Latent variable iterative learning model predictive control for multivariable control of batch processes

A latent variable iterative learning model predictive control (LV-ILMPC) method is presented for trajectory tracking in batch processes. Different from the iterative learning model predictive control (ILMPC) model built from the original variable space, LV-ILMPC develops a latent variable model based on dynamic partial least squares (DyPLS) to capture the dominant features of each batch. In each latent variable space, we use a state–space model to describe the dynamic characteristics of the internal model, and an LV-ILMPC controller is designed. Each LV-ILMPC controller tracks the set points of the current batch projection in the corresponding latent variable space, and the optimal control law is determined and the persistent process disturbances is rejected along both time and batch horizons. The proposed LV-ILMPC formulation is based on general LV-MPC and incorporates an iterative learning function into LV-MPC. In addition, the real physical input that drives the process can be reconstructed from the latent variable space. Therefore, this algorithm is particularly suitable for multiple-input, multiple-output (MIMO) systems with strong coupling and serious collinearity. Three studies are used to illustrate the effectiveness of the proposed LV-ILMPC .     

Speed tracking control for the gimbal system with harmonic drive

This paper presents a composite controller based on a disturbance observer for the gimbal system of double-gimbal magnetically suspended control moment gyro (DGMSCMG) with harmonic drives. The controller removes the influence by coupling moments and nonlinear transmission torques. The disturbances are estimated by the designed disturbance observer. By introducing a state feedback controller, the disturbances can be eliminated from the output channel of the system. The gain selection principle of the disturbance observer is also analyzed. Both the simulation and experimental results indicate that the proposed control method can reject mismatched disturbances and improve system performance.     

Composite DOBC with fuzzy fault‐tolerant control for stochastic systems with unknown nonlinear dynamics

A class of stochastic nonlinear systems with fault and multisource disturbances is concerned. The fault is a general bounded actuator fault, and the multiple disturbances include partial‐known information disturbance and white noise. A stochastic adaptive disturbance observer is constructed to estimate the partial‐known information disturbance, based on which the partial‐known information disturbance can be compensated in the feed‐foreword channel immediately. Also, the multiplicative white noise can be attenuated by the designed feedback controller. To make the composite system is satisfactory, a composite disturbance based‐observer control with fuzzy fault‐tolerant control is proposed. The pole placement and LMI method is applied to attenuate and reject the disturbance. Furthermore, the fault can be compensated simultaneously. To verify the feasibility and availability of the designed control scheme, a simulation example is shown finally.     

基于抗干扰自适应算法的颤振系统的研究与仿真

颤振抑制系统中非线性扰动的干扰是影响抑制效果的一个重要因素,同时对颤振位移等被控量精确测量的能力有限也影响了抑制效果。为了消除扰动影响和减小测量被控量的难度,提出了设计基于抗干扰自适应算法的控制器,对二阶弹性气动模型进行颤振控制。Matlab仿真结果表明,构建的自适应控制器只需要较少并易于测量的被控量,与PID控制器相比能更有效精确地抑制扰动,控制颤振并消除了抑制误差。     

Periodic disturbance cancellation with uncertain frequency

This paper presents a new algorithm to cancel periodic disturbances with uncertain frequency. The disturbances are cancelled using an internal model structure with adaptive frequency, in parallel with a stabilizing controller. The time-varying internal model controller's states, in steady state, can be mapped to two time-invariant variables: the magnitude or energy of the internal model and frequency of the disturbance. An additional integral controller then can be used to reduce the difference between the internal model controller (IMC) and disturbance frequency to zero. The stability of the feedback control system with this algorithm and convergence of the algorithm to the correct frequency with exact disturbance cancellation are justified by singular perturbation and averaging theories. The algorithm is locally exponentially stable, rather than asymptotically stable. Simulations demonstrate the performance of the algorithm, the ability of this algorithm to identify the frequency of periodic disturbances and to reject periodic disturbances with uncertain frequency.     

