Analysis of the cylinder block tilting inertia moment and its effect on the performance of high-speed electro-hydrostatic actuator pumps of aircraft

Electro-hydrostatic actuator (EHA) pumps are usually characterized as high speed and small displacement. The tilting inertia moment on the cylinder block produced by the inertia forces of piston/slipper assemblies cannot be ignored when analyzing the cylinder block balance. A large tilting inertia moment will make the cylinder block tilt away from the valve plate, resulting in severe wear and significantly increased leakage. This paper presents an analytical expression for the tilting inertia moment on the cylinder block by means of vector analysis. In addition, a high-speed test rig was built up, and experiments on an EHA pump prototype were carried out at high speeds of up to 10,000 r/min. The predicted nature of the cylinder block tilt at high speeds corresponds closely to the witness marks on the dismantled EHA pump prototype. It is suggested that more attention should be given to the tilting inertia moment acting on the cylinder block of an EHA pump since both wear and leakage flow between the cylinder block and the valve plate are very much dependent on this tilting moment.     

Effects of splined shaft bending rigidity on cylinder tilt behaviour for high-speed electro-hydrostatic actuator pumps

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.     

Dynamic thermal coupling modeling and analysis of wet electro-hydrostatic actuator

The electro-hydrostatic actuator(EHA) used in more electric aircraft(MEA) has been extensively studied due to its advantages of high reliability and high integration. However, this high integration results in a small heat dissipation area, leading to high-temperature problems. Generally,to reduce the temperature, a wet cooling method of using the pump leakage oil to cool the motor is adopted, which can also increase the difficulty of accurately predicting the system temperature in the early desi...     

Analysis of the dynamic performance of an electro-hydrostatic actuator and improvement methods

As a kind of actuation mechanism for power-by-wire (PBW) actuation systems of more/all electrical aircraft, an electro-hydrostatic actuator (EHA) is a highly integrated local hydraulic actuation system. It is a volume control system consisting of a motor, a pump, an actuator, etc., which has features of high efficiency and reliability. However, the poor dynamic characteristic is one of the main factors restricting its wide application in aircraft. In this paper, the reason for the poor dynamic characteristic of an EHA is revealed from the perspectives of the natural frequency characteristic and the power requirement, respectively. In other words, the insufficiency of the motor output power at a high frequency is the main factor causing the poor dynamic characteristic of the system, and methods which include increasing the maximum output torque of the motor, reducing the rotational inertia of the motor-pump group, and adopting a double-motor-pump group configuration are proposed in this paper, by which the dynamic characteristic of the system can be improved. The feasibility of those methods are verified by simulations. Finally, the dynamic characteristic is tested on an EHA prototype, and results show that saturation of the output torque of the motor is the main factor restricting the dynamic characteristic of the EHA system.     

一体化电动静液作动器(EHA)的设计与仿真分析

一体化电动静液作动系统兼备传统液压作动系统和直接驱动的机电作动系统的优点,也就是同时具备高转距和大功率密度,并且易于模块化。本文阐述了一种一体化电动静液作动器(EHA)的总体结构和工作原理,对电机、泵和液压缸的选用以及系统设计提出了明确的要求,并对其各个模块进行了建模和仿真分析。结果表明,EHA的性能能够满足现代飞机对作动系统的要求,在未来功率电传(PBW)的飞控系统中具有很好的应用前景。     

High-performance EHA controls using an interior permanent magnetmotor

A controller for a high-performance electrohydrostatic actuator (EHA) using an interior permanent magnet (IPM) synchronous motor to produce servo motion is described. The buried-magnet design of the IPM motor yields desired characteristics such as high efficiency, robust rotor construction, and wide operating speed range. Power converter size is minimized by using insulated-gate bipolar transistor (IGBT) power switches combined with high-voltage integrated circuit (HVIC) gate drivers in phase-leg power modules. Experimental results for the demonstrator motor-controller hardware rated at 12 hp (continuous) are presented confirming the IPM motor drive's performance     

Modeling and control of a novel electro-hydrostatic actuator with adaptive pump displacement

The variable pump displacement and variable motor speed electro-hydrostatic actuator (EHA), one of the three types of EHAs, has advantages such as short response time, flexible speed regulation, and high efficiency. However, the nonlinearity of its double-input single-output system poses a great challenge for system control. This study proposes a novel EHA with adaptive pump displacement and variable motor speed (EHA-APVM). A closed-loop position is realized using a servomotor. Moreover, the displacement varies with the system pressure; thus, the EHA-APVM is a single-input and single-output system. Firstly, the working principles of the EHA-APVM and the pump used in the system are introduced. Secondly, a nonlinear mathematical model of the proposed EHA-APVM control system is established, and a feedback back-stepping (FBBS) control algorithm is introduced to transform the complex nonlinear system into a linear system on the basis of the back-stepping control theory. Finally, simulation results prove that the EHA-APVM has a quick response and high robustness to variations of the load and the pump displacement. In this work, the size and weight of the motor are significantly reduced because the maximum power requirement is reduced, which is very beneficial for using the actuator in airborne equipment.     

