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.     

基于延迟补偿的永磁同步电机并行自抗扰控制

为了解决永磁同步电机在多工况下转速易受到内外扰动的影响,提出一种基于延迟补偿的并行线性自抗扰控制策略。 针对永磁同步电机可能受到信号处理、逆变器响应等因素从而引入的外部时滞效应的问题,引入 Smith 预估器与自抗扰控制相 结合,使控制系统更加精确、快速地响应内部参数变化和外部扰动。 同时,针对线性自抗扰控制器(LADRC)在有限带宽内其抗 扰性能较差的问题,设计了并行线性自抗扰控制器,在保持其带宽不变与参数易于整定的同时,有效提高其抗扰动能力。 最后, 对自抗扰控制器的稳定性进行了分析,并在此基础上进行了参数设计与扰动性能分析。 仿真与实验结果表明,所提算法相比 LADRC 在电机受到速度阶跃、负载扰动与内部参数变化时,在调整时间上分别提升了 52. 5% 、49. 5% 与 42. 4% ,从而验证了该 控制策略能有效增强永磁同步电机在多工况下抗内外扰动与速度跟踪能力。     

Modified active disturbance rejection control for time-delay systems

Industrial processes are typically nonlinear, time-varying and uncertain, to which active disturbance rejection control (ADRC) has been shown to be an effective solution. The control design becomes even more challenging in the presence of time delay. In this paper, a novel modification of ADRC is proposed so that good disturbance rejection is achieved while maintaining system stability. The proposed design is shown to be more effective than the standard ADRC design for time-delay systems and is also a unified solution for stable, critical stable and unstable systems with time delay. Simulation and test results show the effectiveness and practicality of the proposed design. Linear matrix inequality (LMI) based stability analysis is provided as well.     

Generalized proportional integral control for periodic signals under active disturbance rejection approach

Conventional repetitive control has proven to be an effective strategy to reject/track periodic signals with constant frequency; however, it shows poor performance in varying frequency applications. This paper proposes an active disturbance rejection methodology applied to a large class of uncertain flat systems for the tracking and rejection of periodic signals, in which the possibilities of the generalized proportional integral (GPI) observer-based control to address repetitive control problems are studied. In the proposed scheme, model uncertainties and external disturbances are lumped together in a general additive disturbance input that is estimated and rejected on-line. An illustrative case study of mechatronic nature is considered. Experimental results show that the proposed GPI observer-based control successfully rejects periodic disturbances even under varying speed conditions.     

基于控制增益实时辨识的BLDCM自抗扰控制

自抗扰控制具有算法简单、性能优良等优点,控制增益b对控制效果的影响较大,高效稳定地在线辨识出该参数对提高控制效果具有重要意义。设计了一种基于模型参考自适应参数辨识的新型自抗扰控制器,核心参数自适应变化使该控制器拥有更好的性能,仿真结果表明参数b辨识准确并且该控制器相对于传统自抗扰控制具有更好的控制效果。     

基于自抗扰重复控制的压电驱动器高精度跟踪控制

针对压电驱动器的高精度控制问题,提出一种自抗扰重复控制设计方法。首先,给出压电驱动系统的动力学模型;然后,在线性自抗扰控制(LADRC)中引入输出反馈积分控制器和一类插入式重复控制器,提出一种具有阶跃、斜坡和周期信号跟踪/抑制能力的自抗扰重复控制策略。进一步,结合小增益定理,分析闭环系统的稳定性及控制系统的设计方法。最后,将所提方法应用于一类压电驱动系统,实验结果表明该方法与LADRC相比,能显著提升控制效果,且高精度跟踪/抑制多种外部信号。     

On the centrality of disturbance rejection in automatic control

In this paper, it is shown that the problem of automatic control is, in essence, that of disturbance rejection, with the notion of disturbance generalized to symbolize the uncertainties, both internal and external to the plant. A novel, unifying concept of disturbance rejector is proposed to compliment the traditional notion of controller. The new controller–rejector pair is shown to be a powerful organizing principle in the realm of automatic control, leading to a Copernican moment where the model-centric design philosophy is replaced by the one that is control–centric in the following sense: the controller is designed for a canonical model and is fixed; the difference between the plant and the canonical model is deemed as disturbance and rejected.     

Fractional active disturbance rejection control

A fractional active disturbance rejection control (FADRC) scheme is proposed to improve the performance of commensurate linear fractional order systems (FOS) and the robust analysis shows that the controller is also applicable to incommensurate linear FOS control. In FADRC, the traditional extended states observer (ESO) is generalized to a fractional order extended states observer (FESO) by using the fractional calculus, and the tracking differentiator plus nonlinear state error feedback are replaced by a fractional proportional-derivative controller. To simplify controller tuning, the linear bandwidth-parameterization method has been adopted. The impacts of the observer bandwidth ω_o and controller bandwidth ω_c on system performance are then analyzed. Finally, the FADRC stability and frequency-domain characteristics for linear single-input single-output FOS are analyzed. Simulation results by FADRC and ADRC on typical FOS are compared to demonstrate the superiority and effectiveness of the proposed scheme.     

