Pivot point-based control for active rear-wheel steering in passenger vehicles

This paper presents a new application of active rear-wheel steering control to improve the lateral vehicle behaviour. In the state of the art, yaw or lateral velocity is used as control variable that means one degree of freedom being not directly controlled. A worse subjective impressions due to movements in the rear end of the vehicle during strong counter-steering are a consequence. To avoid this effect in urban surroundings, an innovative structure to control the pivot point distance of the vehicle is proposed. In this case the coupled elementary states yaw and lateral velocity can be influenced based on a higher level criteria. Analysis show that pivot point fixing provides a comprehensible reference behaviour. Solving the issue of singularity during disappearing yaw movement is the basis to design a performant modified feedforward input–output linearisation. An analytic stability analysis of the internal dynamics shows system immanent limitations which do not influence the target of improving the lateral vehicle dynamics in urban manoeuvres. Finally, the advantages of pivot-based control are highlighted by a comparison with state of the art rear axle control.     

Road classification for two-wheeled vehicles

This publication presents a three-part road classification system that utilises the vehicle's onboard signals of two-wheeled vehicles. First, a curve estimator was developed to identify and classify road curves. In addition, the curve estimator continuously classifies the road curviness. Second, the road slope was evaluated to determine the hilliness of a given road. Third, a modular road profile estimator has been developed to classify the road profile according to ISO 8608, which utilises the vehicle's transfer functions. The road profile estimator continuously classifies the driven road. The proposed methods for the classification of curviness, hilliness, and road roughness have been validated with measurements. The road classification system enables the collection of vehicle-independent field data of two-wheeled vehicles. The road properties are part of the customer usage profiles which are essential to define vehicle design targets.     

Calculation method of underwater acoustic and vibration response of cabin segment based on onshore vibration test北大核心CSCD

[Objective]This paper proposes a method for calculating the acoustic and vibration response of underwater cylindrical shell structures based on land-based vibration test results.[Methods]An axisymmetric boundary element method (BEM) is introduced to describe the radiation acoustic field of the shell. The relationship of acoustic pressure at the nodal point of the generatrix with velocity is obtained by solving the numerical solution of the boundary element integral equation, then the acoustic radiation impedance matrix of the outer surface of the shell and acoustic transfer vector (ATV) are constructed. Based on the assumption that the low-order vibration mode of an underwater cylindrical shell is the same as that of an onshore cylindrical shell, combined with the modes and acoustic radiation impedance matrix of an onshore cylindrical shell, the modal added mass and damping are calculated. [Results]The natural frequency calculation formula of the underwater cylindrical shell is established on the basis of the onshore mode, and the calculation method of underwater vibration response and acoustic radiation characteristics with the vibration response in air as input is obtained based on mode superposition method.[Conclusion ] The numerical results of a typical cylindrical shell with internal structure show that the method meets the engineering accuracy requirements. © 2023 Chinese Journal of Ship Research. All rights reserved.     

Technology application and development trend of intelligent unmanned system北大核心CSCD

Intelligent unmanned system combat is moving from concepts to actual combat applications. The military applications of intelligent unmanned systems are emphasized by focusing on the needs of the combat missions that they will undertake on future battlefields and summarizing the development statuses of land, air and maritime unmanned systems. Aiming at the key problems faced by intelligent unmanned systems and the practical difficulties that will be faced on the battlefield in the future, we analyze the key technologies required for intelligent unmanned systems, including autonomous perception and understanding in complex environments, behavioral decision-making and trajectory planning, autonomous navigation and positioning, multi-scenario autonomous skill learning and intelligent control, unmanned cluster cooperative control, natural human-computer interaction, etc. At the same time, aiming at the problems that will be encountered in the further development of intelligent unmanned systems on the battlefield in the future, we start with individual enhancement and cluster enhancement, and conduct a detailed analysis of the development trends of intelligent unmanned systems. © 2022 Palaeobulgarica. All rights reserved.     

