共查询到20条相似文献,搜索用时 33 毫秒
1.
Wei Wu Yi-Shyong Chou Ching-Tien Liou Yu-Shu Chien 《Chemical Engineering Communications》2000,183(1):187-206
This work concerns the phenomena in which the feedback linearization control is applied to uncertain nonlinear time-delay processes. Under the I/O linearization algorithm, both nonlinear controllers are used to stabilize the closed-loop system with transformed delay inputs. When the effect of input perturbations can converge to zero or asymptotically vanish, these nonlinear feedback designs with only an adjustable parameter can directly improve the tracking performance. The simple linearizing controller can directly regulate the system output at unstable operating point. Combined with deadtime compensation the nonlinear predictive controller with the aid of appropriate state prediction is valid for the real process in the presence of large time delay. Finally, via computer simulation and test of control ability of both feedback control designs the useful comparative results are presented. 相似文献
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In this work advanced nonlinear neural networks based control system design algorithms are adopted to control a mechanistic model for an ethanol fermentation process. The process model equations for such systems are highly nonlinear. A neural network strategy has been implemented in this work for capturing the dynamics of the mechanistic model for the fermentation process. The neural network achieved has been validated against the mechanistic model. Two neural network based nonlinear control strategies have also been adopted using the model identified. The performance of the feedback linearization technique was compared to neural network model predictive control in terms of stability and set point tracking capabilities. Under servo conditions, the feedback linearization algorithm gave comparable tracking and stability. The feedback linearization controller achieved the control target faster than the model predictive one but with vigorous and sudden controller moves. 相似文献
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This work concerns robust controller synthesis using the differential geometric concepts for minimum phase nonlinear systems with unmeasurable disturbances. A pseudo-linearization of the disturbance model at the input-output linearization stage is applied to yield a linear subsystem for controller design. Based on this linear model, a multi-loop controller framework is implemented, whereby μ-synthesis is used to design off-line robust controller in the outer loop while state feedback is implemented in the inner loop. Through proper selection of weights, the outer robust controller is explicitly designed to address both uncertainty and disturbance rejection whereas the inner controller is used for on-line static state feedback. Numerical simulations are used to illustrate robustness of the controller for multi-input multi-output temperature control in two non-isothermal continuous stirred tank reactors in series. 相似文献
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Feedback linearization techniques are used to deal with the nonlinear controller designs which have attracted many researchers' attention in recent years. The approach has been applied successfully to solve a number of practical nonlinear control problems, but typically requires on-line full state measurement which is usually not the case in real chemical process industries. In this paper, we address the problem of synthesizing nonlinear state feedback controllers for time-delay nonlinear systems which are perturbed by disturbances. On-line estimation of the unmeasurable disturbances and unavailable state variables is introduced to facilitate the implementation of coordinate transformations and state feedback and prediction. Two kinds of dynamic compensators are then proposed to handle the process deadtime. Finally numerical simulations in a CSTR example demonstrate the promising performance of the overall nonlinear control structure in disturbance rejection. 相似文献
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This brief paper demonstrates the concept of linear feedback equivalence for an exothermic eontinu-ous stirred tank reactor with first order kinetics. Feedback control is achieved by finding a transformation for the nonlinear system which carries this system into a linear controllable system in Brunovsky canonical form. A linear state feedback controller is then designed which achieves control over a broad range of operating conditions. This example demonstrates how recent developments in nonlinear control theory can be applied to chemical systems without relying on the usual methods of local linearization. 相似文献
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In this work, we develop a method for dynamic output feedback covariance control of the state covariance of linear dissipative stochastic partial differential equations (PDEs) using spatially distributed control actuation and sensing with noise. Such stochastic PDEs arise naturally in the modeling of surface height profile evolution in thin film growth and sputtering processes. We begin with the formulation of the stochastic PDE into a system of infinite stochastic ordinary differential equations (ODEs) by using modal decomposition. A finite-dimensional approximation is then obtained to capture the dominant mode contribution to the surface roughness profile (i.e., the covariance of the surface height profile). Subsequently, a state feedback controller and a Kalman-Bucy filter are designed on the basis of the finite-dimensional approximation. The dynamic output feedback covariance controller is subsequently obtained by combining the state feedback controller and the state estimator. The steady-state expected surface covariance under the dynamic output feedback controller is then estimated on the basis of the closed-loop finite-dimensional system. An analysis is performed to obtain a theoretical estimate of the expected surface covariance of the closed-loop infinite-dimensional system. Applications of the linear dynamic output feedback controller to both the linearized and the nonlinear stochastic Kuramoto-Sivashinsky equations (KSEs) are presented. Finally, nonlinear state feedback controller and nonlinear output feedback controller designs are also presented and applied to the nonlinear stochastic KSE. 相似文献
