Observer-based predictive controller design with network-enhanced time-delay compensation

State feedback control is very attractive due to the precise computation of the gain matrix, but the implementation of a state feedback controller is possible only when all state variables are directly measurable. This condition is almost impossible to accomplish due to the excess number of required sensors or unavailability of states for measurement in most of the practical situations. Hence, the need for an estimator or observer is obvious to estimate all the state variables by observing the input and the output of the controlled system. As such, the goal of this paper is to provide a control design methodology based on a Luenberger observer design that can assure the closed-loop performances of a vehicle drivetrain with backlash, while compensating the network-enhanced time-varying delays. This goal is achieved in a sequential manner: firstly, a piecewise linear model of two inertias drivetrain, which takes into consideration the backlash nonlinearity and the network-enhanced time-varying delay effects is derived; then, a Luenberger observer which estimates the state variables is synthesized and the robust full state-feedback predictive controller based on flexible control Lyapunov functions is designed to explicitly take into account the bounds of the disturbances caused by time-varying delays and to guarantee also the input-to-state stability of the system in a non-conservative way. The full state-feedback predictive control strategy based on the Luenberger observer design was experimentally tested on a vehicle drivetrain emulator controlled through controller area network, with the aim of minimizing the backlash effects while compensating the network-enhanced delays.     

Eso‐Based Adaptive Robust Control of Dual Motor Driving Servo System

Based on extended state observer (ESO), we propose an adaptive robust control (ARC) for a dual motor driving servo system, in which there exist nonlinearities affecting control performance. To apply ESO and estimate the lumped uncertainty online, backlash and friction are analyzed and the nonlinear model of the plant is derived. We achieve several control objectives. First, the bias torque is considered in order to eliminate the effect of backlash. Second, the speed feedback is used to maintain the speed synchronization of motors. Then, to achieve feedforward control, finite‐time ESO is designed to estimate the unknown nonlinearities online. Furthermore, the ESO‐based adaptive robust controller is designed to guarantee L_∞ of tracking error by an initialization method, maintaining the transient performance of tracking behavior. Finally, extensive experimental results on a practical test rig validate the effectiveness of our proposed method.     

基于观测器的一类连续非线性系统的采样控制

首先使用反演方法分别设计了系统的连续时间状态反馈控制器、连续时间观测器和基于连续时间观测器的连续时间控制器. 接下来, 利用零阶保持法对连续时间状态反馈控制器进行离散化, 获得了状态反馈采样控制器; 利用零阶保持法对基于连续时间观测器 的连续时间控制器离散化, 获得了基于连续时间观测器的采样控制器; 利用Euler法对连续时间观测器离散化, 同时利用零阶保持法对控制器离散化, 从而获得了采样观测器和基于采样观测器的采样控制器. 本文论证了上述状态反馈采样控制器和基于连续时间观测器的采样控制器可以保证闭环系统渐近稳定, 而基于采样观测器的采样控制器可以保证被控对象的状态是有界的, 其最终边界依赖于设计参数与采样周期. 最后, 通过选择适当的采样周期, 完成了闭环采样控制系统的设计. 一个船舶航向控制的例子表明应用本文 所提方法设计出的三种采样控制器具有良好的控制效果.     

Time‐varying input delay compensation for nonlinear systems with additive disturbance: An output feedback approach

This paper addresses the output feedback tracking control of a class of multiple‐input and multiple‐output nonlinear systems subject to time‐varying input delay and additive bounded disturbances. Based on the backstepping design approach, an output feedback robust controller is proposed by integrating an extended state observer and a novel robust controller, which uses a desired trajectory‐based feedforward term to achieve an improved model compensation and a robust delay compensation feedback term based on the finite integral of the past control values to compensate for the time‐varying input delay. The extended state observer can simultaneously estimate the unmeasurable system states and the additive disturbances only with the output measurement and delayed control input. The proposed controller theoretically guarantees prescribed transient performance and steady‐state tracking accuracy in spite of the presence of time‐varying input delay and additive bounded disturbances based on Lyapunov stability analysis by using a Lyapunov‐Krasovskii functional. A specific study on a 2‐link robot manipulator is performed; based on the system model and the proposed design procedure, a suitable controller is developed, and comparative simulation results are obtained to demonstrate the effectiveness of the developed control scheme.     

