时滞系统自适应预测控制策略

采用具有纯滞后的一阶惯性环节作为时滞工业控制对象的模型,并将广义预测控制应用于系统中。这种控制方法简单、容易实现,同时在优化过程中不断利用测量信息进行反馈校正,在一定程度上克服了不确定性的影响,具有较好的鲁棒性和抗干扰性能。     

干扰输入影响下离散线性切换系统的反馈控制方法

面对当前使用的平均驻留时间的反馈控制方法、基于切换原理的反馈控制方法受到外界环境干扰,导致控制效果不佳的问题,提出干扰输入影响下离散线性切换系统的反馈控制方法。 分析离散线性切换系统,设定切换信号是唯一的和任意的 2 种情况,由此设计线性切换状态下的反馈控制器,在干扰输入影响下,构建被控对象模型,描述输出反馈问题,简化信号非统一输入过程,确定任意切换时间内存在的 2 个控制量,设计降阶控制律,构造一阶输出反馈律,实现有限时间镇定反馈控制。 实验结果表明,该方法输出的响应曲线与实际最大时延上界为 6 ms 的控制情况一致,说明反馈控制效果较好。     

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。     

Tuning of linear active disturbance rejection controller with robustness specification

Active disturbance rejection control (ADRC) treats all the model uncertainties and all the external disturbances as a generalized disturbance. It uses an extended state observer (ESO) to estimate the generalized disturbance in real time, and compensate it using a state-feedback control law, thus can achieve good disturbance rejection performance. For linear ADRC (LADRC), the parameters can be tuned via the bandwidths of the ESO and the feedback control, thus an LADRC can be regarded as a fixed-structured controller with several parameters to tune, just like a PID controller. To help tuning the parameters of LADRC, a tuning rule is proposed in this paper, with the aim to minimize the load disturbance attenuation performance in the integral of time square error sense, under the constraint of a specified robustness measure for the first-order processes with deadtime. The tuning rule is tested for a variety of benchmark systems and the gravity drained tanks case, and the performances are compared with the well-known PID tuning methods.     

基于灰色预测的永磁同步电动机速度控制

本文针对永磁同步电动机非线性动态数学模型，采用直接反馈线性化控制，建立了闭环系统的输入-输出模型，通过线性化模型来设计控制器，该方法简单适用；同时，为了克服此反馈线性化控制对模型要求精确化这一不足，提出了基于灰色理论的不确定预测器，它能在线预测永磁同步电机的不确定因素并相应的调整反馈线性化控制法则，从而提高了系统的动态性能。仿真与实验结果表明，该方法对永磁同步电机速度控制具有很好的跟踪性能和鲁棒性能。     

几种特殊动态特性对象的预测PI控制

提出了基于一阶加纯滞后、二阶非振荡及振荡加纯滞后、反向特性加纯滞后和积分特性加纯滞后对象的预测 PI控制器的结构形式。这种预测 PI控制器既具有 PI控制器的功能 ,又具有预测功能 ,特别适合大纯滞后系统的控制 ,而且结构简单 ,可调参数少 ,参数的调节方便、直观。通过几种实际对象的模型仿真表明 :在干扰、噪音存在和模型失配的情况下 ,预测 PI控制器仍然具有良好的控制性能 ,是一种值得在实际工程中推广应用的新型控制器     

电动静液压主动悬架的内模-Smith时滞补偿控制

提出一种内模-Smith时滞补偿控制方法进行电动静液压主动悬架的时滞控制。对电动静液压作动器(Electro-Hydrostatic Actuator,EHA)进行了响应特性试验,采用一维线性插值方法对试验数据进行了模型拟合,并得到了含纯时滞的作动器简化模型。针对作动器的惯性响应设计了内模控制器,利用一阶泰勒表达式转化成了PID控制器形式;将作动器的纯时滞视为理想主动力的时滞,设计了Smith时滞补偿控制器。搭建了EHA主动悬架的内模-Smith时滞补偿控制仿真模型,并进行了仿真分析。结果表明,内模-Smith时滞补偿控制能使作动器输出的主动力在时间上得到较好的控制,明显改善了主动悬架的动态性能。     

时变多状态滞后不确定系统的保性能控制

针对时变多状态滞后不确定线性系统 ,研究了状态反馈保性能控制律的设计问题 ,采用线性矩阵不等式方法 ,导出了保性能控制律的存在条件和参数化表示。通过求解一个线性矩阵不等式约束的凸优化问题 ,提出了最优化保性能控制律的设计方法     

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.     

