Position Control Optimization of Aerodynamic Brake Device for High-speed Trains

The aerodynamic braking is a clean and non-adhesion braking, and can be used to provide extra braking force during high-speed emergency braking. The research of aerodynamic braking has attracted more and more attentions in recent years. However, most researchers in this field focus on aerodynamic effects and seldom on issues of position control of the aerodynamic braking board. The purpose of this paper is to explore position control optimization of the braking board in an aerodynamic braking prototype. The mathematical models of the hydraulic drive unit in the aerodynamic braking system are analyzed in detail, and the simulation models are established. Three control functions--constant, linear, and quadratic--are explored. Two kinds of criteria, including the position steady-state error and the acceleration of the piston rod, are used to evaluate system performance. Simulation results show that the position steady state-error is reduced from around 12-2 mm by applying a linear instead of a constant function, while the acceleration is reduced from 25,71-3.70 m/s2 with a quadratic control function. Use of the quadratic control function is shown to improve system performance. Experimental results obtained by measuring the position response of the piston rod on a test-bench also suggest a reduced position error and smooth movement of the piston rod. This implies that the acceleration is smaller when using the quadratic function, thus verifying the effectiveness of control schemes to improve to system performance. This paper proposes an effective and easily implemented control scheme that improves the position response of hydraulic cylinders during position control.

Numerical simulation and optimization on opening angles of aerodynamic braking plates sets for a maglev train

The aerodynamic braking has become an attractive option with the continuous improvement of train speeds.The study aims to obtain the optimal opening angles of multiple sets of braking plates for the maglev train.Therefore,a multi-objective optimization method is adopted to decrease the series interference effect between multiple sets of plates.And the computational fluid dynamics method,based on the 3-D,RANS method and SST k-ωturbulence model,is employed to get the initial and iterative data.Firstly,the aerodynamic drag and lift are analysed,as well as the pressure and velocity distribution of the flow field with the braking plates open at 75°.Then,the aerodynamic forces of each braking plate pre and post optimization are compared.Finally,the correlation between each set of braking plates and the optimized objective is analysed.It is found from the results that the aerodynamic drag and lift of the train have significant differences with or without multiple sets of braking plates.Additionally,the design variable corresponding to the number of iterations of 89 is taken as the rela-tive optimal solution,and its opening angles of braking plates(B2-B5)are 87.41°,87.85°,87.41°,and 89.88°,respectively.The results are expected to provide a reference for the opening angles design scheme for the future engineering application of high-speed maglev train braking technology.

Influence of aerodynamic braking on the pressure wave of a crossing high-speed train

When aerodynamic braking works,the braking wings can change the flow field around the train,which may impact on the comfort and safety.Based on a sliding mesh,the pressure wave and flow field around high-speed trains with aerodynamic braking are analyzed.By comparing three typical intersection situations,the pressure wave of a high-speed train during braking (with or without aerodynamic braking) is studied.The analyses indicate that the pressure wave around the high-speed train body will change while using the aerodynamic braking,causing several pressure pulses on the surface of crossing high-speed trains.The distances between the pressure pulses are equal to the longitudinal distances of the brake wings,but the magnitudes of the fluctuations are less than those induced by the head of crossing trains.During the crossing,a train without aerodynamic braking will not impact the crossing train.