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.

Coefficient Diagram Method Based Load Frequency Control for a Modern Power System

increasing penetration of renewable energy sources with a wide range of operating conditions causing power system uncertainties, conventional controllers are incapable of providing proper performance to keep the system stable. However, controllable or dispatchable loads such as electric vehicles （EVs） and heat pumps （HPs） can be utilized for supplementary frequency control. This paper shows the ability of plug-in hybrid EVs, HPs, and batteries （BTs） to contribute in the frequency control of an isolated power system. Moreover, we propose a new online intelligent approach by using a coefficient diagram method （CDM） to enhance the system performance and robustness against uncertainties. The performance of the proposed intelligent CDM control has been compared with the proportional-integral （PI） controller and the superiority of the proposed scheme has been verified in Matiab/Simulink programs.

Study on Intercepting Method for Nitrogen and Phosphorus in Ecological Ditches and Pond

[Objective] The research aimed to reduce emission load of the farmland runoff by using ecological ditches and pond. [Method] N and P intercepting project construction of the ecological ditches and pond in Zhaiji Village, Xiangcheng District, Suzhou City as research object, by repairing 1 834 m3 of original drainage ditches, newly excavating 6 800 m2 of ecological main ditches and 6 000 m2 of artificial purification ecological pond, etc., runoff emission load in real control area of the project was counted. [Result] Annual net loads of the runoff emission for TN and TP were respectively 2 552.22 and 95.00 kg in 33.3 hm2 of farmland. Annual runoff intercepting loads of TN and TP were respectively 1 225.07 and 50.35 kg in ditches. Annual runoff intercepting loads of TN and TP were respectively 1 327.15 and 44.65 kg in ecological pond. In effluent, TN concentration was 6.32 mg/L and was smaller than 15 mg/L. TP concentration was 0.25 mg/L and was smaller than 0.5 mg/L. They both reached level-one A discharge standard. [Conclusion] The research provided theoretical basis for effective control of the agricultural non-point source pollution in Taihu Lake basin.

STUDY ON ACTIVE CONTROL FOR A FLEXIBLE BEAM UNDER THE CONDITION OF ZERO GRAVITY

The system of coupling structure with controlling is a kind of dynamic feedback system in which the mechanical load and the actuator/controller interact. The mechanical system and the control system can be considered integrally as a close system, and the driving forces actuating the mechanical load can be taken as inner forces in the coupling structure system with controlling. Therefore, one can use the method for dealing with conservative systems to simplify greatly modeling and analyses. The relative equilibrium state of motion of the flexible beam under the condition of zero gravity is studied by using the energy method, in which the characteristics of structure and controlling are considered synthetically. And further, the stability conditions for the relative equilibrium state of the system have been found. If the stability conditions are used as controlling parameters of motion of the system, the kinetic energy of the flexible beam can be converted advantageously into the electromagnetic energy of the motor and controller as well as the vibration of the flexible structure can be reduced rapidly. The results in the research provide a kind of very simple and effective real-time control method reducing the vibration of the flexible beam. The method has been verified in many kinds of experimental systems of flexible beams.

Analysis and Research of Ice Loads Acting on Offshore Structures

Usually, the action of sea ice on offshore engineering structures is one of the controlling loads in cold waters engineering structure design. The reasonable selection of environmental condition and the physical mechanical properties of ice in the region are directly related to the structure design, operation and safety. In this paper, the sea ice force acting on the structure, the physical mechanical properties of ice and the selection of parameters in calculation are discussed. Some suggestions are proposed as to the calculation of various kinds of ice loads acting on the structure.

基于多目标遗传算法的火电机组负荷频率控制方法

常规的负荷频率控制方法以频率协调为主,调频信号指令受到阶跃响应的影响,存在一定的频率偏差,阻碍火电机组频率控制效果。因此,设计了基于多目标遗传算法的火电机组负荷频率控制方法。提取火电机组负荷一次调频特征,将高出允许合理范围的火电机组负荷频率进行调整,增加或减小机组功率,使其达到新的负荷平衡。基于多目标遗传构建火电机组负荷频率控制模型,以机组发电损失与经济投入作为约束条件,优化汽轮机输出功率阶跃响应速度,从而控制火电机组负荷频率。协调机组负荷频率控制分配因子,将火电机组的前馈变负荷速率进行调节,在不影响机组负荷变化率的基础上,修正负荷频率偏差。采用对比实验,验证了方法的控制效果更佳,能够应用于实际生活中。

基于DEST的公共建筑能耗模拟——以阜阳某商业办公楼为例

本研究以阜阳市的某公共建筑为例,使用DEST软件对其全年建筑能耗分析,并采用控制变量法分别探究不同因素对建筑负荷的影响。在本研究中,建筑的窗墙比和全年累计冷负荷和全年累计总负荷成正相关。较大的窗墙比会降低建筑的隔热性能,增加供暖和冷却的能耗。此外综合考虑建筑外窗的传热系数、遮阳系数和外墙的传热系数对建筑负荷的影响;较高的遮阳系数和较低的传热系数可以减少夏季的阳光热量进入室内,降低建筑冷却负荷和热负荷,大幅降低建筑的全年累计能耗。建筑外墙传热系数选择并非越小越好,需要考虑多个因素来确定传热系数的最合适范围。