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Nonlinear control algorithms using feedback input-output linearization and sliding mode control are applied to a lab-scale
batch ester-interchange reaction system. Batch ester-interchange reaction requires no overshoot of reaction temperature in
earlier stage of reaction and tight temperature control throughout the reaction to keep uniform quality of the final product
and to prevent variation of the amount of the byproduct such as diethylene glycol at each batch. Through experimentation we
find that the nonlinear controller of input-output linearization algorithm shows better control performance both at setpoint
tracking and disturbance rejection than the conventional PID controller. Further, sliding mode control algorithm is supplemented
and simulated to show that it improves robustness against plant-model mismatch. 相似文献
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Economic model predictive control of nonlinear time‐delay systems: Closed‐loop stability and delay compensation 下载免费PDF全文
Matthew Ellis Panagiotis D. Christofides 《American Institute of Chemical Engineers》2015,61(12):4152-4165
Closed‐loop stability of nonlinear time‐delay systems under Lyapunov‐based economic model predictive control (LEMPC) is considered. LEMPC is initially formulated with an ordinary differential equation model and is designed on the basis of an explicit stabilizing control law. To address closed‐loop stability under LEMPC, first, we consider the stability properties of the sampled‐data system resulting from the nonlinear continuous‐time delay system with state and input delay under a sample‐and‐hold implementation of the explicit controller. The steady‐state of this sampled‐data closed‐loop system is shown to be practically stable. Second, conditions such that closed‐loop stability, in the sense of boundedness of the closed‐loop state, under LEMPC are derived. A chemical process example is used to demonstrate that indeed closed‐loop stability is maintained under LEMPC for sufficiently small time‐delays. To cope with performance degradation owing to the effect of input delay, a predictor feedback LEMPC methodology is also proposed. The predictor feedback LEMPC design employs a predictor to compute a prediction of the state after the input delay period and an LEMPC scheme that is formulated with a differential difference equation (DDE) model, which describes the time‐delay system, initialized with the predicted state. The predictor feedback LEMPC is also applied to the chemical process example and yields improved closed‐loop stability and economic performance properties. © 2015 American Institute of Chemical Engineers AIChE J, 61: 4152–4165, 2015 相似文献
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The dissolved oxygen (DO) concentration has been an important process parameter in the biological wastewater treatment process
(WWTP). In this paper, we propose a nonlinear control scheme to maintain the dissolved oxygen level of an activated sludge
system. Without any linearization or model reduction, it can directly incorporate the nonlinear DO process model with on-line
estimation of the respiration rate (R) and the oxygen transfer rate (KLa). Simulation results show that it outperforms a control performance of the PID controller. Since it incorporates the process
disturbance and nonlinearity in the controller design, the suggested method can efficiently deal with the operating condition
changes that occur frequently in the wastewater treatment process. 相似文献
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The use of partial linearization by nonlinear state variable feedback has been proposed as a means of reducing the detrimental effects of system nonlinearities upon the performance of linear control schemes used with nonlinear systems. In this paper a set of generalized transformed variables are derived for a single pass shell and tube heat exchanger using this technique. The implementation of these generalized transformed variables, which reduce the apparent nonlinear behavior of single pass heat exchangers, eliminates the need to rederive a nonlinear transformation for each heat exchanger controller design. As shown by open loop transient behavior of the system, the transformed variables reduce the nonlinear characteristics of the system response. The closed loop performance of the heat exchanger system has been evaluated for both servo and regulator control, and the effect of model error upon the robustness of the closed loop controller performance has been investigated. 相似文献
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Limin Wang Shengyong Mo Donghua Zhou Furong Gao Xi Chen 《American Institute of Chemical Engineers》2013,59(6):2033-2045
