基于鲁棒自适应反步的可重复使用飞行器再入姿态控制

考虑惯性矩阵不确定和力矩扰动的影响, 设计再入可重复使用飞行器的鲁棒自适应反步姿态控制器. 首先, 设计虚拟控制时, 通过自适应实现对不确定项的未知边界的估计; 其次, 设计实际控制输入时, 为消除反步法的“计算爆炸”问题, 将虚拟控制导数作为不确定项, 引入鲁棒项消除不确定与力矩扰动的影响; 再次, 基于Lyapunov 理论证明了跟踪误差收敛到任意小邻域; 最后, 基于X-33 的六自由度模型仿真验证了所设计的控制策略的有效性.     

Adaptive disturbance observer‐based finite‐time continuous fault‐tolerant control for reentry RLV

The control effectors of reusable launch vehicle (RLV) can produce significant perturbations and faults in reentry phase. Such a challenge imposes tight requirements to enhance the robustness of vehicle autopilot. Focusing on this problem, a novel finite‐time fault‐tolerant control strategy is proposed for reentry RLV in this paper. The key of this strategy is to design an adaptive‐gain multivariable finite‐time disturbance observer (FDO) to estimate the synthetical perturbation with unknown bounds, which is composed of model uncertainty, external disturbance, and actuator fault considered as the partial loss of actuator effectiveness in this work. Then, combined with the finite‐time high‐order observer and differentiator, a continuous homogeneous second‐order sliding mode controller based on the terminal sliding mode and super‐twisting algorithm is designed to achieve a fast and accurate RLV attitude tracking with chattering attenuation. The main features of the integrated control strategy are that the adaptation algorithm of FDO can achieve non‐overestimating values of the observer gains and the second‐order super‐twisting sliding mode approach can obtain a more elegant solution in finite time. Finally, simulation results of classical RLV (X‐33) are provided to verify the effectiveness and robustness of the proposed fault‐tolerant controller in tracking the guidance commands. Copyright © 2017 John Wiley & Sons, Ltd.     

Adaptive gains to super‐twisting technique for sliding mode design

This paper studies the super‐twisting algorithm (STA) for adaptive sliding mode design. The proposed method tunes the two gains of STA on line simultaneously such that a second order sliding mode can take place with small rectifying gains. The perturbation magnitude is obtained exactly by employing a third‐order sliding mode observer in opposition to the conventional approximations by using a first order low pass filter. While driving the sliding variable to the sliding mode surface, one gain of the STA automatically converges to an adjacent area of the perturbation magnitude in finite time. The other gain is adjusted by the above gain to guarantee the robustness of the STA. This method requires only one parameter to be adjusted. The adjustment is straightforward because it just keeps increasing until it fulfills the convergence constraints. For large values of the parameter, chattering in the update law of the two gains is avoided by employing a geometry based backward Euler integration method. The usefulness is illustrated by an example of designing an equivalent control based sliding mode control (ECBC‐SMC) with the proposed adaptive STA for a perturbed LTI system.     

自适应广义滑模观测器之状态估计和故障重构

针对一类同时具有执行机构故障和输出扰动的不确定性系统,提出了一种自适应广义滑模观测器,实现系统状态的估计和执行机构故障的重构.首先,进行系统变换及状态增广构成一类奇异系统,使得执行机构故障和输出扰动解耦,且输出扰动成为增广系统的状态之一;随后,受未知输入观测器和滑模观测器的启发,设计了一种广义滑模观测器,放宽了传统方法对输出维数的严格约束,并通过融入自适应技术放宽了对故障和不确定性上界已知的要求;最后,利用等效误差注入的思想实现故障重构.针对可重复使用运载器再入段进行的仿真实例,验证了所提方法的有效性.     