Contribution to synthesis of manipulator control

The article addresses the control problem associated with tracking a trajectory which is predefined by the desired position and orientation of the end-effector tip (stage of nominal control). The problem is compounded by the assumption that variations in system parameters may occur thereby requiring that the nominal control be complemented with a controller (stage of perturbed control) which would regulate the disturbance produced by the variation in system parameters. A new formulation of the robot model for control synthesis is presented. The new formulation facilitates the synthesis of regulators for parameter variations using a robust servomechanism approach or a force feedback approach. The two approaches are illustrated using examples. The first example uses robust regulation to reject step input disturbances. The second example simulates the operation of peg-in-hole insertion using force feedback with an LQ controller.     

Speed Tracking Control of Permanent Magnet Synchronous Motor by a Novel Two-step Internal Model Control Approach

The control problem of permanent magnet (PM) synchronous motor has attracted extensive attentions in both control society and industrial applications. Much recently, a local speed tracking and nonlinear disturbance rejection problem of PM synchronous motor was investigated by nonlinear internal model design. In this paper, we propose a novel two-step controller design strategy to achieve speed tracking and nonlinear disturbance rejection of PM synchronous motor with wide speed range, which combines the advantages of classical double-loop control and nonlinear internal model control. It is worth mentioning that the proposed two-step controller design strategy can not only guarantee exact speed tracking with wide speed range, but also reject small nonlinear external disturbances in the load torque, generated by a so-called nonlinear exosystem. Simulation results demonstrate the effectiveness of our design.     

Disturbance rejection of battery/ultracapacitor hybrid energy sources

This paper contributes an active control strategy to reject disturbances in hybrid energy source systems applied in hybrid electric vehicles. The disturbances include persistent disturbances introduced by engine torque ripples compensation, and transient disturbances caused by transient load power demands. The disturbance rejection is achieved via singular perturbation theory. The original system is a Port-Controlled Hamiltonian (PCH) system, and the controller is designed based on interconnection and damping assignment. Experimental results verify the effectiveness of the disturbance rejection control.     

Robust nonlinear generalised predictive control for a class of uncertain nonlinear systems via an integral sliding mode approach

In this paper, a robust nonlinear generalised predictive control (GPC) method is proposed by combining an integral sliding mode approach. The composite controller can guarantee zero steady-state error for a class of uncertain nonlinear systems in the presence of both matched and unmatched disturbances. Indeed, it is well known that the traditional GPC based on Taylor series expansion cannot completely reject unknown disturbance and achieve offset-free tracking performance. To deal with this problem, the existing approaches are enhanced by avoiding the use of the disturbance observer and modifying the gain function of the nonlinear integral sliding surface. This modified strategy appears to be more capable of achieving both the disturbance rejection and the nominal prescribed specifications for matched disturbance. Simulation results demonstrate the effectiveness of the proposed approach.     

一类多变量系统的强抗扰控制

本文在文献[1]的基础上讨论一类多变量系统的强抗扰控制,以实现在幅度及噪声电平约 束下尽量抑制一类外扰造成的动态误差,且保持输出调节.多变量强抗扰控制器由常规的鲁 棒控制器和瞬态补偿器构成.     

轻武器伺服跟踪系统的干扰补偿控制

为提高轻武器伺服跟踪系统的位置跟踪精度,提出一种基于干扰观测器的CMAC-PD复合控制方法。将摩擦、电机力矩波动和模型参数不确定性等影响系统性能的因素视为干扰,采用一种新型的干扰观测器对其进行估计并加以补偿。在此基础上,提出一种基于CMAC与PD的复合控制方法。对比仿真实验表明,基于干扰观测器的CMAC-PD复合控制能更有效地抑制干扰对轻武器伺服跟踪系统动态性能的影响,进而使系统获得更高的跟踪精度。     

A Novel Robust Attitude Control for Quadrotor Aircraft Subject to Actuator Faults and Wind Gusts

A novel robust fault tolerant controller is developed for the problem of attitude control of a quadrotor aircraft in the presence of actuator faults and wind gusts in this paper. Firstly, a dynamical system of the quadrotor taking into account aerodynamical effects induced by lateral wind and actuator faults is considered using the Newton-Euler approach. Then, based on active disturbance rejection control (ADRC), the fault tolerant controller is proposed to recover faulty system and reject perturbations. The developed controller takes wind gusts, actuator faults and measurement noises as total perturbations which are estimated by improved extended state observer (ESO) and compensated by nonlinear feedback control law. So, the developed robust fault tolerant controller can successfully accomplish the tracking of the desired output values. Finally, some simulation studies are given to illustrate the effectiveness of fault recovery of the proposed scheme and also its ability to attenuate external disturbances that are introduced from environmental causes such as wind gusts and measurement noises.      

