基于瞬变流法的管道泄漏定位研究

管道系统的微小泄漏会影响瞬变压力波的波形和衰减特性。用Flowmaster流体仿真软件建立了管道模型,控制阀门小开度快速关闭,使管道内部产生瞬变流动,用短时傅里叶变换对管道泄漏发生前后的压力波信号进行时频分析,提取出前三次谐波分量的归一化幅值,通过指数拟合得到有无泄漏时各谐波分量幅值的衰减率,计算不同谐波分量泄漏衰减率的比值对管道泄漏进行定位。结果表明,用该方法提取的谐波分量可以准确地计算出各次谐波的衰减率,从而提高了泄漏的定位精度并能够检测到0.17%的微小泄漏。     

一种纸厂配浆浓度双闭环智能控制方法

针对配浆浓度控制过程具有突发干扰、阀门开度非线性等特点,设计一种基于智能算法的配浆浓度双闭环控制系统。外环利用遗传模糊控制策略,抑制配浆过程中出现的突发干扰和传感器漂移,依据浓度变化求解最佳稀释水流量;内环根据最优稀释水流量,采用神经网络PID调节稀释水阀门开度,稳定配浆浓度。实际应用效果证明了该方法的有效性。     

柔性机械臂的双时间尺度组合控制

本文研究柔性机械臂的轨迹跟踪和振动抑制问题. 首先, 利用Lagrange法和假设模态法建立柔性机械臂的动态模型, 进而利用奇异摄动理论得到柔性机械臂的双时间尺度模型. 然后, 基于慢时间尺度模型利用滑模控制理论设计轨迹跟踪控制器; 借助于快时间尺度模型利用自适应动态规划设计参数不精确已知情况下的最优振动抑制控制器; 将二者相结合, 构造双时间尺度组合控制器, 利用奇异摄动理论证明闭环系统稳定. 最后, 在Matlab/Simulink环境下进行实验, 与现有方法相比, 本文设计的控制器对柔性振动具有更好的振动抑制效果, 跟踪精度更高.     

LED 晶圆贴片过程中压力的二阶段模糊决策与控制

针对LED 晶圆贴片过程, 设计一种利用阀门的开关和开度控制气缸内气压的压力控制系统, 提出一种多目标分阶段决策和控制的方法, 实现活塞运动和加压控制. 根据活塞的位移和压力, 采用逻辑决策方法, 选择需要控制的阀门. 根据规划压力与实测压力的差值及其差值变化率, 利用模糊自适应PID 控制方法控制阀门的开度. 采用半张量积的方法将逻辑决策和模糊控制中的推理转变成矩阵形式, 以简化运算量, 提高运算速度和控制精确度.

     

基于水平集方法的航拍图片人工区域的分割检测

提出航拍图片中人工区域分割检测的一种新方法.该方法以基于分形误差特征以及经过离散余弦变换得到的纹理边界作为约束,同时引入一种基于简化Mumford-Shah模型的水平集算法,通过演化该模型推导出的偏微分方程,从而得到航拍图片中人工区域与非人工区域的最优划分.该方法避开基于分形误差方法中由于阈值设置不当而产生的较大误差.实验表明本文方法的有效性.     

“电磁阀”讲座：第七讲 水锤现象及其缓和措施

当管路内的液体流速由于阀门突然关闭而发生剧变时,管路内的压力随之也发生剧变,该压力变化时发生类似重锤击打物件的音响.再者,由于水是最常用的介质,而且压力波动也较强烈,所以称之为水锤.     

集气管压力控制系统建模与解耦

焦炉集气管压力系统是一个强干扰、时变、多参数、严重耦合的系统.针对影响焦炉集气管压力系统的主要参数进行了研究,运用机理建模法建立了控制系统的数学模型;并运用前馈补偿法进行解耦,构建阀门问的影响关系模型,实现基于阀门联动关系的集气管压力的自动控制.该控制模型建立了影响集气管压力稳定的主要参数与控制阀门开度之间的映射关系,在压力控制系统中的应用效果良好.     

一种基于最小二乘支持向量回归机的阀门非线性校正方案研究

针对汽轮机阀门存在流量非线性的情况,采集并分析了云南省威信电厂新建2＊600MW火电机组的阀门历史数据,运用最小二乘支持向量回归算法对阀门开度 流量进行辨识,得到机组原有的阀门配汽曲线,之后再对配汽曲线进行校正,得到阀门新的配汽曲线,从而消除阀门自身的流量非线性特性,使机组实发功率对阀门开度的响应不至于过快或者过缓,避免因机组负荷波动引发电网低频振荡事故.     

