双框架控制力矩陀螺框架系统的扰动观测及抑制

内外框架间的耦合力矩、非线性摩擦和未建模动态是影响双框架控制力矩陀螺框架系统高精度角速率伺服控制的主要因素。为提高框架系统的干扰抑制能力,保证框架系统输出角速率精度,本文提出了一种基于非线性级联扩张状态观测器和滑模控制的复合扰动抑制方法。框架系统中的所有干扰都被认为是集总干扰并由设计的NCESO估计,通过滑模控制可从系统输出通道中消除集总干扰的影响。最后,将本文提出的控制方法与线性级联扩张状态观测器和状态反馈结合的复合控制方法进行了对比仿真实验。仿真和实验结果表明,本文提出的方法具有更好的干扰抑制和动态响应性能,内框架角速度波动从0.5(°)/s减小到0.2(°)/s,外框架角速度波动从0.45(°)/s减小到0.15(°)/s;跟踪正弦参考信号时,速度跟踪误差从1.8(°)/s减小到1.2(°)/s,相位滞后从8°减小到1.3°。     

基于滑模扰动观测器的磁轴承主动振动控制

由于磁悬浮控制力矩陀螺转子的不平衡振动会造成控制力矩陀螺系统的同频扰动,影响卫星姿态控制精度与卫星载荷精度,本文提出了基于滑模变结构扰动观测器的磁轴承主动振动控制方法.首先,对不平衡扰动力和力矩作用下的磁轴承-转子系统进行建模;接着,设计了滑模变结构扰动观测器观测不平衡扰动力和力矩;然后,利用跟踪微分器估计位移传感器输出信号的微分获取速度信号,降低观测器的阶数;最后,将滑模扰动观测器的输出引入磁轴承控制器,对观测得到的同频不平衡扰动力和力矩进行补偿.仿真和试验结果均表明,设计的滑模变结构观测器实现了对不平衡扰动的观测,通过控制器有效地实现了对不平衡扰动的补偿,减少了72％的同频振动.     

线性/非线性自抗扰切换控制在变载荷气动加载系统中的应用

针对气动加载系统压力跟踪控制中强非线性、强耦合性、模型不精确性等问题,提出一种线性/非线性自抗扰切换控制器,该控制器结合了线性自抗扰控制器参数整定简便、理论分析简单和非线性自抗扰控制器跟踪精度高、响应快的优点,设计线性/非线性切换扩张状态观测器对系统的耦合项以及不同幅值的扰动等不确定项进行估计,并采用切换状态误差反馈控制律给予实时主动补偿,进而实现系统加载压力的实时控制,并完成了线性/非线性切换扩张状态观测器的收敛性证明。最后,在气动变载荷摩擦磨损试验机试验平台上进行试验验证,与线性自抗扰和非线性自抗扰进行对比,试验结果表明,改进的控制器具有抗干扰性强、跟踪精度高、应用性强等特点。     

地基大口径望远镜伺服系统的抗扰动设计

针对地基大口径望远镜伺服系统的抗扰动问题,提出了一种抗扰动控制算法。该算法采用双闭环控制结构:内环为高带宽的电流环,采用PI控制器;外环为速度环;采用线性自抗扰控制器,通过线性扩张状态观测器辨识出系统扰动,然后将该扰动前馈到系统控制量中去,构成复合校正系统。为解决大动态输入引起的控制器饱和问题,状态观测器的输入控制量加入了抗饱和控制算法,保证了系统的稳定性和良好的动态特性。仿真和实验结果表明:与传统的PI控制器相比,引入抗饱和功能的自抗扰控制器在高低速均可以获得良好的动态性能;在低速平稳跟踪实验中,速度波动误差(RMS)由0.000 68(°)/s降低到0.000 32(°)/s。实验结果证明提出的方法能够有效提高伺服系统抗扰动能力和速度跟踪的平稳性。     

