Nonlinear Mathematical Modeling and Sensitivity Analysis of Hydraulic Drive Unit

The previous sensitivity analysis researches are not accurate enough and also have the limited reference value, because those mathematical models are relatively simple and the change of the load and the initial displacement changes of the piston are ignored, even experiment verification is not conducted. Therefore, in view of deficiencies above, a nonlinear mathematical model is established in this paper, including dynamic characteristics of servo valve, nonlinear characteristics of pressure-flow, initial displacement of servo cylinder piston and friction nonlinearity. The transfer function block diagram is built for the hydraulic drive unit closed loop position control, as well as the state equations. Through deriving the time-varying coefficient items matrix and time-varying free items matrix of sensitivity equations respectively, the expression of sensitivity equations based on the nonlinear mathematical model are obtained. According to structure parameters of hydraulic drive unit, working parameters, fluid transmission characteristics and measured friction-velocity curves, the simulation analysis of hydraulic drive unit is completed on the MATLAB/Simulink simulation platform with the displacement step 2 mm, 5 mm and 10 mm, respectively. The simulation results indicate that the developed nonlinear mathematical model is sufficient by comparing the characteristic curves of experimental step response and simulation step response under different constant load. Then, the sensitivity function time-history curves of seventeen parameters are obtained, basing on each state vector time-history curve of step response characteristic. The maximum value of displacement variation percentage and the sum of displacement variation absolute values in the sampling time are both taken as sensitivity indexes. The sensitivity indexes values above are calculated and shown visually in histograms under different working conditions, and change rules are analyzed. Then the sensitivity indexes values of four measurable parameters, such as supply pressure, proportional gain, initial position of servo cylinder piston and load force, are verified experimentally on test platform of hydraulic drive unit, and the experimental research shows that the sensitivity analysis results obtained through simulation are approximate to the test results. This research indicates each parameter sensitivity characteristics of hydraulic drive unit, the performance-affected main parameters and secondary parameters are got under different working conditions, which will provide the theoretical foundation for the control compensation and structure optimization of hydraulic drive unit.

Variants of Secondary Control with Power Recovery for Loading Hydraulic Driving Device

Current high power load simulators are generally incapable of obtaining both high loading performance and high energy efficiency. Simulators with high energy efficiency are used to simulate static-state load, and those with high dynamic performance typically have low energy efficiency. In this paper, the variants of secondary control（VSC） with power recovery are developed to solve this problem for loading hydraulic driving devices that operate under variable pressure, unlike classical secondary control（CSC） that operates in constant pressure network. Hydrostatic secondary control units are used as the loading components, by which the absorbed mechanical power from the tested device is converted into hydraulic power and then fed back into the tested system through 4 types of feedback passages（FPs）. The loading subsystem can operate in constant pressure network, controlled variable pressure network, or the same variable pressure network as that of the tested device by using different FPs. The 4 types of systems are defined, and their key techniques are analyzed, including work principle, simulating the work state of original tested device, static operation points, loading performance, energy efficiency, and control strategy, etc. The important technical merits of the 4 schemes are compared, and 3 of the schemes are selected, designed, simulated using AMESim and evaluated. The researching results show that the investigated systems can simulate the given loads effectively, realize the work conditions of the tested device, and furthermore attain a high power recovery efficiency that ranges from 0.54 to 0.85, even though the 3 schemes have different loading performances and energy efficiencies. This paper proposes several loading schemes that can achieve both high dynamic performance and high power recovery efficiency.

