Inserts supporting run-flat tire is a key technology in the field of vehicle active safety. When the vehicle is under zero driving condition, the deformation of the inserts supporting run-flat tire due to compression can cause the tire to be crushed, and loss of adhesion between the tire and rim can lead to separation. These situations can reduce the cruising ability of the vehicle. Under zero driving condition, the insert, which is the main support body for the tire, could rub against the inner part of the tire sharply, thereby generating heat in the tire. Heat in the tire is difficult to dissipate and can accumulate rapidly under this condition. As the temperature of the tire and insert increases, the inserts supporting run-flat tire could fail to support the vehicle. To improve heat dissipation of the insert, a finite element model of the inserts supporting run-flat tire under the condition of zero rolling is established. The steady-state temperature field of the inserts supporting run-flat tire is analyzed using ANSYS Workbench. The insert temperature field and heat flux are solved. The optimization design of axial heat dissipation holes and surface heat dissipation grooves based on experimental and simulation results of the insert is presented. Finally, the optimization structure of the insert is verified using a thermal–mechanical coupling simulation method. The conclusions are of great significance for optimizing inserts supporting run-flat tire and improving zero rolling ability of tire.
Emergency start-stop in front of signal lights is one of the main reasons for additional energy consumption and ride discomfort of Electric Vehicle (EV). Existing research on this issue rarely takes into account both energy consumption and ride comfort. Therefore, the layered energy-saving speed planning and control method is proposed. The upper is the layer of energy-saving speed planning. This layer reduces energy consumption of EV by reducing the number of stops on continuous signal lights road and minimizing the range of speed change. On this basis, the sinusoidal variable speed curve is used to smooth the acceleration process to improve ride comfort. Finally, the energy-saving speed considering ride comfort is obtained. This layer makes up for the issue that existing research rarely takes into account both energy consumption and ride comfort of EV, and is an extension and innovation of existing research. The lower is the layer of Model Predictive Controller (MPC)-based speed control. Based on the longitudinal dynamics model of EV, the MPC-based speed controller is established to control EV to track the energy-saving speed. The controller is easy to understand and implement, and it is also suitable for other research on EV, which has certain application value. The simulation results show that under various working conditions, the maximum energy consumption of EV passing through continuous signal lights road without stopping is 604.29 kJ/km, and the minimum is 244.76 kJ/km. The energy consumption is lower than that of actual road test, and it can be saved by 23.18 % compared with the method in the same field. The maximum Root Mean Square of accelerations (RMSa) is 0.25 m/s2, and the minimum is 0.10 m/s2. The values of RMSa above are lower than 0.315 m/s2, which indicates that the ride comfort is good. The utilized method can reduce energy consumption of EV, improve its range and ride comfort, which has important reference significance for promoting the development of EV.
Aiming at the independent development of tracked vehicles, it is urgent to improve its mobility, passability and ride comfort, a new type of flexible road wheel with a "wheel-hinge-hub" combined structure is proposed in this study. The vibration model characteristics of the flexible road wheel were studied by the combination of numerical simulation and experiments. The superelasticity of rubber is obtained through uniaxial tensile experiment of the material and a detail three-dimensional nolinear finite element model of the flexible road wheel is established through finite element software ABAQUS. The free vibration equation of the flexible road wheel is solved by Lanczos vector direct superposition method, and its predicted modes and natural frequencies are compared with experimental results, which verifies the accuracy and reliability of the established finite element model. On this basis, the effects of various key structural or material factors on the natural frequencies of the flexible road wheel are studied using orthogonal experimental design method. Besides, the vibration modal characteristics of the flexible road wheel are also compared with those of the rigid road wheel. The research results provide a theoretical basis for the vibration and noise reduction of flexible road wheel.
Different driving styles should be considered in path planning for autonomous vehicles that are travelling alongside other traditional vehicles in the same traffic scene. Based on the drivers’ characteristics and artificial potential field (APF), an improved local path planning algorithm is proposed in this paper. A large amount of driver data are collected through tests and classified by the K-means algorithm. A Keras neural network model is trained by using the above data. APF is combined with driver characteristic identification. The distances between the vehicle and obstacle are normalized. The repulsive potential field functions are designed according to different driver characteristics and road boundaries. The designed local path planning method can adapt to different surrounding manual driving vehicles. The proposed human-like decision path planning method is compared with the traditional APF planning method. Simulation tests of an individual driver and various drivers with different characteristics in overtaking scenes are carried out. The simulation results show that the curves of human-like decision-making path planning method are more reasonable than those of the traditional APF path planning method; the proposed method can carry out more effective path planning for autonomous vehicles according to the different driving styles of surrounding manual vehicles.
Abstract As the time-varying contact stiffness is one of the most important nonlinear factors, which not only has great influence on dynamic properties, but also on the natural properties. In this paper, the natural properties of a power turret gear system were studied based on varying stiffness. The influence was concluded by natural frequencies.
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