Optimal tracking control of a flexible hub–beam system with time delay

In this paper, a new technique of time-delay compensation is proposed for active control of a flexible hub–beam system. The first-order approximation coupling (FOAC) model proposed recently for dynamics of hub–beam systems is used to verify the applicability of this technique. The FOAC model is first linearized to obtain a linearized equation. The linearized equation with time delay is then transformed into a standard form with no time delay by a particular integral transformation. The time-delay controller is designed based on this standard equation using the classical optimal tracking control theory. Since the controller is a function of modal coordinates, a modal filter is presented to estimate the modal coordinates from physical sensor measurements. The effectiveness of the proposed technique for time delay is demonstrated by numerical simulations. Simulation results indicate that a very small time delay may result in instability of the control system if it is not compensated in control design. The proposed time-delay controller is effective in controlling the system even when the maximum time delay for stability without time-delay compensation is greatly exceeded. Moreover, for the system without time delay, the proposed time-delay controller may possibly obtain much better control effectiveness than the controller without time delay.     

An experimental study on the optimization of controller gains for an electro-hydraulic servo system using evolution strategies

This paper deals with an experimental optimization problem of the controller gains for an electro-hydraulic position control system through evolution strategies (ESs)-based method. The optimal controller gains for the control system are obtained by maximizing fitness function designed specially to evaluate the system performance. In this paper, for an electro-hydraulic position control system which would represent a hydraulic mill stand for the roll-gap control in plate hot-rollings, the time delay controller (TDC) is designed, and three control parameters of this controller are directly optimized through a series of experiments using this method. It is shown that the near-optimal value of the controller gains is obtained in about 5th generation, which corresponds to approximately 150 experiments. The optimal controller gains are experimentally confirmed by inspecting the fitness function topologies that represent system performance in the gain spaces. It is found that there are some local optimums on a fitness function topology so that the optimization of the three control parameters of a TDC by manual tuning could be a task of great difficulty. The optimized results via the ES coincide with the maximum peak point in topologies. It is also shown that the proposed method is an efficient scheme giving economy of time and labor in optimizing the controller gains of fluid power systems experimentally.     

时滞扩散性复杂网络同步保性能控制

针对节点扩张的时滞复杂网络系统, 在节点扩张的条件下, 讨论此类系统的同步保性能控制问题. 首先采用自适应控制方法, 利用Lyapunov-Krasovskii稳定性理论,结合矩阵不等式的凸优化问题处理方法, 得出了时 滞复杂网络系统保性能控制器存在的充分条件; 当系统节点的扩张后, 在原有自适应控制器不能使系统同步稳定的条件下, 设计脉冲控制器, 利用牵制控制原理使系统达到稳定同步. 所设计的自适应动态反馈控制器在保证系统的渐近稳定条件下使系 统性能指标满足一定的要求. 最后给出一个数值仿真说明其有效性.     

原料预热温度的模糊PID-神经元控制

针对具有不确定性、大纯滞后的催化裂化反应再生装置原料预热温度控制,提出了一种模糊PID-神经元控制方法.从介绍催化裂化反应再生装置原料预热被控对象的建模、神经元非模型控制和公式化的模糊控制方法人手,建立了模糊PID-神经元控制系统,设计了模糊神经元混合控制器,并使用神经元来在线调整模糊PID控制器的模糊规则.仿真实验结果表明所提出的模糊PID-神经元控制方法具有强鲁棒性,能有效控制具有大纯滞后和不确定性的对象.     

Research on the Low-order Control Strategy of the Power System With Time Delay

In this paper, the design problem of the low-order controller is considered for the power system with a fixed time delay. A linear model of the power system with time delay is firstly established. Then the proportional-integral-differential (PID) controller, which is the typical low-order controller, is designed to improve the stability of the power system. The stabilizing region of the PID controller is obtained. The control parameters chosen arbitrarily in the resultant region can ensure the stability of the power system. Finally, based on the stabilizing result, the PID controller satisfying the H_∞ performance index is designed, which improves the robustness of the whole power system. The main advantage of the proposed method lies in that there is no need to approximate the model of the power system. The method can be further extended to the power system which is more complex.      

OBSERVER-BASED HYBRID CONTROL OF SAMPLED-DATA UNCERTAIN SYSTEM WITH INPUT TIME DELAY

This paper proposes a new digital redesign method for determining the hybrid controller of a continuous-time system with input time delay using an observer-based digital controller. The proposed method together with the genetic algorithms is used to determine: (1) the interval digital model of a continuous-time uncertain system with input time delay, (2) the interval digital redesign control law and (3) the interval digital observer of the original continuous-time uncertain observer with input time delay. Moreover, the result is less conservative than those obtained by the existing interval methods. A discrete-time observer is built by the original continuous-time observer with input-time-delay control law and a predictor such that the estimated states of the redesigned discrete-time observer closely match those of the original continuous-time observer with input time delay not only at sampling instants but also the behavior of the system state during the sampling interval is optimal by minimizing the hybrid performance index. The digitally redesigned observer-based controller can closely match the states of the digitally redesigned uncertain sampled-data system with those of the original continuous-time observer-based controlled uncertain system with input time delay.     