A simplified predictive control algorithm for disturbance rejection

Model predictive control (MPC) offers several advantages for control of chemical processes. However, the standard MPC may do a poor job in suppressing the effects of certain disturbances. This shortcoming is mainly due to the assumption that disturbances remain constant over the prediction horizon. In this paper, a simple disturbance predictor (SDP) is developed to provide predictions of the unmodeled deterministic disturbances for a simplified MPC algorithm. The prediction is developed by curve fitting of the past information. A tuning parameter is employed to handle a variety of disturbance dynamics and a procedure is presented to find an optimum value of the tuning parameter online. A comparison is made with the commonly used disturbance prediction on three example problems. The results show that an improved regulatory performance and zero offset can be achieved under both regular and ramp output disturbances by using the proposed disturbance predictor.     

Optimal disturbance rejection for PI controller with constraints on relative delay margin

Performance optimization with robustness constraints is frequently encountered in process control. Motivated by the analytical difficulties in dealing with the conventional robustness index, e.g., maximum sensitivity, we introduce the relative delay margin as a good alternative, which gives much simpler robust analysis. This point is illustrated by designing an optimal PI controller for the first-order-plus-dead-time (FOPDT) model. It is first shown that the PI controller parameters can be analytically derived in terms of a new pair of parameters, i.e., the phase margin and gain crossover frequency. The stability region of PI controller is subsequently obtained with a much simpler procedure than the existing approaches. It is further shown that a certain relative delay margin can represent the robustness level well and the contour can be sketched with a simpler procedure than the one using maximum sensitivity index. With constraints on the relative delay margin, an optimal disturbance rejection problem is then formulated and analytically solved. Simulation results show that the performance of the proposed methodology is better than that of other PI tuning rules. In this paper, the relative delay margin is shown as a promising robustness measure to the analysis and design of other advanced controllers.     

Generalized predictor based active disturbance rejection control for non-minimum phase systems

In this paper, a generalized predictor based control scheme is proposed to improve system performance of set-point tracking and disturbance rejection for non-minimum phase (NMP) systems. By using a generalized predictor to estimate the system output without time delay, a model-based extended state observer (MESO) is designed to simultaneously estimate the system state and disturbance. Accordingly, an active disturbance rejection control design is developed which consists of a state feedback control and a feedforward control for the disturbance rejection. The MESO and feedback controllers are analytically derived by specifying the desired characteristic roots of MESO and closed-loop system poles, respectively. To improve the output tracking performance, a pre-filter is designed based on a desired closed-loop transfer function for the set-point tracking. A sufficient condition guaranteeing robust stability of the closed-loop system against time-varying uncertainties is established in terms of linear matrix inequalities (LMIs). Three illustrative examples from the literature are used to demonstrate the effectiveness and merit of the proposed control scheme.     

一种基于自抗扰控制的电子差速控制策略研究

电动车辆转向时,复杂路况及车况综合作用下,驱动轮承载更强扰动的负荷,驱动轮滑移运动所占比重不确定性增大,影响行车稳定与安全.为此,设计基于自抗扰控制(ADRC)的电子差速控制(EDC)策略,并利用混沌粒子群优化算法(CPSO)设计控制器参数.构建7自由度整车模型,以滑移率为控制量、驱动轮电机转矩为输出,设计基于CPSO...     

音圈致动快速反射镜的降阶自抗扰控制

为改善航空光电载荷用音圈致动快速反射镜的控制性能,提出一种降阶自抗扰控制方法。首先,对快速反射镜(Fast Steering Mirror,FSM)模型进行了分析并获取了模型参数。根据自抗扰控制理论,设计了FSM的三阶通用自抗扰控制器。将电涡流传感器的测量结果视为已知,提出降阶扩张状态观测器及其对应的自抗扰控制器设计方法。根据控制器带宽设计思想,推导了对于FSM这类二阶欠阻尼对象的控制律,并给出了加入扰动补偿量的控制律的具体实现形式。实验结果表明,降阶自抗扰控制能明显改善FSM的位置阶跃响应动态性能,能实现无超调与振荡的阶跃响应,稳态时间由11.7 ms提升至9.2 ms,同时能够降低FSM对位置斜坡输入跟踪的稳态误差,并改善其速度响应动态过程,像移补偿稳速时间由10.2 ms提升至7.8 ms,提升约24%。降阶自抗扰控制具有实现简单、运算量小的特点,能够明显提升FSM的动态性能。     

