基于正交投影的闭环子空间辨识方法

针对闭环MIMO系统的辨识问题,提出一种基于投影的子空间辨识方法,可以辨识出具有白噪声干扰的控制对象和控制器的状态空间模型。该方法从控制对象的输入输出来辨识对象模型。通过正交投影使得求得的状态实质为卡尔曼滤波状态,以此来求取控制对象的状态空间模型;对于控制器模型,提出两种不同的辨识求解方法。最后,在Matlab下进行了仿真验证,结果表明该方法的有效性。     

U型梁振动参数的子空间辨识

子空间 (Subspace)方法是辨识结构系统动力学模型的一种新的时域方法。本文应用该方法于一 U型梁试验件的振动参数求取。通过一个二入四出系统对该 U型梁进行了振动试验 ,并直接利用实验测量数据 ,辨识出结构的状态模型 ,进而求得其振动参数 ,获得了准确的结果     

串级时滞过程的解耦控制设计

针对化工串级过程提出了两种新颖的两自由度解耦控制结构。基于鲁棒控制H2最优性能指标设计给定值响应控制器。根据系统运行抗负载干扰要求,在中间级可测量过程的输入和输出端之间设计抑制负载干扰信号的闭环,通过提出期望闭环余灵敏度函数的方法来确定其反馈通道中的扰动观测器,同时给出了该闭环保证鲁棒稳定性的充要条件。最后通过实验显示了该方法相对于其它方法的优越性。     

Fuzzy time-optimal controller (FTOC) for second order nonlinear systems

The motivation behind this paper is to seek alternative techniques to achieve a near optimal controller for non-linear systems without solving the analytical problem. In classical optimal control systems, the system states and optimization co-state parameters generate a two-point boundary value problem (TPBVP) using Pontryagin’s minimum principle (PMP). The paper contributes a new fuzzy time-optimal controller to the existing fuzzy controllers which has two regular inputs and one bang-bang output. The proposed controller closely approximates the output of the classical time-optimal controller. Further, input membership function are tuned on-line to improve the time-optimal output. The new controller exhibits optimal behaviour for second order non-linear systems. The rules are selected to satisfy the stability and optimality conditions of the new fuzzy time-optimal controller. The paper describes a systematic procedure to design the controller and how to achieve the desired result. To benchmark the new controller performance, a sliding mode controller is used for guidance and comparison purpose. Simulation of three non-linear examples shows promising results. The work described here is expected to incite researcher’s interest in fuzzy time-optimal controller design.     

Data-driven modeling and predictive control for boiler–turbine unit using fuzzy clustering and subspace methods

This paper develops a novel data-driven fuzzy modeling strategy and predictive controller for boiler–turbine unit using fuzzy clustering and subspace identification (SID) methods. To deal with the nonlinear behavior of boiler–turbine unit, fuzzy clustering is used to provide an appropriate division of the operation region and develop the structure of the fuzzy model. Then by combining the input data with the corresponding fuzzy membership functions, the SID method is extended to extract the local state-space model parameters. Owing to the advantages of the both methods, the resulting fuzzy model can represent the boiler–turbine unit very closely, and a fuzzy model predictive controller is designed based on this model. As an alternative approach, a direct data-driven fuzzy predictive control is also developed following the same clustering and subspace methods, where intermediate subspace matrices developed during the identification procedure are utilized directly as the predictor. Simulation results show the advantages and effectiveness of the proposed approach.     

Wiener model based GMVC design considering sensor noise and delay

Even though there is a plethora of literature available for assessing linear control loop performance, they cannot be applied to the nonlinear control loops. In this paper, a nonlinear generalized minimum variance (NGMV) controller based on a single input–single output (SISO) Wiener model is proposed. The NGMV controller’s performance is used as a benchmark for a class of nonlinear control loops. The advantage of the proposed method is ability of online parameter estimation of the nonlinear model using common recursive least squares (RLS) method. In real-world applications, sensor and measurement tools force noises and extra delay to the control loop which poses limitations on achievable control performance. Hence, the classic control performance assessment techniques, is not attainable anymore. To handle the limitation caused by sensor delay, the k-step ahead prediction method is utilized. Further, the exponential digital filter is used in order to attenuate impact of the measurement noise on the controller. To show the effectiveness of the proposed method, a simulation test on a pH neutralization process is carried out.     

微隧穿式陀螺仪检测模态的线性二次高斯控制

为了将微隧穿式陀螺仪(MTG)的隧尖与检测电极之间的隧道间隙及其变动量分别维持在1nm和0.1nm并降低系统噪声和扩大带宽,本文为其检测模态设计了线性二次高斯(LQG)闭环反馈系统。在利用微小量法对呈指数规律的隧道效应进行线性化的基础上,建立了MTG检测模态的线性化模型,并将哥氏加速度和电子隧道1/f噪声分别当作主要的过程噪声和输出噪声,设计了由最优状态估计器和线性二次(LQ)状态调节器组成的LQG控制器。搭建了仿真系统和实际的LQG控制电路并进行动态测试。仿真结果显示,LQG控制在将系统的信噪比提高24dB的同时,能够将两个隧道电极之间的间隙的变动量控制在10-4 nm。实验曲线表明,隧道电流噪声的峰峰值为0.4nA,LQG反馈控制系统在动态加速度信号的激励下可维持恒定隧道间隙为1nm。     