基于等价输入干扰滑模观测器的磁悬浮球系统模型预测控制

本文针对系统不确定性和外部干扰引起的磁悬浮球系统控制性能下降的问题,提出了一种基于等价输入干扰滑模观测器的模型预测控制(MPC+EIDSMO)方法.首先将原系统转化为EID系统,采用等价输入干扰滑模观测器对EID系统状态变量及等价输入干扰进行估计;然后基于状态估计值设计模型预测控制器,并将等价输入干扰估计值以前馈的方式...     

严格反馈非线性系统的自适应神经网络输出反馈控制

基于非线性反馈函数,文章设计神经网络状态观测器,解决一类非线性系统的输出反馈控制问题.非线性反馈神经网络观测器在系统存在不确定性函数的情况下实时估计系统状态.利用所获得的状态信号,设计了自适应神经网络动态面控制器,同时保证了闭环系统的稳定性和所有信号的有界性.通过调节设计参数的取值能够达到期望的闭环跟踪性能.数值仿真表明,所设计的状态观测器不需要对原系统做状态变换,能够克服输出反馈滑模控制器带来的抖震问题.     

基于非光滑观测器的间隙三明治系统状态估计

在工业领域, 机械传动系统、液压系统等往往含有间隙特性, 这类系统可以用带间隙的三明治系统描述. 本文针对带间隙的三明治系统特点, 构建了一种非光滑观测器以对系统状态进行估计. 首先根据带间隙三明治系统的特点, 采用分离原理, 建立了描述系统特性的非光滑状态空间方程. 据此构造了能够随系统工作区间变化而自动切换的非光滑观测器, 给出了相应的收敛定理及其证明. 最后通过伺服液压系统的例子, 分别比较了非光滑观测器和传统的观测器对状态的跟踪效果, 比较结果表明非光滑观测器对于带间隙三明治系统状态变量估计的准确性要优于传统的观测器.     

冷带轧机液压伺服位置系统的鲁棒输出反馈控制

载力的干扰项视为未知输入, 构造未知输入观测器, 然后基于所构造的观测器设计鲁棒输出反馈控制器. 理论分析表明, 所提出的控制方法能够保证闭环系统是一致有界稳定的, 并具有鲁棒H1性能. 最后对某个650mm可逆冷带轧机液压伺服位置系统进行仿真研究, 结果验证了所提出方法的有效性.     

DISCRETE‐TIME OBSERVER‐BASED OUTPUT TRACKING CONTROLLER DESIGN FOR NONMINIMUM PHASE SYSTEMS WITH PERTURBATIONS

In this paper, an observer‐based output tracking controller for an SISO nonminimum phase discrete‐time system is proposed. When the disturbances between two consecutive sampling instances do not vary significantly, the observer algorithm can simultaneously estimate the system states and the unknown perturbation, and can render the estimation errors of system states and perturbation constrained in a small bounded region. The control law, including a feedforward term and a feedback input, can make the tracking error constrained in a small bounded region with guaranteed system stability. A numerical example is presented to demonstrate the applicability of the proposed control scheme.     

时滞系统在高速网络下的最优扰动抑制

研究在含有控制时滞与测量时滞的系统在高速通讯网络下最优扰动抑制问题. 首先建立在高速通讯网络下含有控制时滞与测量时滞系统的离散化数学模型, 利用模型转换将时滞系统转化为形式上的无时滞系统. 然后通过求解离散Riccati方程和Stein方程设计含有状态反馈、扰动前馈和控制记忆项的最优控制律, 前馈项和控制记忆项分别补偿了扰动和控制时滞对系统性能的影响. 通过构造降维扰动状态观测器, 设计了含扰动前馈、输出反馈及 控制记忆项的动态控制律, 解决了前馈补偿器的物理不可实现问题. 仿真实例验证了所设计的最优控制律的有效性.     