基于大维数据驱动的油气管网泄漏监控模糊决策方法

输油管网状态量多及工艺复杂,难以建立精确的管网数学模型,为了能够实时监控管网的安全运行情况,本文提出一种基于大维数据驱动的管网泄漏监控模糊决策方法.首先利用管网现有的数据信息,在不对数据进行降维处理的情况下,从信息物理系统的角度出发,将油气管网的拓扑结构、阀门开度等管道物理数据以及压力、流量等运行信息数据结合起来对复杂管网系统建立数据驱动模型.然后基于大维随机矩阵谱理论,将得到的信息物理数据协方差矩阵谱分布及圆环率作为模糊决策的条件对管网运行情况进行判断.当管网拓扑发生动态变化时,提出的方法可以有效地解决误报率高的问题.最后通过仿真及实例的分析,可以证明所提出方法的有效性.     

随机最优切换模型的建立与数值求解

利用动态规划原理,建立了由生产(经营)模式一向模式二切换的随机最优切换模型,得到了一个关于期权价值的偏微分方程互补问题,进而利用罚函数方法求解此问题而得到了一个非线性偏微分方程.在空间离散上采用拟合有限体积法求解此非线性偏微分方程,获得了最优切换模型的最优执行边界.最后进行了数值模拟,并讨论了参数关于最优执行边界的灵敏度.     

Optimal Valve Closure Operations for Pressure Suppression in Fluid Transport Pipelines

When a valve is suddenly closed in fluid transport pipelines, a pressure surge or shock is created along the pipeline due to the momentum change. This phenomenon, called hydraulic shock, can cause major damage to the pipelines. In this paper, we introduce a hyperbolic partial differential equation (PDE) system to describe the fluid flow in the pipeline and propose an optimal boundary control problem for pressure suppression during the valve closure. The boundary control in this system is related to the valve actuation located at the pipeline terminus through a valve closing model. To solve this optimal boundary control problem, we use the method of lines and orthogonal collocation to obtain a spatial-temporal discretization model based on the original pipeline transmission PDE system. Then, the optimal boundary control problem is reduced to a nonlinear programming (NLP) problem that can be solved using nonlinear optimization techniques such as sequential quadratic programming (SQP). Finally, we conclude the paper with simulation results demonstrating that the full parameterization (FP) method eliminates pressure shock effectively and costs less computation time compared with the control vector parameterization (CVP) method.      

液压系统水击振动的主动控制研究

换向阀的启闭动作对液压系统的水击压力有较大的影响.为了定量分析系统运行过程中阀启闭的水击影响作用,对其实施主动控制.运用非线性规划算法,获得了换向阀启闭优化规律曲线,该曲线对水击的控制效果明显,水击压力衰减率近似达7 dB.从实际工程应用出发,对优化启闭规律采用两阶段、三阶段线性化处理,水击压力下降率可达18.2 %.通过实验测试换向阀的两阶段启闭规律时液压缸活塞无杆腔的压力下降了13.04 %,验证了主动控制措施的有效性.     

Dynamic optimization of a natural gas pipeline using a gradient search technique†

With the increasing application of optimization techniques, it is natural to apply tha techniques of boundary control problems to industrial systems characterized by distributed parameters. This paper presents a method which specifies the conditions for the optimal operation of a natural gas pipeline. The performance index of the system is the amount of energy which must be delivered to the natural gas by the compres sor in order to satisfy the time-varying load conditions. The method proceeds by formulating the problem as a boundary control problem for a system described by a set of nonlinear partial differential equations. The equations are linearized and the resulting differential equations are solved.

The optimization technique uses a gradient search algorithm. The technique results in the improved regulation of the pressure at the load end of the pipeline while satisfying the demand and concurrently reducing the energy input requirements by up to 10%. Numerical results of the optimization are presented. The optimization and control procedure developed can be applied effectively to other applications.     

