فهرست مطالب امیر کریمیان

In this study, a new integrated control for the steering and braking of semi-trailer trucks for tracking in longitudinal and lateral combined maneuvers is proposed. For this purpose, a nonlinear model of a tractor semi-trailer with 10 degrees of freedom including the longitudinal, lateral and yaw motion of the tractor unit, the articulation angle and the rotational motion of each wheel is used. Then the active steering and braking controller is designed with the purpose of tracking and utilizing the sliding mode method. Also, for the yaw stability of the vehicle, a lateral stability controller is proposed using the sliding control method. Then, by utilizing multi-objective optimization, a new integrated control strategy is presented in order to optimally allocate the longitudinal and lateral forces of the tires. This strategy is designed based on achieving the purposes of tracking and stability by using the capacity of tire forces in the optimum slip range by using variable weight coefficients. In order to implement the integrated controller, the tractor semi-trailer model presented in the TruckSim software is used. The obtained results indicate the excellent performance of the integrated controller strategy designed for tracking by maintaining lateral stability when performing the lane change maneuver with braking. So, by using the proposed controller, the maximum tracking error of the longitudinal and lateral position, the yaw angle of the tractor and the articulation angle are equal to 1.83, 0.56, 4.42 and 9.53%, respectively. This is while in the case of a vehicle without a controller, due to lateral instability, the reference path is not tracked.

In this study, an active steering system is proposed to control an articulated heavy vehicle during high-speed intelligent lane- change maneuver for obstacle avoidance. For this purpose, a simplified model of an articulated heavy vehicle is created in MATLAB/Simulink, then three control systems, i.e., model predictive controller (MPC), Linear quadratic integral (LQI) controller, and 2-DOF PID controller, are designed for its front axle steering system. Furthermore, the constraints associated with the vehicle lateral stability using the sideslip angles of the truck and the semi-trailer, and the reference articulation angle for the vehicle trajectory is defined, then the stability of the vehicle during moving on dry and slippery roads are investigated. In addition, in order to evaluate the performance of the control systems, two different scenarios, i.e., first, facing an obstacle on a dry road and second, the same situation on a slippery road, are taken into account and are fulfilled on the basis of a co-simulation between MATLAB and TruckSim. In the next step, to optimize the controllers' coefficients, some various tests are performed and implemented in TruckSim software and using an intelligent method, the optimal coefficients are obtained. Finally, the performance of the three controllers are compared to assess their strengths and weaknesses. The comparison shows that model predictive control (MPC) system is advantageous for this purpose.

Reactive mufflers depend on reducing the exhaust noise through a volume depending on reflection of sound noises. Muffler analysis is always challenging task due to complex design, shape and size limitation for specific application. That is why the reduction of exhaust noise generated from engine is in today's world an important issue. Attaching a muffler in the exhaust pipe is the good option for reducing noise. But muffler requires specific design and construction considering various noise parameters produced by the engine. Since early development of mufflers, the main objective of design was attenuation of sound in regular mufflers. A typical sound generated by vibrational waves is usually based on the experience and design experience, which can be enhanced by optimizing the internal structure of the exhaust system. The use of baffles and perforations has a significant effect on reducing the transmission loss in a silencer exhaust system. In order to evaluate the response effect of a silencer, the effect of baffle and perforations, without baffles and perforations, was evaluated in COMSOL5.2 software. Which results in numerical results with close experimental results and the effect of baffle and perforations, have shown a good reduction in transmissibility, and their partial differences are due to the features of geometry design.

Vehicle vibration and noise characteristics play a major role in ride comfort. Noise of tire in contact with the road is one of the main sources of noise in passenger cars, caused by the rolling of tire on uneven surfaces. Excitation imports through tread structure to fluid cavity and noise and vibrations transmission to the rims is of particular importance. In this paper, vibration analysis of coupled acoustic model of tire, rim and fluid acoustic cavity is performed. For this purpose, a coupled numerical finite element model is used. First, tire modeling has been addressed, taking into account the tread and two side walls and steel wheel rim. Then modal analysis has been performed to identify the structural and acoustic resonance frequencies and mode shapes. Then, using the harmonic environment coupled with static and modal analyses, acoustically coupled models of tire, rim and cavity are used to calculate the acoustic pressure of the fluid cavity, and sound pressure level, and the harmonic frequency response of the wheel hub system including the forces of wheel hub is discussed. According to the presented model, the parameters affecting tire noise levels are discussed.