Force Control Compensation Method with Variable Load Stiffness and Damping of the Hydraulic Drive Unit Force Control System

Each joint of hydraulic drive quadruped robot is driven by the hydraulic drive unit（HDU）, and the contacting between the robot foot end and the ground is complex and variable, which increases the difficulty of force control inevitably. In the recent years, although many scholars researched some control methods such as disturbance rejection control, parameter self-adaptive control, impedance control and so on, to improve the force control performance of HDU, the robustness of the force control still needs improving. Therefore, how to simulate the complex and variable load characteristics of the environment structure and how to ensure HDU having excellent force control performance with the complex and variable load characteristics are key issues to be solved in this paper. The force control system mathematic model of HDU is established by the mechanism modeling method, and the theoretical models of a novel force control compensation method and a load characteristics simulation method under different environment structures are derived, considering the dynamic characteristics of the load stiffness and the load damping under different environment structures. Then, simulation effects of the variable load stiffness and load damping under the step and sinusoidal load force are analyzed experimentally on the HDU force control performance test platform, which provides the foundation for the force control compensation experiment research. In addition, the optimized PID control parameters are designed to make the HDU have better force control performance with suitable load stiffness and load damping, under which the force control compensation method is introduced, and the robustness of the force control system with several constant load characteristics and the variable load characteristics respectively are comparatively analyzed by experiment. The research results indicate that if the load characteristics are known, the force control compensation method presented in this paper has positive compensation effects on the load characteristics variation, i.e., this method decreases the effects of the load characteristics variation on the force control performance and enhances the force control system robustness with the constant PID parameters, thereby, the online PID parameters tuning control method which is complex needs not be adopted. All the above research provides theoretical and experimental foundation for the force control method of the quadruped robot joints with high robustness.

Analysis of nonlinearities and effects in direct drive electro-hydraulic position servo system

The direct drive electro-hydraulic servo system is a new approach hydraulic system. It is much smaller and easier controlled than traditional systems and is a perfect energy saver. This paper will briefly introduce the popular nonlinearities in the electro-hydraulic system and analyse the effect of nonlinearities in direct drive electro-hydraulic position servo system by means of simulation research. Some valuable conclusions are given.

Tri-state Modulation Power Driving of Electro-hydraulic Proportional Amplifier

Switch electro-hydraulic proportional amplifier（PA） widely employs single switch modulation power driving（SSMPD） or reverse discharging power driving（RDPD） at present. SSMPD has slow dynamic response, and can＇t adjust independently the dither signal＇s amplitude and frequency; RDPD accelerates the current decay; consequently, it increases current ripple and power loss. For the purpose of solving the above mentioned problem, the tri-state modulation power driving（TSMPD） scheme was proposed for improving the performance of power driving. Detailedly, the hardware circuit for the tri-state modulation power driving is designed; the tri-state modulation algorithm is realized by digital signal processor（DSP）. The tri-state modulation power driving is investigated by experiments, comparetive experiments among the single switch modulation power driving（SSMPD）, reverse discharging power driving（RDPD）, and the TSMPD are implemented, and the experimental results demonstrate that the linearity error of TSMDP meets the requirement of PA; the current response of TSMSP is the best; the amplitude of ripple current of the TSMPD can be reduced without increasing frequency of PWM, in addition, dither signal amplitude and frequency can be adjusted independently for each other. It is very meaningful to guide the development of high performance proportional amplifier for high frequency response proportional solenoid.

The extending length calculation of hydraulic drive non-metallic completion screen pipe running into ultra-short radius horizontal well

Focusing on the extending length restriction of the completion screen pipe resistance running into ultra-short radius horizontal well,this paper proposed technology of hydraulic drive completion tubular string running into ultra-short radius horizontal well.Innovative hydraulic drive tools and string structure are designed,which are composed of guide tubing,hydraulic drive tubing and non-metallic completion screen pipe from inside to outside.A novel mechanical-hydraulic coupling model is established.Based on the wellbore structure of an ultra-short radius horizontal well for deep coalbed methane,the numerical calculations of force and hydraulic load on tubular strings were accomplished by the mechanical-hydraulic coupling model.The results show that the extending length of completion tubular string with the hydraulic drive is 17 times that of conventional completion technology under the same conditions.The multi-factor orthogonal design is adopted to analyze the numerical calculations,and the results show that the extending length of the completion tubular string is mainly affected by the completion tubular string structure and the friction coefficient between the non-metallic composite continuous screen pipe and the wellbore.Two series of hydraulic drive completion tubular string structures suitable for ultra-short radius horizontal wells under different conditions are optimized,with the extending limits of 381 m and 655 m,respectively.These researches will provide theoretical guidance for design and control of hydraulic drive non-metallic composite continuous completion screen pipe running into ultra-short radius horizontal wells.

