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.

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.

A practical nonlinear robust control approach of electro-hydraulic load simulator

This paper studies a nonlinear robust control algorithm of the electro-hydraulic load simulator （EHLS）. The tracking performance of the EHLS is mainly limited by the actuator＇s motion disturbance, flow nonlinearity, and friction, etc. The developed controller is developed based on the nonlinear motion loading model. The problems of the actuator＇s disturbance and flow nonlinearity are considered. To address the friction problem, the friction model of the loading motor is identified experimentally. The friction disturbance is compensated using the obtained friction model. Therefore, this paper considers the main three factors comprehensively. The developed algorithm is easy to apply since the controller can be obtained just with one step back-stepping design. The stability of the developed algorithm is proven via Lyapunov analysis. Both co-simulation and experiments are performed to verify the effectiveness of this method.

Study on Friction Torque Loading with an Electro-hydraulic Load Simulator

This article, in order to precisely impose friction on aircraft and weapon actuation systems, presents a new friction loading method characteristic of ＂torque-zero velocity＂ switching control with an electro-hydraulic load simulator. As the general Stribeck friction model has little related to static friction, it proposes a ＂torque-zero velocity＂ switcher, in which a zero-velocity controller is developed to load the static friction and a torque controller the kinetic friction. With the help of mathematical modeling, this article designs a ＂torque-zero velocity＂ switching controller and, correspondingly, provides a ＂dual-threshold judgment＂ algorithm. Simulation results indicate that the proposed method can be successfully used to carry out the static and kinetic friction simulation with an electro-hydraulic load simulator.

Adaptive Nonlinear Optimal Compensation Control for Electro-hydraulic Load Simulator

Directing to the strong position coupling problem of electro-hydraulic load simulator (EHLS), this article presents an adaptive nonlinear optimal compensation control strategy based on two estimated nonlinear parameters, viz. the flow gain coefficient of servo valve and total factors of flow-pressure coefficient. Taking trace error of torque control system to zero as control object, this article designs the adaptive nonlinear optimal compensation control strategy, which regards torque control output of closed-loop controller converging to zero as the control target, to optimize torque tracking performance. Electro-hydraulic load simulator is a typical case of the torque system which is strongly coupled with a hydraulic positioning system. This article firstly builds and analyzes the mathematical models of hydraulic torque and positioning system, then designs an adaptive nonlinear optimal compensation controller, proves the validity of parameters estimation, and shows the comparison data among three control structures with various typical operating conditions, including proportion-integral-derivative (PID) controller only, the velocity synchronizing controller plus P1D controller and the proposed adaptive nonlinear optimal compensation controller plus PID controller. Experimental results show that systems' nonlinear parameters are estimated exactly using the proposed method, and the trace accuracy of the torque system is greatly enhanced by adaptive nonlinear optimal compensation control, and the torque servo system capability against sudden disturbance can be greatly improved.

An experimental study of the dual-loop control of electro-hydraulic load simulator (EHLS)

This paper investigates motion coupling disturbance（the so called surplus torque）in the hardware-in-the-loop（HIL）experiments.The＇＇velocity synchronization scheme＇＇was proposed by Jiao for an electro-hydraulic load simulator（EHLS）in 2004.In some situations,however,the scheme is limited in the implementation for certain reasons,as is the case when the actuator＇s valve signal is not available or it is seriously polluted by noise.To solve these problems,a＇＇dual-loop scheme＇＇is developed for EHLS.The dual-loop scheme is a combination of a torque loop and a position synchronization loop.The role of the position synchronization loop is to decouple the motion disturbance caused by the actuator system.To verify the feasibility and effectiveness of the proposed scheme,extensive simulations are performed using AMESim.Then,the performance of the developed method is validated by experiments.

灯泡贯流式水轮机增减负荷动态特性分析

水轮机频繁经历变负荷工况转换过程,使得机组在较短时间内工作参数急剧变化,严重影响电站稳定运行。该研究以某贯流式水轮机为研究对象,在考虑自由液面和水体重力的情况下,采用动网格技术对贯流式水轮机相同出力范围下的减、增负荷过渡过程的动态特性进行分析。研究结果表明:由于增负荷和减负荷过渡过程的起始工况导致起始流动状态不同,因此在相同出力时,机组内的流动分布不同,减负荷过程尾水管内的涡流面积及强度明显小于增负荷工况,且尾水管涡带尺度也明显小于增负荷过程;相比于增负荷过程,减负荷过程中转轮叶片大范围的低压区极易引发空化;机组内的水压力脉动主要以尾水管涡带引起的0.1f_n(f_n为转频)低频压力脉动和转轮的旋转引起3f_n的高频压力脉动为主,增负荷过程的压力脉动幅值明显大于减负荷过程,两种压力脉动共同作用,使得贯流式水轮机主要振动区域集中于转轮。研究结果对贯流式水轮机的设计与运行具有一定的指导意义。