四辊卷板机侧辊位移线性自抗扰控制

侧辊位移的精确控制对实现四辊卷板机高效加工至关重要,其核心问题是提高阀控非对称缸电液伺服系统的抗扰能力。由于电液伺服系统具有高度非线性和时变不确定性,传统非线性控制方法很难有效处理包含未知动态、外部扰动以及参数变化等的多源不确定扰动。提出一种四辊卷板机侧辊位移线性自抗扰控制方法。综合考虑各种不确定扰动因素的影响,设计了线性扩张状态观测器进行实时估计,采用状态误差反馈控制律给予主动补偿,并消除跟踪误差,证明了线性扩张状态观测器状态观测误差的收敛性和电液伺服系统的闭环稳定性。试验结果表明,所设计的线性自抗扰控制器能有效抑制电液伺服系统中多源不确定性扰动,实现侧辊位移的快速、精确轨迹跟踪。     

基于MATLAB的广义预测控制设计方法

热工过程控制具有非线性、大迟延、大滞后、时变、耦合性和不确定性的特点,从而使控制难以得到满意的效果。而广义预测控制具有较强的鲁棒性、对模型要求低的特点。并且适用范围非常广泛。本文介绍了广义预测控制的基本原理和特点,并采用隐式广义预测算法在MATLAB中对单输入单输出系统进行验证。仿真结果表明该算法不仅大大减少了计算量。而且具有较好的控制效果。     

Analytical fractional PID controller design based on Bode’s ideal transfer function plus time delay

In this paper, a fractional order PID controller cascaded with a fractional filter is proposed for higher order processes. In this analytical design methodology, one or two reduced fractional orders plus time delay models are used to represent higher order system transfer functions. The controller parameters are determined so as to meet certain frequency domain specifications. A unity feedback reference model is employed where Bode’s ideal loop transfer function plus time delay of the fractional order model is placed in the forward path. The addition of this time delay provides the exact determination of frequency domain specifications if the system either intrinsically owns a time delay or a time delay is injected by its reduced order model. The proposed methodology is compared with two other related methodologies and it has been observed that the proposed controller performs much better than the others. Moreover, some empirical formulas for time domain characteristics of the reference model are numerically derived in terms of certain frequency domain specifications and time delay of the fractional reduced order model. The accuracy of these formulas is tested by simulations. The iso-damping, noise attenuation and load disturbance suppression performances of the proposed controller are also considered and compared with those of other related controllers.     

基于力密度方法的NURBS曲线和曲面变形框架

提出基于力密度方法的统一求解策略,实现NURBS曲线和曲面的精确变形.将控制网格类比为空间索网结构,分别建立外载荷变化最小、外载荷最小、杆阻尼长度最小和节点位移最小等四种表达不同几何和物理意义的最小化模型来驱动变形,并以控制顶点在变形前后的位移为变量,建立统一表达的目标函数方程,便于多个最小化模型组合使用,满足特定的变形需要.由于目标函数的二次性以及约束的线性化处理,优化问题可以通过Lagrange乘子法转化为线性问题进行求解.在计算中引入目标函数快速求解算法,使变形设计可以满足实时交互操作的需要.应用实例表明,该算法可以应用于细节特征设计和反求建模等复杂曲面造型.     

Autotuning of a new PI-PD Smith predictor based on time domain specifications

The paper extends a recent work on a modified PI-PD Smith predictor, which leads to significant improvements in the control of processes with large time constants or an integrator or unstable plant transfer functions plus long dead time for reference inputs and disturbance rejections. Processes with high orders or long time delays are modeled with lower order plant transfer functions with longer time delays. The PI-PD controller is designed so that the delay-free part of the system output will follow the response of a first-order plant or second-order plant, where it is appropriate, assuming a perfect matching between the actual plant and model in both the dynamics and time delay. The provided simple tuning formulas have physically meaningful parameters. Plant model transfer functions and controller settings are identified based on exact analysis from a single relay feedback test using the peak amplitude and frequency of the process output. Examples are given to illustrate the simplicity and superiority of the proposed method compared with some existing ones.     