The dynamic running law study on driving system of hydraulic winder

Dynamic running law of the hydraulic driving system decides the hoisting cage velocity curve in a hoisting cycle and is decided by the characteristic of the hydraulic driving system and by the operating speed of hoist driver. The paper studies the dynamic running law of hydraulic driving system, analyses the influence of driver operating speed on the dynamic running characteristic, and points out the reasonable driver operating speed to control the dynamic stress in rope and to reduce the oscillation of rope system.

丘陵山地果园全液压遥控式履带动力底盘设计与试验

针对目前丘陵山地果园作业农用底盘整机体积大、行驶作业操作繁琐和通过性差等问题,结合丘陵山地果园开沟、除草和修剪等农艺管理环节的实际需求,设计了一款全液压遥控式履带动力底盘。首先,对动力底盘的整机结构和工作原理进行了阐述;其次,对前置挂载机构、行走系、变幅宽底盘、液压系统、遥控系统等关键部件进行设计和相应的匹配选型;最后,对整机进行了性能试验。试验结果表明:动力底盘在最小幅宽(1220 mm)和最大幅宽(1620 mm)的直线行驶偏移率分别为2.24%和2.2%,均满足相应国家标准(≤6%)要求。底盘的转向机动性能良好,最小幅宽原地转弯半径为905 mm,可适应丘陵山地果园相对狭窄的坡地作业环境。遥控操作上下斜坡、翻越田埂、跨越畦沟等过程平稳,满足丘陵山地果园非结构化地形行走要求。挂载链式开沟器进行开沟作业时,沟深稳定系数为88.5%,沟宽稳定系数为92.5%,满足国家标准(≥85%)要求。整机工作性能满足丘陵果园复杂坡度地形管理作业要求,可为丘陵山地果园田间管理作业的有效实施提供综合应用平台和技术支撑。

多轴分布式电驱动车辆电液复合制动控制研究

针对多轴分布式电机驱动车辆电液复合制动中易出现的车辆制动抖动问题,提出了一种建压阶段电机制动力修正策略和一种基于前馈-反馈的协调控制策略,分别在建压阶段和其他阶段通过协调复合制动力来解决制动抖动的问题。针对防抱死控制系统与电机制动系统共同作用时的制动矛盾,提出了一种基于PID控制的ABS控制策略,主要通过改变电机制动力来解决制动矛盾的问题。通过TruckSim、Matlab/Simulink及AMESim联合仿真验证,制动冲击度在建压阶段下降了20.66%,在电机退出阶段下降了92.59%,驾驶感觉得到明显改善。而ABS控制策略也可在保证理想滑移率的同时完成制动能量回收;结合整车制动试验,表明协调控制策略在保证制动效果良好的同时实现了制动能量回收,效果显著。

玉米收获机HMT液压驱动系统的设计与试验研究

玉米是我国重要的粮食作物之一,在我国各个地区都有种植,种植面积相对较大。农业机械化属于极为重要的基础条件,可为保障国内粮食的高产、稳定与安全发挥重要作用,在推进农业可持续发展方面具备显著的现实意义。目前,玉米收获机传动机构多为机械传动,在进行玉米收获时不能进行实时监测与在线控制,自动化及智能化程度较低,影响玉米收获质量与农业生产效率。为此,针对玉米收获机的机械传动系统进行优化,采用HMT液压驱动系统替代传统的机械传动系统,并通过AMESim进行玉米收获机传动系统的仿真分析,验证设计的适用性与合理性。

