Groundwater flow through fractured rocks and seepage control in geotechnical engineering: Theories and practices

Groundwater flow through fractured rocks has been recognized as an important issue in many geotechnical engineering practices.Several key aspects of fundamental mechanisms,numerical modeling and engineering applications of flow in fractured rocks are discussed.First,the microscopic mechanisms of fluid flow in fractured rocks,especially under the complex conditions of non-Darcian flow,multiphase flow,rock dissolution,and particle transport,have been revealed through a com-bined effort of visualized experiments and theoretical analysis.Then,laboratory and field methods of characterizing hydraulic properties(e.g.intrinsic permeability,inertial permeability,and unsaturated flow parameters)of fractured rocks in different flow regimes have been proposed.Subsequently,high-performance numerical simulation approaches for large-scale modeling of groundwater flow in frac-tured rocks and aquifers have been developed.Numerical procedures for optimization design of seepage control systems in various settings have also been proposed.Mechanisms of coupled hydro-mechanical processes and control of flow-induced deformation have been discussed.Finally,three case studies are presented to illustrate the applications of the improved theoretical understanding,characterization methods,modeling approaches,and seepage and deformation control strategies to geotechnical engi-neering projects.

RESEARCH ON MECHANICAL MEASUREMENT-ORIENTED INTELLIGENT VIRTUAL CONTROLS

Intelligent virtual control (IVC) is an intelligent measurement instrumentunit with the function of actual measurement instruments, and the unit can be used as basic buildingblock for a variety of more complex virtual measurement instruments on a PC. IVC is a furtheradvancement from virtual instrument (VI), and it fuses the function modules and the controls modulesso that the relationship between the functions and controls of an instrument is imbedded in one ormore units. The design, implementation and optimization methods of IVCs are introduced. The computersoftware representation of IVCs is discussed. An example of an actual VI constructed with thebuilding blocks of IVCs is given.

Flow Control for a Two-Stage Proportional Valve with Hydraulic Position Feedback

The current research mainly focuses on the flow control for the two-stage proportional valve with hydraulic position feedback which is named as Valvistor valve.Essentially,the Valvistor valve is a proportional throttle valve and the flow fluctuates with the change of load pressure.The flow fluctuation severely restricts the application of the Valvistor valve.In this paper,a novel flow control method the Valvistor valve is provided to suppress the flow fluctuation and develop a high performance proportional flow valve.The mathematical model of this valve is established and linearized.Fuzzy proportional-integral-derivative(PID)controller is adopted in the closed-loop flow control system.The feedback is obtained by the flow inference with back-propagation neural network(BPNN)based on the spool displacement in the pilot stage and the pressure differential across the main orifice.The results show that inference with BPNN can obtain the flow data fast and accurately.With the flow control method,the flow can keep at the set point when the pressure differential across the main orifice changes.The flow control method is effective and the Valvistor valve changes from proportional throttle valve to proportional flow valve.For the developed proportional flow valve,the settling time of the flow is very short when the load pressure changes abruptly.The performances of hysteresis,linearity and bandwidth are in a high range.The linear mathematical model can be verified and the assumptions in the system modeling is reasonable.

Co-Simulation Research of the Mechanical-Hydraulic-Control Coupling System of ITER Tractor

The virtual prototyping models of the mechanical, hydraulic and control system of the ITER tractor were built with CATIA, ADAMS and MATLAB/Simulink respectively according to its heavy load and high precision characteristics, and the data transfer between the different models was accomplished by the integration interface between different software. Consequently the virtual experimental platform for the multi-disciplinary co-simulation was established. A co-simulation study of the mechanical-hydraulic-control coupling system of the ITER tractor was carried out. The synchronization servo control of parallel hydraulic cylinders was implemented, and the tracking control of the preconcerted trajectory of the hydraulic cylinders was realized on the established experimental platform. This paper presents the optimization design and technology rebuilding for the complicated coupling system with its theoretic foundation and co-simulation virtual experimental platform.