光电跟踪平台的观测自适应控制器

为解决导引头稳态跟踪精度与快速目标跟踪能力难以兼容的问题,建立了导引头伺服系统模型,通过分析传统PID控制策略的优势和缺陷,提出了改进自适应控制算法的研究思路。首先,利用自适应方程调节控制器参数以满足对不同速度目标的跟踪能力,并且通过非连续性观测投影对自适应参数进行控制,保证自适应参数始终处于和当前状态匹配的范围内。此外,利用状态识别控制提高响应速度并抑制快速跟踪时带来的噪声放大问题,同时通过线性反馈保证系统对随机扰动的鲁棒性。最后,利用自抗扰控制的过渡函数解决跟踪环带给速度环的超调问题。通过某型号导引头的实验测试,跟踪12(°)/s的运动目标时,观测自适应控制器输出的视线角速度的动态误差为0.05(°)/s(标准差),相比比例制导减小了53%;跟踪10(°)/s以下的目标时,超调量控制在8%以内,动态误差小于0.046(°)/s。结果表明,该算法可以提高光电平台的自适应性和跟踪精度。     

基于扩张状态观测器的永磁同步电机低速滑模控制

为了解决传统滑模控制高性能与系统抖振之间的矛盾,提高基于永磁同步电机驱动的航空光电平台系统的可靠性和指向精度,本文提出了一种新型滑模控制器趋近律,该趋近律可以有效削弱系统抖振并达到更好的跟踪效果。在此基础上,为提高扰动观测器的带宽以提升观测的准确性,将扩张状态观测器引入到光电稳定平台伺服系统中以观测系统的总和扰动,并将观测到的总和扰动补偿进滑模控制器,以更好地抑制系统抖振并提高系统抵抗外扰的能力。实验结果表明,本文提出的滑模控制器结合扩张状态观测器的方法明显优于传统的PI+DOB的控制方法。在匀速跟踪实验中,系统的位置指向误差的RMS值仅为0.005 7°,完全满足航空光电稳定平台的需求,约是经典PI+DOB控制方法精度的3倍;在正弦波跟踪实验中,本文提出的方法很大程度减小了速度跟踪的相位滞后,位置指向误差仅为PI+DOB方法的1/6;在三角波跟踪实验中,位置指向误差RMS值约为PI+DOB的1/3。     

基于干扰补偿的稳定平台控制系统设计

为克服机电伺服系统的摩擦以及其它力矩干扰问题,提出一种基于LuGre模型的摩擦前馈补偿和基于扰动观测器反馈补偿的复合控制策略。以某型号惯性稳定平台的单轴转台为例,首先对单轴转台进行建模分析,根据不变性原理,设计摩擦前馈补偿控制,再根据观测器输入和输出之间存在的数学关系,利用陀螺反馈的角速度信号,设计了基于扰动观测器的力矩补偿控制,最后在试验平台上,采用位置环为离散增量式PID算法,速度环为抗积分饱和PI算法,对提出的复合控制方法进行验证分析。稳定平台的实验结果表明所设计的惯性稳定平台控制系统能有效地抑制机电伺服系统中的摩擦及其它力矩干扰因素,一定程度上提高了惯性稳定平台的稳定性和动态跟踪性能。     

基于死区补偿的电液位置伺服系统自抗扰控制

针对电液位置伺服控制系统的比例阀死区、参数不确定及外部未知扰动等问题,设计了由自抗扰控制器与死区逆补偿构成的串联控制器。首先基于实验辨识构造死区逆模型对死区进行预补偿,然后根据系统特性设计了一阶自抗扰控制器,构造改进的扩张状态观测器对“总扰动”进行实时估计,并通过非线性控制律给予主动补偿。联合仿真与试验结果表明,所提出的串联控制器有效地补偿了比例阀死区,提高了系统动态性能和位置跟踪精度。     

基于扰动力矩观测器的大口径望远镜低速控制

为了增强大口径望远镜跟踪架伺服控制系统的抗扰动性能,提高其低速跟踪精度,提出了基于扰动力矩观测器的力矩补偿方法。该方法采用改进的加减速法控制转台的加减速时间,使得望远镜转台微震;通过测量电机的速度和电流响应曲线,辨识获得望远镜转台的转动惯量。然后,设计了望远镜转台的加速度估计器,根据编码器位置反馈数据,采用双积分和PD控制的方法,估计出当前系统的加速度。最后,基于转动惯量辨识和加速度估计,设计了扰动力矩观测器,根据电机的电流和转台的加速度,计算出外部的扰动力矩,并将扰动前馈补偿到电流控制器的输入端,以修正电流输入参考值。在2m望远镜控制系统中对扰动观测器的性能进行了实验验证,结果表明,加入扰动力矩观测器补偿后,在跟踪斜率为0.36(″)/s的位置斜坡时,跟踪误差值(RMS)由0.012 7″减小到0.007 3″;相比未加入扰动力矩观测器的补偿方法,望远镜的低速跟踪抖动明显减小,提高了伺服系统的低速跟踪精度,实现了对目标的平滑、稳定跟踪。     

