Automotive Science and Engineering
Volume:12 Issue: 2, Spring 2022

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.

In this paper, to address the problem of using displacement sensors in measuring the transverse vibration of engine accessory belt, a novel non-contact method based on machine vision and Mask-RCNN model is proposed. Mask-RCNN model was trained using the videos captured by a high speed camera. The results showed that RCNN model had an accuracy of 93% in detection of the accessory belt during the test. Afterward, the belt curve was obtained by a polynomial regression to obtain its performance parameters. The results showed that normal vibration of the center of the belt was in the range of 2 to 3 mm, but the maximum vibration was 8.7 mm and happened in the engine speed of 4200 rpm. Also, vibration frequency of the belt was obtained 124 Hz. Moreover, the minimum belt oscillation occurred at the beginning point of the belt on the TVD pulley, whereas the maximum oscillation occurred at a point close to the center of the belt at a distance of 16 mm from it. The results show that the proposed method can effectively be used for determination of the transvers vibration of the engine accessory belts, because despite the precise measurement of the belt vibration at any point, can provide the instantaneous position curve of all belt points and the equation of the belt curve at any moment. Useful information such as the belt point having the maximum vibration, belt slope, vibration frequency and scatter band of the belt vibration can be obtained as well.

The adaptive size-independent consensus problem of uni-directional (UD) and bi-directional (BD) decentralized large-scale vehicle convoys with uncertain dynamics has been investigated in this research work. The constant distance plan (CDP) is employed to adjust the distances between successive vehicles. We assume that only relative displacement information between adjacent vehicles is accessible (partial measurement) and other information such as relative velocity and acceleration are not provided. The stability of the convoy can be performed by the analysis of each couple of consecutive vehicles. The main objective is to design an adaptive size-independent control protocol maintaining internal and string stability based on CDP with only partial measurement. Appropriate adaptive rules are derived to estimate the uncertain dynamics by utilizing only relative displacement. It will be proved that the presented adaptive protocol assures both internal stability (asymptotic stability of closed-loop convoy) and string stability (tracking error attenuation) of large-scale decentralized UD and BD convoys under the CDP. Simulations demonstrate the efficiency of the presented control framework.

Hydroforming is employed in the manufacture of hollow monolithic products to reduce the number of joints. This method can reduce the weight and enhance the quality of fluid transfer parts in a vehicle’s hydraulic system. Hydroforming is a process in which parts are formed into the shape of a mold using fluid pressure. An important issue in this process is adopting an optimal loading path.

In the present research, a drop hammer was used to implement the dynamic loading path in the tests. Accordingly, a single energy source was used simultaneously to provide axial feeding and internal pressure. To this end, designing a mold suitable for the dynamic loading path was necessary.

This numerical study investigates tubes’ deformation based on the applied impact and the amount of fluid in the mold. Moreover, axial feeding was provided with the help of different punches on the sides of the tube. Hence, the kinetic energy, amount of fluid, sealing, lubrication, and the material and thickness of the tube must be proportional for the correct forming of the tube. From the smoothed-particle hydrodynamics perspective, it is a meshless method based on interpolation that uses a particle system to examine the system state and predict fields such as displacement, stress, and pressure.

One of the main observations of this research is that selecting side punches with a smaller central hole radius is proportional to the kinetic energy and the amount of fluid. that is effective in achieving the optimal loading path.

This paper aims to examine the influences of heat treatment on forming limit diagrams and mechanical properties of aluminum alloy AA6061 sheets with thicknesses of 1.5 mm. The uniaxial tensile and the micro-hardness tests are employed to specify the mechanical properties and their variations. The Nakazima test is performed to characterize the strain forming limits of this aluminum alloy. Comparison between the results of micro-hardness and forming limit diagrams indicates that by increasing the temperature up to the peaked ageing temperature, the strength of the alloy is increased, but the forming limits are decreased, and after the peaked aged in over the aged state, the strength is decreased and the forming limits are increased. The peaked-aging is touched in this specific alloy after 4 hours heat treatment at 180 oC.

This paper introduces a trajectory planning algorithm for long-term freeway driving for autonomous vehicles including different modes of motion. In the autonomous driving in a freeway, different maneuvers are needed, including free flow, distance adaption, speed adaption, lane change and overtaking. This paper introduces an algorithm that provides all of these driving scenarios in the trajectory planning for an autonomous vehicle. All maneuvers are classified and proper formulation for each driving mode formulated. Then, an algorithm is introduced to show the procedure of decision making and switching between all driving modes. The relative distances and velocities of the other peripheral and front vehicle from autonomous vehicle are considered as the main factors for decision making during the travelling in the freeway. By the developed simulation programming, validity and effectiveness of the algorithm are verified, and pseudo code and flowchart for the simulation programming are introduced. Later in two simulation studies, different driving conditions are generated and results have been discussed and analyzed by detail.