Nonlinear Adaptive Robust Force Control of Hydraulic Load Simulator

This paper deals with the high performance force control of hydraulic load simulator. Many previous works for hydraulic force control are based on their linearization equations, but hydraulic inherent nonlinear properties and uncertainties make the conven- tional feedback proportional-integral-derivative control not yield to high-performance requirements. In this paper, a nonlinear system model is derived and linear parameterization is made for adaptive control. Then a discontinuous projection-based nonlin- ear adaptive robust force controller is developed for hydraulic load simulator. The proposed controller constructs an asymptoti- cally stable adaptive controller and adaptation laws, which can compensate for the system nonlinearities and uncertain parame- ters. Meanwhile a well-designed robust controller is also developed to cope with the hydraulic system uncertain nonlinearities. The controller achieves a guaranteed transient performance and final tracking accuracy in the presence of both parametric uncer- tainties and uncertain nonlinearities; in the absence of uncertain nonlinearities, the scheme also achieves asymptotic tracking performance. Simulation and experiment comparative results are obtained to verify the high-performance nature of the proposed control strategy and the tracking accuracy is greatly improved.

Matching design of hydraulic load simulator with aerocraft actuator

This paper intends to provide theoretical basis for matching design of hydraulic load simulator （HLS） with aerocraft actuator in hardware-in-loop test, which is expected to help actuator designers overcome the obstacles in putting forward appropriate requirements of HLS. Traditional research overemphasizes the optimization of parameters and methods for HLS controllers. It lacks deliberation because experimental results and project experiences indicate different ultimate performance of a specific HLS. When the actuator paired with this HLS is replaced, the dynamic response and tracing precision of this HLS also change, and sometimes the whole system goes so far as to lose control. Based on the influence analysis of the preceding phenomena, a theory about matching design of aerocraft actuator with HLS is presented, together with two paired new concepts of ＂Standard Actuator＂ and ＂Standard HLS＂. Further research leads to seven important conclusions of matching design, which suggest that appropriate stiffness and output torque of HLS should be carefully designed and chosen for an actuator. Simulation results strongly support that the proposed principle of matching design can be anticipated to be one of the design criteria for HLS, and successfully used to explain experimental phenomena and project experiences.

飞轮储能蓄能器挖掘机动臂设计及负载特性分析

对飞轮储能蓄能器进行分析,在动臂驱动系统中加入了蓄能器以及轴向柱塞马达,以实现储存更多挖掘机动臂能量和节能控制的效果。研究利用速度传感器把测试得到的负载速度信号传输到比较器中,根据检测数据完成柱塞马达排量的实施调节功能,最终达到稳定的运行速度。研究结果表明:挖掘机阀控系统中选择一个循环下的液压执行元件进行能量利用率分析,执行元件的能量利用率达到了主泵输出的近81%,动臂能量回收占比为17.5%,回转机构的能量回收比例达到主泵输出能量8.9%。负载从位移为0的初始状态发生线性增大,表现出了稳定的运动性能,最终达到2.8 m的位移。环形活塞的压力与位移之间呈现线性变化的特征。位移由0提高到172 mm,压力则由2.1 MPa提高到3.2 MPa,实现了稳定的控制性能。

基于SimulationX的泵车臂架液压系统建模与仿真

混凝土泵车臂架液压系统作为泵车三大液压系统之一,且具有势能可回收性,为了研究其势能的回收,有必要对其臂架液压系统进行精确的建模与仿真分析。作者根据某型混凝土泵车的臂架液压系统原理图,通过多学科领域建模、仿真与分析软件SimulationX建立了臂架液压系统的仿真模型,并对系统进行了时域动态仿真分析。结果表明:此负载敏感系统简单、可靠,运行状况良好,符合后续研究势能回收所具备的所有要求。