四辊卷板机侧辊位移跟踪控制

针对四辊卷板机侧辊位移跟踪控制存在负载变化、参数摄动和未建模动态等不确定性问题,提出一种基于非线性扰动观测器的自适应滑模控制策略。采用非线性扰动观测器在线获取并补偿等效扰动;针对引入非线性扰动观测器后的系统,采用反步法设计自适应滑模控制器,利用自适应律动态补偿扰动观测误差,以降低滑模控制器的切换增益。该设计方法放宽了滑模切换增益对系统不确定性上界的先验性要求,降低了外界干扰和系统不确定性对侧辊位移跟踪性能的影响。同时,采用李雅普洛夫方法证明了侧辊位移跟踪闭环控制系统的稳定性。根据工程实际参数进行仿真,结果表明,该控制策略对系统的不确定性,特别是负载变化具有较强的鲁棒性,可以满足侧辊位移快速、精确跟踪的要求。     

Sliding mode output feedback control based on tracking error observer with disturbance estimator

For a class of systems who suffers from disturbances, an original output feedback sliding mode control method is presented based on a novel tracking error observer with disturbance estimator. The mathematical models of the systems are not required to be with high accuracy, and the disturbances can be vanishing or nonvanishing, while the bounds of disturbances are unknown. By constructing a differential sliding surface and employing reaching law approach, a sliding mode controller is obtained. On the basis of an extended disturbance estimator, a creative tracking error observer is produced. By using the observation of tracking error and the estimation of disturbance, the sliding mode controller is implementable. It is proved that the disturbance estimation error and tracking observation error are bounded, the sliding surface is reachable and the closed-loop system is robustly stable. The simulations on a servomotor positioning system and a five-degree-of-freedom active magnetic bearings system verify the effect of the proposed method.     

Finite-time sliding mode controller for perturbed second-order systems

This paper presents a novel finite-time sliding mode controller applied to perturbed second order systems. The proposed scheme employs a disturbance observer that can identify growing in time disturbances. Then, the observer is combined with a sliding mode controller to achieve finite-time stabilization of the second-order system. The convergence of the observer as well as the finite-time stability of the closed-loop system is theoretically demonstrated. Besides, it is also shown that the finite-time convergence properties of a given controller can be enhanced when using a compensation term based on the disturbance observer. The proposed controller is compared with a twisting algorithm and a finite-time sliding mode controller with disturbance estimation. Also, a conventional proportional integral derivative (PID) controller is combined with the proposed disturbance observer in a trajectory tracking task. Numerical simulations indicate that the proposed controller attains finite-time stabilization of the second order system by requiring a less amount of power than that demanded by the other control schemes and without being affected by the peaking phenomenon. Besides, the performance of the PID technique is enhanced by applying the proposed control methodology.     

Finite-time tracking control of nth-order chained-form non-holonomic systems in the presence of disturbances

This paper addresses the problem of finite-time tracking controller design for nth-order chained-form non-holonomic systems in the presence of unknown disturbances. To this aim, a generalized disturbance observer based controller is proposed and combined with a recursive terminal sliding mode approach which guarantees finite-time convergence of the disturbance observer dynamic. By introducing a time-varying transformation and introducing a new control law, the existence of the sliding around the recursive terminal sliding mode surfaces is guaranteed. Finally, the proposed approach is applied for a wheeled mobile robot with a fourth-order chained-form non-holonomic model. The simulation results demonstrate the desirable and robust tracking performance of the proposed approach in the presence of unknown disturbance.     

Design and implementation of continuous finite-time sliding mode control for 2-DOF inertially stabilized platform subject to multiple disturbances

Control performances of inertially stabilized platforms (ISPs) are always affected by various disturbed phenomena such as cross-couplings, mass unbalance, parameter variations, and external disturbances in real applications. To improve the dynamic response and the disturbance rejection ability of the ISP, a continuous finite-time sliding mode control (SMC) approach with cascaded control structure is proposed. By constructing a finite-time disturbance observer, the multiple disturbances are precisely estimated in real time without the complex modeling and calibration work. Under the field oriented control framework, for the stabilized loop subsystem, an improved super-twisting controller incorporating the disturbance estimates is developed whereas for the current loop subsystem, the super-twisting control method is directly employed. Finite-time convergence of the inertial angular rates is guaranteed with the continuous control action such that chattering is alleviated remarkably. Moreover, by utilizing the manner of disturbance compensation, the feedback control gains can be tuning down without sacrificing the disturbance rejection ability. Comparative experiments are performed to verify the effectiveness of the proposed control approach.     