Decentralized PID controller for TITO systems using characteristic ratio assignment with an experimental application

This paper presents a decentralized PID controller design method for two input two output (TITO) systems with time delay using characteristic ratio assignment (CRA) method. The ability of CRA method to design controller for desired transient response has been explored for TITO systems. The design methodology uses an ideal decoupler to reduce the interaction. Each decoupled subsystem is reduced to first order plus dead time (FOPDT) model to design independent diagonal controllers. Based on specified overshoot and settling time, the controller parameters are computed using CRA method. To verify performance of the proposed controller, two benchmark simulation examples are presented. To demonstrate applicability of the proposed controller, experimentation is performed on real life interacting coupled tank level system.     

Recursive subspace identification for on-line tracking of structural modal parameter

The objective of this paper is to develop an on-line tracking of system parameter estimation and damage detection techniques using response measurements. To avoid the singular-value-decomposition in data Hankel matrix, a new subspace identification algorithm was developed. Seismic response data of a 3-story steel frame with abrupt change of inter-story stiffness from the shaking table test was used to verify the proposed recursive subspace identification (RSI) method by using both input and output measurements. With the implementation of forgetting factor in RSI method the ability of on-line damage detection of the abrupt change of structural stiffness can be enhanced. Then, the recursive stochastic subspace identification (RSSI) algorithm is also developed for continuous structural health monitor of structure by using the output-only measurements. Verification of the proposed RSSI method by using the white noise response data of a 2-story reinforced concrete frame from its low level white noise excitation was used. Discussion of the subspace identification model parameters is also investigated.     

高阶非线性液压辊缝系统的Backstepping动态面控制

针对某四辊冷轧机的液压辊缝系统,考虑系统干扰的情况下,建立了高阶非线性系统数学模型,利用Backstepping动态面算法设计了辊缝闭环控制器。该方法由于在逆递推设计过程中结合使用了一阶低通滤波器,无需对模型的非线性部分重复微分,从而避免了因"微分项的膨胀"而引起的算法复杂性。理论分析和仿真结果均表明所设计的控制器能够保证系统的半局稳定性,输出渐近跟踪期望轨迹,使系统对于给定位置跟踪具有良好的动态性能,对外部干扰也有较强的鲁棒性。     

Discrete-time domain two-degree-of-freedom control design for integrating and unstable processes with time delay

A discrete-time domain two-degree-of-freedom (2DOF) design method is proposed for integrating and unstable processes with time delay. Based on a 2DOF control structure recently developed, a controller is analytically designed in terms of the H₂ optimal control performance specification for the set-point tracking, and another controller is derived by proposing the desired closed-loop transfer function for load disturbance rejection. Both controllers can be tuned relatively independent to realize control optimization. Analytical expression of the set-point response is given for quantitatively tuning the single adjustable parameter in the set-point tracking controller. At the meantime, sufficient and necessary conditions for holding robust stability of the closed-loop control system are established for tuning another adjustable parameter in the disturbance rejection controller, along with numerical tuning guidelines. Illustrative examples from the literature are used to demonstrate the effectiveness of the proposed method.     

惯性稳定平台自适应前馈控制

结合反馈控制提出了一种自适应前馈控制方法来提高惯性稳定平台稳定控制的指令跟踪性能。应用子空间辨识算法,由输入输出数据辨识稳定平台动态模型的状态空间描述;采用频域回路成型方法设计反馈回路控制器,用于抑制外部扰动。应用递推最小二乘(RLS)自适应滤波器构建反馈控制回路逆模型,构造指令信号的全通特性,提高指令跟踪能力。针对不同的指令信号进行跟踪实验,验证了自适应前馈控制方法的有效性。实验结果表明:提出的自适应前馈方法对阶跃指令响应快,超调量可由反馈控制的30%降低至4.5%,对30 Hz正弦信号的响应幅值无衰减,相位滞后由反馈控制的90°降低至54°。得到的结果显著提高了系统的暂态性能,控制性能优于单独的反馈控制回路。     

车辆主动悬架控制器的仿真设计

建立了基于1/4车辆动力学和单轮路面输入模型,应用最优控制理论进行车辆主动悬架的线性二次型最优(LQC)控制器的设计,并运用MATLAB/SIMULINK软件进行路面输入和1/4车辆仿真分析。仿真结果表明采用LQG控制方法的主动悬架可以较好地改善车辆的行驶平顺性和乘坐舒适性。     

Adaptive MPC based on MIMO ARX-Laguerre model

This paper proposes a method for synthesizing an adaptive predictive controller using a reduced complexity model. This latter is given by the projection of the ARX model on Laguerre bases. The resulting model is entitled MIMO ARX-Laguerre and it is characterized by an easy recursive representation. The adaptive predictive control law is computed based on multi-step-ahead finite-element predictors, identified directly from experimental input/output data. The model is tuned in each iteration by an online identification algorithms of both model parameters and Laguerre poles. The proposed approach avoids time consuming numerical optimization algorithms associated with most common linear predictive control strategies, which makes it suitable for real-time implementation. The method is used to synthesize and test in numerical simulations adaptive predictive controllers for the CSTR process benchmark.     

