Showing 337 results for Type of Study: Research
Sasan Zanganeh, Dr Mohammad Hassan Shojaeefard, Dr Gholam Reza Molaeimanesh, Dr Masoud Dahmardeh, Mahdi Mohammadi Aghdash,
Volume 12, Issue 4 (12-2022)
Abstract
As alternatives for future refrigeration, heat pumping, air conditioning, or even power generation plants are emerging due to the regulatory changes, R744 (carbon dioxide) is considered as a serious alternative to be the successor of other Halogenated Hydrocarbons Refrigerants (HHR) for the AC-system of vehicles. This paper investigates the heat transfer performance of R744 through a subcritical vehicular condenser, designed and manufactured for the first product based on NP01 platform (Iranian vehicle), at different operating conditions in terms of refrigerant mass flow rate and wind velocity. The experiments carried out in order to investigate the effect of mass flow rate, the R744 inlet temperature was observed to have sudden fluctuations. At the condenser outlet, for the smallest mass flow rate, the least variation of temperature was observed. It was also found out that for higher air velocities through the condenser, the stabilized temperature after the condenser was lower. The results show that the performance of the designed and manufactured automotive condenser based on R744 refrigerant is acceptable which makes it a suitable candidate for automotive applications.
As alternatives for future refrigeration, heat pumping, air conditioning, or even power generation plants are emerging due to the regulatory changes, R744 (carbon dioxide) is considered as a serious alternative to be the successor of other Halogenated Hydrocarbons Refrigerants (HHR) for the AC-system of vehicles. This paper investigates the heat transfer performance of R744 through a subcritical vehicular condenser, designed and manufactured for the first product based on NP01 platform (Iranian vehicle), at different operating conditions in terms of refrigerant mass flow rate and wind velocity. The experiments carried out in order to investigate the effect of mass flow rate, the R744 inlet temperature was observed to have sudden fluctuations. At the condenser outlet, for the smallest mass flow rate, the least variation of temperature was observed. It was also found out that for higher air velocities through the condenser, the stabilized temperature after the condenser was lower. The results show that the performance of the designed and manufactured automotive condenser based on R744 refrigerant is acceptable which makes it a suitable candidate for automotive applications.
Mr. Mohammad Yar-Ahmadi, Mr. Hamid Rahmanei, Prof. Ali Ghaffari,
Volume 13, Issue 1 (3-2023)
Abstract
The primary purpose of each autonomous exit parking system is to facilitate the process of exiting the vehicle, emphasizing the comfort and safety of driving in the absence of almost any human effort. In this paper, the problem of exit parking for autonomous vehicles is addressed. A nonlinear kinematic model is presented based on the geometric relationship of the vehicle velocities, and a linear time-varying discrete-time model of the vehicle is obtained for utilizing the optimal control strategy. The proposed path planning algorithm is based on the minimization of a geometric cost function. This algorithm works for ample space exit parking in Single-Maneuver and tight spaces in Multi-Maneuver exit parking. Finally, an optimal discrete-time linear quadratic control approach is hired to minimize a quadratic cost function. To evaluate the performance of the proposed algorithm, the control system is simulated by MATLAB/Simulink software. The results show that the optimal control strategy is well able to design and follow the desired path in each of the exit parking maneuvers.
Dr Hossein Chehardoli,
Volume 13, Issue 1 (3-2023)
Abstract
In this paper, the consensus of second-order nonlinear self-driving vehicle convoys (SDVCs) is studied. We assume that each self-driving vehicle (SDV) communicates only with one front and one rear SDVs. Each SDV’s nonlinear dynamics consisting of the rolling resistance and the air drag force is a function of SDV’s speed and is investigated in SDVC’s modeling and consensus design. Since the speed is bounded, all vehicles’ nonlinearities are also bounded. Due to engine saturation of each SDV, the control input is limited. We involve this limitation by introducing the arctan(.) function to control protocol. The inter-SDV’s distances are assumed to be constant during motion. The distance tracking error associated with each SDV is defined as distance between it and the leading SDV. The error dynamics of the proposed SDVC is derived after applying the consensus law to each SDV. To prove the internal stability, the Lyapunov theorem is employed. We will prove that under this consensus algorithm, the SDVC will be internal stable. To validate the effectiveness of this method, a SDVC comprising a leading and 6 following SDVs will be studied. It will be verified that under the proposed consensus law, all the SDVs reach a unique consensus.