基于光滑二阶滑模的可重复使用运载器有限时间再入姿态控制

针对可重复使用运载器(reusable launch vehicle,RLV)的六自由度再入模型,考虑模型不确定和外界干扰对再入姿态控制的影响,提出了一种非线性鲁棒控制策略.首先,根据多时间尺度特性将RLV的再入姿态模型分为姿态角子系统和姿态角速率子系统.其次,对每个子系统分别设计光滑二阶滑模控制器和滑模干扰观测器实现子系统的有限时间稳定.利用干扰观测器可以实现对不确定和外界干扰的精确估计,从而对控制器进行有效的补偿.进而,基于Lyapunov理论证明了整个系统的有限时间稳定.最后,通过仿真验证了提出的控制策略具有良好的控制性能和鲁棒性.     

Output feedback stabilization using super‐twisting control and high‐gain observer

An output feedback controller is designed for a class of uncertain nonlinear systems with relative degree higher than one. A super‐twisting sliding mode state feedback controller is designed and implemented using a high‐gain observer. It is proved that the controller achieves practical stabilization and the ultimate bound can be reduced by decreasing a design parameter. The performance of the controller is illustrated by simulation.     

Payload pendulation and position control systems for an offshore container crane with adaptive‐gain sliding mode control

When container ports are not available for heavy ships, the offshore ship‐to‐ship transfer operation is an alternative method to an inland container terminal. This process is performed between a large container ship and a smaller ship, which is equipped with a container crane, called the mobile harbor or the ship‐mounted crane. The sea‐state condition is a crucial factor in open‐sea operations. The presence of waves, wind, and current disturbances excite the pendulum oscillations of the crane's hanging container. In this study, the problem of payload pendulation and container position for an offshore container crane using an adaptive‐gain sliding mode control (SMC) scheme is investigated. The primary control task during the loading and unloading process is to keep the container in the desired region under the harsh oceanic environment. The proposed control architecture incorporates an adaptive‐gain SMC with a compensation part and a prediction mechanism. Therein, a sliding surface is design to combine the desired sway motion of the payload with the desired trolley trajectory. Furthermore, a varying control gain is proposed in the sliding control, obtained by an adaption law that transitions the system into sliding mode. By constructing an appropriate Lyapunov function, we show that the proposed control law ensures the asymptotic stability of the ship‐mounted crane. Numerical simulations are presented to show the effectiveness and robustness of the proposed control system.     

模糊滑模控制和负载转矩补偿的异步电动机直接转矩控制

针对异步电动机(IM)转矩脉动以及抗干扰能力差的问题,设计了基于模糊滑模控制(FSMC)与负载转矩补偿的新型直接转矩控制(DTC),取代传统PID速度调节器的是一种滑模控制器.为解决滑模控制器中负载转矩脉动的问题,用模糊逻辑控制器取代了传统滑模控制律中的不连续部分,可以明显降低异步电动机在低速运转时的转矩脉动.提出了一种负载转矩观测器来估计未知的负载转矩.负载转矩观测器用来估计负载转矩扰动,估计作为速度环的前馈补偿.仿真结果表明:在低速负载转矩扰动时,该设计具有更好的动态响应和速度性能、更高鲁棒性和更强的抗干扰能力.     

基于Terminal 滑模的高超声速飞行器姿态控制

针对高超声速飞行器六自由度再入模型,考虑模型参数不确定和外界干扰对再入姿态控制的影响,基于Terminal滑模对再入过程中姿态角的跟踪控制问题进行研究.为了减少外界高频噪声对系统性能的影响,首先,利用多时间尺度技术将姿态模型划分为双环结构;然后,分别针对各环路设计Terminal滑模控制器,并通过Lyapunov理论和奇异摄动理论对系统的稳定性进行证明.仿真结果表明,对于六自由度再入模型,该控制方法能够很好地跟踪再入制导指令.     

基于高阶滑模观测器的自适应时变滑模再入姿态控制

针对再入飞行器鲁棒姿态控制问题, 提出一种基于高阶滑模观测器的自适应时变滑模控制器设计方法. 首先, 设计了一种时变滑模面, 并在此基础上推导了相应的时变滑模控制律, 其中滑模控制中切换增益通过一种自适应算法获得, 消除了控制器设计过程中对系统不确定性上界已知的要求; 然后, 利用高阶滑模观测器对控制器设计过程中用到的姿态角导数信息进行观测, 同时能够获得系统扰动估计值, 从而构造一种基于观测器的控制器形式; 最后, 通过仿真验证了所提出的控制算法在提高再入飞行器姿态控制精度以及系统鲁棒性方面的有效性.     

