sadeghian ,
Volume 19, Issue 8 (8-2019)
Abstract
High speed atomic force microscopy (HS-AFM) is one of the widely used techniques in nanotechnology applications due to high resolution and the ability of 3D imaging. Despite its advantages and although it is known as a nondestructive technique, tip or sample damage can occur if maximum repulsive force is higher than the failure stress of the sample or tip, as a result of tip-sample interactions. Several studies in understanding the peak repulsive forces in tapping mode AFM have been carried out, but mostly in steady state situations. In transient situation when tip encounters a sudden steep upward step, the repulsive force can be much higher than that in the steady state situation and, consequently, damage could happen. Therefore, if appropriate parameters’ values are not tuned, the tip-sample stress may exceed yield stress of the tip or the sample. This paper presents the comparison of maximum transient interaction forces in time periods of net attractive and repulsive forces and the effects of important scanning parameters on maximum transient stress of compliant samples with the elastic modulus in the range of 2GPa together with lateral resolution and scanning speed diagrams, using theoretical analysis as a novelty of this paper, so that selecting cantilever stiffness in the range of 0.1-1N/m, free air amplitude 60-100nm, amplitude ratio 0.8-0.9, quality factor 50-100, tip radius 10-40 nm, and scanning speed 0.1-0.3mm/s relative to required lateral resolution indeed leads to safe high speed microscopy.
H. Araghi, Y. Nemati Asl,
Volume 19, Issue 9 (9-2019)
Abstract
Leed titanate as an ionic Perovskite is ferroelectric at the lower of the below 766 K, which is called the transition temperature (Curie temperature), and at the above of this temperature is in the paraelectric phase. Studying the influence of mechanical parameters on the ferroelectric properties of PbTiO3 is important in the industrial application (such as RAM) of PbTiO3. In this study, using the molecular dynamics simulation method, the stress-strain effects on the polarization of lead titanate in the ferroelectric phase have been investigated. For modeling the atomic potential and interactions between ions in the ferroelectric phase, the short-range Buckingham potential and long-range coulombic potential, and, in addition, the fourth-order potential of oscillatory springs using a shell model (a model for calculating the polarization of a system) has been used. In this study, the effects of mechanical stress-strain action in the ferroelectric phase were investigated in two tensile and compression uniaxial stress-strain. In tensile stress-strain mode, the application of external stress leads to an increase in the polarization of the system, while applying compression stress-strain results in the decrease of the polarization of the system, so that by applying stress-strain, the polarization of the system reaches zero.
M. Akbari, A.m. Khoshnood, S. Irani,
Volume 19, Issue 10 (10-2019)
Abstract
Gas turbines have a wide range of application in different industries. There are different models of the gas turbine for its analysis and diagnosis. In this paper, a hybrid model is considered for the gas turbine. This model combines thermodynamic relations and data-based equations which cause to eliminate dynamic loops of thermodynamic relations. Also, the compressor performance curve is considered in the proposed model which leads to noticing physical and geometric characteristic of a gas turbine. The model is dynamic and nonlinear that cause to adapt to a different condition and increase the accuracy of modeling. The model is accurate, simplified and nonlinear state space form. For these reasons, the model is suitable for analyzing of controllers and observers. The proposed controller is a new sliding model controller for implementing in the model. The controller is based on the l_1 norm and frequency analysis. Since the sliding mode is robust and the l_1 norm is optimizer than the l_2 norm, the controller tracks fuel command with acceptable accuracy and minimizing the control fluctuations.
Also, the data that is used in this paper is the data of an industrial gas turbine (IGT25) of Iran's national turbine which is logged in different ambient and functions conditions.
Y. Hojjat, B. Ghavami Namin,
Volume 19, Issue 11 (11-2019)
Abstract
The aim of this research is to design and fabricate an actuator, which operates based on reaction forces between current carrying stator coils and magnetic arrays (Halbach arrays) connected to the mover, in order to move a motion stage for positioning objects. Thus, according to the initial and intended position of the mover, current commutation in stator coils is changed in a way that required force for transporting the mover to the desired position is provided. In this research, the integration of two perpendicular synchronous linear motors is utilized in order to create the planar motion. The stator consists of two sets of rectangular coils, which are placed perpendicular to each other. Mover consists of four Halbach arrays, which two Halbach arrays are used for x-axis motion and the other two arrays are used for y-axis motion. First, the analytic relationship between the applied magnetic force and current commutation was introduced. Then, the design parameters such as mover dimensions and stator workspace were determined. Concerning these parameters, dimensions of cubic magnets for Halbach array fabrication were obtained and with respect to array dimensions, the dimensions and number of turns for stator coils were determined. Using these design parameters and commutation equations, the planar motion of the actuator was simulated. The simulation results showed good agreement with the analytical results. Experimental tests were conducted in order to investigate the positioning capabilities and 2 dimensional motion. The precision of the fabricated actuator is 5mm and the minimum response time of actuator is 0.5sec. The minimum position error occurs at 25mm position that is due to the closeness to motor magnetic period.