Ali Modarresi, Saman Samiezadeh, Ali Qasemian,
Volume 13, Issue 1 (3-2023)
Abstract
In recent years, the automotive industry has experienced a dramatic mutation in the develop ment of electric vehicles. One of the most important aspects of this type of vehicle is its thermal management. Among the various parts of an electric vehicle that are subjected to thermal management, the battery is of particular importance. Battery cell temperatures may exceed the allowable range due to continuous and high-pressure operation and various weather conditions, and this, in addition to performance, severely affects battery life. Therefore, the appropriate cooling system is essential. In this research, the most common methods of battery cooling are investigated. First, three-dimensional thermal analysis on the battery is performed using the computational fluid dynamics method in transient and steady-state phases. Then, the effect of changing the cooling flow rate on the maximum temperature of the battery cell as well as the temperature difference of the cells in the battery pack is investigated. The effect of changing inlet coolant temperature change on battery cell temperature distribution is also investigated. The results show that by increasing the flow rate from 0.5 to 1.2 liter per minute, the maximum temperature in the battery pack and the temperature difference between the cells decrease to 44.4 and 2.51 ° C, respectively. Also, by changing the temperature of the inlet coolant from 15 to 30 ° C, the maximum temperature in the battery pack increases up to 42.2 ° C and the temperature difference is negligible.
Dr. Hossein Bagherian Farahabadi, Mr. Amirhossein Pahnabi, Mr. Reza Youneszadeh, Dr. Mohammad Ali Alirezapouri, Mr. Mohammad Rezaei Firuzjaei,
Volume 13, Issue 1 (3-2023)
Abstract
One of the most important components of fuel cell power systems is the power conditioning subsystem. DC/DC converters play the leading role in the power conditioning subsystem and fuel cell hybridization with other electric power sources and storage. DC/DC converters control the load voltage and, in some cases, the fuel cell current, while current-controlled DC/DC converters control the loading level. Some advantages of designing converters in a multi-layer topology include reduced input current ripple and increased power density. Lower current-rating semiconductor devices can be used due to the current division among the layers and lower values of inductors and capacitors can be used due the lower input current and output voltage ripples, respectively. Furthermore, failure of one layer does not result in a complete system outage; the other layers can deliver a fraction of the nominal power. A fuel cell power system based on a 16 kW proton exchange membrane fuel cell stack and a multi-layer DC/DC boost converter is designed and implemented in this paper. The power system is intended for marine air-independent propulsion systems. The power system is modeled and analyzed using the MATLAB/Simulink software environment. The power system is implemented to verify the analysis and simulation results.
Mohsen Motahari-Nezhad,
Volume 13, Issue 1 (3-2023)
Abstract
In this study, feedback neural networks namely Elman and Jordan are used for prediction of exhaust valve temperature for air cooled engines. Input-output data are extracted from an experimental setup including the valve mechanism of an air cooled engine. Inverse heat transfer problem applying the Adjoint problem is used to address the thermal flux through exhaust valve and seat. Elman and Jordan neural networks are used to predict the transient valve temperature using the experimental data. The results show that Elman and Jordan neural networks predicts well the transient exhaust valve temperature. However, Jordan neural network with training algorithm of Gradient Descent with Adaptive Learning Rate performs better with RMSE error of 16.3 for prediction of exhaust valve temperature.
Mahdi Khoorishandiz, Abdollah Amirkhani,
Volume 13, Issue 1 (3-2023)
Abstract
As electric vehicles become more popular, we need to keep improving the lithium-ion batteries that power them. Electrochemical impedance spectroscopy (EIS) is used based on a discrete random binary sequence (DRBS) to reduce excitation time in the low-frequency region and excite the input of the battery. In this paper, voltage and current signals are processed with wavelet transform for impedance evaluation. In using wavelet transform, choosing the most optimal mother wavelet is crucial for impedance evaluation since different mother wavelets can produce different results. We aim to compare three types of continuous Morse mother wavelet, continuous Morlet, and continuous lognormal wavelet, which are among the most important mother wavelets, to determine the best method for impedance evaluation. We used the dynamic time-warping algorithm to quantify the difference between the initial values obtained from standard laboratory equipment and the impedance evaluation through three different continuous wavelets. Our proposed method (lognormal wavelet) has the lowest difference (3.4086) from the initial values compared to the Morlet (3.5504), and Morse (3.5457) methods. As a result, our simulation shows that the lognormal wavelet transform is the best method for impedance evaluation compared to Morlet and Morse wavelets.