A fast non-singular terminal sliding mode control based on perturbation estimation for piezoelectric actuators systems

Piezoelectric actuators (PEAs) are the key devices in micro/nano positioning system. However, the PEA performance is significantly degraded by the inherent non-linear behaviour. This behaviour is a consequence of the hysteresis properties contained within PEAs. Therefore, in micro/nano positioning applications, a robust control system has to be adopted for such actuators. This paper proposes a systematic control method that utilises a fast non-singular terminal sliding mode (FNTSM) based on online perturbation estimation technique for PEAs. Unlike other sliding mode methods, the FNTSM control method is characterised by chatter free. Besides, a zero error convergence can be guaranteed in finite time in the presence of disturbance and system uncertainties (i.e., hysteresis and gain changes). The design of the FNTSM control based on perturbation estimation (FNTSMPE) is presented. A model-free robust exact differentiator is used to estimate the states of the feedback system from merely measurable position signal. Theoretical analysis and the experimental results of FNTSMPE control reveal that high-precision and robust performance is achieved in comparison with ordinary FNTSM control.     

High‐order sliding mode control design based on adaptive terminal sliding mode

High‐order sliding mode control techniques are proposed for uncertain nonlinear SISO systems with bounded uncertainties based on two different terminal sliding mode approaches. The tracking error of the output converges to zero in finite time by designing a terminal sliding mode controller. In addition, the adaptive control method is employed to identify bounded uncertainties for eliminating the requirement of boundaries needed in the conventional design. The controllers are derived using Lyapunov theory, so the stability of the closed‐loop system is guaranteed. In the first technique, the developed procedure removes the reaching phase of sliding mode and realizes global robustness. The proposed algorithms ensure establishment of high‐order sliding mode. An illustrative example of a car control demonstrates effectiveness of the presented designs. Copyright © 2011 John Wiley & Sons, Ltd.     

PMSM有效磁链滑模观测器及转矩精确控制

为了改善轨道交通永磁同步电动机转矩控制的性能,提出了一种改进的有效磁链滑模观测器,实现了永磁同步电动机的精确转矩闭环控制。采用有效磁链的概念,建立了基于有效磁链的内置式永磁同步电机数学模型;在[α-β]静止坐标系建立了有效磁链的滑模观测器,并基于滑模等值控制方法实现了有效磁链的观测,进而进行转矩的实时估算,以此和转矩给定值形成精确转矩闭环控制。通过仿真验证该方法的可行性和有效性。结果表明提高永磁同步电动机的转矩控制精度,改善了轨道永磁同步电动机控制系统的性能。该方法不仅适用于内置式永磁同步电机,而且适用于表贴式永磁同步电机。     

Robust Attitude Control for Reusable Launch Vehicles Based on Fractional Calculus and Pigeon-inspired Optimization

In this paper, a robust attitude control system based on fractional order sliding mode control and dynamic inversion approach is presented for the reusable launch vehicle (RLV) during the reentry phase. By introducing the fractional order sliding surface to replace the integer order one, we design robust outer loop controller to compensate the error introduced by inner loop controller designed by dynamic inversion approach. To take the uncertainties of aerodynamic parameters into account, stochastic robustness design approach based on the Monte Carlo simulation and Pigeon-inspired optimization is established to increase the robustness of the controller. Some simulation results are given out which indicate the reliability and effectiveness of the attitude control system.      