高精度稳定平台伺服系统的自抗扰控制

提出了一种应用于高精度稳定平台伺服系统的设计方法。为满足稳定平台快速隔离扰动、稳定视轴的要求,将自抗扰控制应用于平台系统的速度环,和常规PID控制的电流环一起构成ADRC-PID控制。Simulink仿真结果表明,与传统PID控制相比,采用自抗扰控制后系统响应速度快,隔离度有较大的提高。ADRC-PID控制可满足高精度光电稳定平台的性能要求,系统具有响应速度快,隔离度好,鲁棒性强,稳定性高等特点。     

Limit cycle analysis of active disturbance rejection control system with two nonlinearities

Introduction of nonlinearities to active disturbance rejection control algorithm might have high control efficiency in some situations, but makes the systems with complex nonlinearity. Limit cycle is a typical phenomenon that can be observed in the nonlinear systems, usually causing failure or danger of the systems. This paper approaches the problem of the existence of limit cycles of a second-order fast tool servo system using active disturbance rejection control algorithm with two fal nonlinearities. A frequency domain approach is presented by using describing function technique and transfer function representation to characterize the nonlinear system. The derivations of the describing functions for fal nonlinearities and treatment of two nonlinearities connected in series are given to facilitate the limit cycles analysis. The effects of the parameters of both the nonlinearity and the controller on the limit cycles are presented, indicating that the limit cycles caused by the nonlinearities can be easily suppressed if the parameters are chosen carefully. Simulations in the time domain are performed to assess the prediction accuracy based on the describing function.     

基于滑模自抗扰的PMLSM电流偏差解耦控制

针对永磁直线同步电动机(PMLSM)存在电流耦合以及在运行过程中易受参数变化的影响使系统鲁棒性降低,本文设计了一种基于滑模自抗扰的电流偏差解耦控制(SADRC-CDDC)方法.从参考电流与实际电流作差处引入两轴交叉耦合支路,建立含耦合项的电流控制方程,计算出耦合量并对系统进行补偿,设计电流偏差解耦控制器(CDDC),用...     

基于 GA-模糊 RBF 的发电机组滑模自抗扰控制

针对燃煤发电机组风烟系统大惯性、大滞后、参数不稳定等特点，提出一种基于发电机组的滑模自抗扰控制策略。选择模糊径向基函数(RBF)算法辨识模型，以梯度下降法和遗传算法分别对神经网络权值进行粗调和细调，通过扩张状态观测器估计系统内外部扰动，将非线性状态误差反馈控制律与滑模控制策略相结合以克服系统惯性、滞后和扰动的问题，并设计Lyapunov函数验证控制系统稳定性。仿真结果表明，滑模自抗扰控制与串级比例-积分-微分(PID)控制、滑模控制和自抗扰控制相比，在模型适配的情况下，所设计的控制策略在38 s达到设定值，无超调量；当向系统施加20%的反向阶跃干扰时，系统调节时间为39.5 s,超调量为3.4%。在模型失配情况下的调节时间为43.2 s,无超调量；当向系统施加20%的反向阶跃干扰时，系统调节时间为46.4 s,超调量为3.87%。工程应用结果表明，一次风量控制偏差在±10 000 m³/h以内，相比串级PID控制策略波动范围降低21%,系统抗干扰能力和鲁棒性得到有效提升。     

永磁同步电机位置伺服系统改进变结构自抗扰控制

为进一步提高传统变结构自抗扰控制器的控制精度,增强永磁伺服驱动系统的抗干扰能力,提出一种改进变结构自抗扰控制策略。该方法在基于变结构原理设计的扩张状态观测器中引入位置、速度的观测误差以实现状态变量的无差估计,采用基于指数趋近律设计的非线性状态误差反馈控制律实现线性控制与非线性控制的平滑过渡,并在此基础上引入位置跟踪误差,提高伺服系统的跟踪性能。通过实验分析比较了改进变结构自抗扰控制与传统变结构自抗扰控制两种控制策略,结果显示改进控制策略较传统控制策略的位置跟踪误差减少了约30%。当负载突变时,传统控制策略的跟踪误差约为负载突变前最大跟踪误差的3.4倍,而改进变结构自抗扰控制策略仍能准确跟踪给定信号。     

光电跟踪系统自抗扰伺服控制器的设计

考虑系统扰动对光电跟踪伺服系统精度的影响,提出了采用自抗扰的控制方案,并分析了实现自抗扰的工作原理。对某型光电跟踪系统进行了结构分析,将目标运动速度视为外部扰动,系统内部参数摄动视为内部扰动,采用扩张状态观测器从系统响应的输入、输出信号中估计出扰动,并进一步用跟踪微分器提取扰动的一阶导数来提高对扰动的估计精度,以最大程度地补偿扰动。实验结果表明,在载体扰动下,跟踪最大角速度为40mrad/s,最大角加速度为8mrad/s2,机动目标的误差0.1mrad,且响应速度快,超调10%。该方案结构简单,控制鲁棒性强;无需额外的传感器对目标运动进行测量、滤波和预测,即可有效提高系统高精度捕获、跟踪快速机动目标的能力。