Automotive Science and Engineering

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This paper presents the prediction of vehicle's velocity time series using neural networks. For this purpose, driving data is firstly collected in real world traffic conditions in the city of Tehran using advance vehicle location devices installed on private cars. A multi-layer perceptron network is then designed for driving time series forecasting. In addition, the results of this study are compared with the auto regressive (AR) method. The least root mean square error (RMSE) and median absolute percentage error (MDAPE) are utilized as two criteria for evaluation of predictions accuracy. The results demonstrate the effectiveness of the proposed approach for prediction of driving data time series.

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In this paper, an adaptive rule based controller for an anti-lock regenerative braking system (ARBS) of a series hybrid electric bus (SHEB) has been proposed. The proposed controller integrates the regenerative braking and wheel anti-lock functions by controlling the electric motor of the hybrid vehicle, without using any conventional mechanical anti-lock braking system. The performance of the proposed system is evaluated by a comprehensive vehicle dynamics model in MATLAB/Simulink. Using the designed ARBS, the braking and regenerative performances of SHEB have significantly improved in slippery roads while the slip ratios are kept between 0.15 and 0.20.

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Non-linear characteristic of tire forces is the main cause of vehicle lateral dynamics instability, while direct yaw moment control is an effective method to recover the vehicle stability. In this paper, an optimal linear quadratic regulator (LQR) controller for roll-yaw dynamics to articulated heavy vehicles is developed. For this purpose, the equations of motion obtained by the MATLAB software are coded and then a control law is introduced by minimizing the local differences between the predicted and the desired responses. The influence of some parameters such as the anti roll bar, change the parameters of the suspension system and track wide in articulated heavy vehicles stability has been studied. The simulation results show that the vehicle stability can be remarkably improved when the optimal linear controller is applied

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The suspension system of a vehicle is one of the most important parts which is involved in the process of vehicle designing. When a vehicle suspension system is designed, the evaluation of its performance against the road disturbances such as shocks and bumps are very important. The most commonly used systems consist of four hydraulic Jacks with mobility in vertical line with low speed and low exactitude. This paper offers a new mechanism for inspecting the suspension system of a vehicle using a parallel robot called Stewart. This robot is a special kind of parallel robots with capability of movements in different directions with high speed, accuracy and repeatability. In this paper the suspension system is evaluated on a quarter model of a simulated vehicle with control and guidance of Stewart robot using PID controller. The Stewart robot simulates the isolated and uneven bumps on a flat road in order to evaluate the given suspension system, and to investigate some criteria such as comforting of the passengers and remaining of the vehicle on the road. The results of the simulations show that the proposed method has a high accuracy, applicability and flexibility as well as simplicity, compared to currently used mechanisms.

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In this study, stability control of a three-wheeled vehicle with two wheels on the front axle, a three-wheeled vehicle with two wheels on the rear axle, and a standard four-wheeled vehicle are compared. For vehicle dynamics control systems, the direct yaw moment control is considered as a suitable way of controlling the lateral motion of a vehicle during a severe driving maneuver. In accordance to the present available technology, the performance of vehicle dynamics control actuation systems is based on the individual control of each wheel braking force known as the differential braking. Also, in order to design the vehicle dynamics control system the linear optimal control theory is used. Then, to investigate the effectiveness of the proposed linear optimal control system, computer simulations are carried out by using nonlinear twelvedegree- of-freedom models for three-wheeled cars and a fourteen-degree-of-freedom model for a fourwheeled car. Simulation results of lane change and J-turn maneuvers are shown with and without control system. It is shown that for lateral stability, the three wheeled vehicle with single front wheel is more stable than the four wheeled vehicle, which is in turn more stable than the three wheeled vehicle with single rear wheel. Considering turning radius which is a kinematic property shows that the front single three-wheeled car is more under steer than the other cars.

