Adaptive control for a class of MIMO nonlinear time delay systems against time varying actuator failures

This paper investigates an adaptive controller for a class of Multi Input Multi Output (MIMO) nonlinear systems with unknown parameters, bounded time delays and in the presence of unknown time varying actuator failures. The type of considered actuator failure is one in which some inputs may be stuck at some time varying values where the values, times and patterns of the failures are unknown. The proposed approach is constructed based on a backstepping design method. The boundedness of all the closed-loop signals is guaranteed and the tracking errors are proved to converge to a small neighborhood of the origin. The proposed approach is employed for a double inverted pendulums benchmark and a chemical reactor system. The simulation results show the effectiveness of the proposed method.     

A comparison of traditional and adaptive control strategies for systems with time delay

A recently developed tuning method is compared to an adaptive Smith Predictor control strategy. The robustness of each method is considered for time-varying plant parameters. Examples with simulations are provided to compare the methods and present conclusions on the advantages and disadvantages of each.     

Tuning of an optimal fuzzy PID controller with stochastic algorithms for networked control systems with random time delay

An optimal PID and an optimal fuzzy PID have been tuned by minimizing the Integral of Time multiplied Absolute Error (ITAE) and squared controller output for a networked control system (NCS). The tuning is attempted for a higher order and a time delay system using two stochastic algorithms viz. the Genetic Algorithm (GA) and two variants of Particle Swarm Optimization (PSO) and the closed loop performances are compared. The paper shows that random variation in network delay can be handled efficiently with fuzzy logic based PID controllers over conventional PID controllers.     

Some long time delay sliding mode control approaches

This paper presents a combined approach of predictive structures with sliding mode control (SMC). Control schemes have been proposed looking for performance and robustness improvement. These structures were designed for processes that can be approximated either by a first order plus time delay or an integral first order plus time delay model broadly used on chemical processes. The proposed schemes were tested for performance and robustness against set point changes and disturbances as compared with classical approaches.     

Predictive active disturbance rejection control for processes with time delay

Active disturbance rejection control (ADRC) has been shown to be an effective tool in dealing with real world problems of dynamic uncertainties, disturbances, nonlinearities, etc. This paper addresses its existing limitations with plants that have a large transport delay. In particular, to overcome the delay, the extended state observer (ESO) in ADRC is modified to form a predictive ADRC, leading to significant improvements in the transient response and stability characteristics, as shown in extensive simulation studies and hardware-in-the-loop tests, as well as in the frequency response analysis. In this research, it is assumed that the amount of delay is approximately known, as is the approximated model of the plant. Even with such uncharacteristic assumptions for ADRC, the proposed method still exhibits significant improvements in both performance and robustness over the existing methods such as the dead-time compensator based on disturbance observer and the Filtered Smith Predictor, in the context of some well-known problems of chemical reactor and boiler control problems.     

针对纯滞后系统的RBF神经网络智能控制的研究

针对工业控制过程中普遍存在的大惯性、纯滞后、时变性、非线性对象的控制问题,采用传统的控制方法不能达到满意的控制效果,提出了基于RBF神经网络的PID自适应控制方案。采用神经网络辨识器在线辨识系统模型,自动调整PID控制器参数,从而实现系统的智能控制。仿真结果表明：该方法对于纯滞后控制系统能进行有效的控制并且具有很好的自适应性和鲁棒性。     

大时滞过程新型模糊控制策略研究进展

工业控制过程中普遍存在着大惯性、纯滞后对象的控制问题,而大时滞过程的控制依然是控制领域中的研究热点.该文就大时滞系统的各种改进型模糊控制策略的研究及其应用进行综述,并指出模糊控制与传统滞后控制方法的结合对大时滞过程的控制是有效的,可望在工业实践中得到广泛应用.     

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.     

Nonlinear stabilization for a class of time delay systems via inverse optimality approach

This paper is devoted to obtain a stabilizing optimal nonlinear controller based on the well known Control Lyapunov-Krasovskii Functional (CLKF) approach, aimed to solve the inverse optimality problem for a class of nonlinear time delay systems. To determine sufficient conditions for the Bellman's equation solution of the system under consideration, the CLKF and the inverse optimality approach are considered in this paper. In comparison with previous results, this scheme allows us to obtain less conservative controllers, implying energy saving (in terms of average power consumption for a specific thermo-electrical process). Sufficient delay-independent criteria in terms of CLKF is obtained such that the closed-loop nonlinear time-delay system is guaranteed to be local Asymptotically Stable. To illustrate the effectiveness of the theoretical results, a comparative study with an industrial PID controller tuned by the Ziegler-Nichols methodology (Z-N) and a Robust-PID tuned by using the D-partition method is presented by online experimental tests for an atmospheric drying process with time delay in its dynamics.     

