压力闭环下的轧机变刚度控制

指出了在压力闭环下进行变刚度控制的必要性 ,从轧机变刚度定义出发提出了压力闭环下变刚度控制的基本方程 ,给出了压力闭环下 BISRA、厚度计型和动态设定型变刚度控制模型 ,并对其相互关系进行了分析讨论     

工控机在多级节流井控系统中的应用

多级节流智能控制系统是一套复杂的机．电、液一体化系统,涉及多项技术,其中最关键的技术是应用计算机对井控节流阀压降的实时控制;系统采用计算机电液比例闭环控制,通过研究建立了系统的数学模型,并结合石油天然气井控的相关知识采用PID控制算法,对液动节流阀的阀芯位移和阀压降进行比较准确的控制：设计最大井控压力105MPa,压力控制误差小于0.5MPa;通过现场试验,表明该系统工作平稳,控制精度高,其安全性、可靠性和可操作性完全能够满足现场压井作业的需要。     

Closed loop trajectory optimization based on reverse time tree

This paper addresses the general methods for creating the approximately optimal closed loop stabilization controllers that depend on given rigid body systems. The optimal stabilization controllers calculate the optimal force (torque) inputs that depend on the current states of the systems. In this paper, a creation method for approximately optimal controllers named closed loop optimizer based on reverse time tree (CLO-RTT) is proposed. In the open loop optimization phase, this method creates approximately optimal open loop solutions using rapid semi-optimal motion planning (RASMO). In the closed loop optimization phase, this method selects a solution from the RTT according to the measured current state of a system. The proposed method was validated in the time optimal stabilization problem of a double inverted pendulum model. The proposed method successfully stabilized the model quickly. When the resolution of RASMO was higher, the motion time was shorter.     

Optimal control of fuel processing system using generalized linear quadratic Gaussian and loop transfer recovery method

This paper proposes an optimal control system that consists of both feedforward and state‐feedback controllers designed using a generalized linear quadratic Gaussian and loop transfer recovery (GLQG/LTR) method for a fuel processing system (FPS). This FPS uses natural gas as fuel and reacts with atmospheric air through a catalytic partial oxidation (CPO) response. The control objective is focused on the regulatory performance of the output vector in response to a desired stack current command in the face of load variation. The proposed method provides another degree of freedom in the optimal control design and gives the compensated system a prescribed degree of stability. Finally, the numerical simulations of compensated FPS reveal that the proposed method displays better performance and robustness properties in both time‐domain and frequency‐domain responses than those obtained by the traditional LQ Method. Copyright © 2010 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society     

Dynamic analysis and control of sieve tray gas absorption column using MATALB and SIMULINK

The present work highlights the powerful combination of SIMULINK/MATLAB software as an effective flowsheeting tool which was used to simulate steady state, open and closed loop dynamics of a sieve tray gas absorption column. A complete mathematical model, which consists of a system of differential and algebraic equations was developed. The S-Functions were used to build user defined blocks for steady state and dynamic column models which were programmed using MATLAB and SIMULINK flowsheeting environment. As a case study, the dynamic behaviour and control of a sieve tray column to absorb ethanol from CO₂ stream in a fermentation process were analysed. The linear difference equation relating the actual and equilibrium gas phase compositions was solved analytically to relate the actual gas phase composition to the liquid phase with Murphree tray efficiency as a parameter. The steady state mathematical model was found to be nonlinear (w.r.t. number of stages) due to the introduction of the Murphree tray efficiency. To avoid the solution of large linear algebraic system, a sequential steady state solution algorithm was developed and tested through the idea of tearing the recycle stream in the closed loop configuration. The number of iterations needed to achieve a given tolerance was found to be function of the Murphree tray efficiency. The open-loop dynamic analysis showed that the gas phase composition response was nonlinear with respect to the inlet gas flow rate, while it was linear with respect to inlet gas composition. The nonlinearity increased along the column height and was maximum at the top tray. On the other hand, the Murphree tray efficiency had little effect on the dynamic behaviour of the column. The controlled variable was found to exhibit fairly large overshoots due to step change in the inlet gas flow rate, while the PID controller performance was satisfactory for step change in the inlet gas composition. The closed-loop dynamic analysis showed that the controlled variable (outlet gas phase composition) had a fairly linear dynamics due to step changes in the set point.     