螺旋桨负载平衡装置控制系统设计及仿真

以一螺旋桨负载平衡装置为研究对象,通过对该装置在俯仰及偏转位置角度的控制,以达到对该装置方位控制和负载力平衡的目标。基于该系统强的耦合特性,通过状态反馈策略实现对系统解耦,并结合位置控制,实现该装置方位和俯仰角度的精确控制。同时,为了应对负载突变扰动对该装置位置及姿态影响,一个干扰观测器被设计出以用于实时观测外部干扰推力大小,最后,通过前馈补偿的方式提高该装置对干扰抑制的响应效果。通过系统动态模型建立、解耦设计、位置控制设计、扰动观察器设计和基于该观察输出的前馈干扰抑制补偿设计等研究,实现了当外载荷突变时的扰动抑制及姿态控制。研究结果表明引入干扰观测器及前馈补偿调节控制器时的扰动抑制能力得以增强。这对于基于该装置的平台的稳定性提高有着极大的工程应用价值。     

非线性系统的主动容错控制

对一般的非线性系统提出了一种新的主动容错控制方法.系统正常工作时,采用基于迭代学习观测器的输出反馈控制策略,控制器为迭代学习观测器的状态和调节参数的函数,此输出反馈控制器能良好地镇定该非线性系统.当系统发生故障后,进行控制器重组,在调节参数的自适应调节律中引入了故障估计的信息,使得系统发生故障后包含故障估计信息的重组控制器仍然能使系统稳定,实现了非线性系统的主动容错控制.计算机模拟显示所提出算法的有效性.     

永磁同步电机伺服系统的自适应模糊滑模控制

针对永磁同步电机伺服系统的跟踪控制问题,提出了一种基于扰动观测器的自适应模糊滑模控制方法.通过扰动观测器估计等效扰动,改善了系统的动态性能和稳态性能,并且只需要等效扰动的变化有界,而不是为零,放宽了要求;根据模糊控制原理引入3条模糊规则,在保证滑模条件的前提下有效地削弱了抖振;采用自适应策略估计模糊系统参数的最优值,简化了控制器的设计.实验结果表明,与常规自适应模糊滑模控制相比,本文提出的控制方法不仅能够有效地减小跟踪误差,而且能够改善参数估计过程,保证了参数估计的有界性.     

线性系统的动态输出反馈最优扰动抑制

首先通过求解Riccati方程和Sylvester方程,推导出前馈反馈最优扰动抑制控制律．然后构建了能同时预估状态和扰动的降维观测器,解决了前馈控制的物理不可实现问题．进而结合降维观测器和前馈反馈最优控制律,提出了一种动态输出反馈扰动抑制控制器的设计算法．最后通过仿真实例表明本文提出的控制算法的可行性．     

基于误差系统的信息融合最优预见跟踪控制

针对期望轨迹和干扰可预见的最优跟踪问题, 提出了一种基于误差系统的信息融合最优控制方法. 将线性伺服系统转化为误差系统; 利用信息融合估计方法, 通过融合期望轨迹、干扰输入、误差系统状态等信息, 获得误差系统协状态以及控制增量的最优估计. 构建了由积分项、状态反馈控制项和预见前馈补偿项组成的最优预见控制系统. 线性直流电机系统的控制仿真结果表明, 信息融合最优预见控制下的位置跟踪精度比传统最优预见控制下的要高.     

MIMO非仿射非线性系统的自适应模糊控制

针对一类多输入多输出非仿射非线性系统,设计了一种自适应模糊H∞控制方案,该方案把自适应模糊控制和高增益观测器结合起来.利用多变量的隐函数定理,证明了非仿射系统控制器的存在性.通过设计高增益观测器,解决了系统的状态不可测量问题,实现系统的输出反馈控制,模糊自适应控制增强了系统在线逼近干扰及处理系统不确定的能力.仿真结果表明了控制方案的有效性及优越性.     