A guaranteed cost control scheme is proposed for batch processes described by a two‐dimensional (2‐D) system with uncertainties and interval time‐varying delay. First, a 2‐D controller, which includes a robust feedback control to ensure performances over time and an iterative learning control to improve the tracking performance from cycle to cycle, is formulated. The guaranteed cost law concept of the proposed 2‐D controller is then introduced. Subsequently, by introducing the Lyapunov–Krasovskii function and adding a differential inequality to the Lyapunov function for the 2‐D system, sufficient conditions for the existence of the robust guaranteed cost controller are derived in terms of matrix inequalities. A design procedure for the controller is also presented. Furthermore, a convex optimization problem with linear matrix inequality (LMI) constraints is formulated to design the optimal guaranteed cost controller that minimizes the upper bound of the closed‐loop system cost. The proposed control law can stabilize the closed‐loop system as well as guarantee H∞ performance level and a cost function with upper bounds for all admissible uncertainties. The results can be easily extended to the constant delay case. Finally, an illustrative example is given to demonstrate the effectiveness and advantages of the proposed 2‐D design approach. © 2013 American Institute of Chemical Engineers AIChE J, 59: 2033–2045, 2013 相似文献
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Farshad Merrikh‐Bayat 《加拿大化工杂志》2012,90(6):1400-1410
For two main reasons optimal tuning the PIλDµ controllers is a challenging task: First, the search space is very large in dealing with such controllers, and second, there is not any generally applicable method for stability testing of the linear feedback systems containing both time delay and fractional‐order controllers. Hence, easy‐to‐use and effective rules for optimal tuning such controllers are highly demanded. In this paper, explicit formulas for optimal tuning the parameters of the PIλDµ controller, when it is applied in series with a first‐order plus time‐delay process in a standard output‐feedback system, are proposed. © 2012 Canadian Society for Chemical Engineering 相似文献
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The high-purity distillation column system is strongly nonlinear and coupled, which makes it difficult to control. Active disturbance rejection control (ADRC) has been widely used in distillation systems, but it has limitations in controlling distillation systems with large time delays since ADRC employs ESO and feedback control law to estimate the total disturbance of the system without considering the large time delays. This paper designs a proportion integral-type active disturbance rejection generalized predictive control (PI-ADRGPC) algorithm to control the distillation column system with large time delay. It replaces the PD controller in ADRC with a proportion integral-type generalized predictive control (PI-GPC), thereby improving the performance of control systems with large time delays. Since the proposed controller has many parameters and is difficult to tune, this paper proposes to use the grey wolf optimization (GWO) to tune these parameters, whose structure can also be used by other intelligent optimization algorithms. The performance of GWO tuned PI-ADRGPC is compared with the control performance of GWO tuned ADRC method, multi-verse optimizer (MVO) tuned PI-ADRGPC and MVO tuned ADRC. The simulation results show that the proposed strategy can track reference well and has a good disturbance rejection performance. 相似文献
15.
Lin Cong Xinggao Liu Yexiang Zhou Youxian Sun 《American Institute of Chemical Engineers》2013,59(11):4133-4141
A new model‐based control strategy for the internal thermally coupled distillation column (ITCDIC) is presented. Based on the nonlinear wave theory that describes the nonlinear dynamics in the separation processes, a simplified nonlinear wave model is established that concerns both the wave propagation and the profile shape. An advanced controller (WGGMC) is formulated by combining the nonlinear wave model with a generalized generic model control (GGMC). Compared with a conventional generic model controller based on a data‐driven model (TGMC), and another wave‐model based generic model controller (WGMC) developed in our previous work, WGGMC exhibits the best performances in both servo control and regulatory control. Furthermore, WGGMC can handle a very‐high‐purity system of ITCDIC with top product composition of 0.99999, while the other two controllers fail to work. © 2013 American Institute of Chemical Engineers AIChE J, 59: 4133–4141, 2013 相似文献
16.
周硕 《化工自动化及仪表》2011,38(2):149-152
针对一类非线性不确定时滞系统,结合Lyapunov稳定性定理和H∞理论,得到系统渐进稳定和状态反馈H∞控制器存在的充分条件,并且给出了此类非线性不确定时滞系统的鲁棒H∞状态反馈控制律设计方案.最后通过具体数值仿真说明了设计方案的有效性. 相似文献
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A direct nonlinear adaptive control of state feedback linearizable single-input single-output systems is proposed in the case when parametric uncertainties are represented linearly in the unknown parameters. The main feature of the proposed nonlinear adaptive control system is that the linearizing coordinate transformation and the state feedback are updated by parametric adaptive law, derived using the second method of Lyapunov. The proposed adaptive control scheme is relatively straightforward and simple in the sense that it does not use the concept of augmented error. This adaptive control scheme is numerically applied to an exothermic chemical reactor system and is compared with the nonadaptive stale feedback linearization which has an integral action. The simulation shows that the proposed adaptive control scheme can be applied effectively to highly nonlinear, uncertain chemical systems. 相似文献