Papers by Author: Ji Ye Zhang

Abstract: In the real automated highway system, various factors to vehicles which are moving make the velocity of vehicles change suddenly. In this paper, assuming that the mass of vehicles, the drag coefficient and the resistance of the ground were uncertain, the controller for a class of time-varying delayed look-ahead vehicle longitudinal following system with impulsive effect was designed by using the idea of quasi-sliding mode control. An example is given at last to test the controller proposed in this paper.

Abstract: A fast approach to high-speed train co-simulation between aerodynamics and train-track coupling dynamics is presented. With this method, the fluid-structure dynamic performances of a high-speed train are simulated with different crosswind velocity and train velocity. The aerodynamic forces and train dynamics are compared under off-line simulation and equilibrium state method. Considering the fluid-structure interaction, there is significant influence on the head aerodynamics and train dynamics. The results show that it is necessary to consider changing attitude in crosswind

Abstract: Mesh stability is the property of damping or eliminating disturbances as they travel in an interconnected system. In this paper, the mesh stability of a class of look-ahead vehicle following system is studied under the assumption that the all isolated subsystems are exponentially stable. Via idea of vector Lyapunov function theory and by using of Cauchy inequality technique, the sufficient condition to ensure the global mesh exponential stability is obtained. The obtained condition which shows the relationship and domain of the parameters is convenient to apply to design controller in practice.

Abstract: A permanent magnet brushless DC motor speed control system based on PI controller with fuzzy parameters regulators is studied in this paper. First, the simulation models of motor body, inverter, PWM and logic commutation are established, and the generators of Back-EMF and hall signal are obtained by means of s-Function to improve the simulation speed and accuracy; secondly a PI controller with fuzzy parameters regulators is given; lastly designs of the fuzzy controller and of the traditional PI controller are compared with each other by the MATLAB/SIMULINK emulation. The result shows that the simulation model can simulate the actual motor well, and the PI controller with fuzzy parameters regulator is obviously superior to the traditional PI controller in both dynamic and steady-state performance.

Abstract: As the speed of train increases, flow-induced vibration of trains passing through tunnels has become a subject of discussion, to investigate this phenomenon, a simplified geometric model and a vehicle dynamics model of a high-speed train traveling through a tunnel were built. To analyze the unsteady three-dimensional flow around the train, the 3-D, transient, viscous, compressible Reynolds-averaged Navier-Stokes equations combined with the k- two-equation turbulence model were solved with the finite volume method. The motion of the train was carried out using the technique of sliding grid method. The dynamics response of the train was obtained by means of the computational multi-body dynamics calculation. Meanwhile the running safety and riding comfort of the train were analyzed. With the numerical simulation, the variation of aerodynamic forces was obtained. The research founds that, vibration of the train increases drastically during it passing through a tunnel. The running safety and riding quality of the train are reduced greatly but they are in the safe range.

Abstract: Numerical Simulation of oscillating flow over a circular cylinder is calculated when the Reynolds number is 100. The space-time finite element method is used to solving the two-dimensional incompressible Navier-Stokes equations. Considering the oscillating flow over a variation of perturbation amplitudes and frequency ratios, the trends of lift coefficient with amplitude and frequency ratio are compared respectively. Besides, the FFT of the lift coefficient curves are analyzed. There is a suddenly change in main frequency and second frequency when A=0.1. The excited frequencies of lift coefficient are discussed, which could be the combination of vortex shedding natural frequency and perturbation frequency, such as |fe－f0|, fe, 2fe－f0, fe＋f0, 2fe＋f0, etc.