LVP Modeling and Dynamic Characteristics Prediction of A Hydraulic Power Unit in Deep-Sea

A hydraulic power unit （HPU） is the driving ＂heart＂ of deep-sea working equipment. It is critical to predict its dynamic performances in deep-water before being immerged in the seawater, while the experimental tests by simulating deep-sea environment have many disadvantages, such as expensive cost, long test cycles, and difficult to achieve low-temperature simulation, which is only used as a supplementary means for confirmatory experiment. This paper proposes a novel theoretical approach based on the linear varying parameters （LVP） modeling to foresee the dynamic performances of the driving unit. Firstly, based on the varying environment features, dynamic expressions of the compressibility and viscosity of hydranlic oil are derived to reveal the fluid performances changing. Secondly, models of hydraulic system and electrical system are accomplished respectively through studying the control process and energy transfer, and then LVP models of the pressure and flow rate control is obtained through the electro-hydraulic models integration. Thirdly, dynamic characteristics of HPU are obtained by the model simulating within bounded closed sets of varying parameters. Finally, the developed HPU is tested in a deep-sea imitating hull, and the experimental results are well consistent with the theoretical analysis outcomes, which clearly declare that the LVP modeling is a rational way to foresee dynamic performances of HPU. The research approach and model analysis results can be applied to the predictions of working properties and product designs for other deep-sea hydraulic pump.

Dynamic characteristics of hydraulic power steering system with accumulator in load-haul-dump vehicle

Using hydraulic power steering system of model EIMCO 922 load-haul-dump vehicle as a simulation example, the dynamic characteristics of hydraulic power steering system in load-haul-dump vehicle were simulated and discussed with SIMULINK software and hydraulic control theory. The results show that the dynamic characteristics of hydraulic power steering system are improved obviously by using bladder accumulator, the hydraulic power steering system of model EIMCO 922 load-haul-dump vehicle generates vibration at the initial stage under the normal steering condition of pulse input, and its static response time is 0.25 s shorter than that without bladder accumulator. Under the normal steering working condition, the capacity of steering accumulator for absorbing pulse is directly proportional to the cross section area of connecting pipeline, and inversely proportional to the length of connecting pipeline. At the same time, the precharge pressure of nitrogen in steering accumulator should be 60%80% of the rated minimum working pressure of hydraulic power steering system. Under the abnormal steering working condition, the steering cylinder piston may obtain higher motion velocity, and the dynamic response velocity of hydraulic power steering system can be increased by reducing the pressure drop of hydraulic pipelines between the accumulator and steering cylinder and by increasing the rated pressure of hydraulic power steering system, but the dynamic characteristics of hydraulic power steering system in load-haul-dump vehicle have nothing to do with the precharge pressure of nitrogen in steering accumulator.

Optimization Study on Expansion Energy Used Air-Powered Vehicle with Pneumatic-Hydraulic Transmission

Pneumatic-hydraulic transmission has been developed for years. However, its dynamic properties are not good enough for application. In this paper, in order to increase the output characteristics, a late-model air-powered vehicle using expansion energy is proposed which can boost energy through a pneumatic-hydraulic transmission. The dynamic characteristics of the air-powered vehicle is modeled and verified by conducting experiment. In addition,the influence of the key parameters of the air-powered vehicle is researched for the optimization of the system performance. Through the results, the author got the conclusion that, firstly, comparison of the results of model and experiment proves the built model to be effective; secondly, input air pressure should be set according to the request of the practical loads, and range of 0.65 to 0.75 MPa can be chosen; thirdly, as a key structure parameter of the airpowered vehicle, ratio of the areas is considered to be set to approximate 8; what’s more, a bigger orifice with a limit will promote the system dynamic characteristic property, and the limit is about 3.5 mm; last but not the least, not too farther position of the rings will increase the quality of output dynamic characteristics. This paper can be a reference for system design of air-powered vehicle and dynamic improvement.

