关键词： 双机械端口电机   混合动力汽车   控制策略   模糊控制   遗传算法  

摘要： 在能源与环境问题日益严峻的背景下,汽车产业作为国内实体经济的主要载体,正在加大向电动化迈进的步伐,加快向新能源转型的速度。新能源汽车成为当前汽车产业发展的大势所趋。混合动力汽车同时具备发动机和动力电池两个动力源被认为是纯燃油车和纯电动汽车的结合体,兼具两者的优点,具有较好的动力性、经济性和较低的排放,避免了电池技术瓶颈和里程焦虑问题。而对于混合动力汽车,合理的控制策略是其提高动力性和燃油经济性的关键。基于双机械端口电机的新型动力系统将发动机与整车工况解耦,传动效率高,非常适用于混合动力汽车。本文以某款纯燃油SUV为原型,对其动力系统进行基于双机械端口电机的设计、选型和参数匹配,包括发动机、双机械端口电机、电池组和主减速器。基于AVL-Cruise软件对上述动力系统部件进行模块化建模,并建立整车模型,以此为基础进行控制策略的研究。首先,根据该动力系统的工作原理和车辆行驶需求设计六种车辆工作模式,根据工作模式设计基于逻辑门限规则的控制策略。其次,应用Matlab/Simulink搭建基于逻辑门限规则的控制策略模型,与AVL-Cruise共同构建联合仿真平台。在此平台中对控制策略进行仿真测试,验证其有效性和可行性。为了合理评价测试结果,基于能量守恒原理提出电耗—油耗的转换系数,将循环电耗和循环油耗统一为综合油耗。在车辆参数不变的条件下,应用模糊控制理论,以整车需求转矩和电池组SOC为输入,双机械端口电机输入轴转矩为输出,搭建基于模糊规则的控制策略。相较于逻辑门限规则的控制策略,该策略降低了工作模式频繁切换带来的能量损失,优化了动力系统中的转矩分配,使得整车经济性有一定的提升;针对模糊控制器的设计过程存在主观性较大的问题,应用遗传算法对模糊控制器的隶属度函数论域划分进行优化。为了避免电池过度充电和放电,在寻优过程中加入基于SOC的惩罚因子。优化后的仿真结果表明,电池组SOC循环波动稳定在在1%以内,发动机油耗降低20.1%,整车综合油耗降低23.1%,油耗表现有较大的提升。基于遗传算法优化的模糊控制策略使得车辆的动力分配更加合理,充分发挥了该新型动力系统的节油潜力。

关键词： 软体机械臂   绝对节点坐标法   超弹性本构   动力学模型   逆动力学模型  

摘要： 相比于传统的刚性机械臂,软体机械臂以其高灵活性、高适应性、高安全性等优点在军工、医疗、探测、航天航空等领域具有更广泛的应用前景,同时也是软体机器人研究领域的热点之一。然而由于软体机械臂的高自由度、低刚性以及易受外力和约束影响等特点,致使建立和求解软体机械臂的静力学、动力学和逆动力学模型变得较为困难。 本文采用基于绝对节点坐标法的低阶梁单元,建立了单节气动软体机械臂的静力学模型、动力学模型和逆动力学模型,并分别对软体机械臂在不同负载下的末端点工作空间、不同驱动气压下轴线位姿和末端点位置以及机械臂末端点位置的前馈控制系统进行了研究。主要工作内容如下: 首先,采用基于绝对节点坐标法的三维二节点低阶梁单元建立了软体机械臂的系统静力学和系统动力学方程,推导了广义弹性力及其雅可比矩阵、广义气压力及其雅可比矩阵、约束方程及其雅可比矩阵。 其次,根据机械臂的系统静力学方程计算了软体机械臂在同气压不同载荷条件下的末端点工作空间,并对工作空间的变化情况进行了分析;通过机械臂的系统动力学方程分别计算了软体机械臂在同负载不同气压条件下的轴线姿态和末端点位置,并与ABAQUS软件的仿真结果进行了对比验证。 最后通过对系统动力学方程引入目标轨迹约束条件,建立了软体机械臂逆动力学方程,由此设计了软体机械臂末端点位置的前馈控制系统,并以三种不同的目标轨迹算例验证了该控制系统的可行性。

标准号: GB/T 20969.4-2021

摘要： 本文件规定了内燃动力机械在海拔2000 m~5 000 m高原自然环境条件下的试验导则。本文件适用于工程机械用内燃动力机械在高原自然环境条件下的性能试验和可靠性试验。

