Current Issue : July - September Volume : 2020 Issue Number : 3 Articles : 5 Articles
In this research, the residual gas, peak firing pressure increase, and effective release energy\nwere completely investigated. To obtain this target, the experimental system is installed with a\ndynamo system and a simulation model was setup. Through combined experimental and simulation\nmethods, the drawbacks of the hardware optimization method were eliminated. The results of the\nresearch show that the valve port diameter-bore ratio (VPD/B) has a significant effect on the residual\ngas, peak firing pressure increase, and effective release energy of a four-stroke spark ignition engine.......................
This article reviews the current status of automotive brake disc research and the prospects\nfor future research. At present, the research of brake disc performance mainly includes thermal\nconductivity, thermal fatigue resistance, wear resistance, and brake noise. It is found that a new alloy\ncomposite, heat treatment process, ceramic composite, new structure, and new materials are emerging.\nAt the same time, it was found that ceramic and resin were used as the matrix, fiber materials\nwere used as reinforcements to prepare brake discs, the addition of new fillers and the study of\nspecial reinforcement materials have become new hotspots in the study of brake discs. In the future\ndevelopment, carbon-fiber ceramic brake discs may become the main research focus of brake discs....
Planetary gears are widely used in automobiles, helicopters, heavy machinery, etc., due to the high speed reductions in compact\nspaces; however, the gear fault and early damage induced by the vibration of planetary gears remains a key concern. The timevarying\nparameters have a vital influence on dynamic performance and reliability of the gearbox. An analytical model is proposed\nto investigate the effect of gear tooth crack on the gear mesh stiffness, and then the dynamical model of the planetary gears with\ntime-varying parameters is established. The natural characteristics of the transmission system are calculated, and the dynamic\nresponses of transmission components, as well as dynamic meshing force of each pair of gear are investigated based on varying\ninternal excitations induced by time-varying parameters and tooth root crack. The effects of gear tooth root crack size on the\nplanetary gear dynamics are simulated, and the mapping rules between damage degree and gear dynamics are revealed. In order to\nverify the theoretical model and simulation results, the planetary gear test rig was built by assembling faulty and healthy gear\nseparately. The failure mechanism and dynamic characteristics of the planetary gears with tooth root crack are clarified by\ncomparing the analytical results and experimental data....
In order to improve the safety, stability, and efficiency of lane change operating, this paper proposes a multivehicle-coordinated\nstrategy under the vehicle network environment. The feasibility of collaborative lane change operation is established by\nestablishing a gain function based on the incentive model. By comparing lane change gain with lane keeping gain, whether it is\nfeasible to perform the collaboration under current conditions can be judged. Based on the model predictive control (MPC), a\nmultiobjective optimization control function for cooperative lane change is established to realize the distributed control. A novel\ntwo-stage cooperative lane change framework is proposed, which divides the lane change process into the lane change phase and\nthe longitudinal headway adjustment phase. It is significant to solve the difficult numerical problem caused by the dimension of\ncollision-avoidance constraints and the nonlinearity of vehicle kinematics. In the first stage, the subject vehicle completes lane\nchange operation. Both longitudinal and lateral movements of the vehicle are considered to optimize the acceleration and the error\nof following distance at this stage; in the second stage, the operation of adjusting longitudinal headway between vehicles in the\ntarget lane is completed, and at this period, only the longitudinal motion of the vehicle is considered to optimize the vehicle\nacceleration error. The rolling optimization time domain algorithm is used to solve the optimization control problem step by step.\nFinally, based on the US NGSIM open-source traffic flow database, the accuracy and feasibility of the proposed strategy\nare verified....
For passengers, the most common feeling during running on the bumpy road is continuous vertical discomfort, and when the\nvehicle is braking, especially the emergency braking, the instantaneous inertia of the vehicle can also cause a strong discomfort of\nthe passengers, so studying the comfort of the vehicle during the braking process is of great significance for improving the\nperformance of the vehicle. This paper presented a complete control scheme for vehicles equipped with the brake-by-wire (BBW)\nsystem aiming at ensuring braking comfort. A novel braking intention classification method was proposed based on vehicle\nbraking comfort, which divided braking intention into mild brake, medium comfort brake, and emergency brake. Correspondingly,\nin order to improve the control accuracy of the vehicle brake system and to best meet the driverâ??s brake needs, a\nbraking intention recognizer relying on fuzzy logic was established, which used the road condition and the brake pedal voltage and\nits change rate as input, output real-time driverâ??s braking intention, and braking intensity. An optimal brake force distribution\nstrategy for the vehicle equipped with the BBW system based on slip rate was proposed to determine the relationship between\nbraking intensity and target slip ratio. Combined with the vehicle dynamics model, improved sliding mode controller, and brake\nforce observer, the joint simulation was conducted in Simulink and CarSim. The cosimulation results show that the proposed\nbraking intention classification method, braking intention recognizer, brake force distribution strategy, and sliding mode control\ncan well ensure the braking comfort of the vehicle equipped with the BBW system under the premise of ensuring brake safety....
Loading....