Robust disturbance rejection control of a biped robotic system using high-order extended state observer

This study addressed the problem of robust control of a biped robot based on disturbance estimation. Active disturbance rejection control was the paradigm used for controlling the biped robot by direct active estimation. A robust controller was developed to implement disturbance cancelation based on a linear extended state observer of high gain class. A robust high-gain scheme was proposed for developing a state estimator of the biped robot despite poor knowledge of the plant and the presence of uncertainties. The estimated states provided by the state estimator were used to implement a feedback controller that was effective in actively rejecting the perturbations as well as forcing the trajectory tracking error to within a small vicinity of the origin. The theoretical convergence of the tracking error was proven using the Lyapunov theory. The controller was implemented by numerical simulations that showed the convergence of the tracking error. A comparison with a high-order sliding-mode-observer-based controller confirmed the superior performance of the controller using the robust observer introduced in this study. Finally, the proposed controller was implemented on an actual biped robot using an embedded hardware-in-the-loop strategy.     

Disturbance observer-based backstepping sliding mode fault-tolerant control for the hydro-turbine governing system with dead-zone input

This paper investigates a backstepping sliding mode fault-tolerant tracking control problem for a hydro-turbine governing system with consideration of external disturbances, actuator faults and dead-zone input. To reduce the effects of the unknown random disturbances, the nonlinear disturbance observer is designed to identify and estimate the disturbance term. To drastically decrease the complexity of stability functions selection and controller design, the recursive processes of the backstepping technique are employed. Additionally, based on the nonlinear disturbance observer and the backstepping technique, the sliding mode fault-tolerant tracking control approach is developed for the hydro-turbine governing system (HTGS). The stability of HTGS is rigorously demonstrated through Lyapunov analysis which is capable to satisfy a tracking control performance. Finally, comprehensive simulation results are presented to illustrate the effectiveness and superiority of the proposed control scheme.     

Hybrid finite-time trajectory tracking control of a quadrotor

In this paper, accurate trajectory tracking control problem of a quadrotor with unknown dynamics and disturbances is addressed by devising a hybrid finite-time control (HFTC) approach. An adaptive integral sliding mode (AISM) control law is proposed for altitude subsystem of the quadrotor, whereby underactuated characteristics can decoupled. Backstepping technique is further deployed to control the horizontal position subsystem. To exactly attenuate external disturbances, a finite-time disturbance observer (FDO) combining with nonsingular terminal sliding mode (NTSM) control strategy is constructed for attitude subsystem, and thereby achieve finite-time stability. Using the compounded control scheme, trajectory tracking errors can be stabilized rapidly. Simulation results and comprehensive comparisons show that the proposed HFTC scheme has remarkably superior performance.     

A new fractional-order sliding mode controller via a nonlinear disturbance observer for a class of dynamical systems with mismatched disturbances

This paper investigates the stabilization and disturbance rejection for a class of fractional-order nonlinear dynamical systems with mismatched disturbances. To fulfill this purpose a new fractional-order sliding mode control (FOSMC) based on a nonlinear disturbance observer is proposed. In order to design the suitable fractional-order sliding mode controller, a proper switching surface is introduced. Afterward, by using the sliding mode theory and Lyapunov stability theory, a robust fractional-order control law via a nonlinear disturbance observer is proposed to assure the existence of the sliding motion in finite time. The proposed fractional-order sliding mode controller exposes better control performance, ensures fast and robust stability of the closed-loop system, eliminates the disturbances and diminishes the chattering problem. Finally, the effectiveness of the proposed fractional-order controller is depicted via numerical simulation results of practical example and is compared with some other controllers.     

挖掘机基于干扰观测器的滑模控制

针对挖掘机工作装置的参数不确定和存在干扰的问题,将滑模控制用于挖掘机工作装置的轨迹跟踪控制中。为了削弱滑模控制中存在的抖振,设计了干扰观测器,对干扰项进行有效估计以降低滑模控制中的切换增益。利用Matlab／Simulink工具箱对所设计的控制器进行了仿真,给出了基于干扰观测器的滑模控制的跟踪性能及误差。