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.     

Control of unstable processes with time delays via ADRC

Active disturbance rejection control (ADRC) treats the external disturbance and internal uncertainties as a general disturbance, and uses an extended state observer (ESO) to estimate it in real-time and feeds it back in the control loop, thus can achieve good disturbance rejection performance. However, ADRC is not quite suitable for unstable delayed processes due to its inherent structure. In this paper, a two-degree-of-freedom (2DOF) control structure is proposed for unstable time- delayed systems. Set-point tracking and disturbance rejection are separated in this structure and ADRC is solely responsible for disturbance rejection. A method to tune the ADRC parameters using all the information of the system is proposed, and robustness and performance of the proposed method are analyzed. Simulation examples show that 2DOF-ADRC can achieve good tracking and disturbance rejection performance.     

自适应线性自抗扰控制器的设计

自抗扰控制器对于抑制不确定的扰动有良好的效果,但其控制器参数较多且整定困难。为了实现自适应的线性自抗扰控制器,对线性自抗扰控制器的参数整定策略展开了研究。首先,设计了基于观测误差的线性扩张观测器参数自适应整定算法。接着,设计了自抗扰控制器线性反馈环节的参数的自适应整定算法。最后,利用李雅普诺夫方法,证明上述自适应整定算法得到的参数可以保证扩张状态观测器的观测误差和被控系统最终输出误差都收敛至零。实验结果表明:精密气浮运动平台低速工况下,自适应线性自抗扰控制器的参数在0.8s内即可迅速完成整定计算;线性扩张观测器观测误差绝对值小于2nm;被控精密气浮运动平台的速度波动不大于5%。自适应线性自抗扰控制器实现了控制器参数在线整定,控制器的性能表现满足要求。     

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.     

Direct energy balance based active disturbance rejection control for coal-fired power plant

The conventional direct energy balance (DEB) based PI control can fulfill the fundamental tracking requirements of the coal-fired power plant. However, it is challenging to deal with the cases when the coal quality variation is present. To this end, this paper introduces the active disturbance rejection control (ADRC) to the DEB structure, where the coal quality variation is deemed as a kind of unknown disturbance that can be estimated and mitigated promptly. Firstly, the nonlinearity of a recent power plant model is analyzed based on the gap metric, which provides guidance on how to set the pressure set-point in line with the power demand. Secondly, the approximate decoupling effect of the DEB structure is analyzed based on the relative gain analysis in frequency domain. Finally, the synthesis of the DEB based ADRC control system is carried out based on multi-objective optimization. The optimized ADRC results show that the integrated absolute error (IAE) indices of the tracking performances in both loops can be simultaneously improved, in comparison with the DEB based PI control and H_∞ control system. The regulation performance in the presence of the coal quality variation is significantly improved under the ADRC control scheme. Moreover, the robustness of the proposed strategy is shown comparable with the H_∞ control.     

基于自抗扰技术的风扇磨直吹锅炉主汽压力控制系统的研究

文章针对由于被控对象的时变和非线性特性给风扇磨直吹式锅炉主汽压力自动调节带来的控制品质恶化问题,采用了自抗扰控制(ADRC)策略,这种控制算法只需被控对象的输入输出信息就能很好的估计出系统的实时内外扰动总和、并将其加以补偿,该控制器具有结构简单、响应快、鲁棒性强等优点.仿真表明这种控制器能有效改善该类系统的控制品质.     