标准号: GB/T 20969.1-2021

摘要： 本文件规定了海拔2 000 m~5 000 m高原地区使用的内燃动力机械的要求,试验方法、标志,包装、运输和贮存等。本文件适用于工程、建筑,起重、运输、内燃发电机组等机械配套用内燃动力机械。

关键词： Graphene networks   Thickness effect   Length distribution   Mechanical properties   Deformation mechanisms   Molecular dynamics simulation  

摘要： Assembling graphene into three-dimensional (3D) structure while preserving the superior physical properties of graphene have attracted a great deal of attention for its potential applications. Here, to reveal the effects of graphene thickness and length distribution on the mechanical behaviors of graphene networks, molecular dynamics simulations were performed based on a coarse-grained graphene model, which demonstrates that the thickness of graphene layers plays an important role in the mechanical properties of 3D graphene networks. Monolayer graphene is flexible and can be easily crumpled, thus strengthening interaction between different graphene sheets. High strength and modulus can be achieved for monolayer graphene networks both under uniaxial tensile and compressive loading, which is attributed to the combination of out-of-plane deformation of monolayer graphene and inter-graphene slippage. Comparing with the graphene networks with different structure, the networks with Gaussian distributed graphene length shows slightly higher compressive mechanical properties due to the higher density. This work can provide guidelines for the design of graphene networks with better mechanical properties and might promote the application of 3D graphene networks.

关键词： Probes  

摘要： Material properties of the genome are critical for proper cellular function - they directly affect timescales and length scales of DNA transactions such as transcription, replication and DNA repair, which in turn impact all cellular processes via the central dogma of molecular biology. Hence, elucidating the genome's rheology in vivo may help reveal physical principles underlying the genome's organization and function. Here, we present a novel noninvasive approach to study the genome's rheology and its response to mechanical stress in form of nuclear injection in live human cells. Specifically, we use Displacement Correlation Spectroscopy to map nucleus-wide genomic motions pre/post injection, during which we deposit rheological probes inside the cell nucleus. While the genomic motions inform on the bulk rheology of the genome pre/post injection, the probe's motion informs on the local rheology of its surroundings. Our results reveal that mechanical stress of injection leads to local as well as nucleus-wide changes in the genome's compaction, dynamics and rheology. We find that the genome pre-injection exhibits subdiffusive motions, which are coherent over several micrometers. In contrast, genomic motions post-injection become faster and uncorrelated, moreover, the genome becomes less compact and more viscous across the entire nucleus. In addition, we use the injected particles as rheological probes and find the genome to condense locally around them, mounting a local elastic response. Taken together, our results show that mechanical stress alters both dynamics and material properties of the genome. These changes are consistent with those observed upon DNA damage, suggesting that the genome experiences similar effects during the injection process.

关键词： Friction   Molecular dynamics simulation   Polyimide   Rare earth oxide  

摘要： Purpose The purpose of this paper is to investigate the effect of lanthana (La2O3) on the mechanical and tribological properties of polyimide (PI). Design/methodology/approach The mechanical and tribological properties of PI nanocomposites filled with La2O3 were studied by molecular dynamic simulations to explore the deep mechanisms from an atomic or molecular view. Findings The results showed that the hardness of the PI matrix increased after La2O3 modification with a decrease of 72.4% nanoindentation depth. Besides, the friction coefficient of PI decreased by 72.2% after filling La2O3, and the shear deformation was largely reduced under the same conditions. The adsorption effect of La2O3 on the PI molecular, which reduced the atomic relative concentration, velocity, interaction with counterpart Fe layer and the temperature rise in the frictional interface, contributed to the improvement of the mechanical and tribological performance. Originality/value This study reveals the friction and wear mechanism of PI composites filled with rare earth oxide at the nanoscale.

关键词： 动态结构   传动系统   机械动力   模组   蒸汽朋克   齿轮  

摘要： 在上一期中,小约给大家介绍了"机械动力"模组的传动系统,看着齿轮与齿轮互相咬合,不断旋转,你是否感受到一种神秘的、来自工业文明初期的气息呢?今天,小约将给大家介绍各种机械的作用,并使用轴承来建造真正的动态结构。事不宜迟,让我们出发吧!

关键词： 机械   仿真   非线性因素   动力学  

摘要： 在测试负载位置跟踪性能时,推导了气舵负载、永磁同步发电机与机械传动机构的动力学和运动学方程,以及气阻的动力学和运动学方程,永磁同步电机与机械作动器传动机构可以从电能、动能、摩擦损失和弹性能的相互转换角度解释电流跳跃现象。电流突变现象导致传动机构的瞬时反向摩擦的仿真和实验结果表明,该模型改进了机械作动器的仿真分析,再现了电流突变现象,对机械作动器的功率损耗仿真计算和误差预测具有重要意义。