Control for Time‐Varying Delay Systems by Integrating Semi‐Discretization and Hysteresis‐Based Switching

In this paper, we develop an innovative control method for linear systems with time‐varying delay by integrating the semi‐discretization method and the hysteresis‐based switching algorithm. The semi‐discretization method is adopted to design an optimal controller for each fixed time‐delay and form a candidate controller family. The switching algorithm acts as the principal law for switching among various controllers according to the instantaneous value of the time‐delay. A theoretical proof is presented regarding the stability of the switching time‐delay system. It is shown that the most significant factors that affect the system stability are the size of the candidate controller family, the value of the switching coefficient, and the changing rate of the time‐delay. Two case studies are presented to show the effectiveness of the proposed method.     

多采样率不确定离散时滞系统的鲁棒预见控制

研究一类输入多采样率型不确定离散时滞系统的鲁棒预见控制问题.首先,利用离散提升技术从形式上消除输入时滞和多采样率特点,将多采样率不确定系统的鲁棒预见控制问题转化为一个普通的单采样率不确定系统的鲁棒预见控制问题;然后根据预见控制的基本方法,构造出包含未来目标信息的扩大误差系统,并对其相应的标称系统设计预见控制器;最后,根据所设计的控制器和Lyapunov稳定性理论,给出不确定闭环系统的鲁棒稳定性判据.数值仿真结果验证了所提出设计方法的有效性.     

Guaranteed Cost Synchronization of Complex Network Systems with Delay

The guaranteed cost synchronization control problem of some general complex dynamical networks with time delay is investigated. A dynamic feedback controller is designed for the system guaranteed cost synchronization. Meanwhile, due to many nodes in the complex networks and the complex of the direct control, use of the the pinning control to make the system achieve guaranteed cost synchronization is also investigated. Based on the Lyapunov stability theory and the matrix inequality, the sufficient conditions are obtained for the existence of the guaranteed cost controller with time delay in complex network. The dynamic feedback controller is designed to ensure the asymptotic stability conditions of the system and make the performance index of the system meet certain requirements. Finally, the feasibility of the proposed method is demonstrated by numerical examples.     

Optimal control of non-minimum phase integrating processes with time delay using disturbance observer-based control scheme

A systematical design method of optimal control for non-minimum phase integrating processes with time delay using disturbance observer-based (DOB) control scheme is presented. All stabilising controllers and the filter of DOBs for integrating plants are developed. Then the optimal set-point tracking controller and the optimal filter of DOB are systematically derived by minimising the H₂ norm performance specifications. The proposed design method has three main advantages. First, the design procedure is systematical and simple. Specified weight functions are chosen for step inputs and inputs similar to steps. The designed set-point tracking controller and the filter of DOB are given in analytical forms. Second, the designed set-point tracking controller and the filter of the DOB are optimal. They are derived from minimising the performance indexes of set-point tracking and input load disturbance rejection (ILDR). Finally, the set-point tracking performance specification and ILDR specification can be quantitatively achieved by conveniently tuning the adjustable parameters. Numerical simulations are given to illustrate the effectiveness of the proposed method.     

Complementary compound set-point control by combining muscular internal force feedforward control and sensory feedback control including a time delay

This paper proposes a new set-point control method for a musculoskeletal arm by combining muscular internal force feedforward control with feedback control including a large time delay. The proposed method accomplishes robust and rapid positioning with a relatively small muscular force. In the positioning by the muscular internal force feedforward controller, a large muscular force is required to achieve good performance. On the other hand, in the positioning by the feedback controller including the large time delay, the system can easily fall into an unstable state. A simple linear combination of these two controllers makes it possible to improve the control performance and to overcome the drawbacks of each controller in a complementary manner. First, a two-link six-muscle arm model is considered as a musculoskeletal system in this study. Second, the new set-point control method, which consists of the feedforward control signal and the feedback control signal including the time delay, is designed. Third, the stability of the proposed method is investigated using the Lyapunov–Razumikhin method. Finally, the results of numerical simulations and experiments are presented to demonstrate the advantages of the proposed method.     

Guaranteed cost active fault-tolerant control of networked control system with packet dropout and transmission delay

The problem of guaranteed cost active fault-tolerant controller (AFTC) design for networked control systems (NCSs) with both packet dropout and transmission delay is studied in this paper. Considering the packet dropout and transmission delay, a piecewise constant controller is adopted. With a guaranteed cost function, optimal controllers whose number is equal to the number of actuators are designed, and the design process is formulated as a convex optimal problem that can be solved by existing software. The control strategy is proposed as follows: when actuator failures appear, the fault detection and isolation unit sends out the information to the controller choosing strategy, and then the optimal stabilizing controller with the smallest guaranteed cost value is chosen. Two illustrative examples are given to demonstrate the effectiveness of the proposed approach. By comparing with the existing methods, it can be seen that our method has a better performance.     

