高速客车路面不平度干扰转向及影响因素研究

为改善高速客车的路面不平度稳定性,研究了高速客车路面不平度干扰转向的机理及其影响因素。首先建立反映客车高速行驶时受到不平路面干扰产生转向运动的动力学模型,并推导出其状态方程。然后就前轴静态负荷、轮胎侧偏刚度、转向系统阻尼、前轮定位回正力矩等主要影响因素进行变参数动态仿真及单因素影响分析,得出增大前轴静态负荷、前轮定位回正力矩及减小转向系统阻尼是减小高速客车前端最大偏移量较为可行的措施。最后通过实车试验对采取改进措施后的效果进行了验证,结果显示关于该客车路面不平度稳定性的仿真结果与试验结果基本吻合。上述研究结果可为改善高速客车产品的路面不平度稳定性提供理论参考。

基于GA的认知物联网功率自适应PIS算法

针对并发频谱接入模型下的认知物联网(C-IoT:Cognitive Internet of Things)系统中的干扰管理问题,提出一种基于遗传算法(GA:Genetic Algorithm)的C-IoT功率自适应部分干扰转向(PIS:Partial Interference Steering)算法。该算法能在同时保证主用户(PU:Primary User)和认知用户(CU:Cognitive User)服务质量的前提下提高系统的频谱效率。仿真结果表明,该算法能在寻求系统最优频谱效率时快速收敛,求出此时PU和CU期望信号的最佳发射功率。在主发射机、PU和CU相对位置确定的场景下,根据用户的平均违反约束程度D(cvave),能求解出可接入授权频谱认知发射机的最佳空间分布区域。

H∞ control of novel active steering integrated with electric power steering function

Based on the traditional active steering system, a novel active steering system integrated with electric power steering function was introduced, which can achieve the functions of both active steering and electric power steering. In view of the interference from road random signal and sensor noise in the novel active steering system, the H∞ control model of the novel active steering system was built. With satisfying steering feel, good robust performance and steering stability being the control objectives, the H∞ controller for the novel active front steering (AFS) system was designed. The simulation results show that the novel AFS system with H∞ control strategy can attenuate the road interference quickly, and there is no resonance peak in the bode diagram. It can make the driver obtain more useful information in the low frequency range, and attenuate the road interference better in the high frequency range, thus the driver can get more satisfying road feeling. Therefore, the designed H∞ controller can synthesize the advantages of both robust performance and robust stability, and has certain contribution to the design of novel AFS system.

An experimental study on the effects of relative rotation direction on the wake interferences among tandem wind turbines

An experimental study was conducted to investigate the effects of relative rotation direction on the wake interferences among two tandemwind turbines models.While the oncoming flow conditions were kept in constant during the experiments,turbine power outputs,wind loads acting on the turbines,and wake characteristics behind the turbines were compared quantitatively with turbine models in either co-rotating or counter-rotating configuration.The measurement results reveal that the turbines in counter-rotating would harvest more wind energy from the same oncoming wind,compared with the co-rotating case.While the recovery of the streamwise velocity deficits in the wake flows was found to be almost identical with the turbines operated in either co-rotating or counter-rotating,the significant azimuthal velocity generated in the wake flow behind the upstream turbine is believed to be the reason why the counter-rotating turbines would have a better power production performance.Since the azimuthal flow velocity in the wake flow was found to decrease monotonically with the increasing downstream distance,the benefits of the counter-rotating configuration were found to decrease gradually as the spacing between the tandem turbines increases.While the counter-rotating downstream turbine was found to produce up to 20%more power compared with that of co-rotating configuration with the turbine spacing being about 0.7D,the advantage was found to become almost negligible when the turbine spacing becomes greater than 6.5D.It suggests that the counter-rotating configuration design would be more beneficial to turbines in onshore wind farms due to the smaller turbine spacing(i.e.,~3 rotor diameters for onshore wind farms vs.~7 rotor diameters for offshore wind farms in the prevailing wind direction),especially for those turbines sited over complex terrains with the turbine spacing only about 1–2 rotor diameters.