Site Earthquake Characteristics and Dynamic Parameter Test of Phase Ⅲ Qinshan Nuclear Power Engineering

The earthquake characteristics and geological structure of the site to sitting the Qinshan Nuclear Power Station are closely related. According to site investigation drilling, sampling, seismic sound logging wave test in single-hole and cross-hole, laboratory wave velocity test of intact rock, together with analysis of the site geological conditions, the seismic wave test results of the site between strata lithology and the geologic structure were studied. The relationships of seismic waves with the site lithology and the geologic structure were set up. The dynamic parameters of different grades of weathering profile were deduced. The results assist the seismic design of Phase Ⅲ Qinshan Nuclear Power Plant, China.

机械反馈式伺服阀流量测试动态缸参数选用分析

相比电反馈伺服阀动态特性可直接通过阀芯位移响应测试获得,机械反馈式流量伺服阀的动态特性,通常需利用动态缸作为流量传感器间接测量获得。测试结果受动态缸泄漏、阻尼、质量惯性等固有非理想化因素的影响,通常无法准确表达伺服阀本身的性能指标。基于一套实际阀控缸系统,建立Matlab-Simulink仿真模型,解析获得的频带宽结果相比实测结果误差小于0.5%,由此建立了可准确表达阀与缸性能特性的仿真模型。在此基础上,理论给出了伺服阀本身的频率特性指标,即无泄漏无阻尼及无限刚度动态缸条件下的系统频率特性。以此为依据,分析了实际动态缸活塞质量、活塞粘性阻尼以及泄漏变化情况下,阀控缸系统频率特性偏离理想条件的变化规律。

水电机组轴系-调速耦合系统动态特性分析

水电机组轴系-调速耦合系统动态特性尚未揭示,制约机组调节优化控制。为此,建立了水电机组不同运行模式轴系-调速耦合系统非线性数学模型,研究分析了耦合系统的非线性动态响应特性。首先,采用Hopf分岔理论分析调速系统稳定域和分岔特性。进一步,仿真分析机组不同运行模式轴系-调速耦合系统的时频动态响应特性。结果表明:机组孤网和并网运行调速系统均存在超临界Hopf分岔,机组并网模式调速器参数稳定域较孤网模式增大。机组并网模式调速系统机组、电网频率动态响应存在多频特性,轴系振动会引发调压室水位动态响应超超低频振荡。并网与孤网模式相比并网模式系统动态响应超调量增大,调节时间缩短。机组孤网和并网运行轴系振动均为多频拟周期振动,但孤网模式轴系振动特性更复杂。

应用AMESim双转向器全液压转向系统特性分析

为全液压转向系统设置双转向器可以解决大排量需求的问题,但此种布置会影响系统的动态响应特性,因此分析系统的可行性。根据某自卸车全液压转向系统的结构特点,对单转向器系统的关键参数进行分析和设计,获取各参数的数值;根据车辆转向参数的需求,对转向系统的压力损失和温升进行校核,以验证系统可否满足需求;根据前述分析,采用AMESim搭建分析模型,通过转角输入验证模型准确性,并验证负载、输入变化对系统特性的影响;基于转向系统试验台,通过输出特性分析,对前述设计和分析模型进行验证。结果可知:双转向器系统压力损失满足要求,最高温升控制在56.8℃,控制在系统要求的范围内;影响双转向器系统输出特性和油液流量的因素主要是方向盘转速和系统负载,其他因素基本无影响,仅对系统的响应时间产生影响;试验测试平台获取的角速度阶跃输入下的,转向器输出口压力、流量放大器输出口流量与仿真分析结果误差控制在5%以内,表明分析模型和结果的可靠性,为此类分析设计提供参考。

快速功率波动下大型定/变速机组的响应特性研究

本文对定速机组和变速机组应对快速功率波动时的响应情况进行了对比仿真,研究了九种不同大小、不同频率的功率波动下定速机组和变速机组的响应情况,并利用功率差的平均值、标准值、功率上升(下降)响应时间的平均值、功率延迟时间这四个量化评估指标对定速机组和变速机组的功率响应特性进行了具体分析。结果表明变速机组不仅能有效应对秒级时间内快速波动的新能源出力,对快速新能源出力波动的响应能力也远优于传统定速机组,进一步说明了变速机组应对新能源波动的有效性。

