多输入离散时滞系统的变结构控制设计

研究多输入时滞离散系统的变结构控制问题．首先将离散时滞系统简化为无时滞离散系统,在此基础上提出一种新的变结构控制设计算法．该算法能使从空间任意点出发的运动在有限时间内准确到达并保持在切换面上,不发生切换面的穿越,有效地消除了抖振．数值计算和仿真结果表明了该方法的有效性．     

具有控制时滞的离散系统的无抖振滑模控制

研究含时滞的线性离散系统的变结构控制问题. 首先将之简化为不含时滞项的线性离散系统. 然后对简化系统提出一种新的无抖振滑动模态控制算法. 该算法使滑模控制分为两个阶段,当系统轨迹在滑模某邻域以外时, 利用传统的到达控制律使系统状态轨迹单调趋近滑模面; 当系统轨迹进入该邻域内, 无抖振控制律使其轨迹一步到达滑模面. 该控制律有效地削除了由离散系统解轨迹的不连续性产生的抖振现象. 仿真结果表明了这种方法的有效性.     

Existence of solutions to a class of nonlinear convergentchattering-free sliding mode control systems

Sliding mode control is a nonlinear control technique, which is robust against some classes of uncertainties and disturbances. However, this control produces chattering which can cause instability due to unmodeled dynamics and can also cause damage to actuators or the plant. There are essentially two ways to counter the chattering phenomenon. One way is to use higher order sliding mode, and the other way is to add a boundary layer around the switching surface and use continuous control inside the boundary. The problem with the first method is that the derivative of a certain state variable is not available for measurement, and therefore methods have to be used to observe that variable. In the second method, it is important that the trajectories inside the boundary layer do not try to come outside the boundary after entering the boundary layer. Control laws producing chattering-free sliding mode using a boundary layer have been proposed and the existence of solutions to the system using these control laws are presented     

A transformed Lure problem for sliding mode control and chatteringreduction

The sliding mode control problem is investigated with the frequency domain approach. The authors show that the sliding mode control can be transformed into a Lure problem. With this formulation, it is shown that the conventional sliding mode control with a nonlinear sign function can only guarantee to make the overall system stable but not asymptotically stable. The authors also consider a practical situation where the sign nonlinearity may contain a hysteresis loop. For this situation, they show that even if the hysteresis loop is very small, there still exists a limit cycle. However, chattering phenomenon caused by the limit cycle behavior can be eliminated by a certain class of nonlinearities     

基于可拓控制的离散变结构系统的组合控制

提出了一种新的离散变结构系统组合控制策略和一种改进的变速趋近律.众所周知,由于变结构控制系统中存在高频抖振,这一现象限制了变结构控制方法在各种工程设计领域中的应用.新的离散变结构系统组合控制策略的目的是使系统在最短的时间内完成正常运动从而系统的鲁棒性得以提高.对于滑动模态的到达问题,提出了基于改进的变速趋近率、指数趋近率和可拓控制的组合控制策略.这种新的控制策略能有效地削弱抖振提高系统的动态性能.最后通过将传统组合控制策略与所提出的组合控制策略仿真比较,其结果表明新的组合控制策略能够获得令人满意的结果.     

一种新的约束变速趋近律离散滑模控制方法

考虑惯性执行器输出速度有限的实际,引入趋近律变化速率的控制函数,设计了一种新的无抖振离散滑模变速趋近律算法. 首次提出了通过设计趋近律变化速率来构造离散滑模趋近律的思想,使得控制器的物理意义更加明显,设计更加灵活和简单.对于标称系统, 该算法可以使切换函数在有限时间内快速无抖振地收敛至零;对于满足匹配条件的不确定系统,切 换函数能够收敛至与不确定性及控制参数相关的某一数值,通过设置控制参数,可使这一数值任意小.     

新的离散时间系统变结构趋近律

针对离散时间系统变结构控制的设计问题进行了研究。为了改善离散指数趋近律的趋近过程,提出了一种新的趋近律,利用该趋近律设计的变结构控制器,不仅能够大幅度削弱抖振,使系统运动最终趋于原点不存在稳态振荡,而且能使系统的准滑动模态保持步步穿越切换面的基本属性,有效地改善了趋近过程,提高了控制品质。仿真分析验证了该方法的合理性与有效性。     

基于模糊神经网络的滑模控制

研究了一类不确定性非线性系统的滑模变结构控制,提出了一种基于模糊神经网络（Ｆｕｚｚｙ Ｎｅｕｒａｌ Ｎｅｔｗｏｒｋｓ）的滑模变结构设计方法,设计了控制器的结构,利用动态反向传播算法实现滑模控制,这种方法与一般变结构控制相比不但具有强的鲁棒性而且还能有效地消除抖动现象,同时在设计中不需要知识系统中不确定性和扰动的上界,另外还运用Ｌｙａｐｕｎｏｖ函数从理论上分析上了系统的稳定性。仿真结果说明了本文所提     

An adaptive reaching law of chattering-free discrete-time sliding mode control for systems with external disturbance

An adaptive reaching law of chattering-free discrete-time sliding mode control is proposed for the systems with external disturbance. An adaptive function is proposed in the reaching law which can increase reaching speed as sliding variable is far away from zero and avoid undesired chattering when sliding variable is close to origin. Moreover, a third-order backward difference of disturbance is added to obtain a narrower quasi-sliding mode band (QSMB). Both the closed-loop system performance and finite reaching steps to achieve the desired QSMB are theoretically analyzed. The simulation results verify the effectiveness of the proposed control strategy.     