Laplace transform finite volume modeling of water hammer along fluid–structure interaction

Water hammer or propagation of pressure waves generates profound forces through pipelines of industrial high pressure processes which causes structural vibration of the pipe in both radial and axial directions. To model the sudden rupture of a pipeline system the fluid–structure interaction, FSI, is taken into account by coupling the structural vibration equations to the fluid dynamic equation. In this paper, Laplace transform finite volume, LTFV, which is a new technique along the finite element method is developed to treat fluid transient and the structural vibration equations respectively.To evaluate the numerical results, a Thermal Hydraulic Test Loop (THTL facility) which has been designed and constructed for experimental research on the physical phenomena, characteristics and performance of the safety systems involved in plants is used. To conduct tests for representing a sudden break condition in the loop, the THTL facility has been equipped by devices and sensors to record pressure and vibration signals during simulated accidents. Under steady condition, by an electrical signal an electric valve, Break valve, is opened and simultaneously pressure along pipe vibration signals close to valve is recorded. Comparing the experimental data to results from numerical modeling validated the implemented method.     

Scalable Pareto set generation for multiobjective co-design problems in water distribution networks: a continuous relaxation approach

In this paper, we study the multiobjective co-design problem of optimal valve placement and operation in water distribution networks, addressing the minimization of average pressure and pressure variability indices. The presented formulation considers nodal pressures, pipe flows and valve locations as decision variables, where binary variables are used to model the placement of control valves. The resulting optimization problem is a multiobjective mixed integer nonlinear optimization problem. As conflicting objectives, average zone pressure and pressure variability can not be simultaneously optimized. Therefore, we present the concept of Pareto optima sets to investigate the trade-offs between the two conflicting objectives and evaluate the best compromise. We focus on the approximation of the Pareto front, the image of the Pareto optima set through the objective functions, using the weighted sum, normal boundary intersection and normalized normal constraint scalarization techniques. Each of the three methods relies on the solution of a series of single-objective optimization problems, which are mixed integer nonlinear programs (MINLPs) in our case. For the solution of each single-objective optimization problem, we implement a relaxation method that solves a sequence of nonlinear programs (NLPs) whose stationary points converge to a stationary point of the original MINLP. The relaxed NLPs have a sparse structure that come from the sparse water network graph constraints. In solving the large number of relaxed NLPs, sparsity is exploited by tailored techniques to improve the performance of the algorithms further and render the approaches scalable for large scale networks. The features of the proposed scalarization approaches are evaluated using a published benchmarking network model.     

自由时间最优控制问题的一种控制向量参数化方法

针对自由时间最优控制问题,提出一种控制向量参数化（CVP）方法.通过引入时间尺度因子,将自由时间最优控制问题转化为固定时间问题,并将终端时刻作为优化参数.基于CVP方法,最优控制问题被转化为一个非线性规划（NLP）问题.建立目标和约束函数的Hamiltonian函数,通过求解伴随方程获得目标和约束函数的梯度,采用序列二次规划（SQP）方法获得问题的数值解.对于控制有切换结构的优化问题,给出了一种网格精细化策略,以提高控制质量.补料分批反应器最优控制问题的仿真实验验证了所提出方法的有效性.     

Nonlinear model predictive control scheme for stabilizing annulus pressure during oil well drilling

This paper presents a nonlinear model predictive control scheme for stabilizing the well pressure during oil well drilling. While drilling, a fluid is pumped through the drill string and the drill bit, and is returning through the annulus between the drilled well and the drill string. Varying reservoir conditions and fluctuation in circulation flow rates cause sudden variations in the pressure conditions along the well. To compensate for these pressure fluctuations, the annulus choke valve opening can be adjusted. The proposed control scheme is based on a first-principles two-phase flow model using spatial discretization of the complete well. The optimal future choke settings are found using the Levenberg–Marquardt optimization algorithm. This control scheme is evaluated against two other control methods, a manual control scheme and a standard feed-back PI-control scheme of the choke valve with feed-forward control of the pump rates. The PI-control parameters are found using the Ziegler–Nichols closed-loop method based on simulations from a low-order model. The results show that both the PI-control scheme and the model predictive control scheme are superior to manual control. However, the PI-control scheme requires that the control parameters are re-designed when the operating conditions are deviating from the original design conditions. The model predictive control scheme will perform within the operating limits as long as the detailed model is able to describe the actual conditions of the well.     

协同进化遗传算法在减压阀优化配置中的应用

漏损管理中,为了取得更好的经济效益和控制效果,需要将减压阀配置在最优的位置及最优的开度.针对供水管网漏损管理问题,研究了减压阀优化配置问题,提出了减压阀的漏损管理优化控制数学模型,应用协同进化遗传算法,对算例管网进行了数值仿真,验证了方法的有效性.