多雨环境下市政排水系统污染负荷控制方法研究

多雨环境易造成城市市政系统防洪排涝难度增大,同时,水环境中的污染物也会经雨洪下泄排放到各处,对环境和居民生活造成严重影响。为此,研究多雨环境下市政排水系统污染负荷控制方法。采用源头建设与合流制溢流调蓄池建设联合,设计市政排水系统污染负荷控制策略;并结合雷达反演降雨量模拟和污染负荷削减率计算,由此确定最佳年径流总量与安全系数,实现污染负荷控制。实验证明:当年径流总量控制在60%以上时,化学需氧量、氨氮与总磷污染负荷削减率均在最低控制标准以上;安全系数在1.2~1.4之间时,可提升市政排水系统的污染负荷削减率。

考虑动态三相不平衡度的输电线路线损控制方法

为了精准计算线路三相不平衡度并降低线路损耗,治理三相电流不平衡度,研究考虑动态三相不平衡度的输电线路线损控制方法。估算输电线路的三相电压不平衡度,并以其为参考计算输电线路三相电流不平衡度,结合等值电阻法与不平衡度因素计算输电线路的线损,当线路损耗过高时,通过在线路中接入基于电压控制的统一潮流控制器,降低输电线路中的电阻功率值与阻抗,实现输电线路线损控制。实验结果证明,该方法可以有效分析三相不平衡负载下输电线路两端电压、电流波形变化,并准确计算输电线路中三相电流不平衡度,且线损率计算结果准确,控制后线损率呈明显下降趋势。

计及典型控制的风电场调频能力量化评估及影响因素分析

为尽可能充分利用风电场支撑功率,避免资源浪费,有必要量化评估风电场的调频能力。然而,风电场调频能力缺乏定义且难以评估,运行参数及边界约束对支撑能力的影响机理不明。为此,定义了多时间尺度、多能量形式、多评估层次的指标,从而精准量化评估调频能力。基于所提评估指标,通过分析风电场运行参数对调频能力的作用机理,揭示了转速是低风速和低减载工况下的主要影响因素,而载荷与容量是高风速和高减载工况下的主要影响因素等结论。进一步,提出了基于非线性规划模型的方法对评估指标进行精确计算。最后,对四机两区域系统中下垂和减载控制下的单机聚合风电场进行了算例分析,验证了所提评估指标的合理性和评估方法的准确性,以及关键影响因素分析结论的正确性。

电力动态负荷数据概率区间预测方法设计

电力负荷具有较大的波动性,且负荷数据存在噪声、缺失或异常值等问题,影响概率区间预测结果的准确性。为此,提出一种优化的电力动态负荷数据概率区间预测方法,并对该方法展开验证分析。根据当前预测需求及标准的变化,对电力动态负荷数据预处理,计算动态负荷数据概率感知区间合适值,压缩概率感知区间范围。采用多层级的方式,细化负荷数据概率区间预测范围。设计电力动态负荷数据概率区间预测流程,采用多目标PF-Elman集成处理,实现概率区间预测。测试结果表明,此次所设计的动态负荷数据概率区间预测方法最终得出的APFE值均被较好地控制在4以下,当前所设计的预测方法更加灵活、高效,预测的效率更佳,预测结果的区间覆盖率都在95%以上,具有实际的应用价值。

基于扰动观测器的电压源型逆变器负载电流前馈控制方法研究

传统的电压源型逆变器负载电流前馈控制方法主要依赖前馈控制环路,虽然逆变器电流局部控制效果更佳,但很难满足前馈控制的需求。为此,设计了一种基于扰动观测器的电压源型逆变器负载电流前馈控制方法。该方法通过提取逆变器负载扰动电流的前馈特征,引入扰动电流作为前馈信号,将前馈点作为输出电压,得到了逆变器负载电流的动态变化规律。同时,基于扰动观测器控制电压源型逆变器的电流偏差量,将负载电流作为外部扰动信号来抑制非线性负载的干扰,以满足对负载电流的前馈控制需求。通过仿真实验验证了该方法具有较好的前馈控制效果。

基于荷载扰动深度的矿山采动场地稳定性分析

荷载扰动下的安全临界深度作为判别矿山采动场地稳定性的关键指标,对矿山地质安全与变形控制具有重要指导意义。采用极限平衡法分析壁式开采采空区破裂岩体自然平衡应力拱结构特征,利用角点法计算矩形均布荷载作用下地基中附加应力影响深度,推导了地下开采工作面与上方荷载扰动下的临界深度计算公式。以山东省济宁市某矿山采动场地稳定性评价为工程实例的研究结果表明:顾及上覆荷载附加应力的采空区活化的临界深度为159.5m,与采用开采条件判别法和地表移动变形判别法得到的场地稳定性评价结果一致。研究成果可为相似地质采矿条件下采空区破裂岩体结构特征分析与矿山安全地质危险性评价提供理论指导。