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Hybrid Electric Vehicles (HEVs) are driven by two energy convertors, i.e., an Internal Combustion (IC) engine and an electric machine. To make powertrain of HEV as efficient as possible, proper management of the energy elements is essential. This task is completed by HEV controller, which splits power between the IC engine and Electric Motor (EM). In this paper, a Genetic-Fuzzy control strategy is employed to control the powertrain. Genetic-Fuzzy algorithm is a method in which parameters of a Fuzzy Logic Controller (FLC) are tuned by Genetic algorithm. The main target of control is to minimize two competing objectives, consisting of energy cost and emissions, simultaneously. In addition, a new method to consider variations of Battery State of Charge (SOC) in the optimization algorithm is proposed. The controller performances are verified over Urban Dinamometer Driving Cycle (UDDS) and New Europian Driving Cycle (NEDC). The results demonstrate the effectiveness of the proposed method in reducing energy cost and emissions without sacrificing vehicle performance.

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The directional response and roll stability characteristics of a partly filled tractor semi-trailer vehicle, with cylindrical tank, are investigated in various maneuvers. The dynamic interaction of liquid cargo with the tractor semi-trailer vehicle is also evaluated by integrating a dynamic slosh model of the partly filled tank with five-degrees-of-freedom of a tractor semi-trailer tank model. The dynamic fluid slosh within the tank is modeled using three-dimensional Navier-Stokes equations, coupled with volume-of-fluid equations and analysed using the FLUENT software. The coupled tank-vehicle model is subsequently analysed to determine the roll stability characteristics for different maneuvers. The results showed the interaction of fluid slosh with vehicle's dynamic. Another findings of this investigation also revealed that the roll stability of a tractor semi-trailer tank carrying liquid was highly affected by fluid sloshing and caused degradation of roll stability in comparison with vehicle carrying rigid cargo.

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In the present study, a model of a large Lithium Polymer (Li-Po) battery for use in the simulation of Hybrid Electric Vehicles (HEVs) is developed. To attain this goal, an Equivalent Circuit (EC) consisting of a series resistor and two RC parallel networks is considered. The accuracy and the response time of the model for use in an HEV simulator are studied. The battery parameters identification and model validation tests are performed in low current with a good accuracy. Similar test process is implemented in high current for another cell and the simulation is verified with experimental results. The validation tests confirm the accuracy of the model for use in HEV simulator. Finally, the battery model is used to model a Vehicle, Fuel and Environment Research Institute (VFERI) hybrid electric city bus using ADVISOR software and its compatibility with other components of the vehicle simulator are demonstrated in a drive cycle test.

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This paper presents a reduce roll vibration of the full vehicle model with passive suspension systems using vibration absorber to change the dynamic system matrix stat’s eigenvalue. Since using the controller system has been splurged and required to energy consuming, in this research the vehicle body roll vibration has been reduced and supplied vehicle stability using a vibration absorber for the passive suspension system. In this paper a new manner is introduced to reduce body roll angle and body's roll acceleration. The transverse instability in the independent suspension is a main problem, roll angle decreased transverse stability, that it has been reduced using vibration absorber. The optimal value of vibration absorber’s mass, spring and damping coefficient has been determined by using genetic algorithms (GA) to achieve developed roll angle behavior. The main purpose of this article is to reduce vehicle body roll angle that has been acquired using vibration absorber, this manner is better than other ways for roll reduction of vehicle body because it has done without any energy consuming.

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Nonlinear vibration of parabolic springs employed in suspension system of a freight car has been studied in this paper. First, dynamical behavior of the springs is investigated by using finite element method and the obtained results are then used in vibration analysis of a railway freight car. For this purpose, dynamics of a parabolic spring subjected to a cyclic excitation has been studied in the frequency range of 2 to 15 Hz. By utilizing an experimental setup, equivalent static and dynamic stiffness and damping of the spring have been obtained and compared with theoretical results. Different classes of rail irregularities are taken into account to excite the vehicle. Bond Graph method is employed to extract the equations of motion of the system and validity of the obtained equations is investigated. Finally, a parametric study is carried out and the influence of vehicle velocity and rail irregularity on vertical acceleration of the freight car has been examined.