基于模糊-PID的高空台液压加载系统智能控制

为了改善航空发动机高空模拟试车台(简称高空台)液压加载系统的控制性能,解决手动调节控制精度低且闭环控制快速性较差的问题,提出了一种将开环模糊控制与闭环PID控制相结合的智能复合控制方法。首先,结合高空台液压加载试验特点和设备特性,利用真实试验数据基于最小二乘系统辨识搭建了系统的分段线性模型。其次,使用频域法设计参数调度的PID控制器,解决了手动调节控制精度低的问题。最后,结合试验操作人员提供的经验知识和历史试验数据结论搭建了模糊开环控制器,设计控制器选择模块和积分补偿模块,将模糊开环控制器与闭环PID控制器相结合形成智能复合控制器。通过仿真验证得出,智能复合控制器的控制效果在精度上明显优于人工手动调节,在快速性上明显优于PID控制器,调节时间缩短了39%~87%。

小型航空发动机液压装配车架设计及仿真

针对目前小型航空发动机装配车架结构形式单一、空间运转自由度不足等问题,设计了一种新型小型航空发动机装配车架,增加了主支点翻转支撑机构和液压系统升降机构,并引入了负载敏感系统对液压回路进行控制,从而保证了发动机上所有零部件的装、拆、检测等操作均位于最佳工作平面上。仿真表明,新型小型航空发动机装配车架具有机体安装可靠、操作简单和换向平稳等优点,最大限度降低了操作人员的劳动强度,提高了生产效率,保证了发动机的装配质量。

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。

基于轻量化BIM的高空台液压加载试验智能管控技术

为了使航空发动机高空模拟试车中的液压加载试验智能高效地运行,完善并优化其试验平台,提出一种基于轻量化建筑信息模型(BIM)的液压加载试验智能管控技术。建立了支持管控平台运行的高空台液压加载试验软硬件协同运行架构,提出了基于WebGL的数据在Web端3维模型上实时展示的技术,以提高试验操作人员对试验进行监测的直观性。所设计的智能管控平台同时集成了试验设置与试验操作、数据管理、试验过程分析、故障诊断分析等功能。结果表明:所提出的基于轻量化BIM的智能管控技术可使试验操作人员直观、便捷、高效地进行试验流程管控、数据综合管理、设备健康状况分析,提高了高空台液压加载系统试验的智能化、自动化水平。

高空台液压加载系统试验智能运行技术研究

为了满足航空发动机高空模拟试验智能化需求,以高空台液压加载系统为研究对象,研究其试验智能运行的关键技术。通过深入分析液压加载系统设备组成及试验智能化存在的传感器数据利用不充分、控制精度不高和数据可视化展示不直观等问题,提出基于层次分析法的数据分组关联架构,设计数据融合架构对传感器数据进行预处理并对数据进行数据层、特征层和决策层融合。针对控制精度不高且须满足快速性的要求,提出一种基于设备特性与加载谱的智能复合控制框架用于智能化控制。针对液压加载系统子设备众多且易发生故障并存在性能退化的问题,提出基于深度学习的故障诊断方法与基于支持向量机的健康预测方法。同时,提出一种基于WebGL框架下的液压加载系统工艺流程可视化展示方法并建立了三维可视化模型,实现液压加载系统动态模拟的运行状态显示。

船舶机械液压系统中液压马达测试系统开发

船舶机械液压系统的稳定可靠工作对船舶安全运输具有非常重要的作用。液压马达是液压系统中的关键部件,本文提出一种基于深度神经网络的液压马达测试系统,详细分析了液压马达的基本结构,对液压马达测试系统的整体结构进行设计,包括数据采集与控制以及测试装置,重点对负载模拟装置进行设计,并研究了基于深度神经网络的液压马达故障测试流程,最后对某型号液压马达进行测试,结果表明系统具有较好的准确性和稳定性,能够实现对不同类型液压马达的测试工作。

集成式电液制动耐久测试系统中模拟卡钳负载的设计与仿真

在集成式电液制动系统耐久测试中,对于不同排液量的产品需更换不同的卡钳负载。针对这一问题,设计了缸体容积可调以适应不同需液量的模拟卡钳负载。基于仿真软件AMESim搭建了仿真模型,对其需液量-液压特性进行分析。基于CAN通讯研发了一套集成式电液制动系统耐久测试系统,对被测产品进行常规制动功和ABS等功能的耐久测试,负载机构通过球阀可以选择模拟卡钳装置或者实车卡钳。实验结果表明模拟卡钳负载可以满足被测产品进行耐久测试,且与卡钳负载对比后相差很小,符合厂商的测试需求。