Hamidreza Ebrahimi, Mohammadhassan Shojaeifard, Salman Ebrahimi-Nejad,
Volume 13, Issue 2 (6-2023)
Abstract
The present study aims to optimize a two-chamber muffler’s geometry and improve its acoustic performance. Mufflers with a circular cross-section are used in this study and then underwent the vibroacoustic analysis using COMSOL Multiphysics software. Several geometries, including a reference model and new ones, are designed and their geometry is optimized by Parametric and grid optimization methods, which are the software’s optimization methods. First, the reference paper is validated to ensure the simulation produces the least error. The results obtained in this study have a good match with those of the reference. Then, by changing dimensions such as length, diameter, and inner design of the mufflers, the best geometry in terms of transmission loss and bandwidth was selected and compared with the results acquired by the reference model. It was found that the acoustic performance of the optimized design (two-chamber muffler with four inner tubes) outperforms the model used in the reference. That is, the results indicate that the optimized design is able to attenuate sound up to 78dB in the range of 0 to 500Hz, 45dB higher than that of the conventional model. Further, the muffler’s weight is reduced by a quarter, using a 0.9mm thickness.
J Bidadi, H Hampaiyan Miandowab1, H Saeidi Googarchin,
Volume 13, Issue 2 (6-2023)
Abstract
The aim of the study was to examine the deformation modes and also degradation of an adhesively bonded rectangular cross section beam used in the automotive body structure. The study included: (1) performing new experimental investigations on the three-point bend behavior of a rectangular cross section beam made by adhesive bonding method. (2) developing a finite element (FE) model to predict the mechanical load displacement behavior and also the degradation modes (i.e. delamination between the adhesive layer and beam wall). The agreement between experimental and FE results demonstrates that the investigated structural element's numerical model was created utilizing accurate assumptions. Finally, the effects of beam wall thickness and overlap length have been investigated in a parametric study using the validated FE model. It was shown that increasing the beam wall thickness resulted in delamination between the adhesive layer and beam wall.
Mr. Hamid Rahmanei, Dr. Abbas Aliabadi, Prof. Ali Ghaffari, Prof. Shahram Azadi,
Volume 13, Issue 2 (6-2023)
Abstract
The coordinated control of autonomous electric vehicles with in-wheel motors is classified as over-actuated control problems requiring a precise control allocation strategy. This paper addresses the trajectory tracking problem of autonomous electric vehicles equipped with four independent in-wheel motors and active front steering. Unlike other available methods presenting optimization formulation to handle the redundancy, in this paper, the constraints have been applied directly using the kinematic relations of each wheel. Four separate sliding mode controllers are designed in such a way that they ensure the convergence of tracking errors, in addition to incorporating the parametric and modeling uncertainties. The lateral controller is also designed to determine the front steering angles to eliminate lateral tracking errors. To appraise the performance of the proposed control strategy, a co-simulation is carried out in MATLAB/Simulink and Carsim software. The results show that the proposed control strategy has enabled the vehicle to follow the reference path and has converged the errors of longitudinal and lateral positions, velocity, heading angle, and yaw rate. Furthermore, the proposed control system shows promising results in the presence of uncertainties including the mass and moment of inertia, friction coefficient, and the wind disturbances.
Abbas Zarenezhad Ashkezari, Reza Zirak,
Volume 13, Issue 2 (6-2023)
Abstract
In the present study, different regimes of wall impingement in biodiesel spray were investigated in terms of emissions of diesel engines and performance and the best model for simulating the DI diesel engines fueled by biodiesel blends was presented. As shown by the findings, all aspects of wall impingement were considered in Walljet model, and it properly predicted the fuel droplet size generated by decomposition and penetration. Thus, it is possible to use it for simulating the biodiesel fuel spray atomization at varying engine operating conditions through the adjustment of the model constants.