加强盘式转子支承设计技术

针对航空发动机高速转子支承结构设计难点,以某加强盘式结构的高压压气机试验件为研究对象,基于该试验件具有转子跨距长、质量大、轴向力大的设计特点,分析转子支承方案设计要求和转子动力特性影响因素,总结了转子支承设计技术特点和需求条件;开展支承方案的确立及筛选设计,采用通过理论和数值计算分析优选出的1-1-1型支承方案,综合优化支点跨距、转子质量、支承刚度和支点阻尼4个设计变量,满足全转速范围内的性能录取需求。结果表明:优化方案在工作转速范围内存在2阶临界转速并均处于性能录取转速以下,应变能分别为9.3%和16%。试验件最终顺利完成了全部转速下的性能参数录取,在试验过程中运行平稳,整体振动水平较低,轴向力始终处于轴承承载范围,验证了转子支承方案的合理性。     

驻室式处理机匣——内部流动及扩稳机理的数值研究

通过定常模拟的方法,研究了驻室式处理机匣对高负荷、高马赫数孤立转子性能的影响.结果表明:相同的处理机匣结构在不同的转速下取得的效果存在较大差异,在设计转速时,处理机匣并没有使风扇转子的失速裕度得到改善,并且效率下降约2.8%;在非设计转速时,处理机匣扩稳作用得到充分体现,转子稳定性得到较大程度的加强,并且没有导致转子性能的下降.通过对处理机匣内部流场的详细分析,揭示了驻室式处理机匣的扩稳机理.      

某轴流式血液泵的实验与改进设计

原型血液泵LAP-00的数值模拟及实验结果表明,在设计转速9000r/min下,最大效率点对应的设计点流量为11L/min,远大于临床所需38L/min的流量,致使血液泵在实际应用时效率偏低;而静子区域存在的流动分离与回流,极易造成血流停滞进而引发血栓.改进后的血液泵LAP-23,将设计转速从9000r/min降低至8000r/min,减小了转子叶尖切应力对血细胞的破坏;设计点流量降低至6L/min,并消除了静子区域内的分离和回流.      

小流量高速离心泵的一种优化方法

建立了小流量高速离心泵机组的性能预测模型 ,分析了轮盘直径和辅助系统出口压力对小流量高速离心泵系统效率的影响 ,并以其为设计变量 ,建立了以泵机组的效率作为目标值的优化设计方法 ,在此基础上对一小流量高速离心泵进行了优化设计 ,效果显著。本文所采用的设计方法对小流量高速离心泵的应用与发展有重要工程意义。     

对转发动机模拟低压转子动力特性研究

建立了对转发动机模拟低压转子动力特性有限元分析模型,对转子的动力特性—临界转速和振型进行了计算分析,在高速旋转试验器上完成了全转速范围内的动力特性验证试验,并对计算结果和试验结果进行了对比分析。研究表明:计算模型能反映模拟低压转子的真实动力特性,转子在额定工作转速范围内存在3阶弯曲临界转速,各阶临界转速均满足设计准则要求,各阶振型全部为弯曲振型,这是1个非常典型的带柔性轴的柔性转子。     

最小离地速度合格审定飞行试验优化方法研究

最小离地速度是制定起飞操作程序表的重要基准速度之一,而最小离地速度飞行试验又是民用飞机适航取证中的高风险科目之一.介绍了起飞速度制定过程中各起飞特征速度间的关系,分析研究了最小离地速度在起飞速度制定中的作用,提出了一种基于起飞速度制定原则的最小离地速度合格审定飞行试验的优化方法.该方法可以优化最小离地速度飞行试验安排,节省适航取证成本和时间.     

飞机电静液作动器滑模 PID控制器设计

在多电飞机应用环境中,由于电静液作动器（Electro Hydrostatic Actuator,以下简称EHA）系统本身的强非线性与承载交变动载荷的不确定性,简单PID控制无法达到理想控制效果。提出了滑模 PID复合控制,电机电流环和转速环构成控制系统内环,以PI控制器实现电机调速;作动筒位置环为外环,以滑模控制提升系统的快速性和鲁棒性。建立了EHA数学模型,并设计了滑模控制器结构。仿真结果表明,滑模 PID复合控制方法能有效地消除超调和减小跟随误差,实现对EHA位置的精确控制。     

对旋风机对旋叶轮级间流场的实验研究

采用实验方法对对旋风机对旋叶轮级间流场进行了研究。在改变级间间隙和前后级转速的情况下,采用五孔探针对级间压力场和速度场进行了了测量,并对结果进行了分析。研究表明:前后级动叶加功量的分配在对旋风机的气动设计中占有很重要的地位,这种分配可以通过转速的匹配来实现;在气动设计中,应增加对旋叶轮级间间隙的控制设计。      