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Robust control design of vehicles addresses the effect of uncertainties on the vehicle’s performance. In present study, the robust optimal multi-objective controller design on a non-linear full vehicle dynamic model with 8-degrees of freedom having parameter with probabilistic uncertainty considering two simultaneous conflicting objective functions has been made to prevent the rollover. The objective functions that have been simultaneously considered in this work are, namely, mean of control effort (MCE) and variance of control effort (VCE).The nonlinear control scheme based on sliding mode has been investigated so that applied braking torques on the four wheels are adopted as actuators. It is tried to achieve optimum and robust design against uncertainties existing in reality with including probabilistic analysis through a Monte Carlo simulation (MCS) approach in multi-objective optimization using the genetic algorithms. Finally, the comparison between the results of deterministic and probabilistic design has been presented. The comparison of the obtained robust results with those of deterministic approach shows the superiority robustness of probabilistic method.

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Nowadays, the use of small vehicles is spreading among urban areas and one sort of these vehicles are three-wheeled vehicles (TWVs) which can be competitive with four-wheeled urban vehicles (FWVs) in aspects such as smallness, simple manufacturing, and low tire rolling resistance, fuel consumption and so on. The most critical instability associated with TWVs is the roll over. In this paper a tilt control mechanism has been modeled which can reduce the danger of roll over by leaning the vehicle towards the turning center in order to decrease the amount of lateral load transfer (LLT), and by doing so, system combines the dynamical abilities of a passenger car with a motorcycle. A 3 degree of freedom vehicle model is simulated at constant speed in MATLAB-Simulink environment and a fuzzy algorithm is developed to control such a non-linear system with appropriate tilting torque. Results are interpreted in presence and absence of controller with different longitudinal speeds and steering inputs the results are also compared to behavior of a similar FWV and this is concluded that the tilt control system could countervail deficiencies of the TWV compared to the FWV.

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Many studies have been done on hybrid vehicles in the past few years. The full hybrid vehicles need a large number of batteries creating up to 300 (V) to meet the required voltage of electric motor. The size and weight of the batteries cause some problems. This research investigates the mild hybrid vehicle. This vehicle includes a small electric motor and a high power internal combustion engine. In most cases the car’s driving force is created by an internal combustion part. A small electric motor, which can operate as engine starter, generator and traction motor, is located between the engine and an automatically shifted multi-gear transmission (gearbox). The clutch is used to disconnect the gearbox from the engine when needed such as during gear shifting and low vehicle speed. The power rating of the electric motor may be in the range of about 15% of the IC engine power rating. The electric motor can be smoothly controlled to operate at any speed and torque, thus, isolation between the electric motor and transmission is not necessary. The present study evaluates the properties of the mild hybrid vehicle, its structure and performance and proposes an energy control model for its optimum operation.

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Due to the increasing development in various branches of the automotive industry, the need for a comfort climate in the cabin is more sensible. However, to achieve climate comfort, HVAC system consumes a considerable amount of engine power. Hence, improving HVAC system performance leads to more energy saving of the vehicle which is a critical factor for nowadays automotive. Besides, one crucial task of HVAC system is defrosting/defogging of windshield which is considered as a mandatory requirement in most countries. In the current study, the defrosting/defogging performance of HVAC system in the main product of national vehicle platform is numerically evaluated based on the ECE-78-715 legal requirement. For this purpose, after validation and mesh independency study, the transient air flow in three-dimensional cabin geometry is simulated by SSTk-ω turbulence model via ANSYS Fluent software and the windshield thermal condition is reported during defrosting/defogging. Besides, two national HVAC standards of AERC-10-01 and AERC-10-02 are also checked. The results demonstrate that HVAC system of the main product of the national vehicle platform can satisfactorily fulfill ECE-78-715, AERC-10-01 and AERC-10-02.

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In the present paper, the modal analysis on a full finite element model of an off-road vehicle. This vehicle was modeled in the CATIA software and then meshed in the HYPERMESH software. The free vibration analysis was conducted by the ABAQUS software. By applying an external displacement, the forced vibration analysis was also performed. As a result, natural frequencies and shape modes were extracted to detect critical regions. Then, some improvements were suggested to have better vibration behavior of the vehicle.

