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High-speed axial piston pumps are hydraulic power supplies for electro-hydrostatic actuators(EHAs). The efficiency of a pump directly affects the operating performance of an EHA, and an understanding of the physical phenomena occurring in the cylinder/valve plate interface is essential to investigate energy dissipation. The effects of the splined shaft bending rigidity on the cylinder tilt behaviour in an EHA pump need to be considered, because the deflection and radial expansion of a steel shaft rotating at a high speed cannot be ignored. This paper proposes a new mathematical model to predict the cylinder tilt behaviour by establishing a quantitative relationship between the splined shaft deflection, the cylinder tilt angle, and the tilt azimuth angle. The moments exerted by the splined shaft are included in the equilibrium equation of the cylinder. The effects of solid and hollow splined shafts equipped in an EHA pump prototype are compared at variable speeds of 5000–10,000 r/min. With a weight saving of 29.7%, the hollow shaft is experimentally found to have almost no influence on the volumetric efficiency, but to reduce the mechanical efficiency by 0.6–2.4%. The results agree with the trivial differences of the simulated central gap heights of the interface between the two shafts and the enlargement of the simulated tilt angles by the hollow shaft. The findings could guide designs of the cylinder/valve plate interface and the splined shaft to improve both the efficiency and power density of an EHA pump. 相似文献
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基于小偏差理论,推导了三体动力学模型的误差线性模型,并将此假设下的控制归纳为终端固定的有限时间调节器问题。在此基础上,进一步利用该最优控制方法推导了晕轨道周期内的连续小推力控制方案,验证了控制加速度及状态量的收敛。同时针对整周期控制方式在超调后状态量收敛速度慢的问题,通过分段连续推力控制模式(Sectional Continuous Thrust Control,SCTC)来近似瞬时脉冲推力控制模式,给出了最短分段控制时间的计算方法。实验表明,SCTC模式加快了轨道状态的收敛速度。对于km级入轨偏差,通过1次控制即可使实际轨道收敛至标称轨道。 相似文献
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比率分析法是目前西方财务报表分析中应用最普遍的方法之一。以国外航空公司特别是英航的财务数据为基础,就国外被广泛采用的重要财务比率进行了分析,并选择了国外几大航空公司的比率进行了比较,旨在为中国航空公司进行财务报表分析提供比率分析方面的比较和借鉴。 相似文献
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为了改善旋转电动舵机的控制输出中存在的系统振荡问题,针对电动舵机中连杆及摇臂等传动结构导致的非线性不确定特性,文章通过建立传动机构的数学模型,根据其位置变化量及速度变化量关系,确立了控制输出与实际输出在传动过程中的正逆运动学方程,分析了传动机构运动时所引入的非线性环节,并提出了通过修正传动参数来补偿非线性的影响,为伺服系统的分析及控制器设计提供参考,对提高舵机系统的控制性能与控制精度有重要作用。 相似文献
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Axial piston pumps have been widely used in aircraft hydraulic systems to supply the system with pressurized fluid. The continuous improvement of the aircraft performance has put forward the demand on aviation piston pumps for high power density, safety, and reliability. The lubricating interfaces in axial piston machines are the key design issue that greatly determines the pump performance and service life. The cylinder block/valve plate interface is one of these critical lubricating interfaces and has received considerable attention from many researchers in the last half century. This study aims to review the state‐of‐the‐art literature on the cylinder block/valve plate interface comprehensively and systematically. First, we introduce various theoretical models developed to investigate the lubrication behaviors of the interface and compare them in terms of their assumptions and limitations. Second, the experimental studies on the cylinder block/valve plate interface are presented comprehensively, where the involved test rigs are divided into three types according to their fidelity levels and measurement functionality. Third, we summarize some typical approaches of structure optimization, surface shaping, and surface strengthening, which help improve the load-carrying and anti-wear capacities of the interface under severe operating conditions. Finally, the challenges and future trends of the cylinder block/valve plate interface research are discussed briefly. 相似文献
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动物具有优秀的空间自主定位导航能力,能够实现在无先验环境信息下的导航定位和导航决策过程。针对智能体在连续空间中面向目标导航问题,研究了一种基于生物学放电时间依赖可塑性学习规则的智能体面向目标导航算法。首先分析了动物面向目标导航决策过程中的生理学机理,在此基础上,构建了基于脉冲神经网络的位置细胞和动作细胞模型。动作细胞间权值采用横向竞争模型更新,通过环境奖励信号的更新,采用放电时间依赖可塑性学习规则对位置细胞前馈动作细胞模型的突触权重进行权值调节,利用动作细胞群的脉冲放电现象表征智能体运动方向和速度。最后,对所提算法进行了仿真实验验证。仿真结果表明,所提出的类脑面向目标导航算法能够在单障碍环境中实现30 ms左右的规划速度,相比传统强化学习Q学习方法平均路径规划长度缩短了15.9%。 相似文献
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基于小波分析的航空发动机故障诊断方法研究 总被引:4,自引:3,他引:4
小波变换是一种多分辨率的时频分析方法,应用在振动信号处理、故障诊断方面较传统方法优越。在阐述小波分析理论基础上,对某型航空发动机的振动信号进行分析,采用小波分解和信号重构的方法,提取了噪声掩盖下振动信号中的故障信息,根据航空发动机整机振动的典型故障特征频率,判断该发动机是否发生故障。 相似文献