基于自抗扰控制器的磁浮平台水平推力控制

介绍一种新型的磁浮平台,针对该磁浮平台水平运动这一多变量、非线性、强耦合的系统,提出一种改进的自抗扰控制器,克服常规自抗扰控制器非线性状态误差反馈控制律中非线性函数的不平滑性,并探索出一套行之有效的控制器参数整定规则,同时利用扩张状态观测器观测出内部扰动和外部扰动,并对它们进行补偿。仿真对比分析和试验结果表明,这种改进的自抗扰控制器具有很好的动态、静态特性及鲁棒性。     

A GA-based parameters tuning method for an ADRC controller of ISP for aerial remote sensing applications

This paper presents a parameters tuning method based on the genetic algorithm (GA) for an active disturbance rejection control (ADRC) of a three-axis inertially stabilized platform (ISP) with imaging sensors. To improve the stabilization accuracy and robustness of an aerial ISP under multi-source disturbances environment, an ADRC control scheme is first proposed. Then, to accurately identify and tune the parameters in the ADRC controller, a GA-based parameters tuning method is proposed. In this way, the performance of the ADRC is superior to the empirical method. To validate the proposed method, the simulations and experiments are carried out. The results show that the proposed ADRC with GA-based parameters tuning method has significant disturbance rejection ability which can improve the stabilization accuracy obviously. Compared with the ADRC with empirically tuning method, the stabilization error (RMS) under movable base is decreased up to 50.09%.     

On the rejection of internal and external disturbances in a wind energy conversion system with direct-driven PMSG

This paper deals with the critical issue in a wind energy conversion system (WECS) based on a direct-driven permanent magnet synchronous generator (PMSG): the rejection of lumped disturbance, including the system uncertainties in the internal dynamics and unknown external forces. To simultaneously track the motor speed in real time and capture the maximum power, a maximum power point tracking strategy is proposed based on active disturbance rejection control (ADRC) theory. In real application, system inertia, drive torque and some other parameters change in a wide range with the variations of disturbances and wind speeds, which substantially degrade the performance of WECS. The ADRC design must incorporate the available model information into an extended state observer (ESO) to compensate the lumped disturbance efficiently. Based on this principle, a model-compensation ADRC is proposed in this paper. Simulation study is conducted to evaluate the performance of the proposed control strategy. It is shown that the effect of lumped disturbance is compensated in a more effective way compared with the traditional ADRC approach.     

Survey on methods of increasing the efficiency of extended state disturbance observers

This survey presents various methods of improving the overall estimation quality in the class of extended state observers (ESO), which estimate not only the conventional states of the system, but the acting disturbance as well. This type of observers is crucial in forming the active disturbance rejection control structure (ADRC), where the precision of online perturbation reconstruction and cancellation directly influences the robustness of the closed-loop control system. Various aspects of the observer-based disturbance estimation/rejection loop are covered by this work and divided into three categories, related with observer: structure, tuning, and working conditions. The survey is dedicated to researchers and practitioners who are interested in increasing the efficiency of their ADRC-based governing schemes.     

基于遗传算法的ADRC参数整定及其应用

自抗扰控制器(ADRC)通过对模型不确定因素和外扰进行补偿，使得控制系统对外扰和不确定因素均有很好的适应能力。它能够有效控制多种工业上较为难控的对象．并表现出极强的鲁棒性和抗干扰性。遗传算法在参数寻优方面，有着其他算法无法比拟的全局寻优能力．本文给出了基于遗传算法的自抗扰控制器的参数整定．并将其应用在几类不同的对象当中，仿真实例表明了通过遗传算法整定的ADRC的良好控制效果。     

Modified reduced order observer based linear active disturbance rejection control for TITO systems

This paper proposes an observer based control approach for two input and two output (TITO) plant affected by the lumped disturbance which includes the undesirable effect of cross couplings, parametric uncertainties, and external disturbances. A modified reduced order extended state observer (ESO) based active disturbance rejection control (ADRC) is designed to estimate the lumped disturbance actively as an extended state and compensate its effect by adding it to the control. The decoupled mechanism has been used to determine the controller parameters, while the proposed control technique is applied to the TITO coupled plant without using decoupler to show its efficacy. Simulation results show that the proposed design is efficiently able to nullify the interactions within the loops in the multivariable process with better transient performance as compared to the existing proportional-integral-derivative (PID) control methods. An experimental application of two tanks multivariable level control system is investigated to present the validity of proposed scheme.     