A high-performance flight control approach for quadrotors using a modified active disturbance rejection technique

In practice, the parameters of the flight controller of the quadrotors are commonly tuned experimentally with respect to a certain type of reference, such as the step reference and the unit-ramp reference. In this way, the performance of the flight controller might be affected by the variations of the references in real-time flights. Besides, real-time dynamic effects such as measure noises, external disturbances and input delays, which are usually neglected in the reported works, could easily deteriorate the performances of the flight controllers. This work is thereby motivated to develop a high-performance flight control approach utilizing a modified disturbance rejection technique for the quadrotors suffering from input delays and external disturbances. This control approach is developed in a cascaded structure and the attitude angles are chosen as the pseudo control inputs of the translational flight of the quadrotors. To facilitate the development, the dynamic model of the quadrotors is firstly formulated by including the effects of input delays, and the dynamics of the pseudo control variables are identified through real-time experiments. Based on the identified model, the flight control approach is proposed with a modified active disturbance rejection technique, which consists of a time optimal tracking differentiator, an extended state observer/predictor, and a nonlinear proportional–derivative controller. The tracking differentiator is designed to generate smooth transient profiles for the references, and the extended state observer/predictor is implemented for lumped disturbance estimation and state estimation considering the input delays. With the aid of the tracking differentiator and the extended state observer/predictor, the nonlinear proportional–derivative controller can thereby establish a fast tracking control and effectively reject the estimated disturbances. To verify the feasibilities of this development, comparative tests are carried out in both simulations and experiments. The results show that in the presence of small lumped disturbances, such as the measurement zero-drift, the steady-state errors of the proposed control approach for the ramp responses are less than 2 cm, and in the tests of sinusoidal trajectory tracking, the cross-tracking errors are less than 0.04 m. When with large disturbance airflow that is equivalent to strong breeze, the steady-state error achieved by the proposed flight controller is also less than 10 cm. All of these facts demonstrate the effectiveness of this development.     

一类分布式系统的自适应跟踪和扰动抑制

研究直接自适应状态反馈控制策略解决一类有故障和摄动关联链接的分布式大系统渐进跟踪和扰动抑制问题. 根据特殊的分布式结构, 在所有关联故障因子, 关联通道摄动和子系统外部干扰的上界都未知下, 提出自适应率在线升级控制器参数. 基于自适应策略信息, 构造一类分布式状态反馈控制器自动补偿故障和摄动影响, 同时抑制外部扰动. 在关联通道有故障摄动和外部扰动情况下, 所提出的自适应鲁棒跟踪控制器可以保证所得自适应闭环大系统稳定, 及每个子系统渐进输出跟踪所对应参考信号. 最后由一个仿真例子评估所提技术的有效性.     

基于定量反馈理论的时滞系统自抗扰控制参数整定

工业过程对象普遍存在时滞、模型参数不确定性和外部扰动多等特点,传统Smith预估控制方法难以设计出满足期望性能的鲁棒控制器.针对模型参数不确定性和外部扰动,本文采用自抗扰控制技术进行估计和补偿.针对系统存在时滞的特点,本文提出改进Smith预估器结构,提升扩张状态观测器对于扰动估计的实时性.在此基础上,本文以一阶时滞系统为例提出了控制器参数整定方法.首先根据最优参数选取准则确定预估器模型,然后在等效模型框架下采用定量反馈理论整定自抗扰控制器参数,确保控制系统达到预期性能指标.在仿真实验中,将所提出方法与几种常见时滞系统控制方法进行比较,通过设定值跟踪、抗扰及蒙特卡罗实验验证了所提出方法具有良好抗扰能力与鲁棒性.     

