Showing 5 results for majidi
Dr Ali Akbar Majidi-Jirandehi, Hossein Dehghani,
Volume 10, Issue 2 (6-2020)
Abstract
Today most countries, examine the problem of car pollution. They enacted laws to prevent environmental polluting cars. They also try to find out wither pollution standards are applied by cars manufacturers or not. The purpose of this study is to rank domestically produced cars quality based on manufacturing technology and exhaust emissions. Variables HC, CO, O2, CO2, and λ are analyzed for 10 selected car types, and results are presented with a box chart and finally, the considered cars are ranked according to the scored values. In practice, regarding the results of pollution variable, domestically produced cars can be ranked in terms of pollution quality parameters. According to the numeric range determined for each variable, a number is assigned to each car and finally, the average score is calculated for each car.
Ali Akbar Majidi-Jirandehi, Moslem Mohammadi Soleymani, Hossein Dehghani,
Volume 11, Issue 3 (9-2021)
Abstract
Today, many car manufacturers can achieve emission standards through catalytic converters. The goals of this research was in tow sections. Initially, the amount of pollutants was measured to determine the role of the catalytic converters in the reduction of pollutants for 3 types of vehicles and in 50 cases, in the two stages before and after the catalytic converter. Then, to achieve the useful life of the catalytic converter, out of 750 test vehicle emissions were tested. Data analysis was done by SPSS software, which shows that catalytic converters can reduce up to 80% of exhaust emissions. This is independent of the type of vehicle. The useful life of the catalytic converters is up to 36 months, so they should be replaced at least every three years. Also, the pollutant standards of the technical examination centers are reviewed. For this purpose, the pollutants have been measured in 2200 vehicles. Due to the huge difference in technology, cars are divided into two main categories of carburetor and injector and are analyzed statistically. Eventually, for each group of these vehicles, the values of HC, CO and O2 are obtained.
Yavar Nourollahi Golouje, Seyyed Mahdi Abtahi, Majid Majidi,
Volume 12, Issue 2 (6-2022)
Abstract
In this paper, analysis and control of the chaotic vibrations in bounce dynamic of vehicle have been studied according to the comparison of controller based on the nonlinear control and chaos controller on the basis of the chaotic system properties. After modeling the vehicle dynamic, the chaotic behavior of the uncontrolled system was determined using combination of the numerical analysis including bifurcation diagrams and max Lyapunov exponent. The system parameters values were then identified in the quasi-periodic and chaotic behavior system. In order to eliminate the chaotic vibrations, the control signal was first developed using a nonlinear fast-terminal sliding mode control algorithm that its control gains are estimated online by fuzzy logic which was designed for vehicle vertical dynamics. Then the delayed feedback control was designed based on the development of Pyragas algorithm to control the system based on the properties of the chaotic system and generation of a small control signal. Comparison of the feedback system depicts priority of the Fuzzy-Pyragas controller in less energy consumption and better behavior.
Yavar Nourollahi Golouje, Seyyed Mahdi Abtahi, Majid Majidi,
Volume 12, Issue 3 (9-2022)
Abstract
The chaotic dynamic analysis along with chaos controller of an active suspension in vehicles has been studied in this paper. The unstable periodic orbits of the system are stabilized using the developed delay feedback control algorithm based on the fuzzy sliding mode system. Firstly, the equations of motions in the chaotic half-vehicle model are derived via Newton-Euler rules and simulated by the fourth order Runge-Kutta method. Then, forcing frequency has been used to confirm nonlinear phenomenon such as jump and chaos in the vehicle system. Critical values of the control parameters in the forcing frequency demonstrate the changes of system behavior from the periodic to the irregular chaotic responses. In order to eliminate the chaotic behaviors in the vertical dynamics of vehicle, a novel fuzzy sliding delay feedback control algorithm is developed on the active suspension with chaotic responses. Using fuzzy logic, the controller gain of the sliding delay feedback control is online estimated that is caused to reject the chattering phenomenon in the sliding mode algorithm beside the improvement of the responses. Simulation results of the control system depict a reduction of settling time and energy consumption along with eliminating the overshoots and chaotic vibrations
Dr Moslem Mohammadi Soleymani, Benyamin Sohrabinejad, Dr Aliakbar Majidi Jirandehi,
Volume 14, Issue 2 (6-2024)
Abstract
In the automobile sector, stainless steel and resistance spot welding (RSW) are often used. In this work, RSW was used to join five samples of 316L stainless steel joints at currents of 15, 20, 25, 30, and 35 kA while the heat input parameters varied. The welded joints' microstructure, hardness, and mechanical properties were examined and evaluated. The base metal, heat-affected zone (HAZ), and weld areas' microstructures were all examined using optical microscopy. The mechanical characteristics of the joints were assessed using room-temperature tensile-shear testing and hardness testing. The microstructure findings revealed ferrite in many weld regions and an austenitic structure overall. In the samples with welding currents of 15, 20, 25, 30, and 35 kA, the average hardness of the weld zone was 329, 258, 251, 238, and 235 Vickers, in that order. The hardness of the weld zone exhibited an inverse connection with the welding current, as an increase in welding current resulted in a drop in the resistance spot welded area's hardness. Furthermore, when heat input increased, the hardness of the HAZ reduced and increased relative to the 316L steel. The joint strength of the RSW increased with increasing welding current, as demonstrated by the tensile-shear test results for all five welded samples with varying currents. As a result, the samples with 30 and 35 kA currents failed at the weld with a force greater than 3 kN, while the other samples with lower welding currents had a failure force of less than 2 kN.