On performance analysis of ADRC for a class of MIMO lower-triangular nonlinear uncertain systems

This paper designs the active disturbance rejection control (ADRC) to achieve desired performance for a class of MIMO lower-triangular nonlinear systems with large uncertainties under un-matched condition. We develop the ADRC with a set of extended state observers, and prove that the closed-loop system can achieve satisfied dynamic performance. The theoretical results illustrate the relationship between the bound of the concerned error and the bandwidth of extend state observers.     

A novel active disturbance rejection-based control strategy for a gun control system

To compensate for the nonlinearity and to achieve finely-tuned tracking accuracy of a gun control system driven by an AC machine, an improved active disturbance rejection control (IADRC) strategy with neural network embedding (NN-IADRC) is developed in this paper. The proposed IADRC, which has amnestic memory effects, can be regarded as an extension of the conventional ADRC (CADRC), making it a special case of the IADRC. To further attenuate the dependence on system models and enhance the disturbance rejection capacities of the IADRC strategy, an on-line NN-based optimum updating approach is also developed in this paper. Finally, a series of experiments are conducted on the semi-physical simulation platform to estimate the performance of the control system and the effects of the memory factor on the system. The experimental results confirm that the proposed NN-IADRC is highly robust. The results also confirm that it performs more excellently than the CADRC and that its fine tuning has attained tracking accuracy.     

基于优化ADRC的单臂机器人轨迹跟踪研究

针对机器人在不确定环境下受到内外界挠动的影响，末端执行器不能跟踪已规划的轨迹运行，以Kinova MICO2机器人为例，研究轨迹自抗挠跟踪模型。建立了机器人关节空间运动模型，根据挠动特点构造了二阶ADRC框架模型，解决了末端执行器偏离规划轨迹的问题。分析了机器人ADRC参数对轨迹跟踪的意义，为了确保系统跟踪的动态稳定性，建立GA-RBF网络优化了原始ADRC。最后分析轨迹跟踪前后的离散点绝对误差，验证机器人轨迹跟踪的可靠性。实验结果表明，GA-RBF优化的ADRC使得机器人实际轨迹能较好收敛于理想的规划轨迹，为工业应用中对轨迹要求较高的任务提供算法参考。     

陀螺稳定平台扰动的自抗扰及其滤波控制

分析了影响陀螺稳定平台隔离控制精度的主要因素,包括被控系统模型中的未建模部分、状态的随机扰动以及输出信号的测量噪声等。研究了综合解决各方面影响因素的控制方案以进一步提高陀螺稳定平台隔离精度。针对上述影响因素,设计一个两步控制策略。第一步,利用自抗扰对系统中未建模部分进行观测及其前向补偿,将自抗扰控制中的反馈控制设计为PID控制,以实现抗平台扰动的调节控制;第二步,利用Kalman滤波器对系统中的状态扰动及测量噪声进行滤波消除。详细描述了提出的控制策略并对其性能进行了系统仿真实验及参数优化。结果表明,该方案在幅值为3°、频率为1/6Hz的载体扰动下能达到4.61%的隔离度,与非线性摩擦力建模辨识及其前向补偿策略控制实际陀螺稳定平台达到的隔离度的最好值9.39%相比,文中提出的控制隔离性能提高了50.9%,具有更高的实用价值。     

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。     

三阶线性自抗扰控制器的液压伺服流量控制

针对阀控液压马达系统受非线性复杂扰动导致流量输出不稳定的问题,提出一种基于三阶线性自抗扰控制器(LADRC)的液压伺服流量控制方法。基于高阶LADRC理论,提出将ADRC应用于非线性的液压伺服系统控制,分析并验证了跟踪微分器的跟踪误差前馈增益具有抑制系统超调的作用。采用跟踪误差前馈与扩张状态观测器扰动反馈相分离的办法,提出一种针对复杂非线性三阶被控系统的改进的三阶LADRC算法。最后验证了该算法对一类大范围复杂不确定性液压伺服系统具有较PID更强的扰动抑制能力。     

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。     

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。