基于LQR的倒立摆最优控制系统研究

基于LQR对单级倒立摆进行了最优控制系统设计，并针对LQR最优控制中加权矩阵Q和R难以确定的问题，进行了倒立摆实验研究与分析，找出了倒立摆系统的动态响应与Q和R阵之间遵循的基本规律。实验结果显示了该结论的正确性和实用性，也为在利用该方法进行其它控制系统的设计中Q和R的选取提供了参考。     

大滞后过程的模糊免疫自整定PID控制

目前大滞后过程的控制问题仍然是控制理论研究的重要课题,本文研究提出了一种模糊免疫PID控制器,针对一阶大时滞模型进行数字仿真。仿真结果证明了该方案在一定的时滞范围内具有很好的动静态响应特性和较强的鲁棒性,为解决大滞后过程的控制问题提供了一种可行的方法。     

双容时滞过程的 MCP-PID控制参数整定法

针对典型的双容时滞过程,应用了新的MCP-PID控制参数整定方法。仿真试验结果表明：相比ZN-PID控制,MCP-PID控制具有超调量小、调整时间短和鲁棒性高的优势。在双容时滞过程模型拟合成单容时滞过程模型时,选用纯时滞拟合误差较大的过程模型设计MCP-PID控制器更有利于得到超调量小和鲁棒性强的控制效果。     

飞机地面压力加油延迟时间的算法研究

从流体网络算法和时间微分思想出发,建立了一种用于计算飞机地面压力加油延迟时间的计算模型,模型很好地解决了飞机地面压力加油系统管路复杂,加油延迟时间计算困难的问题.针对某型飞机地面压力加油系统的具体要求,计算了在一定地面加油压力下,各组油箱的满油延迟时间.计算结果用于某型飞机地面压力加油系统的验证计算,效果良好.该计算模型对飞机地面压力加油系统的设计及性能分析具有指导意义.     

网络控制系统的研究现状综述

文中首先介绍了网络控制系统,并对它的优缺点做了分析,然后从建模、时滞、稳定性、扰动及网络预测器、减少网络控制系统上的通信量、控制器设计及调度、性能评估等方面对网络控制系统的研究现状做了比较详细的综述.     

Robust fault-tolerant control for networked control systems subject to random delays via static-output feedback

This paper focuses on the problem of fault-tolerant controller (FTC) design for uncertain networked control systems (NCSs) with random delays and actuator faults. A new fault model is proposed to represent more class of actuator faults. More precisely, the NCSs with random delays and the possible actuator faults are modeled as a Markovian jump system (MJS) with incomplete transition probabilities (TPs) and then LMI-based sufficient conditions are derived to ensure the stochastic stability of the closed-loop system. The sufficient conditions are constructed to synthesize the mode-dependent static-output feedback (SOF) control laws. Feasibility and reliability of the proposed FTC against actuator faults are indicated through simulation results.     

单级倒立摆的两种控制方法的仿真研究

针对多变量、非线性、强耦合性的倒立摆系统,运用牛顿-欧拉方法建立了倒立摆的数学模型。然后对该模型分别进行LQR控制和模糊控制,并在MATLAB环境下进行仿真,其对比结果对该方向的研究具有理论指导意义。     

Enhanced disturbance rejection for open-loop unstable process with time delay

The present study suggests a disturbance estimator design method for application to a recently published, two-degree-of-freedom, control scheme for open-loop, unstable processes with time delay. A simple PID controller cascaded with a lead-lag filter replaces the high-order disturbance estimator for enhanced performance. A new analytical method on the basis of the IMC design principle, featuring only one user-defined tuning parameter, is developed for the design of the disturbance estimator. Several illustrative examples taken from previous works are included to demonstrate the superiority of the proposed disturbance estimator. The results confirm the superior performance of the proposed disturbance estimator in both nominal and robust cases. The proposed method also offers several important advantages for industrial process engineers: it covers several classes of unstable process with time delay in a unified manner, and is simple and easy to design and tune.     

Ionospheric delay contribution to the uncertainty of time and frequency measurements by one-way satellite time transfer method

The results of international time and frequency comparisons between INPL reference and BIPM using GPS satellite system are presented. The uncertainty of time and frequency comparison by the one-way satellite time transfer method is discussed. Ionospheric delay contribution to this uncertainty is evaluated. The diurnal, seasonal and long-term variations of ionospheric delay are presented and discussed. Ionospheric delay has daily and seasonal oscillations with amplitudes of about 20–60 and 20 ns, respectively. These oscillations are due to variations of solar activity and the variations of total electron content in ionosphere. Long-term variations of ionospheric delay correlate with 11-year sunspot cycle. The difference between ionospheric delay values at minimum (in 1996) and maximum (in 2002) solar activity is 3 times. The increased values of ionospheric delay have caused the increase of the standard deviation of the time comparison results in the same proportion.     

基于改进型灰色预测大时滞过程的自适应PID控制研究

针对传统PID控制对大时滞控制效果不佳的情况,提出一种基于改进灰色预测模型的自适应PID控制系统。采用等维新信息、改变初始条件和精指数拟合法对G（1,1）模型进行改进,将改进后的G（1,1）模型与传统PID结合,组成灰色预测控制系统。用预测结果代替被控对象测量值,克服了大时滞系统控制效果不能及时反馈的不足,并在控制运算中,沿二次型性能指标的负梯度方向对加权系数进行在线修改,实现了自适应PID的优化控制。仿真结果表明了该预测控制算法的响应速度快、鲁棒性强,有较好的适应性。     

鲁棒控制在网络控制器设计中的应用研究

为了解决网络诱导延时对网络控制系统带来的不良影响,将网络控制系统的延时环节转化为不确定块,利用鲁棒控制中μ分析的D-K迭代法设计出网络控制器.该控制器可以在延时大于采样周期,并且无需知道系统延时统计规律的基础上保证系统在一定的延时范围内的稳定性和鲁棒性.