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Electric vehicles (EVs) have gained the attention of many authorities, automakers and researchers due to their considerable energy saving and emission reduction. One of the main issues that must be considered in design of a road vehicle is the calculation of aerodynamic forces. This issue also must be scrutinized in the design of EVs. Installation of rear spoiler is one of the solutions proposed for reduction of aerodynamic drag in racing cars and consequently increasing their maximum speed. This study focuses on the effects of installing a rear spoiler on an EV. The vehicle's drag and lift coefficients are determined by solving a 3D steady-state incompressible solution of Navier-Stokes equations with computational fluid dynamic (CFD) analysis in ANSYS FLUENT. In order to verify the effects of installing a rear spoiler on an EV, all the components were modelled in MATLAB /SIMULINK also, practical tests were performed to confirm and verify the simulation results. The results show that installing a rear spoiler on an EV, not only improves the aerodynamic characteristics of vehicle but also improves operating efficiency of electric motor and some operational aspects of batteries. In addition, it is shown that an EV with a rear spoiler is able to travel more in comparison with an EV without rear spoiler.

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In this paper, a two-surfaces sliding mode controller (TSSMC) is proposed for the voltage tracking control of a two input DC-DC converter in application of electric vehicles (EVs). The imperialist competitive algorithm (ICA) is used for tuning TSSMC parameters. The proposed controller significantly improves the transient response and disturbance rejection of the two input converters while preserving the closed-loop stability. The combination of the proposed controller and ICA, realizes a fast transient response over a wide transient load changes and input voltage disturbances. For modeling the equations governing the system, state-space average modeling technique is used. In order to analyzing the results, the two input converter equipped with the proposed controller, was modeled in MATLAB/SIMULINK environment. Simulation results are reported to validate the theoretical predictions and to confirm the superior performance of the proposed nonlinear controller when it is compared with a conventional pure SMC.

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The designing of advanced driver assistance systems and autonomous vehicles needs measurement of dynamical variations of vehicle, such as acceleration, velocity and yaw rate. Designed adaptive controllers to control lateral and longitudinal vehicle dynamics are based on the measured variables. Inertial MEMS-based sensors have some benefits including low price and low consumption that make them suitable choices to use in vehicle navigation problems. However, these sensors have some deterministic and stochastic error sources. These errors could diverge sensor outputs from the real values. Therefore, calibration of the inertial sensors is one of the most important processes that should be done in order to have the exact model of dynamical behaviors of the vehicle. In this paper, a new method, based on artificial neural network, is presented for the calibration of an inertial accelerometer applied in the vehicle navigation. Levenberg-Marquardt algorithm is used to train the designed neural network. This method has been tested in real driving scenarios and results show that the presented method reduces the root mean square error of the measured acceleration up to 96%. The presented method can be used in managing the traffic flow and designing collision avoidance systems.

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In the current paper, a biomechanical model of human body with unique structure is developed for evaluating the biodynamic responses, the vibration transmissibility and the transmitted accelerations to vertical vibration for the seated position with ignoring backrest support. In this regard, the 6-DoF Lumped-parameter model with six concentrated masses which are connected with linear springs and dampers is presented. Further, the full vehicle model is developed in ADAMS/CAR software in order to utilize the accelerations of seat under various roads excitation for different amount of vehicle speeds. Also, the vibration transmissibility and transmitted accelerations in vertical direction are measured for the different segments of human body including: Pelvis, Abdomen and Diaphragm, Chest, Torso, Back, Head and Neck. Finally, vibration transmissibility and transmitted accelerations due to the roughness of the roads surfaces are investigated for the different segments of human body in frequency domain from 0 to 50 Hz. As it is illustrated the maximum values for transmissibility for different body segments occurred for frequencies equivalent 20 to 30 Hz, it can be concluded that the human body is more sensitive to vibration with frequencies under 30 Hz.

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