顾及交叉路口和车辆模态的轨迹重构与分析

由于数据传输和存储成本的限制,大多数轨迹数据采样率低且不确定,而城市精细模型往往需要高频轨迹数据,例如,微观交通碳排模型需要时间间隔为1 s的轨迹数据。因此,对低频轨迹数据进行高频重构有非常重要的意义。提出了一种顾及交叉路口和车辆模态的轨迹重构方法,采用高频轨迹数据训练车辆运动模态的理论概率模型,结合交叉路口来确定低频轨迹点之间的模态序列,并通过遗传算法求解理论概率模型来完成各模态时间和距离的分配,进而完成轨迹点的高频重构。结果表明,所提方法重构轨迹的均方根误差(root mean square error,RMSE)值相较于传统的数学插值方法降低了62.9%,相较于未考虑交叉路口的模态方法,降低了12.2%。因此,该方法在低频轨迹数据重构中具有很好的应用价值。

某车辆滑行工况排气系统引起的车内轰鸣声研究

依据NVH源、传递路径到响应点的研究准则,从系统集成的角度对某车辆滑行工况下的车内轰鸣声加以研究。结果表明滑行工况下的车内轰鸣声主要由排气尾管2阶噪声与车辆空腔模态耦合所致,且滑行工况下自动变速箱降档策略使发动机转速频繁经过问题转速点从而加剧问题发生的频次。采用矩形管道声学传播理论可以快速近似计算出车辆的前几阶声腔模态频率,有利于问题原因快速排查;在排气系统设计上采用赫姆霍兹共振腔结构来降低源头的激励解决车内轰鸣声抱怨也是一项经济有效的措施。

Dynamic Resonant Frequency Bands of Suspension System of Vehicles with Varying Speeds Based on Time⁃Frequency Spectrum

The dynamic responses of suspension system of a vehicle travelling at varying speeds are generally nonstationary random processes,and the non-stationary random analysis has become an important and complex problem in vehicle ride dynamics in the past few years.This paper proposes a new concept,called dynamic frequency domain(DFD),based on the fact that the human body holds different sensitivities to vibrations at different frequencies,and applies this concept to the dynamic assessment on non-stationary vehicles.The study mainly includes two parts,the first is the input numerical calculation of the front and the rear wheels,and the second is the dynamical response analysis of suspension system subjected to non-stationary random excitations.Precise time integration method is used to obtain the vertical acceleration of suspension barycenter and the pitching angular acceleration,both root mean square(RMS)values of which are illustrated in different accelerating cases.The results show that RMS values of non-stationary random excitations are functions of time and increase as the speed increases at the same time.The DFD of vertical acceleration is finally analyzed using time-frequency analysis technique,and the conclusion is obviously that the DFD has a trend to the low frequency region,which would be significant reference for active suspension design under complex driving conditions.

Trajectory tracking control for underactuated unmanned surface vehicles with dynamic uncertainties

The trajectory tracking control problem for underactuated unmanned surface vehicles(USV) was addressed, and the control system took account of the uncertain influences induced by model perturbation, external disturbance, etc. By introducing the reference, trajectory was generated by a virtual USV, and the error equation of trajectory tracking for USV was obtained, which transformed the tracking problem of underactuated USV into the stabilization problem of the trajectory tracking error equation. A backstepping adaptive sliding mode controller was proposed based on backstepping technology and method of dynamic slide model control. By means of theoretical analysis, it is proved that the proposed controller ensures that the solutions of closed loop system have the ultimate boundedness property. Simulation results are presented to illustrate the effectiveness of the proposed controller.

Practical Model for Real Structure and Performance of Heavy Vehicles

In this paper, a new practical model for real heavy vehicle structure is developed to investigate dynamic responses under steering/acceleration or braking maneuvers. The generalized six DoFs （degrees-of-freedom） nonlinear vehicle model M1 including longitudinal, lateral, yaw, vertical, roll and pitch dynamics is validated using the measured data reported in different studies. This model takes the CG （center of gravity） of sprung mass, unsprung mass and total vehicle mass into account. Based on this model, the effects of the inertia parameters on the vehicle dynamic responses are investigated for more comprehensive assessments of the model structure. Another nonlinear vehicle model 342 derived from M1 which assumes that the vehicle has a single CG as reported in literature is also developed. The dynamic responses of the vehicle model Mj are compared with those of the model M2 to demonstrate the performance potential of the proposed nonlinear model. The results of dynamic responses with the nonlinear vehicle model MI suggest that the model could offer considerable potential in realizing enhanced ride and handling performance, as well as improved roll and pitch properties in a flexible manner.

Dynamic behaviors of pretensioned cable AERORail structure

The AERORail, a new aerial transport platform, was chosen as the object of this work. Following a review of the literature on static behaviors, model tests on the basic dynamic mechanical characteristics were conducted. A series of 90 tests were completed with different factors, including tension force, vehicle load and vehicle speed. With regard to the proper tension and vehicle load, at a certain speed range, the tension increments of the rail's cable were proved relatively small. It can be assumed that the change of tension is small and can be reasonably ignored when the tension of an entire span is under a dynamic load. When the tension reaches a certain range, the calculation of the cable track structure using classical cable theory is acceptable. The tests prove that the average maximum dynamic amplification factor of the deflection is small, generally no more than 1.2. However, when the vehicle speed reaches a certain value, the amplified factor will reach 2.0. If the moving loads increase, the dynamic amplification factor of dynamic deflection will also increase. The tension will change the rigidity of the structure and the vibration frequency; furthermore, the resonance speed will change at a certain tension. The vibration is noticeable when vehicles pass through at the resonance speed, and this negative impact on driving comfort requires the right velocity to avoid the resonance. The results demonstrate that more design details are required for the AERORail structure.