Farid Raoof, Javad Rezapour, Sina Gohari Rad, Reza Rajabiehfard,
Volume 13, Issue 2 (6-2023)
Abstract
Thin-walled tubes can avoid the transition of injurious acceleration and excessive forces to the protected section and minimize the damage severity. They absorb energy under axial loading circumstances as crashworthiness structures. The present study deals with the investigation of the density effects of foam on the quasi-static loading response of foam filled and empty cylindrical tubes. To investigate energy absorption parameters by varying in foam density, two different densities of polyurethane foam were used to evaluate the efficacy of polyurethane foam density under axial quasi-static loading. According to the results, the use of foam as a filler also influences the tubes’ deformation behavior in addition to the effects of thickness. It was revealed that by incrementing the thickness to 20%, the peak load increased by 25.2%. Two densities of foam were considered as 40 and 85kg/m3 to assess the effect of density of polyurethane foam as filler on the energy absorption behavior of tubes under axial loading. Result showed that when foam density increased by about two times, the peak load increased by 1%. According to the results, filling tube by foam also influences the tubes deformation behavior in addition to the effects of thickness
Dr. Abbas Soltani, Mr. Milad Arianfard,
Volume 13, Issue 2 (6-2023)
Abstract
In this study, an adaptive sliding mode controller (ASMC) based on estimation of tire-road friction coefficient is proposed for engagement control of automotive dry clutch. The control of clutch engagement is one of the most important parts of gear-shift process for automated manual transmission. Accurate amount of drive shaft torque in modelling of powertrain system is essential to guarantee smooth engagement of the clutch and rapid response of the control system. As the tire-road friction coefficient has significant influence on drive shaft torque, an estimator is designed to calculate this parameter. The ASMC is proposed for the clutch control to overcome the system uncertainties and a proportional integral (PI) controller is adopted to engine speed control. In addition, a nonlinear estimator utilizing unscented Kalman filter is applied to estimate the state variables that are measured hardly such as wheel slip and longitudinal vehicle velocity. The simulation results demonstrate the high effectiveness of the combined use of presented controller and road friction coefficient estimator for improving the smooth clutch engagement in comparison to the control system without estimator.
Mr David Zarifpour, Mr Mehdi Dadashi, Dr Javad Marzbanrad,
Volume 13, Issue 3 (9-2023)
Abstract
This paper presents an experimental study on the effect of adhesive thickness on the maximum load of adhesive joints under static and impact loading, using the double cantilever beam (DCB) test method. The DCB specimens were prepared with varying adhesive thicknesses and subjected to impact loading using a drop weight impact tester. The maximum load was recorded for each specimen. The results indicated that the maximum load of the adhesive joints increases with increasing adhesive thickness up to 5 mm, beyond which the maximum load decreases with further increase in adhesive thickness. Moreover, the failure mode of the adhesive joint was found to be strongly dependent on the adhesive thickness, with thicker adhesive layers exhibiting an adhesive failure mode but in thinner thicknesses, the adhesive mode is cohesive. These findings provide important insights into the design and optimization of adhesive joints for applications that are subject to impact loading.
Mr Arash Darvish Damavandi, Dr Behrooz Mashhdi, Dr Masoud Masih-Tehrani,
Volume 13, Issue 3 (9-2023)
Abstract
This paper investigates the performance of the hydraulically interconnected suspension system with the full vehicle model of ride and handling. A sensitivity analysis has been performed by changing the coefficients of the cylinder and accumulator valves and the initial conditions of the accumulators in the default hydraulic circuits to determine the effect on the frequency and damping of the system response such as roll, pitch, and bounce. This study highlights the importance of the influence of all system parameters to investigate vehicle vibration characteristics. The results provide valuable insights for designers and engineers working on improving automotive suspension system performance. Damping and frequency of modes change up to 179% with the change of cylinder valves and 141% with the change of accumulator valves and 74% for the initial pressure of accumulators change in mentioned range.
Ms Ali Ghiasi Noghabi, Dr Mansour Baghaeian, Dr Hamid Reza Goshayeshi,
Volume 13, Issue 3 (9-2023)
Abstract
| In this research, the effect of using three Nano fluids contains graphene oxide (GO), titanium oxide (TiO2) and aluminum oxide (Al2 O3) was analyzed on the heat transfer of the car radiator by experiment in physical conditions on the car engine. Distilled water and ethylene glycol (60:40) as the base fluid was companied with three nanoparticles contain graphene oxide, titanium oxide and aluminum oxide that each one separately with 0.1, 0.2 and 0.3 weight percent and flow rates of 10, 20, 32 and 40 liters per minute were used at normal engine temperature. After the temperature of the radiator cooling fluid reached 90 degrees Celsius and the fan was turned on for one minute, the results showed that increasing the weight percentage of nanoparticles to the base fluid increases the displacement heat transfer coefficient and most increase in the coefficient of heat transfer at 0.3 weight percent to an approximate value of 5.2% in aluminum oxide, 11.9% for titanium oxide and 28.7% for graphene oxide compared to the base fluid was received. With the increase in weight percentage, the pressure drop and Nusselt number increased. The highest percentage increase in the radiator pressure drop for all three Nano fluids with 0.3 weight percentage and 2.2% for aluminum oxide, 3.5% for Titanium oxide and 5.24% for graphene oxide were received. |
Dr Mohammad Mahdi Taskhiri,
Volume 13, Issue 3 (9-2023)
Abstract
This paper presents an inhomogeneous lens to radiate a control-table Fan Shaped pattern for long-range automotive applications. Fan Shaped pattern of the designed lens covers more angles in azimuth. The proposed circular aperture inhomogeneous lens is designed based on the critical angle theorem. The profile of the dielectric constant of the proposed lens changes in 3 directions of ρ, φ, and z. The lens is matched to the source and surroundings. A closed-form formula is offered for an arbitrary fan-shaped pattern lens antenna. A compact circular lens with a diameter of 20 mm and thickness of 2.25 mm is simulated in CST full-wave software to validate the design structure.