Biomimetic Lightweight Design of Legged Robot Hydraulic Drive Unit Shell Inspired by Geometric Shape of Fish Bone Rib Structure

The lightweight design of hydraulic quadruped robots,especially the lightweight design of the leg joint Hydraulic Drive Unit(HDU),can improve the robot's response speed,motion speed,endurance,and load capacity.However,the lightweight design of HDU is a huge challenge due to the need for structural strength.This paper is inspired by the geometric shape of fish bones and biomimetic reinforcing ribs on the surface of the HDU shell are designed to increase its strength and reduce its weight.First,a HDU shell with biomimetic fish bone reinforcing ribs structure is proposed.Then,the MATLAB toolbox and ANSYS finite element analysis module are used to optimize the parameters of the biomimetic reinforcing ribs structure and the overall layout of the shell.Finally,the HDU shell is manufactured using additive manufacturing technology,and a performance testing platform is built to conduct dynamic and static performance tests on the designed HDU.The experimental results show that the HDU with biomimetic fish bone reinforcing ribs has excellent dynamic performance and better static performance than the prototype model,and the weight of the shell is reduced by 20%compared to the prototype model.This work has broad application prospects in the lightweight and high-strength design of closed-pressure vessel components.

基于深度学习的异步风力发电机组功率振荡抑制方法

由于引起异步风力发电机组功率振荡的因素较多,难以保障功率振荡抑制的效果,为此,提出基于深度学习的异步风力发电机组功率振荡抑制方法的研究。从风力机动态特性、发电机组动态特性以及传动链动态特性3个角度分析了异步风力发电机组功率振荡状态,借助长短期记忆网络实现对振荡的有效抑制。在测试结果中,设计的振荡抑制方法应用效果不仅更高效,且对于基础振荡幅度的控制效果更好。

含定速与变速机组的抽水蓄能电站一次调频动态特性研究

鉴于含定速与变速机组的抽水蓄能电站安全、稳定、高效联合运行是充分发挥变速机组技术优势的关键,基于数值仿真方法,开展含定速与变速机组的抽水蓄能电站一次调频动态特性研究。首先建立含定速与变速机组的抽水蓄能电站一次调频仿真模型,然后分析定速与变速机组单独运行一次调频动态特性,最后分析定速与变速机组联合运行一次调频动态特性。结果表明,相同的调速器和变频器参数下,变速机组频率阶跃减的幅值越大,动态响应时间越长、速度越快;频率阶跃增幅值越大,动态响应时间越短、速度越快;定速与变速机组联合运行可提高定速机组的出力和有功功率动态响应速度及变速机组的出力动态响应速度,但对变速机组的有功功率动态响应速度的影响较小。

某型航空发动机抗电源失效设计与试验验证

为应对外部电源可能出现的失效问题,某航空发动机控制系统开展电子控制器储能电路设计,并选用具有零偏功能的电液伺服阀。通过改造台架电源配置、增加延时继电器,实现模拟电源短时中断50ms和完全失效功能。整机电源失效试验表明,某航空发动机电子控制器CPU在外部电源短时中断50ms条件下可保持稳定工作,可取消配套应急电源设备;在电源完全失效情况下可通过切断关闭主燃油、调节几何角度使发动机安全停车,发动机性能和操纵性未发生变化,满足飞机使用要求。

抽水蓄能发电机组转子自动化动平衡试验方法

针对抽水蓄能发电机组转子动平衡试验依赖人工经验反复进行试验,过程繁冗且周期较长的问题,提出一种抽水蓄能发电机组转子自动化动平衡试验方法。该方法主要包括转子动平衡数据处理算法、转子动平衡试验算法、转子动平衡影响系数计算算法,辅助技术人员实施配重。转子动平衡试验测试结果表明,该方法仅需两次配置,便实现了抽水蓄能发电机组转子动平衡参数的调整,相较于传统的人工调整方式,不仅减少了试验次数,还提高了试验效率。