Robust observer-based OMF vibration control of flexible linkage mechanisms using piezoelectric films

Based on the state-space model of the flexible linkage mechanism equipped with piezoelectric films, a robust control methodology for actively suppressing the elastodynamic responses of the high-speed flexible linkage mechanism with linear structured time-varying parameter perturbations by employing an observer-based optimal model-following (OMF) controller is presented. The advantage of the proposed robust observer-based OMF control methodology is that it not only can avoid the problem of how to choose the appropriate weighting matrices in the quadratic cost function of the linear-quadratic/linear-quadratic-Gaussian (LQ/LQG) control method but also can make the controlled closed-loop system to have the specified system response characteristics. Besides, in order to guarantee that the designed observer-based OMF controller can make the controlled flexible linkage mechanism system to avoid the possibilities of both spillover-induced instability and time-varying-parameter-perturbation-induced instability, a robust stability criterion is also presented in this paper. The control method, presented in this paper, can not only make the controlled closed-loop system to have the specified system response characteristics, but also guarantee the controlled closed-loop system to have robust stability properties by using the proposed robust stability criterion; while those control methods reported recently do not have these above-mentioned merits. Finally, an active robust vibration control problem of a slider-crank mechanism is provided for illustrating the applicability of the proposed method.     

Unified dead-time compensation structure for SISO processes with multiple dead times

This paper proposes a dead-time compensation structure for processes with multiple dead times. The controller is based on the filtered Smith predictor (FSP) dead-time compensator structure and it is able to control stable, integrating, and unstable processes with multiple input/output dead times. An equivalent model of the process is first computed in order to define the predictor structure. Using this equivalent model, the primary controller and the predictor filter are tuned to obtain an internally stable closed-loop system which also attempts some closed-loop specifications in terms of set-point tracking, disturbance rejection, and robustness. Some simulation case studies are used to illustrate the good properties of the proposed approach.     

Idle speed modeling and optimal control of a spark-ignition engine

A model of engine dynamics is developed. The model is a MISO (Multi Input Single Output) linear model which has two inputs and one output. One input is the spark timing, and the other is the ISCV (Idle Speed Control Valve) position. The output is the angular speed of an engine. The reliability of the developed model is confirmed by comparing the measured response of the engine to step inputs and external disturbance with the simulation results. In order to reduce the steady state error, an integrator state is inserted to the state equation. An engine idle speed controller is designed using optimal control theory based on the model. The performance variation of the controller to the various design parameters is simulated. On the basis of the simulation and the experimental data, the design parameters are determined. The developed controller reduced the idle speed drop caused by an external load change and recovered the desired idle speed in one second.     

Classifying flexible measures in data envelopment analysis: A slack-based measure

Data envelopment analysis (DEA) has gained a wide range of applications in measuring comparative efficiency of decision making units (DMUs) with multiple incommensurate inputs and outputs. The standard DEA method requires that the status of all input and output variables be known exactly. However, in many real applications, the status of some measures is not clearly known as inputs or outputs. These measures are referred to as flexible measures. This paper proposes a flexible slacks-based measure (FSBM) of efficiency in which each flexible measure can play input role for some DMUs and output role for others to maximize the relative efficiency of the DMU under evaluation. Further, we will show that when an operational unit is efficient in a specific flexible measure, this measure can play both input and output roles for this unit. In this case, the optimal input/output designation for flexible measure is one that optimizes the efficiency of the artificial average unit. An application in assessing UK higher education institutions used to show the applicability of the proposed approach.     

Adaptive output feedback tracking of nonlinear systems with uncertain nonsymmetric dead-zone input

In this paper, the problem of adaptive practical tracking is investigated by output feedback for a class of uncertain nonlinear systems subject to nonsymmetric dead-zone input nonlinearity with parameters of dead-zone being unknown. Instead of constructing the inverse of dead-zone nonlinearity, an adaptive robust control scheme is developed by designing an output compensator including two dynamic gains based respectively on identification and non-identification mechanism. With the aid of dynamic high-gain scaling approach and Backstepping method, stability analysis of the closed-loop system is proceeded using non-separation principle, which shows that the proposed controller guarantees that all closed-loop signal is bounded while the output of system tracks a broad class of bounded reference trajectories by arbitrarily small error prescribed previously. Finally, two examples are given to illustrate our controller effective.     

On-line identification of cascade control systems based on half limit cycle data

An on-line identification procedure is presented for cascade control systems in which both inner and outer loop process dynamics are modelled simultaneously by performing a single experiment. Departing from the conventional relay autotuning method where the controller is replaced by a relay, the proposed method is carried out on-line without breaking the closed-loop control. Exact analytical expressions are derived for process model parameters in terms of a few critical parameters of half period data of limit cycle output. Simulation examples are included to demonstrate the effectiveness of the proposed method.