A high-gain scaling technique for adaptive output feedback control of feedforward systems

In this note, we propose an adaptive output feedback control design technique for feedforward systems based on our recent results on dynamic high-gain scaling techniques for controller design for strict-feedback systems. The system is allowed to contain uncertain functions of all the states and the input as long as the uncertainties satisfy certain bounds. Unknown parameters are allowed in the bounds assumed on the uncertain functions. If the uncertain functions involve the input, then the output-dependent functions in the bounds on the uncertain functions need to be polynomially bounded. It is also shown that if the uncertain functions can be bounded by a function independent of the input, then the polynomial boundedness requirement can be relaxed. The designed controllers have a very simple structure being essentially a linear feedback with state-dependent dynamic gains and do not involve any saturations or recursive computations. The observer utilized to estimate the unmeasured states is similar to a Luenberger observer with dynamic observer gains. The Lyapunov functions are quadratic in the state estimates, the observer errors, and the parameter estimation error. The stability analysis is based on our recent results on uniform solvability of coupled state-dependent Lyapunov equations. The controller design provides strong robustness properties both with respect to uncertain parameters in the system model and additive disturbances. This robustness is the key to the output feedback controller design. Global asymptotic results are obtained.     

基于扩张状态观测器和有限时间控制的感应电机直接转矩控制

对感应电机直接转矩控制系统中存在的干扰,本文结合扩张状态观测器(ESO)和有限时间控制(FTC)提出一种复合控制方法来提高系统的抗干扰能力.首先采用扩张状态观测器估算系统的扰动,用此观测值作为前馈量补偿到输入端;然后运用连续有限时间控制方法设计系统前向通道中的反馈控制器.文中对控制器的稳定性进行了证明.与传统的PI控制以及P+ESO控制方法进行仿真与实验结果比较,验证了方法的有效性.     

Finite time state and disturbance estimation for robust performance of motion control systems using sliding modes

In this paper, simultaneous state and disturbance estimation of a drive system composed of motor connected to a load is proposed. Such a system is represented by a two mass model realising in a fourth-order plant. Backlash is introduced as the nonlinear disturbance in gears which is proposed to be estimated and in turn compensated. For this motion control system, a two-stage higher order sliding-mode observer is proposed for state and backlash estimation. The novelty lies in the fact that for this fourth-order system, output is considered from the motor end only, i.e. its angular displacement. The unmeasured states consisting of output derivative, load-side angular displacement and its derivative along with backlash are estimated in finite time. This disturbance due to backlash is unmatched in nature. The estimated states and disturbance are used to devise a robust sliding-mode control. This proposed scheme is validated in simulation and experimentation.     

Observer‐based adaptive robust control of a class of nonlinear systems with dynamic uncertainties

In this paper, a discontinuous projection‐based adaptive robust control (ARC) scheme is constructed for a class of nonlinear systems in an extended semi‐strict feedback form by incorporating a nonlinear observer and a dynamic normalization signal. The form allows for parametric uncertainties, uncertain nonlinearities, and dynamic uncertainties. The unmeasured states associated with the dynamic uncertainties are assumed to enter the system equations in an affine fashion. A novel nonlinear observer is first constructed to estimate the unmeasured states for a less conservative design. Estimation errors of dynamic uncertainties, as well as other model uncertainties, are dealt with effectively via certain robust feedback control terms for a guaranteed robust performance. In contrast with existing conservative robust adaptive control schemes, the proposed ARC method makes full use of the available structural information on the unmeasured state dynamics and the prior knowledge on the bounds of parameter variations for high performance. The resulting ARC controller achieves a prescribed output tracking transient performance and final tracking accuracy in the sense that the upper bound on the absolute value of the output tracking error over entire time‐history is given and related to certain controller design parameters in a known form. Furthermore, in the absence of uncertain nonlinearities, asymptotic output tracking is also achieved. Copyright © 2001 John Wiley & Sons, Ltd.