分布式光伏用户侧负荷参与电网调峰控制方法

为提高调峰速率,提出分布式光伏用户侧负荷参与电网调峰控制方法。确定调峰控制约束参数,设置侧负荷参与电网调峰调度目标函数,设计削峰填谷优化调度控制,实现侧负荷参与电网调峰控制。实验结果表明,该方法能够更好地应对电力负荷的波动,增强电网的稳定性和可靠性。

基于数值模拟分析的煤场软土地基处理

东南沿海地基软土地基处理对各类建设工程至关重要。为控制工后沉降,保障沿海大面积堆场地基稳定性和安全性,开展堆场地基处理及投产后加荷过程中沉降变形与数值模拟研究。以舟山某燃煤发电厂煤场地基处理工程为例,对天然地基、塑料排水板堆载预压法地基处理的沉降量进行了计算,并利用有限元软件PLAXIS2D对堆载下的地基稳定进行分析。研究结果表明,煤场如采用天然地基在堆煤作用下,工后沉降大,固结沉降时间长,地基处理应尽早进行;煤场采用真空联合堆载预压排水固结的方式进行地基处理,可有效改善地基沉降问题。

调峰运行下中压调门参与供热调节的应用研究

火电供热机组参与调峰运行时,如何确保低负荷工况下汽轮机仍能满足热用户的用汽需求,是一个值得研究的议题。以某350 MW火电机组的低负荷供热工况为研究对象,提出了中压调门参与供热调节的方案。通过改变中压调门开度来调整对外供热蒸汽压力,可以实时匹配热用户的用汽参数需求,有效解决调峰运行下供热蒸汽压力参数偏低的问题,使得该供热机组具备了40%~100%宽负荷供热能力。实施结果表明,采用该方案后,该机组能够满足调峰运行工况下热用户的用汽需求,该方案的工程应用价值得到了验证。研究成果可为同类型火电供热机组兼顾电网调峰要求和满足热用户用汽需求的优化方案的设计提供参考。

基于启发式搜索法与动态负荷跟踪的中央空调能耗全局控制方法

非线性且时滞的中央空调运行模式,导致运行能耗较高,为提高中央空调全局能耗控制效果,减少核函数和模型相关参数的相对误差,提出一种中央空调能耗全局控制方法。利用支持向量机算法,考虑变风量预测中央空调动态负荷,选择合适核函数、中央空调能耗相关参数,实时监测中央空调能耗运行总能耗,反复训练动态负荷跟踪模型,自适应调节参数并指导变频控制过程,以总能耗数据作为启发式搜索法优化目标,搜索最佳控制频率,完成中央空调能耗全局控制。实验表明,该方法降低了动态负荷预测模型的相对误差,提高了能耗控制的全局性。

有限元分析的位移控制法及其应用

对于非线性问题的有限元分析 ,位移控制法 (DCM)比常用的载荷控制法 (LCM)有着更广泛的应用和更强的适应能力。但因DCM在求解技术上的一些难度 ,限制了其在岩土力学中的应用。本文利用Sherman Morrison定理 ,使得DCM仅需很少的运算量 ,对经典的LCM程序做少量的修补 。

操纵负荷系统电液伺服加载控制方式的比较研究

在飞行模拟器操纵负荷控制系统中,采用电液伺服加载实现驾驶员在操纵时的力感觉时,常采用位置闭环控制、速度闭环控制和力闭环控制三种方式。为比较三种方式的跟踪性能,基于MAT-LAB平台进行了计算机仿真,同时在所构建的原理样机上进行了实验验证。仿真结果表明力闭环控制方式的跟踪控制精度最高,稳态误差最小;其次为速度闭环控制方式,它的跟踪误差大于力闭环控制方式,稳态误差最大;跟踪性能最差的是位置闭环控制方式,它存在较大的时间滞后,跟踪性能不好。为了验证仿真结果的有效性,在原理样机中进行了位置闭环控制和力闭环控制的力加载实验,实验结果验证了位置闭环和力闭环控制仿真结果的正确性,同时也验证了数学模型以及三种控制方式仿真的有效性。

基于可靠度理论的混凝土桥梁安全性评估方法研究

通过分析我国公路桥梁设计规范承载能力设计表达式,提出了汽车荷载效应调整系数和抗力调整系数的概念,确定了不同破坏形式下在役混凝土桥梁安全性能评估表达式和目标可靠指标,建立了相应的可靠度评估方法。在此基础上,从便于工程应用的角度出发,建立了基于不同需求的在役混凝土桥梁安全性能实用评估方法——基于"双控"思想的安全性实用评估方法,即抗力控制法和汽车荷载效应控制法,并通过工程实例验证了该方法的可行性。