Design of remotely located and multi-loop vibration controllers using a sequential loop closing approach

In some applications, vibration control objectives may require reduction of levels at locations where control system components cannot be sited due to space or environmental considerations. Control actuators and error sensors for such a scenario will need to be placed at appropriate locations which are potentially remote from the points where ultimate attenuation is desired. The performance of the closed loop system, therefore, cannot be assessed simply by the measurement obtained at this local error sensor. The control design objective has to take into account the vibration levels at the remote locations as well. A design methodology was recently proposed that tackles such problems using a single-loop feedback control architecture. The work in this paper describes an extension of this control design procedure to enable the systematic design of multiple decentralised control loops. The approach is based upon sequential loop closing and conditions are provided that ensure that closed loop stability is maintained even in the event of failure in some control loops. The design procedure is illustrated through its application to a laboratory scale slab floor that replicates the problems associated with human induced vibration in large open-plan office buildings. The experimental results demonstrate the efficacy of the approach and significant suppression of the dominant low frequency modes in the floor is achieved using two independent acceleration feedback control loops.     

An effective direct closed loop identification method for linear multivariable systems with colored noise

Multivariable control systems with colored noise widely exist in the most industrial fields, while the system identification under the closed loop conditions is needed in many cases. In view of the above two situations, it needs to find a convenient and effective method to solve the problem. Firstly, the design of the external input signals ensures the identifiability of closed loop system. Secondly, to make the direct method feasible for closed loop identification, the noise model selected is reasonably flexible and independently parameterized. On this basis, this paper proposes an improved method combining the direct closed loop identification approach with the iterative least squares parameter estimation algorithm, which can be an practical solution to the closed loop identification of multivariable systems with colored noise. The presented algorithm based hierarchical identification principle has a strong anti-jamming capability to effectively deal with colored noise existed in the system. Finally, the illustrative examples are given to demonstrate the effectiveness and accuracy of the proposed algorithm.     

Robust output regulation and the preservation of polynomial closed‐loop stability

In this paper, we study the robust output regulation problem for distributed parameter systems with infinite‐dimensional exosystems. The main purpose of this paper is to demonstrate the several advantages of using a controller that achieves polynomial closed‐loop stability, instead of a one stabilizing the closed‐loop system strongly. In particular, the most serious unresolved issue related to strongly stabilizing controllers is that they do not possess any known robustness properties. In this paper, we apply recent results on the robustness of polynomial stability of semigroups to show that, on the other hand, many controllers achieving polynomial closed‐loop stability are robust with respect to large and easily identifiable classes of perturbations to the parameters of the plant. We construct an observer based feedback controller that stabilizes the closed‐loop system polynomially and solves the robust output regulation problem. Subsequently, we derive concrete conditions for finite rank perturbations of the plant's parameters to preserve the closed‐loop stability and the output regulation property. The theoretical results are illustrated with an example where we consider the problem of robust output tracking for a one‐dimensional heat equation.Copyright © 2013 John Wiley & Sons, Ltd.     

Hybrid simulation of adaptive open loop control for parabolic systems

The “adaptive open loop control” is a compromise between the open loop and the closed loop controls. It consists in estimating the state of the system periodically in such a way that the control can be corrected, taking into account the estimated state, the final desired state and the criterion to be minimized. For a hybrid simulation, a linear parabolic system has been considered, with homogeneous boundary conditions and unknown initial condition. The purpose is to reach, in a finite time, a desired state profile, by minimising an energy criterion. The control is applied through a finite number of actuators (pointwise or by zones); the observation is made through a finite number of sensors. By using the eigenfunction method, it is possible to transform the original model into an infinite dimension set of decoupled ordinary differential equations. A hybrid simulation was carried out in real time, involving a truncated differential system simulated on the analog computer; the state estimation and the control being computed on the digital computer.     