Analysis of impact damage characteristics of marine carbon fiber composite laminates embedded with PEI film北大核心CSCD

[目的]在传统船用碳纤维复合材料层合板层间添加热塑性相材料能有效提升船用复合材料的抗冲击性能,为探究其冲击损伤特性,开展实验研究。[方法]使用光学显微镜观察层合板的热塑性/热固性界面,分析两相材料的结合方式;对不同结构的复合材料层合板进行低、中、高3种不同能量的低速冲击;通过超声C扫描与电子显微镜,对各试件的损伤形貌进行观测,以研究各试件的冲击响应及损伤机理。[结果]结果显示,相较于碳纤维层合板,含热塑性相的船用复合材料层合板具有更好的损伤阻抗;内部嵌膜层合板试件在冲击能量为8和12 J的冲击下,内部分层损伤分别减少了19%和39%,且受到12 J冲击后,内部结构损伤较小,完整性较好。[结论]将PEI热塑性膜嵌于内部能提升层合板的韧性,显著减少内部分层损伤,明显提升内部嵌膜层合板的抗冲击性能。     

Constructal design of tree-shaped microchannel disc heat sink with wavy walls北大核心CSCD

［Objective］To meet the efficient thermal management needs of electronic devices such as ships and underwater vehicles, this study focuses on the constructal design of a tree-shaped microchannel disc heat sink with wavy walls. ［Method］A design prototype of the heat sink with wavy walls is first proposed. Based on constructal theory, the amplitude and wavelength of the wavy walls are designed under the constraints of fixed heat sink volume and fixed microchannel volume by maximizing the comprehensive performance evaluation criteria (PEC) while considering both heat transfer and flow pressure drop. ［Results］The results show that the wavy walls increase the heat transfer surface areas and generate vortices in their cavities, effectively reducing the maximum temperature. When the inlet Reynolds number is fixed at 700, 900 or 1100 respectively, the maximum temperature is reduced by 13.5 K by increasing the amplitude of the wavy walls, while the pressure drop increases significantly; and the maximum temperature is reduced by 4.7 K by reducing the wavelength of the wavy walls, while the pressure drop increases slightly. There are optimal amplitudes that raise the comprehensive performance evaluation criteria to extreme values for given larger wavelengths, while the comprehensive performance evaluation criteria increase monotonously as the amplitude increases for given smaller wavelengths. ［Conclusion］Wavy walls can significantly improve the thermal performance of tree-shaped microchannel disc heat sinks, and the use of constructal design can realize optimal geometric constructs with optimal comprehensive performance evaluation criteria. © 2023 Authors. All rights reserved.     

Analysis of naval warship blast and shock resistance technology system北大核心CSCD

舰船抗爆和抗冲击技术概念宏观,内涵广泛,对其认识理解、设计研究都需要技术体系的顶层划分和牵引。首先,基于武器攻击对舰船的爆炸毁伤类型,对舰船抗爆与抗冲击这两个概念进行划分;然后,基于舰船总体抗爆抗冲击设计技术需求,区分不同的研究对象及技术的基础理论,提出包含6大类型的舰船抗爆抗冲击技术体系的划分方案,即水上/水下防护结构设计、新型抗爆结构与毁伤分析、设备系统及人员抗冲击、舰船抗爆抗冲击试验验证及技术标准规范;最后,分别对舰船抗爆和抗冲击技术内涵进行详细阐述。所做研究可为我国舰船抗爆抗冲击技术体系的形成提供一个初步构想,供从事舰船抗爆抗冲击设计、研究及管理人员参考。     

Robust adaptive course-keeping control of under-actuated ships with the rudder failure北大核心CSCD

[目的]针对舵机故障、控制增益未知和海洋环境干扰情况下的欠驱动船舶航向保持问题,设计一种考虑舵机故障的船舶鲁棒自适应航向保持控制算法。[方法]通过结合鲁棒神经阻尼技术和自适应方法,对繁重的神经网络权值进行横向压缩,仅需设计2个自适应学习参数对未知增益和舵机故障参数在线补偿,以确保船舶在舵机故障的情况下能够有效执行航向保持任务。通过李雅普诺夫理论,证明所提出的控制器半全局最终一致稳定有界(semi-global uniform and ultimately bounded,SGUUB)。最后以“育鲲”轮为仿真对象,建立非线性Nomoto数学模型,在海洋干扰下进行对比仿真试验验证。[结果]结果表明,在此策略下,“育鲲”轮在舵机故障情况下平均舵角输出比仿真试验中所对比的传统方法降低了51%,可改善航向保持控制效果。[结论]研究结果可为欠驱动船舶的航向保持控制问题提供借鉴。