液电混动履带底盘电液系统联合仿真与试验

针对传统以液压驱动或纯电驱动的履带式农机装备功耗大、系统响应慢、电池续航短、功率扭矩输出不足等问题,本文提出了一种高效液电混动履带式行走底盘,集成了液压驱动和电驱动两套独立动力系统,双液压马达及双伺服电机的四轮驱动结构,可实现整机大扭矩输出,利于整机轻量化设计;通过伺服电机速度及力闭环控制,适应匹配底盘外负载的变化,可显著改善闭式液压驱动系统的动态输出特性,提高整机动态控制性能并降低工作能耗。基于AMESim与Matlab建立了电液混动系统的联合仿真模型,对比分析整机在平地直线行驶、山地爬坡、原地转向等不同工况的行驶动态性能,试验结果表明所设计的液电混合驱动履带底盘最大行驶速度可达1.1 m/s,原地转弯时间最快为2.4 s,最小转弯直径为150 cm,可实现丘陵山地复杂地形转弯及调头;履带底盘直线行驶偏移率不大于3.3%;在相同工况下与液压驱动相比,液电混合动模式下整机能耗可减少9.3%,提高了整机工作效率。

基于变量马达控制的喷雾机驱动防滑系统设计与试验

高地隙自走式喷雾机因其作业环境复杂易产生车轮滑转,影响静液压驱动系统流量及压力稳定性,严重时导致整机失去通过性能,故须进行防滑控制,保证其具备驱动稳定性和脱困能力。本文提出一种高地隙自走式喷雾机静液压驱动系统防滑控制方法,采用双线性模型定义滑转率与附着系数之间的关系,设计了滑模控制器,并通过田间非道路试验验证了驱动防滑系统的控制性能。试验结果表明,该系统可将喷雾机滑转率控制在0.15以内。在起步加速与匀速工况下,喷雾机滑转率均值为0.020和0.019;在越沟工况下,可2 s内实现整机快速脱困。以上结果验证了所设计的喷雾机滑模驱动防滑系统具有良好的防滑性能,能够保证喷雾机在典型工况下平稳行驶,有效减少了地面不利条件对整机行驶稳定性的影响。

一种液压驱动顶驱下套管装置的研制与应用

随着顶驱技术的发展和广泛应用,我公司研制了一种液压驱动的顶驱下套管装置,该装置顶端与顶驱主轴连接,通过驱动油缸驱动楔形卡瓦卡紧套管,结合顶驱的旋转和起下功能,完成下套管作业。下套管装置设计有芯轴密封结构,该结构能够与套管内孔形成密封,可在下套管同时进行泥浆循环,减少了下套管作业时井内事故的发生。该装置目前已完成42口井下套管作业,作业成功率100%,下套管装置应用降低了工人劳动强度、提升了下套管作业效率和下套管作业成功率。

某型船用大功率液控离合器传动系统联合仿真研究

进行了有关船用大功率液压驱动齿式离合器运动学及接触动力学的Adams和AMESim联合仿真流程研究,并进行了联合仿真交互操作界面开发,在给定参数下,能够输出可视化的计算结果。仿真分析结果表明,齿式离合器轴向接合过程的动态特性与冲击载荷受到主动端扭转刚度与轮齿端面结构的影响;减压阀最大开口压力为2.5 MPa,该压力下的最大推力为1.884×10^(5) N;在内外圈发生碰撞时,油压会急速上升,如果减压阀的流量不足,则进油油路会泄漏。经过多次联合仿真发现,进口压力在0.008~0.01 MPa就能实现在4 s左右完成离合器的接合脱开过程。

双马达混合驱动及汇流结构研究

针对应急抢险、军事后勤等用途对轮式工程机械高速机动性能的特殊需求,结合其结构特点,提出一种双马达混合驱动系统方案,并分析其传动原理。以某轮式工程机械底盘为对象,以实现机动性能和动力性能为目标,对传动参数设计、液压泵、马达选型计算等进行系统分析。根据设计计算结果,完成了汇流齿轮箱的结构设计,展示了系统总体结构,并对关键承载件进行了结构和模态分析。结果显示:整机最高车速可达70 km/h,最大爬坡度31°,具备Ⅳ级以上路面高速越野机动能力。