INTELLIGENT CONTROL FOR ELECTRO-HYDRAULIC PROPORTIONAL POSITION SERVO SYSTEM

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Intelligent Integrated Control of Underactuated Mechanical Systems with Second-order Nonholonomic Constraints

This paper describes an intelligent integrated control of an acrobot, which is an underactuated mechanical system with second-order nonholonomic constraints. The control combines a model-free fuzzy control, a fuzzy sliding-mode control and a model-based fuzzy control. The model-free fuzzy controller designed for the upswing ensures that the energy of the acrobot increases with each swing. Then the fuzzy sliding-mode controller is employed to control the movement that the acrobot enters the balance area from the swing-up area. The model-based fuzzy controller, which is based on a Takagi-Sugeno fuzzy model, is used to balance the acrobot. The stability of the fuzzy control system for balance control is guaranteed by a common symmetric positive matrix, which satisfies linear matrix inequalities.

RESEARCH ON THE PERFORMANCE OF NEW TYPE OF PROPORTIONAL PESSURE AND FLOW CONTROL VALVE

A new closed loop flow controlling principle through correcting the valve'sopening area while load pressure is changing is carried out. Further more a principle using only oneproportional valve to compound control pressure and flow is suggested. By using very simpleproportional throttle valve in structure, the functions that five kinds of proportional valves orany two of them combined possess can be complimented. After analyzing, comparing, and testing thedynamic and static characteristics of valve with different controlling principles and main valvestructure styles, the optimized structure styles and control methods are achieved.

Dynamic Modelling and Design of a Servomechanism for Hydraulic Directional-Control Valves

This paper analyses a control strategy applicable in heaVy-duty hydraulic Systems,namely, the introduction of a servovalve to achieve smoother operation of direCtional-control valves that serve also as flow-control valves over two fanges of operating conditions. A mathematical model of the dynamics of the System is etallished and design criteria are obtained from a linearised form of that model. The influence of variations in tile axial force on the spool of the main valve is investigated, and the use of the resultS in the design of systems of the proposed kind is discussed.

Amplification mechanism of perturbation energy in controlled backward-facing step flow

A body force resembling the streamwise Lorentz force which decays exponentially in the wall-normalwise direction is applied in the primary and secondary separation bubbles to modify the base flow and thereby adjust the amplification rate of the perturbation energy.The amplification mechanisms are investigated numerically via analyzing the characteristics of the terms in the Reynolds-Orr equation which describes the growth rate of the perturbation energy.The results demonstrate that the main convective term always promotes the increase in the growth rate while the viscous terms usually play the reverse role.The contours of the product of the wall-normalwise and streamwise perturbation velocities distribute on both sides of the isoline,which represents the zero wall-normalwise gradient of the streamwise velocity in the base flow,due to the Kelvin-Helmholtz(KH)instability.For the case without control,the isoline downstream the reattachment point of the primary separation bubble is closer to the lower wall,and thus the viscous term near the lower wall might suppress the amplification rate.For the case in which the body force only acts on the secondary separation bubble,the secondary separation bubble is removed,and the magnitude of the negative wall-normalwise gradient of the base flow streamwise velocity decreases along the streamwise direction,and thus the growth rate of the perturbation energy is smaller than that for the case without control.For the case where the body force acts on both the separation bubbles,the secondary separation bubble is removed,the isoline stays in the central part of the channel,and thereby the viscous term has less effects on the amplification rate of which the peak value could be the maximum one for some control number.

High Precision Motion Control of Hybrid Five-Bar Mechanism with an Intelligent Control

Hybrid mecihanism is a new type of planar controllable mechanism. Position control acouracy of system determines the output aconracy of the mechanism. In order to achieve the desired high acowacy, nonlinear factors as friction nmst be accurately compensated in the real-time servo control algoritinn. In this paper, the model of a hybrid five-bar mechanism is introduced. In terms of the characteristics of the hybrid mechanism, a hybrid intelligent control algorithm based on proportional-integral-derivative （PID） control and cerebellar model articulation control techniques was presented and used to perform control of hybrid five-bar mechanism for the lust time. The sinmulation results show that the hybrid control method can improve the control effect remarkably, compared with the traditional PID control strategy.

A New Approach to Intelligent Model Based Predictive Control Scheme

This paper describes a new approach to intelligent model based predictive control scheme for deriving a complex system. In the control scheme presented, the main problem of the linear model based predictive control theory in dealing with severe nonlinear and time variant systems is thoroughly solved. In fact, this theory could appropriately be improved to a perfect approach for handling all complex systems, provided that they are firstly taken into consideration in line with the outcomes presented. This control scheme is organized based on a multi-fuzzy-based predictive control approach as well as a multi-fuzzy-based predictive model approach, while an intelligent decision mechanism system (IDMS) is used to identify the best fuzzy-based predictive model approach and the corresponding fuzzy-based predictive control approach, at each instant of time. In order to demonstrate the validity of the proposed control scheme, the single linear model based generalized predictive control scheme is used as a benchmark approach. At last, the appropriate tracking performance of the proposed control scheme is easily outperformed in comparison with previous one.