虑及多转速的核心机转子高速动平衡试验

为满足航空发动机整机动平衡对转子不平衡振动精稳抑制的需求，采用虑及多转速状态的转子高速动平衡优化配平方 法，开展了核心机转子动平衡试验。以核心机转子系统为对象，研究在高压压气机转子第4、9级盘上配重抑制高压涡轮振动的可 行性。综合考虑核心机转子在多转速下的振动状态，以残余振动平方和及残余振动最大值为目标函数，采用优化算法对配平方案 进行优化，制定了核心机转子高速动平衡方案。在核心机转子系统试验台上分别进行了单平面-单转速、单平面-多转速、双平面- 单转速以及双平面-多转速动平衡的试验。结果表明：采用虑及多转速状态的转子高速动平衡优化配平方法能使因不平衡引起的 核心机转子振动在工作转速区间内均有所减小。     

一种新型液压泵变排量机构的设计与仿真

为提高一体化电液作动器(EHA)的性能,对新型EHA中广泛使用的变排量液压泵中的变量机构进行了优化设计。采用锥蜗轮蜗杆传动代替了原来的齿轮传动体系并与泵壳体进行了一体化设计,采用solidworks进行了三维实体化建模,运用AMESim搭建了改进前后EHA系统的仿真模型并进行对比分析。经过仿真实验,改进后的EHA系统在整体刚度提升了31%,频率响应提升了11.2%,显著改善了系统性能,验证了设计的正确性。     

Test sequencing problem arising at the design stage for reducing life cycle cost

Previous test sequencing algorithms only consider the execution cost of a test at the application stage. Due to the fact that the placement cost of some tests at the design stage is considerably high compared with the execution cost, the sequential diagnosis strategy obtained by previous methods is actually not optimal from the view of life cycle. In this paper, the test sequencing problem based on life cycle cost is presented. It is formulated as an optimization problem, which is non-deterministic polynomial-time hard (NP-hard). An algorithm and a strategy to improve its computational efficiency are proposed. The formulation and algorithms are tested on various simulated systems and comparisons are made with the extant test sequencing methods. Application on a pump rotational speed control (PRSC) system of a spacecraft is studied in detail. Both the simulation results and the real-world case application results suggest that the solution proposed in this paper can significantly reduce the life cycle cost of a sequential fault diagnosis strategy.     

结冰风洞试验水滴直径选取方法

结冰风洞是开展飞机结冰研究的主要设备,确定合理的试验水滴大小,是选取结冰风洞试验条件的重要内容。为了研究结冰风洞试验水滴直径的选取原则,针对结冰风洞试验水滴的大小主要取决于试验速度的大小,在推导结冰风洞试验水滴直径选取公式的基础上,用数值方法预测并对比了不同试验速度对水滴大小选取效果及试验结果的影响。采用欧拉法数值计算了不同试验速度及相应试验水滴条件下,试验模型表面的水滴收集率,并与全尺寸物体表面的水滴收集率进行了对比。研究发现:对于小水滴,当参考速度较低时,试验速度与参考速度的比值不能取得太低,参考速度升高到一定程度之后,试验速度与参考速度的比值又不能取得太高;对于大水滴,当参考速度较低时,试验速度与参考速度的比值也不能取得太低,当参考速度升高到一定程度之后,试验速度和相应试验水滴直径的改变对模型表面的水滴收集率影响较小,试验速度与参考速度的比值在0.3～1.0之间变动,均可以在模型和全尺寸物体上得到一致的水滴收集率。     

航空发动机滑片泵数值模拟

利用计算流体力学软件Star-cd二次开发功能模拟了某一航空发动机滑片泵的内部流场,分析了计算中是否引入空化模型对计算结果的影响,以及滑片泵定子和滑片间隙大小对滑片泵性能的影响,预测了不同工况下,滑片泵内出现空化的位置和区域大小.计算结果表明:由于滑片泵叶片转动,从而引起空化区域范围的缩小和增大,泵油量也相应地增加和减小,使得滑片泵进口瞬时流量较为平稳,而出口瞬时流量有较大的脉动,进、出口周期平均流量与计算总平均流量的误差小于1.5%,计算总平均流量与该滑片泵样件的台架实验测试结果之间的误差小于3%;滑片泵转子叶片与定子壁面间隙增大,泄漏量增加,滑片泵的平均流量减小;间隙为0.07mm的滑片泵计算总平均流量相对于间隙为0.02mm的计算总平均流量减小3.1%.从计算结果可以推断,滑片泵的进口流道应与吸油腔正对,可以减少进口流道内空化区域和流动阻力.