压缩空气储能发电频率特性分析

当前阶段,我国主要的电力来源是煤、石油和天然气这三种广泛使用的传统能源。未来,我国火电发电的量将在很长一段时间内保持下降的趋势,将会难以满足调峰以及调频的需求,因此,储能是解决电力供需平衡的有效手段。压缩空气储能是一种容量较大的储能技术,在压缩空气储能技术的背景下,研究了一种将液体作为驱动介质,利用高压压缩空气进行发电的方法。在系统中建立了压缩空气的热力学模型、液压马达的数学模型以及同步发电机的数学模型,并将这些模型在Simulink中进行仿真搭建,分析了储气罐压力和马达排量对于系统中马达转速的影响,并对这些参数进行设计选取,针对马达转速波动过大无法并网发电的问题,采取传统PID的方法来减小马达的转速波动,稳定系统的输出,保证发电机的平稳运行。

变排量液压马达旋转驱动系统角位移控制技术

变排量液压马达旋转驱动系统具有效率高、响应快、高负载匹配性、低功率需求等优势,能够大幅提高飞机液压旋转驱动系统的效率。为实现对变排量液压马达旋转驱动系统的精确控制,需开展系统角位移控制技术研究。建立了系统的数学模型,搭建了AMESim仿真模型,分析了系统的运动特性及频域控制特性,提出了由排量回路、转速回路和角位移回路组成的三闭环串级控制方案,研究了不同控制参数对系统控制特性的影响。研究结果表明,双闭环控制无法满足旋转驱动系统的稳定条件,三闭环控制引入转速负反馈克服了双闭环控制中角位移对转速的正反馈效应,增大了位置回路的阻尼,能实现系统稳定控制。同时研制了原理样机并进行了测试验证,测试数据表明,三闭环控制方案能实现旋转驱动系统高精度位置控制,为变量马达在飞机液压旋转驱动系统中的应用提供了参考。

液压足式机器人关节驱动系统实验台研究

为测试液压足式机器人关节驱动系统的控制性能,实现对外负载力的精确模拟并研究高性能控制策略,设计液压足式机器人关节驱动系统实验台。介绍了关节驱动系统实验台的工作原理、机械结构、液压系统及测控系统;在MATLAB/Simulink平台中建立了关节驱动系统实验台仿真模型,通过仿真分析,验证了实验台的负载模拟能力及控制性能。研究结果表明,实验台能够实现负载力加载并实现精确控制,为后续液压足式机器人关节驱动系统的研究提供平台。

多级径向涡轮水力驱动套管鞋在海上油田的应用

为解决大斜度井、水平井井段套管下入困难、下不到位的难题,同时提高井眼质量与固井效率,研制出一种多级径向涡轮水力驱动套管鞋。该工具由定子总成、转子总成以及轴承系统三大模块组成,定子与转子互相配合,利用水力驱动,通过多级专用的径向涡轮增大驱动扭矩,配合外侧镶嵌有合金齿的螺旋筋条,增强耐磨、修整井眼和扩眼的能力。该工具长度为传统涡轮结构套管鞋的1/3~1/5,结构简单可靠,尺寸紧凑,通过狗腿度能力强,输出扭矩可达传统划眼工具的5~10倍。多口现场案例井作业表明,该工具可保障复杂井段套管安全下入到位,大幅减少固井过程中的非生产作业时间和通井时间。

泵控直驱式线控制动单元的设计与分析

为简化传统汽车制动系统结构,更好地满足智能网联汽车对制动力快速调节的需求,提出了一种泵控直驱式线控制动单元,采用泵控直驱容积伺服技术,通过伺服电机直接驱动双向齿轮泵,实现对制动轮缸压力的控制和快速调节,消除阀控系统的节流损失,有效提升系统效率。在泵控直驱式线控制动单元参数设计及数学建模的基础上,试制了制动单元样机与性能测试平台,分析了轮缸压力变化的响应曲线以及跟随特性。仿真和试验结果证明了泵控直驱式线控制动单元的可行性,12 MPa压力阶跃响应时间为200 ms,系统具有良好的响应速度和稳定性,为线控制动技术提供了一种新的实施方案。