Mechanism of Electromagnetic Flow Control Enhanced by Electro-Discharge in Water

Pulsed discharge utilized to achieve large current density in the electromagnetic flow control is numerically studied. A mathematic discharge model is established to calculate the plasma channel, and an actuator is designed to generate the Lorentz force in the micro plasma channel. During the discharge process, the resistance in the channel decreases rapidly and a large current density appears between the discharge electrodes. After the actuator is applied in the leading edge of a flat plate, the separation region and downstream turbulent boundary layer on the plate disappear. Meanwhile, a skin-friction drag force reduction is achieved.

A new classification of seepage control mechanisms in geotechnical engineering

Seepage flow through soils,rocks and geotechnical structures has a great influence on their stabilities and performances,and seepage control is a critical technological issue in engineering practices.The physical mechanisms associated with various engineering measures for seepage control are investigated from a new perspective within the framework of continuum mechanics;and an equation-based classification of seepage control mechanisms is proposed according to their roles in the mathematical models for seepage flow,including control mechanisms by coupled processes,initial states,boundary conditions and hydraulic properties.The effects of each mechanism on seepage control are illustrated with examples in hydroelectric engineering and radioactive waste disposal,and hence the reasonability of classification is demonstrated.Advice on performance assessment and optimization design of the seepage control systems in geotechnical engineering is provided,and the suggested procedure would serve as a useful guidance for cost-effective control of seepage flow in various engineering practices.

Experimental Study on the Flow Characteristics of a Plate with a Mechanically Choked Orifice

The mechanically choked orifice plate (MCOP) is a new type of device for flow control by which choking conditionsfor incompressible fluids can be obtained with relatively small pressure losses. Given the lack of relevant results anddata in the literature, in the present study, we concentrate on the experimental determination of the flow coefficientfor the annular orifice, the pressure distribution in the MCOP, and the characteristics of the choked flow itself. Asconfirmed by the experimental results, the Reynolds number, the orifice plate thickness, the plug taper, and theeccentricity have an obvious influence on the aforementioned flow coefficient. The pressure drop in the MCOPis mainly generated near the orifice plate, and the pressure upstream of the orifice plate is slightly reduced in theflow direction, while the pressure downstream of the orifice plate displays a recovery trend. The choked flow rateof the MCOP can be adjusted by replacing the spring with a maximum flow control deviation of 4.91%.

Research on an Urban Traffic Control System Based on DGPS

The basic principles of GPS (Global Positioning System) and DGPS (Differential GPS) are described. The principle and structure of vehicle navigation systems, and its application to the urban traffic flow guidance are analyzed. Then, an area coordinated adaptive control system based on DGPS and a traffic flow guidance information system based on DGPS are put forward, and their working principles and functions are researched. This is to provides a new way for the development of urban road traffic control systems.

基于模糊神经网络PID的煤矿掘进机俯仰控制研究

目前煤矿掘进机俯仰控制主要采用PID控制方法,在掘进机俯仰控制时变性与液压系统非线性情况下的控制精度不高。掘进机俯仰控制通过控制液压缸行程实现,将传统PID算法与模糊控制、神经网络等相结合,可有效提高液压缸行程控制精度。提出了一种基于模糊神经网络PID的煤矿掘进机俯仰控制方法。通过分析掘进机支撑部运动学关系,得到俯仰角与支撑部液压缸的数学关系;介绍了掘进机俯仰控制液压系统工作原理,建立了液压系统及其传递函数模型;将模糊控制与神经网络相结合,形成模糊神经网络,利用模糊神经网络优化PID控制参数,再结合支撑机构数学模型和液压系统传递函数模型,建立掘进机俯仰角模糊神经网络PID控制模型,实现煤矿掘进机俯仰机构自动精确控制。该方法可使掘进机俯仰机构更加快速、准确到达预设位置,解决掘进机俯仰控制中的时变性与非线性难题。仿真结果表明:模糊神经网络PID控制算法相较于模糊PID和PID控制算法,跟踪误差分别降低了69.34%和74.49%。通过液压缸位移控制模拟煤矿掘进机在突变工况和跟随工况下的俯仰控制,结果表明:模糊神经网络PID控制算法相比模糊PID和PID控制算法,俯仰控制跟踪误差最小,对位置信号的平均响应时间分别缩短了27.22%和50.33%,动态控制性能更好。