H. Vatanjou, Yousef Hojjat, M.r. Karafi,
Volume 19, Issue 11 (11-2019)
Abstract
In this paper nonlinear dynamic behavior of bending actuators of dielectric elastomer or Dielectric Elastomer Minimum Energy Structure (DEMES) is studied and the effects of viscoelasticity of dielectric film on system response are investigated. Considering hyper-elasticity and viscoelasticity of dielectric film, the equation of motion of the actuator is extracted using Euler-Lagrange method. The natural frequency of small amplitude oscillations around the equilibrium state is calculated by linearizing the original nonlinear equation and the effects of dielectric film pre-stretch and excitation amplitude on natural frequency is investigated. The numerical simulation of the nonlinear equation of motion for periodic excitation shows that the system possesses harmonic resonances as well as sub-harmonic and super-harmonic resonances. By increasing the damping ratio of the dielectric film, resonance frequency increases for all harmonics and their excitation amplitude decreases. The analytical results show that excitation amplitude of harmonic resonance in chaotic behavior changes to a quasi-alternate and then an alternative behavior by increasing damping ratio.
S.a. Khalilpour Seyedi , R. Khorrambakht, A.r. Bourbour, H.r. Taghirad,
Volume 19, Issue 11 (11-2019)
Abstract
Despite the intense development of cable-driven robot in recent years, they have not yet been vastly utilized in their potential applications because of difficulties in their performing accurate installation and calibration. This paper aims to present a suitable control method, relieving the limitation of accurate calibration and installation requirement in the suspended cable-driven parallel robot. In this paper, kinematics and dynamics uncertainties are investigated and based on their bounds, a robust controller is proposed. The main innovation of this article is providing a new control method to cost reduction by eliminating accurate measurement tools such as a camera in position control of a deployable cable-driven robot. Using this approach, reducing costs in building a robot and increasing the speed of installation and calibration is achieved. Another problem investigated in this paper is the problem of joint space controllers applied to redundant cable-driven parallel robots, namely the loosened redundant cable. To solve this problem, the embedded force sensor and a new sliding surface for the controller is proposed. In fact, in this paper, the conventional joint-space controllers are modified to become applicable to the control of cable-driven robots. Finally, by conducting some experiments using ARAS suspended cable-driven parallel robot, the proposed algorithms are verified and it is shown that there are feasible solutions for stable robot maneuvers.
M. Mokhtari, M. Taghizadeh, M. Mazare,
Volume 19, Issue 12 (12-2019)
Abstract
Reference trajectory tracking and guarding against system disturbances and uncertainties are the important factors in the realm of lower limb exoskeleton robots control. Sliding mode PID is one of the robust controllers, which has a sliding manifold in the form of the PID controller. Chattering is the substantial predicament of the PIDSMC so that boundary layer around the sliding manifold is applied to eliminate the phenomenon. In this step, not only the chattering phenomenon is not eliminated but the robustness of the controller is also mitigated. In this study, supper twisting PID sliding mode controller (STPIDSMC) was used to eradicate the chattering phenomenon and enhancing controller robustness. The STPIDSMC robustness is protected indigenously and without defining the boundary layer, and the chattering phenomenon is reduced. Furthermore, to meet the external disturbances and uncertainties with unlimited amplitude, adaptive active force control method is combined by STPIDSMC as a modifying input control loop. In the active force control approach, the control input is online modified based on the estimation of moment inertia of the robot links. In order to accomplish maximum performance, control parameters were optimized using harmony search algorithm. In the optimal state, the performance of the proposed controller has been compared with PIDSMC and STPIDSMC that revealed the priority of the proposed controller rather than other controllers. The results indicate that the three error criteria, ITAE, ITASE, and IASE experience significant reduction about 39, 48, and 66 percent respectively compared to STPIDSM.