High‐gain observer with higher order sliding mode for state and unknown disturbance estimations

In this paper, we consider the estimation problem of a class of single‐input–single‐output nonlinear Lipschitz systems with nonmatching uncertainty or disturbance, where the distribution vector may include the unknown states. A hybrid nonlinear observer structure that combines a high‐gain feedback with higher order sliding mode term is proposed. The high‐gain feedback works to constrain the estimation error to within an invariant set, and the sliding mode term will asymptotically track the uncertainty if the system satisfies strict structure assumptions. Furthermore, with the higher order sliding mode, the chattering effect will be effectively attenuated without sacrificing robustness, and the system uncertainty can be recovered without filtering effect. Copyright © 2013 John Wiley & Sons, Ltd.     

永磁同步电机伺服系统的自适应滑模最大转矩/电流控制

为了增强永磁同步电机(PMSM)伺服系统的抗干扰能力,本文设计了一种基于最大转矩/电流(MTPA)原理的自适应滑模控制器.控制器根据MTPA控制方法确定定子直轴和交轴电流,并利用滑模控制增强了系统的抗干扰能力,但同时给系统带来抖振.为了削弱系统抖振,设计了一种改进的自适应滑模趋近律用于位置控制.为了增加控制器的实用性,MTPA控制采用函数曲线拟合法.仿真结果表明,所提出的控制器有效增强了系统的动态性能、稳态性能及鲁棒性,并有效削弱了滑模控制带给系统的抖振.     

Sliding mode control of wind-induced vibrations using fuzzy sliding surface and gain adaptation

Although fuzzy/adaptive sliding mode control can reduce the chattering problem in structural vibration control applications, they require the equivalent control and the upper bounds of the system uncertainties. In this paper, we used fuzzy logic to approximate the standard sliding surface and designed a dead-zone adaptive law for tuning the switching gain of the sliding mode control. The stability of the proposed controller is established using Lyapunov stability theory. A six-storey building prototype equipped with an active mass damper has been used to demonstrate the effectiveness of the proposed controller towards the wind-induced vibrations.     

Optimization‐based adaptive sliding mode control with application to vehicle dynamics control

This paper presents the design of a new adaptive optimization‐based second‐order sliding mode control algorithm for uncertain nonlinear systems. It is designed on the basis of a second‐order sliding mode control with optimal reaching, with the aim of reducing the control effort while maintaining all the positive aspects in terms of finite‐time convergence and robustness in front of matched uncertainties. These features are beneficial to guarantee good performance in case of vehicle dynamics control, a crucial topic in the light of the increasing demand of semiautonomous and autonomous driving capabilities in commercial vehicles. The new proposal is theoretically analyzed, as well as verified relying on an extensive comparative study, carried out on a realistic simulator of a 4‐wheeled vehicle, in the case of a lateral stability control system.     

Second-order terminal sliding mode control for hypersonic vehicle in cruising flight with sliding mode disturbance observer

This paper focuses on the design of nonlinear robust controller and disturbance observer for the longitudinal dynamics of a hypersonic vehicle (HSV) in the presence of parameter uncertainties and external disturbances. First, by combining terminal sliding mode control (TSMC) and second-order sliding mode control (SOSMC) approach, the secondorder terminal sliding control (2TSMC) is proposed for the velocity and altitude tracking control of the HSV. The 2TSMC possesses the merits of both TSMC and SOSMC, which can provide fast convergence, continuous control law and hightracking precision. Then, in order to increase the robustness of the control system and improve the control performance, the sliding mode disturbance observer (SMDO) is presented. The closed-loop stability is analyzed using the Lyapunov technique. Finally, simulation results illustrate the effectiveness of the proposed method, as well as the improved overall performance over the conventional sliding mode control (SMC).     

An adaptive solution for robust control based on integral high‐order sliding mode concept

A new high‐order sliding mode controller is proposed. The main features are gain adaptivity and the use of integral sliding mode concept. The gain adaptation allows a reduction of the chattering and gives a solution to control uncertain nonlinear systems whose the uncertainties/perturbations have unknown bounds. The concept of real high‐order sliding mode detector is introduced given that it plays a key role in the adaptation law of the gain. This new control approach is applied by simulation to an academic example to evaluate its efficiency. Copyright © 2014 John Wiley & Sons, Ltd.