Dr Hossein Chehardoli,
Volume 13, Issue 3 (9-2023)
Abstract
In this article, the optimal robust H2 / H∞ control of self-driving car platoons (SDCPs) under external disturbance is investigated. By considering the engine dynamics and the effects of external disturbance, a linear dynamical model is presented to define the motion of each self-driving car (SDC). Each following SDC is in direct communication with the leader. By utilizing the relative position of following SDCs and the leader, the error dynamics of each SDC is calculated. The particle swarm optimization (PSO) method is utilized to find the optimal control gains. To this aim, a cost function which is a linear combination of H2 and H∞ norms of the transfer function between disturbance and target variables is constructed. By employing the PSO method, the cost function will be minimized and therefore, the robustness of the controller against external disturbance is guaranteed. It will be proved that under the presented robust control method, the negative effects of disturbance on system performance will significantly reduce. Therefore, the SDCP is internally stable and subsequently, each SDC tracks the motion of the leader. In order to validate the proposed method, simulation examples will be presented and analyzed.
Mr. Hosein Hamidi Rad, Prof. Mohsen Esfahanian, Prof. Saeed Behbahani,
Volume 13, Issue 3 (9-2023)
Abstract
This study examines the impact of a fuzzy logic-based control strategy on managing peak power consumption in the auxiliary power unit (APU) of a hybrid electric bus. The APU comprises three components: an air compressor, a power steering system, and an air conditioning system (AC) connected to an electric motor. Initially, these components were simulated in MATLAB-SIMULINK software. While the first two were deemed dependent and independent of vehicle speed, respectively, the stochastic behavior of the steering was emulated using the Monte Carlo method. Subsequently, a fuzzy controller was designed and incorporated into the APU to prevent simultaneous operation of the three accessories as much as possible. The results of repeated simulations demonstrated that the designed fuzzy controller effectively distributed the operation of the accessories throughout the driving cycle, thereby reducing overlaps in auxiliary loads. Consequently, the APU's average and maximum power consumption exhibited significant reductions. Furthermore, through multiple simulations with an upgraded power system model integrating the new APU-controller package, it was established that the proposed strategy for managing auxiliary loads in the bus led to lower fuel consumption and emissions.
Hossein Ghanbari, Mostafa Shabani, Dr Emran Mohammadi,
Volume 13, Issue 4 (12-2023)
Abstract
Portfolio optimization is the process of distributing a specific amount of wealth across various available assets, with the aim of achieving the highest possible returns while minimizing investment risks. There are a large number of studies on portfolio optimization in various cases, covering numerous applications; however, none have focused exclusively on the automotive industry as one of the largest manufacturing sectors in the global economy. Since the economic activity of this industry has a coherent pattern with that of the global economy, the automotive industry is very sensitive to the booms and busts of business cycles. Due to the volatile global economic environment and significant inter-industry implications, providing an appropriate approach to investing in this sector is essential. Thus, this paper aims to provide an appropriate approach to investing in this sector. In this study, an extended Conditional Drawdown at Risk (CDaR) model with cardinality and threshold constraints for portfolio optimization problems is proposed, which is highly beneficial in practical portfolio management. The feature of this risk management technique is that it admits the formulation of a portfolio optimization model as a linear programming problem. The CDaR risk functions family also enables a risk manager to control the worst ( 1-α)×100% 
drawdowns. In order to demonstrate the effectiveness of the proposed model, a real-world empirical case study from the annual financial statements of automotive companies and their suppliers in the Tehran Stock Exchange (TSE) database is utilized.