Active DIsturbance Rejection Control of Surface Vessels Using Composite Error Updated Extended State Observer

In this paper, a composite‐errors‐based active disturbance rejection control law is proposed for surface vessels with exogeneous disturbances. The low‐frequency disturbances from wind, wave and ocean currents are estimated by a novel composite‐errors‐based extended state observer (ESO). Since the composite errors are composed of trajectory tracking errors and estimation errors, the disturbance rejection control is feedforward‐feedback composite control. The advantages of feedforward control and feedback control are exploited to reject system disturbances. Compared with conventional ESO‐based active disturbance rejection control, smaller estimation errors and smaller tracking errors can be achieved by the proposed disturbance compensation control. The effectiveness and superiority of the designed control law are illustrated by theoretical analysis and simulation results.     

Adaptive sliding mode control for discrete-time multi-input multi-output systems

In this paper, robust adaptive sliding mode tracking control for discrete-time multi-input multi-output systems with unknown parameters and disturbance is considered. The robust tracking controller is comprised of adaptive control and sliding mode control design. Bounded motion of the system around the sliding surface and stability of the global system in the sense that all signals remain bounded are guaranteed. If the disturbance and the reference signal are slowly varying with respect to the sampling frequency, the proposed sliding mode controller can reject the disturbance and output tracking can be approximately achieved. Simulation results are presented to illustrate the proposed approach.     

LQ suboptimal decentralised controllers with disturbance rejection property for hierarchical systems

This article is concerned with decentralised output regulation of hierarchical systems subject to input and output disturbances. It is assumed that the disturbance can be represented as the output of an autonomous linear time invariant (LTI) system with an unknown initial state. The primary objective is to design a decentralised controller with the property that not only does it reject the degrading effect of the disturbance on the output (to achieve a satisfactory steady-state performance), it also results in a small linear quadratic (LQ) cost function (implying a good transient behaviour). To this end, the underlying problem is treated in two phases. In the first step, a number of modified systems are defined in terms of the original system. The problem of designing an LQ centralised controller which stabilises all the modified systems and rejects the disturbance in the original system is considered, and it is shown that this centralised controller can be found efficiently by solving a linear matrix inequality (LMI) problem. In the second step, a method recently presented in the literature is exploited to decentralise the designed centralised controller. It is shown that the obtained controller satisfies the prescribed design specifications including disturbance rejection. Finally, in a more pragmatic context, the system is assumed to be subject to input delay, and a robustness analysis is carried out accordingly. Simulation results elucidate the efficacy of the proposed control law.     

一种新的模糊滑模控制器设计方法

针对具有较大且不可观测外界干扰的一类不确定系统,提出一种新的模糊滑模控制器设计方法.首先基于模糊滑模控制原理,引入全局快速终端滑模控制,使系统在有限时间内达到稳态;然后构造以李雅普诺夫函数导数的绝对值为补偿的自适应干扰估计项,对外界干扰进行准确估计,进而提出一种双层递阶指数趋近全局快速终端模糊滑模控制器,通过指数趋近率来调节滑模面的动态品质,该控制器能快速收敛到稳定状态,且有效消除控制器的抖振情况;最后通过仿真算例验证所提方法的有效性.     

Reduced-order Generalized Proportional Integral Observer Based Continuous Dynamic Sliding Mode Control for Magnetic Levitation System with Time-varying Disturbances

In order to reduce the influence of time-varying disturbances for magnetic levitation system, we propose a reduced-order generalized proportional integral observer (RGPIO) based continuous dynamic sliding mode control scheme for magnetic levitation system in this paper. Unlike the popular extended state observer (ESO), it could deal with constant or slowing varying disturbances from theoretical point of view, the reduced-order generalized proportional integral observer (RGPIO) is designed to estimate the time-varying disturbances and system states, then the dynamic sliding mode surface is developed and deduce a continuous sliding mode controller (CSMC) for magnetic levitation system. Compared with ESO based continuous sliding mode controller, the proposed method not only ensures the position tracking accuracy, but also obtain better time-varying disturbance reject ability. Simulation and experimental results are also given to verify the effectiveness.