QFT Parameter-Scheduling control design for linear Time-Varying systems based on RBF networks

For most of linear time-varying (LTV) systems, it is difficult to design time-varying controllers in analytic way. Accordingly, by approximating LTV systems as uncertain linear time-invariant, control design approaches such as robust control have been applied to the resulting uncertain LTI systems. In particular, a robust control method such as quantitative feedback theory (QFT) has an advantage of guaranteeing the frozen-time stability and the performance specification against plant parameter uncertainties. However, if these methods are applied to the approximated linear time-invariant (LTI) plants with large uncertainty, the resulting control law becomes complicated and also may not become ineffective with faster dynamic behavior. In this paper, as a method to enhance the fast dynamic performance of LTV systems with bounded time-varying parameters, the approximated uncertainty of time-varying parameters are reduced by the proposed QFT parameter-scheduling control design based on radial basis function (RBF) networks.     

Robust stabilizing first-order controllers for a class of time delay systems

In this paper, stabilizing regions of a first-order controller for an all poles system with time delay are computed via parametric methods. First, the admissible ranges of one of the controller’s parameters are obtained. Then, for a fixed value of this parameter, stabilizing regions in the remaining two parameters are determined using the D-decomposition method. Phase and gain margin specifications are then included in the design. Finally, robust stabilizing first-order controllers are determined for uncertain plants with an interval type uncertainty in the coefficients. Examples are given to illustrate the effectiveness of the proposed method.     

Embedded Model Control calls for disturbance modeling and rejection

Robust control design guarantees closed-loop stability of a model-based control law in the presence of parametric uncertainties. Stability is guaranteed by introducing some ignorance coefficients and restricting the feedback control effort. Embedded Model Control shows that the model-based control law can be kept intact in the case of uncertainty, if the controllable dynamics is complemented by a suitable disturbance dynamics. The disturbance state must be driven by an unpredictable input vector, the noise, which can only be estimated from the model error i.e. the difference between plant and model output. The uncertainty-based design concerns the noise estimator, so as to prevent the model error from conveying uncertainty components which are command-dependent and thus prone to destabilizing the controlled plant. Separation of the components in the low and high frequency domain by the noise estimator itself allows stability recovery and guarantee, and the rejection of low frequency components. Two simple case studies help to understand the key assets of the methodology.     

Robust adaptive sliding mode control for uncertain systems with unknown time-varying delay input

This article focuses on robust adaptive sliding mode control law for uncertain discrete systems with unknown time-varying delay input, where the uncertainty is assumed unknown. The main results of this paper are divided into three phases. In the first phase, we propose a new sliding surface is derived within the Linear Matrix Inequalities (LMIs). In the second phase, using the new sliding surface, the novel Robust Sliding Mode Control (RSMC) is proposed where the upper bound of uncertainty is supposed known. Finally, the novel approach of Robust Adaptive Sliding ModeControl (RASMC) has been defined for this type of systems, where the upper limit of uncertainty which is assumed unknown. In this new approach, we have estimate the upper limit of uncertainties and we have determined the control law based on a sliding surface that will converge to zero. This novel control laws are been validated in simulation on an uncertain numerical system with good results and comparative study. This efficiency is emphasized through the application of the new controls on the two physical systems which are the process trainer PT326 and hydraulic system two tanks.     

Robust control for a class of time varying systems via switching hypersurface design with output signals

Sliding mode control methods have been used widely since they provide robustness against parameter variations and disturbances. This paper focuses on the problem of a robust output-sliding control design for linear uncertain multi-input multi-output time-varying systems with norm-bounded uncertainty. Output signals are used for the definition of switching hypersurfaces. The formulation of a control law is emphasized. Output tracking can be achieved against a class of time varying parameter variations and external disturbances. The effectiveness of the proposed output-sliding control is confirmed by an application example.     

Robust discrete time tracking control using sliding surfaces

This paper deals with the robustness issues associated with the feedforward tracking control with respect to unmodeled plant uncertainties. Based on the Diophantine equation, a new discrete time sliding functions has been defined and utilized for the robust feedforward tracking control law. The robustness is achieved by using a sliding function-based nonlinear feedback. As for model/plant mismatches the plant order uncertainty and parameter uncertainty are taken into account for robustness analysis. Noncircular machining has been adopted as an application example of this algorithm. Through computer simulation it has been shown that the robust discrete time tracking control is effective for unmodeled plant uncertainties.