A closed‐loop nonlinear control and sliding mode estimation strategy for fluid flow regulation

Novel sliding mode observer (SMO) and robust nonlinear control methods are presented, which are shown to achieve finite‐time state estimation and asymptotic regulation of a fluid flow system. To facilitate the design and analysis of the closed‐loop active flow control (AFC) system, proper orthogonal decomposition–based model order reduction is utilized to express the Navier‐Stokes partial differential equations as a set of nonlinear ordinary differential equations. The resulting reduced‐order model contains a measurement equation that is in a nonstandard mathematical form. This challenge is mitigated through the detailed design and analysis of an SMO. The observer is shown to achieve finite‐time estimation of the unmeasurable states of the reduced‐order model using direct sensor measurements of the flow field velocity. The estimated states are utilized as feedback measurements in a closed‐loop AFC system. To address the practical challenge of actuator bandwidth limitations, the control law is designed to be continuous. A rigorous Lyapunov‐based stability analysis is presented to prove that the closed‐loop flow estimation and control method achieves asymptotic regulation of a fluid flow field to a prescribed state. Numerical simulation results are also provided to demonstrate the performance of the proposed closed‐loop AFC system, comparing 2 different designs for the SMO.     

Closed loop steering of unicycle like vehicles via Lyapunovtechniques

With a special choice for the system state equations, the use of the simplest quadratic form as candidate Lyapunov function directly leads to the definition of very simple, smooth and effective closed loop control laws for unicycle-like vehicles, suitable to be used for steering, path following, and navigation. The authors provide simulation examples to show the effectiveness and, in a sense, the “natural behavior” of the obtained closed loop motions (when compared with everyday driving experience)     

Identification in closed loop: a powerful design tool (better design models,simpler controllers)

The paper¹ is focused on system identification in closed loop as a tool for obtaining improved models for control design and reduced order controllers. The methodology for plant model identification in closed loop will be briefly surveyed and illustrated by experimental results. The interaction with robust control design will be emphasized. The use of identification in closed loop as a tool for controller reduction will be discussed and illustrated by experimental results. Some general remarks and directions of current research will conclude the paper.     

Controller reduction with closed loop H infinity performance constraints: A QFT perspective

Assume that an initial stabilizing controller K₀₍s₎, which satisfies various closed loop frequency domain specifications, has been a priori synthesized using, e.g. H infinity control, mu synthesis techniques or closed loop convex synthesis. Remembering that the order of K₀₍s₎ is typical y at least equal to the order of the plant to be controlled, the aim of this paper is to find a stabilizing reduced order controller, which also satisfies the performance specifications and which moreover minimizes the open loop bandwidth. To this aim, the structured singular value mu is used to translate at each frequency closed loop frequency domain specifications into requirements on the frequency response of the controller. The principle of our reduction method is thus very close to the original idea of the SISO QFT design approach, except that the problem of translating closed loop frequency domain specifications into open loop ones is much more complex in the MIMO case. The problem reduces to the issue of finding a controller, whose frequency response belongs at each frequency to a template. The convexity of these templates greatly facilitates the practical realization of the controller. As a final point, the method is successfully applied to a standard H problem, which is extracted from the mu Analysis and Synthesis Toolbox of Matlab, namely the synthesis of an autopilot for the space shuttle.     

