工况驾驶规范性及客观评价指标相关性的试验研究

通过引入驾驶评价指标和制动压力的控制及其要求规范了驾驶行为，为提高测试的准确性以及可重复性提供了保障。利用8名具有多年底盘测功机驾驶经验的驾驶员及两台轻型汽油车，在底盘测功机上开展了大量的新欧洲驾驶循环测试 （New European Driving Cycle，NEDC） 和全球轻型车统一循环测试 （Worldwide Harmonized Light Vehicles Test Cycle，WLTC），并以10 Hz为采样频率连续记录数据进行综合计算，得到驾驶评价指标结果。通过相关性分析，认定驾驶风格对油门扰动性的影响在 NEDC工况下比在 WLTC工况下的更大，主因是驾驶员在稳定工况下拥有更多的自由度。对于NEDC工况，可以通过设定IWR及EER限值来实现规范驾驶；对于WLTC工况，可以通过设定IWR和RMSSE限值来实现规范驾驶。此外，通过限制工况驾驶过程中的最大制动压力还为规范驾驶提供了有效途径。不仅为降低不同驾驶员对燃料消耗量测试的影响提供了参考，在我国汽车领域实现“双碳”目标的背景下，也为乘用车碳排放大数据采集的准确性提供了借鉴。     

全尺寸汽车空气动力学风洞相关性及修正研究

全尺寸汽车空气动力学风洞是汽车空气动力性能重要的研究平台与开发工具。但风洞间测试结果普遍存在差异，这对气动性能的研究与分析造成了一定的困难，因此有必要开展风洞间的横向相关性和修正研究，提高风洞测试结果的统一性和一致性。分别对德国和中国的两座全尺寸汽车风洞进行实车风洞测试，开展风洞相关性及修正研究。研究表明，对于同一工况，不同风洞间的测试结果存在一定差异，但不同工况与基础工况间差异变化趋势一致，大小相似，不同风洞间的测试结果能建立较好的相关关系，形成相关性线性函数。通过空气阻力系数C D 修正方法，可以减小风洞间由结构尺寸、流场参数导致的系统性误差，修正后的风洞间空气阻力系数C D 测试结果差异降低了近60%。     

Nonstationary response of floating structures to random waves

Even if ocean waves are treated as a stationary random process, dynamic responses of floating structures to random waves at the transient state are always nonstationary. When nonstationary response statistics is desired, a common technique is to apply Monte Carlo simulations; however, its implementation is costly in computational time. Analytically, this article develops an efficient method for computing nonstationary response statistics, including evolutionary power spectrum and time-varying mean-square values. Assuming a hydrodynamic software has been employed to get various frequency response functions, a prerequisite of the proposed method is to get the elevation-to-motion transfer function formulated in its pole-residue form. The proposed method is applicable to arbitrary wave spectrum and has been based on pole-residue operations implemented in the Laplace domain to obtain closed-form solutions for the response evolutionary power spectrum. Numerical examples choose a single-degree-of-freedom Spar model and a six-degree-of-freedom Floating Production Storage and Offloading model to a Pierson–Moskowitz wave spectrum, and the correctness of the computed mean-square values is verified by Monte Carlo simulations.     

由路面引起的汽车振动能量耗散特性频域分析

针对行驶过程中由路面引起的汽车振动能量耗散问题，提出了基于汽车振动二自由度单轮模型的能量耗散特性频域分析方法。采用汽车振动二自由度单轮模型推导了模型的频率响应，确定了能量耗散振动响应量及其频率响应。将路面激励功率谱密度与振动响应量的功率谱密度和均方根值相结合，建立了能量耗散振动响应量统计特性和振动能量耗散平均功率的表示。采用Matlab开发了汽车振动二自由度单轮模型的能量耗散特性频域分析仿真程序，通过3种分析方案研究了由路面引起的汽车振动能量耗散特性。结果表明，汽车振动能量耗散平均功率与速度和路面等级相关，受到路面等级的影响较大；在以B级路面为主的国内城市行驶工况下，由路面引起的汽车振动能量耗散平均功率比较低。     

Time-domain shielding effectiveness analysis based on DGTD method北大核心CSCD

[目的]为精确分析金属屏蔽腔的时域屏蔽效能,提出一种基于局部时间步进技术和并行技术的时域不连续伽辽金(DGTD)算法。[方法]利用DGTD算法,对金属屏蔽腔进行全波电磁仿真,进而计算时域屏蔽效能(TDSE);利用局部时间步进(LTS)技术增大时间步长,然后结合并行技术显著缩短计算时间;分析金属屏蔽腔的孔径尺寸、腔体厚度、阵列孔间距等设计参数对时域屏蔽效能的影响。[结果]数值算例结果显示,所提方法正确、有效。[结论]所提方法为电磁屏蔽问题的仿真提供了一种有效的工具,对金属屏蔽腔的设计具有一定的指导意义。     

低速柴油机推进轴系频域稳态扭转振动分析

以载重10 000 t低速柴油机推进轴系为研究对象，创建其当量系统模型。基于系统矩阵法对推进轴系进行自由振动分析，求得扭转振动固有频率和振型。研究柴油机在全转速下的气体和往复惯性激励力矩，针对推进轴系在柴油机和螺旋桨共同激励下的频域稳态扭转振动响应特性进行计算，求得推进轴系扭转振动的主谐次、共振转速点和推进轴系各部件的应力值。结果表明，推进轴系在低阶频率振动时气缸和中间轴振幅较大，推进轴系应力远小于材料的屈服强度，船舶能够安全稳定航行，同时为推进轴系时域瞬态扭转振动研究打下基础。     

Seabed collision emergency decision-making of AUV based on safety domain model北大核心CSCD

［Objectives］To ensure safety and prevent seabed collisions in complex unknown underwater environments, this study proposes a seabed safety domain model and tiered emergency response strategies. ［Methods］A vertical motion simulation model is established and verified by surpassing the test results, then used to calculate the active and passive safety domain distance of an autonomous underwater vehicle (AUV), thereby establishing a seabed safety domain model. An AUV emergency control system and emergency strategies are then built on the basis of the dynamic safety domain model. The trim and distance from the seabed of the AUV are used to calculate the current and future risk factors. Based on the weighted sum, the comprehensive risk factor is employed to provide the AUV with emergency response strategies.［Results］Lake tests with the AUV sailing at a fixed depth and height show a strong dependency of the comprehensive risk coefficient on seabed height when it is close to the boundary of the AUV's active safety domain. In the opposite case, there is a weak dependency of the comprehensive risk coefficient on seabed height. The results show that the proposed AUV emergency control system can reduce emergency false alarms caused by frequently changing riverbed heights and sailing altitudes close to the seabed. In such cases, reasonable emergency strategies can be realized under complex rough terrain.［Conclusions］The AUV seabed safety domain model and tiered emergency response strategies based on vertical motion equations proposed herein can be applied to evaluate seabed collision risk in various cases. Finally, this paper provides emergency response strategies to avoid seabed collision accidents, which can enhance the safety of AUV navigation. © 2023 Chinese Journal of Ship Research. All rights reserved.