Damage evolution and dynamic response of cement asphalt mortar layer of slab track under vehicle dynamic load

The damage evolution and dynamic performance of a cement asphalt(CA)mortar layer of slab track subjected to vehicle dynamic load is investigated in this paper.Initially,a statistical damage constitutive model for the CA mortar layer is developed using continuous damage mechanics and probability theory.In this model,the strength of the CA mortar elements is treated as a random variable,which follows the Weibull distribution.The inclusion of strain rate dependence affords considering its influence on the damage development and the transition between viscosity and elasticity.Comparisons with experimental data support the reliability of the model.A three-dimensional finite element(FE)model of a slab track is then created with the commercial software ABAQUS,where the devised model for the CA mortar is implemented as a user-defined material subroutine.Finally,a vertical vehicle model is coupled with the FE model of the slab track,through the wheel-rail contact forces,based on the nonlinear Hertzian contact theory.The evolution of the damage and of the dynamic performance of the CA mortar layer with various initial damage is investigated under the train and track interaction.The analysis indicates that the proposed model is capable of predicting the damage evolution of the CA mortar layer exposed to vehicle dynamic load.The dynamic compressive strain,the strain rate,and the induced damage increase significantly with an increase in the initial damage,whereas the dynamic compressive stress exhibits a sharp decrease with the increasing initial damage.Also,it is found that the strain rate dependence significantly influences the damage evolution and the dynamic behavior of the CA mortar layer.

Vehicle height control of electronic air suspension system based on mixed logical dynamical modelling

Due to the coexistence and coupling of continuous variables and discrete events, the vehicle height adjustment process of electronic air suspension system can be regarded as a typical hybrid system. Therefore, the hybrid system theory was applied to design a novel vehicle height control strategy in this paper. A nonlinear mechanism model of the vehicle height adjustment system was established based on vehicle system dynamics and thermodynamic theory for variable-mass gas charge/discharge system. In order to model both the continuous/discrete dynamics of vehicle height adjustment process and the on-off statuses switching of solenoid valves, the framework of mixed logical dynamical(MLD) modelling was used. On the basis of the vehicle height adjustment control strategy, the MLD model of the adjustment process was built by introducing auxiliary logical variables and auxiliary continuous variables. Then, the co-simulation of the nonlinear mechanism model and the MLD model was conducted based on the compiling of HYSDEL. The simulation and experimental results show that the proposed control strategy can not only adjust the vehicle height effectively, but also achieve the on-off statuses direct control of solenoid valves.

Maneuver control of the hypersonic gliding vehicle with a scissored pair of control moment gyros

A maneuver control approach using a scissored pair of control moment gyros is proposed to improve the penetration ability of a hypersonic gliding vehicle(HGV) with a relatively high lift-drag ratio. Then, a multivariable strong coupling nonlinear bank-toturn dynamical model is established for the case of lateral maneuvering of an HGV equipped with a scissored pair of control moment gyros. According to the requirement of coordinated turning of the HGV in a lateral maneuver, a decoupling controller based on feedback linearization and a linear quadratic optimal algorithm is designed. Finally, the large airspace maneuvering trajectories of the HGV including S-shaped, cycloid and spiral maneuvering modes are designed by applying overload control technology. Simulations demonstrate that the designed maneuvering trajectory significantly increases the airspace range and flexibility of the vehicle. The coordinated turn control system achieves an accurate and rapid tracking of the maneuvering trajectories in large airspace.

Dynamic analysis of a high-speed train operating on a curved track with failed fasteners

A high-speed train-track coupling dynamic model is used to investigate the dynamic behavior of a high-speed train operating on a curved track with failed fasteners. The model considers a high-speed train consisting of eight vehicles coupled with a ballasted track. The vehicle is modeled as a multi-body system, and the rail is modeled with a Timoshenko beam resting on the discrete sleepers. The vehicle model considers the effect of the end connections of the neighboring vehicles on the dynamic behavior. The track model takes into account the lateral, vertical, and torsional deformations of the rails and the effect of the discrete sleeper support on the coupling dynamics of the vehicles and the track. The sleepers are assumed to move backward at a constant speed to simulate the vehicle running along the track at the same speed. The train model couples with the track model by using a Hertzian contact model for the wheel/rail normal force calculation, and the nonlinear creep theory by Shen et al. (1984) is used for wheel/rail tangent force calculation. In the analysis, a curved track of 7000-m radius with failed fasteners is selected, and the effects of train operational speed and the number of failed fasteners on the dynamic behaviors of the train and the track are investigated in detail. Furthermore, the wheel/rail forces and derailment coefficient and the wheelset loading reduction are analyzed when the high-speed train passes over the curved track with the different number of continuously failed fasteners at different operational speeds. Through the detailed numerical analysis, it is found that the high-speed train can operate normally on the curved track of 7000-m radius at the speeds of 200 km/h to 350 km/h.