异质交通流环境下无信号T形交叉口控制策略

针对无信号控制T形交叉口,提出一种异质交通流环境下交叉口的分级限速控制模型.根据异质交通流的车辆运行特性提出分级限速的概念,并建立交叉口的车辆信息矩阵.构建以车流通过冲突区域时间最短为优化目标,以保证冲突车辆安全行驶的时间间隔为约束条件的线性规划模型.通过MATLAB搭建仿真平台对所提出的模型有效性进行试验验证.结果表明:在混合行驶的交通环境下,当车辆到达率为0.30~0.50时,本研究所提模型可以在传统控制模型的基础上提升交叉口通行能力约20%;分级限速控制模型下智能网联车辆渗透率达到0.90时,最多可以增加交叉口约17%的通行能力;所提模型能有效提高道路资源利用效率,保证主路运行通畅的情况下大幅降低支路车辆延误.

新型能量隔离防护智能管控系统的设计与应用

为解决现有的危险能量隔离/上锁挂牌程序存在的现场操作繁琐、安全管理缺乏统筹管理等问题,设计了新型能量隔离防护智能管控系统,对现有的程序进行了改进。结果表明,新型能量隔离防护智能管控系统能有效提升企业的生产/检修作业安全管理水平,对降低危险能量意外释放、减少员工人身伤害有显著的改善效果。

综掘工作面混合式风流调控下的粉尘沉降研究

煤矿掘进过程中粉尘聚集严重,目前针对综掘工作面混合式风流调控下粉尘沉降规律及优化的研究还不够深入。基于混合式风流调控系统,依托陕煤集团神木柠条塔矿业有限公司综掘工作面,分析了压风口距工作面距离、压风口右偏角度、压风口口径、抽风口距工作面距离和压抽比等混合式风流调控参数对粉尘沉降规律的影响:随着压风口距工作面距离增加,司机处和回风侧行人呼吸带截面大颗粒粉尘占比先增后减再增,小颗粒粉尘占比增加;随着压风口右偏角度增加,司机处和回风侧行人呼吸带截面大颗粒粉尘占比变化明显;随着压风口口径增加,司机处截面小颗粒粉尘占比先增后减再增,回风侧行人呼吸带截面大颗粒粉尘占比先增后减;随着抽风口距工作面距离增加,司机处截面大颗粒粉尘占比先增后减,小颗粒粉尘占比先增后减再增,回风侧行人呼吸带截面粉尘粒径分布变化不大;随着压抽比增大,司机处和回风侧行人呼吸带截面小颗粒粉尘占比减小。以上述风流调控各参数为自变量,回风侧行人呼吸带全尘平均浓度和司机处呼尘平均浓度最低为优化目标,建立了粉尘沉降优化回归模型,利用粒子群优化算法求解模型,得到最优风流调控方案:压风口距工作面距离为8.9 m,压风口右偏角度为14.8°,压风口口径为0.9 m,抽风口距工作面距离为4.3 m,压抽比为1.1。搭建了风流调控下粉尘沉降实验平台,实验结果表明:测试值与粉尘沉降优化回归模型的模拟值误差在13%以内,验证了模型的准确性;优化后粒径为71~100μm的粉尘受风流调控参数影响明显,沉降在掘进机前方;优化后回风侧行人呼吸带全尘平均浓度和司机处呼尘平均浓度分别降低了47.4%和42.4%,降尘效果明显。

电力信息物理系统中信息系统物理化的建模及分析方法

该文基于信息系统物理化的设想提出电力信息物理系统(cyber-physical power system,CPPS)中的信息流建模和计算分析方法。采用连续时间函数来刻画信息流的特征,并定义信息网络运行参数为流量累积函数、信息流速和时延。首先,基于遍历法搜索出信息流路径,建立信息流速矩阵的范式;然后利用改进的网络演算(network calculus,NC)特性赋值流速矩阵的元素;进一步采用流量累积函数表征信源数据发送规律,从而显式求解时延上界。最后将提出的信息流建模方法应用于智能变电站自动化系统的时延计算,通过与OPNET的仿真结果相比较,验证所提出模型的有效性,而且该方法可以提供定量分析指标以优化变电站组网方案设计中的信息流分布。