液压电机叶片泵样机的性能试验

针对研制出的液压电机叶片泵样机,建立了电机泵性能试验系统,获得了样机的输入电量参数、输出液压能参数及内部转子转速和壳体内部压力等参数,得到了液压电机叶片泵样机的转子转速、噪声、功率和效率等随输出压力变化的特性,并与同等功率液压电机油泵组的试验结果进行了对比。与电机油泵组相比,电机叶片泵样机的体积减小50%、轴向尺寸减小61%,噪声降低约7 dB,液压电机叶片泵内部转子转速随输出压力升高而明显下降;同时,试验也发现样机存在内部流道狭窄引起的气泡析出和内部密封不良引起额外泄漏的问题,提出了相应的解决方法,为电机泵的后续优化及工业化提供了参考依据。

NF-6风洞洞体有限元计算与水压试验

简要介绍了西北工业大学翼型研究中心NF 6高速增压连续式风洞洞体基于有限元方法的应力应变静态和动态特性分析,并与风洞水压试验结果进行对比。结果表明,有限元计算中所采用的结构和边界条件简化方法合理可行,在数量级和变化趋势上,实测点和对应计算点的应变值比较一致,最大应力在材料的许用应力之内,实际风洞洞体及支撑是安全的,风洞的前三阶振动模态分析为风洞的安全运行提供了参考依据。

大功率拖拉机电液提升器比例下降阀仿真与优化

为改善液压系统响应特性,提高控制精度,基于状态空间法,建立了大功率拖拉机电液提升器比例下降阀的动态数学模型及仿真模型,在Matlab/Simulink中进行仿真及参数优化设计,选用四阶龙格库塔算法,得到阀结构参数和性能参数对开闭过程、流量变化动态特性的影响。最终确定先导阀阻尼孔直径为1.0 mm,主阀阻尼孔直径为1.2 mm,主阀大端直径为20 mm,先导阀阀芯直径为8 mm。

自动发电控制优化控制策略研究与应用

针对江苏利港电力有限公司2台350MW直吹式机组,在对机组动态特性进行分析及对原AGC控制方案进行研究的基础上,提出新型的AGC优化控制策略。仿真和实际运行表明,改进后的新型AGC优化控制策略可最大限度地利用锅炉蓄热并尽可能加快锅炉的负荷主控指令,有效提高机组负荷的升、降速率。对机组所能达到的最大负荷升、降速率进行分析,并提出评估和提高机组负荷升、降速率的一般性准则。

直驱容积控制电液伺服系统模型与动态特性

为了研究直接驱动容积控制电液伺服系统动态响应特性不高的原因,分别建立直驱容控电液驱动系统的电机控制、液压动力机构和液压执行机构等子系统的力学模型,并建立直驱容控电液伺服作动器的数学模型.利用MATLAB软件对系统主要部件进行数值仿真分析.结果表明,系统动态特性不高的根本原因是泵控动力机构的动态特性不高.对系统各组成部件的动态特性进行了分析,并提出改进系统性能的措施与策略.

惯性通道-解耦膜式液压悬置动特性分析

本文以Audi 100轿车动力总成液压悬置为例,建立了惯性通道-解耦膜式液压悬置的非线性力学模型和数学模型,对其原点动特性和跨点动特性进行了仿真计算,经与试验结果相比较,二者吻合良好。文中深入分析了各参数对动特性的影响规律,初步提出了惯性通道-解耦膜式液压悬置的参数选择原则。

国内外混合式断路器发展与研究现状

混合断路器综合了传统开关的优点,克服了各自的缺点,是未来智能电网的发展趋势与研究热点。为此探讨了国内外混合断路器的发展与研究现状,并根据混合断路器的结构及工作原理对其进行了分类,重点对基于真空与SF_6串联构成的混合断路器及基于电力电子的混合断路器的工作原理、结构型式、应用领域及发展趋势进行了综述,基于真空与SF_6串联的混合断路器的动态绝缘特性、操动机构精度及最佳协同控制策略的研究,将推进其在高压大电流领域的应用。基于电力电子开关的混合断路器的电流转移特性、快速操动结构及短路开断控制策略等关键技术的突破,将为其在低压直流开断领域的应用奠定基础。