基于CompactPCI测试平台的管道煤气监控系统的设计

针对城市管道煤气输送的安全性和实时性的要求,设计了管道煤气监控系统,提出了采用负压力波祛实时监测管道煤气输送网的压力,控制采用变频技术以及闭环控制的方式实时控制煤气的流量的技术方案;为了使煤气输送流量和压力稳定,系统设计采用先进的基于CompaetPCI控制器;大量的实验和现场运行结果说明系统运行效果良好,设计的系统方便,可靠,稳定性较好。     

Dual closed‐loop tracking control for wheeled mobile robots via active disturbance rejection control and model predictive control

A dual closed‐loop tracking control is proposed for a wheeled mobile robot based on active disturbance rejection control (ADRC) and model predictive control (MPC). In the inner loop system, the ADRC scheme with an extended state observer (ESO) is proposed to estimate and compensate external disturbances. In the outer loop system, the MPC strategy is developed to generate a desired velocity for the inner loop dynamic system subject to a diamond‐shaped input constraint. Both effectiveness and stability analysis are given for the ESO and the dual closed‐loop system, respectively. Simulation results demonstrate the performances of the proposed control scheme.     

Type-III closed loop control systems-Digital PID controller design

The problem of tuning digital PID controllers for type-III control loops is investigated in this work. Type-III control loops are capable of achieving perfect tracking of step, ramp and parabolic reference signals with zero steady state position, velocity and acceleration error. The proposed PID control law involves any dominant time constants of the process itself, and any parasitic dynamics introduced by both the process and the controller, i.e. time delays within the closed control system. The development of the proposed control law takes place in the frequency domain and basis of the theory is the principle of the Magnitude Optimum criterion. The final control law consists of closed form expressions which involve also the controller's sampling time T_s. The potential of the proposed theory is justified for the control of several benchmark process models throughout simulation examples. The affect of the choice of the controller's sampling time is investigated further to the step and frequency response of the control loop both for the output of the control loop and the controller's command signal.     

单神经元自适应PID控制器的应用

对单神经元自适应PID控制器的控制算法进行了研究；利用Matlab／Simulink对复杂对象进行了闭环仿真，将单神经元自适应PID控制算法与常规PID控制算法进行了比较。结果表明单神经元自适应PID控制算法明显优于常规PID控制算法；将单神经元自适应PID控制器应用到焦炉集气管压力控制系统，集气管压力系统的抗干扰能力得到提高，取得了良好的控制效果。     

Closed‐loop performance metrics for fault detection and isolation filter and controller interaction

Fault detection and isolation (FDI) filters are typically synthesized for open‐loop or closed‐loop systems. The controller affects the FDI filter performance in the closed‐loop system. FDI filter performance and closed‐loop controller–filter interaction in the presence of uncertain dynamics were investigated as was the role of controller robustness on the FDI filter performance. The NASA Generic Transport Model aircraft was considered as a motivating application. Multiple example scenarios were presented to highlight the utility of FDI filter performance metrics. For example, comparing fault detection performance of different filters under identical uncertain plant dynamics and controller, the effect of different controllers on the FDI filter performance, and the effect of model uncertainty on filter performance. The Generic Transport Model aircraft FDI filter results are validated using worst‐case analysis and linear simulations. Copyright © 2011 John Wiley & Sons, Ltd.     

Adaptive open loop control for a class of distributed parameter systems

The real time implementation of closed loop control laws obtained by the minimization of a quadratic criterion with finite time intervals is a difficult problem, if we consider computing time and the eventual determination of the state variables. It would seem useful therefore to define, for complex systems such as distributed parameter systems, a control type which unites the advantages of open loop control, with its relative simplicity of implementation, and those of closed loop control, with its ability to reduce perturbations. It is for this reason that we use the principle of adaptive open loop control. In this paper, we describe the principles of such a method and results obtained from one example studied by numerical computation or hybrid simulation in real time.     

煤气混合流量配比及热值串级模糊控制系统

文中将模糊控制技术运用到煤气混合串级调节系统中,介绍了系统的构成、原理及控制算法,有效地实现了混合煤气热值的检测和控制。