带有时滞的区间不确定正系统的约束控制

研究具有时变时滞的连续不确定正系统的约束控制问题.基于线性规划方法,首先设计状态反馈控制器使得相应的闭环系统是正系统且渐近稳定;然后建立在正性约束下有界的鲁棒状态反馈控制器存在的充分条件,同时给出控制器的设计方法;最后利用仿真算例验证所提出方法的有效性.     

Active fault-tolerant control against actuator fault and performance analysis of the effect of time delay due to fault diagnosis

This paper discusses the problem of fault-tolerant control against actuator fault, derives the time spent at each steps in fault diagnosis which is called as the time delay due to fault diagnosis and quantitatively analyzes its effect on the faulty system’s performance. A fault diagnosis algorithm is first proposed. The proposed fault tolerant controller is designed to guarantees that all signals in the closed-loop system are semi-globally uniformly ultimately bounded, where the controller singularity is avoided without projection algorithm. What’s more, the analytical expression of the time delay is derived strictly. Further, the quantitative analysis of system performance which is degraded by the time delay is developed, and the conditions that the magnitudes of the faults should be satisfied such that the faulty system controlled by the normal controller remains bounded even stable during the time delay are derived. In addition, the corresponding solution to the adverse effect of the time delay is proposed. Finally, an experimental test shows that the proposed control algorithm has a very reliable efficiency.     

基于HJB方程的无线传感器网络系统Minimax控制器设计

针对工业环境下无线传感器网络系统在受到外部较大干扰时的系统稳定性问题,提出Hamilton-JacobiBellman (HJB)方程与Minimax控制相结合的方法.首先,针对无线传感器网络在复杂工况环境下出现的网络时延和连续丢包有界的情况,给出具有时延和丢包的无线传感器网络系统模型;然后,在Minimax性能指标函数下,利用HJB方程设计系统的Minimax最优控制器,进一步通过检验函数得出有关最大干扰的表达形式,从而推导出系统稳定的充分条件;最后,通过数值算例和仿真验证系统在突发较大干扰时采用所提方法的可行性和有效性.     

风扰影响下的无人机非线性广义最小方差跟踪控制

本文以鱼鹰型固定翼无人机为研究对象,基于非线性广义最小方差(nonlinear generalized minimum variance,NGMV)最优控制理论,研究了受到非线性阵风干扰影响下的无人机跟踪控制问题.首先对鱼鹰型无人机动力学模型解耦,在解耦后的横向和纵向模型上分别实现跟踪控制;然后针对阵风非线性模型的特定形式,根据NGMV理论设计了增维的非线性广义最小方差控制器,使得模型充分考虑了阵风干扰的特性.所设计的NGMV最优控制器的主要优势在于它能处理带有干扰和时滞环节的非线性系统.多组阵风扰动的仿真试验结果表明,非线性广义最小方差最优控制器具有跟踪性和收敛性.     

Observer-based adaptive fuzzy control for a class of nonlinear time-delay systems

An observer-based adaptive fuzzy control is presented for a class of nonlinear systems with unknown time delays. The state observer is first designed, and then the controller is designed via the adaptive fuzzy control method based on the observed states. Both the designed observer and controller are independent of time delays. Using an appropriate Lyapunov-Krasovskii functional, the uncertainty of the unknown time delay is compensated, and then the fuzzy logic system in Mamdani type is utilized to approximate the unknown nonlinear functions. Based on the Lyapunov stability theory, the constructed observer-based controller and the closed-loop system are proved to be asymptotically stable. The designed control law is independent of the time delays and has a simple form with only one adaptive parameter vector, which is to be updated on-line. Simulation results are presented to demonstrate the effectiveness of the proposed approach.     

Robust Stabilization of the Distributed Parameter System With Time Delay via Fuzzy Control

In this paper, stabilization of the distributed parameter system (DPS) with time delay is studied using Galerkin's method and fuzzy control. With the help of Galerkin's method, the dynamics of DPS with time delay can be first converted into a group of low-order functional ordinary differential equations, which will be used for design of the robust fuzzy controller. The fuzzy controller designed can guarantee exponential stability of the closed-loop DPS. Some sufficient conditions are derived for the stabilization together with the linear matrix inequality design approach. The effectiveness of the proposed control design methodology is demonstrated in numerical simulations.     

Disturbance-observer-based robust control for time delay uncertain systems

A robust control scheme is proposed for a class of systems with uncertainty and time delay based on disturbance observer technique. A disturbance observer is developed to estimate the disturbance generated by an exogenous system, and the design parameters of the disturbance observer are determined by solving linear matrix inequalities (LMIs). Based on the output of the disturbance observer, a robust control scheme is proposed for the time delay uncertain system. The disturbance-observer-based robust controller is combined of two parts: one is a linear feedback controller designed using LMIs and the other is a compensatory controller designed with the output of the disturbance observer. By choosing an appropriate Lyapunov function candidate, the stability of the closed-loop system is proved. Finally, simulation example is presented to illustrate the effectiveness of the proposed control scheme.