基于变结构控制理论的某型导弹平滑导引律研究

基于变结构控制理论,提出了一种设计简单、具有很好鲁棒性及准确性的平滑导引律,解决了某型导弹因采用变结构导引律攻击机动目标时,视线倾角增量变化律的来回切换产生抖动的缺陷.     

Adaptive fuzzy control with smooth inverse for nonlinear systems preceded by non-symmetric dead-zone

In this study, the adaptive output feedback control problem of a class of nonlinear systems preceded by non-symmetric dead-zone is considered. To cope with the possible control signal chattering phenomenon which is caused by non-smooth dead-zone inverse, a new smooth inverse is proposed for non-symmetric dead-zone compensation. For the systematic design procedure of the adaptive fuzzy control algorithm, we combine the backstepping technique and small-gain approach. The Takagi–Sugeno fuzzy logic systems are used to approximate unknown system nonlinearities. The closed-loop stability is studied by using small gain theorem and the closed-loop system is proved to be semi-globally uniformly ultimately bounded. Simulation results indicate that, compared to the algorithm with the non-smooth inverse, the proposed control strategy can achieve better tracking performance and the chattering phenomenon can be avoided effectively.     

离散时间系统变结构控制基于衰减控制的趋近律

讨论了利用离散趋近律设计离散时间系统的变结构控制问题, 在衰减控制的基础上, 提出了衰减变速趋近律和衰减幂次趋近律. 理论分析和仿真结果表明, 本文所提的方法是有效的, 既保证了闭环系统的渐进稳定性, 又大大减少了系统的抖动现象.     

时滞离散广义不确定系统的变结构控制

研究了一类线性离散时滞广义不确定系统的变结构控制的综合与设计问题.首先引入了一种新的受限系统等价分解形式,把所给的系统分解成两个低维的不确定子系统.其次,在上述分解的基础上,根据离散时滞广义系统鲁棒稳定性的有关结果,设计了带有差分补偿器的切换函数,使得系统在准切换流形上的运动渐近稳定.然后设计了离散变结构控制律,使得在此控制律的作用下,系统的运动轨迹要么在有限步内到达准切换流形并在其上渐近滑向原点;要么在有限步内进入准切换流形的一个较小的邻域内并稳定于原点附近的某个小的抖振.最后，给出了两个数值例子以说明该综合设计方法的有效性与实用性.     

Chattering free full-order sliding-mode control

In conventional sliding-mode control systems, the sliding-mode motion is of reduced order. Two main problems hindering the application of the sliding-mode control are the singularity in terminal sliding-mode control systems and the chattering in both the conventional linear sliding-mode and the terminal sliding-mode control systems. This paper proposes a chattering-free full-order terminal-sliding-mode control scheme. Since the derivatives of terms with fractional powers do not appear in the control law, the control singularities are avoided. A continuous control strategy is developed to achieve the chattering free sliding-mode control. During the ideal sliding-mode motion, the systems behave as a desirable full-order dynamics rather than a desirable reduced-order dynamics. A systematic design method of full-order sliding-mode control for nonlinear systems is presented, which allows both the chattering and singularity problems to be resolved. Simulations validate the proposed chattering free full-order sliding-mode control.     

Frequency domain analysis of noise‐induced control chattering in sliding mode controls

The switching sliding mode control is robust with respect to disturbances, but its control signal has the so‐called chattering phenomenon that can damage the actuator and the system. To remove the chattering phenomenon, it has been proposed that one can use a continuous boundary layer design to replace the switching control. This paper shows, via the frequency domain analysis, that even when a boundary layer design is used, stochastic measurement noise can still induce the chattering phenomenon in control signals. Such noise‐induced chattering is almost unavoidable in noisy environments when the control accuracy requirement is high. Copyright © 2010 John Wiley & Sons, Ltd.     

无抖振离散滑模趋近律

针对离散滑模趋近律形式多样且容易产生高频抖振的问题,提出了离散滑模趋近律的一般形式,并给出了无抖振的到达条件及其理论证明,从一般意义上为离散滑模趋近律的设计提供了理论依据。针对满足匹配条件的不确定系统,给出了切换函数收敛域的推导方法,推导了无抖振的最小收敛域。以典型的高氏指数趋近律为例,利用无抖振的到达条件,对其一般形式进行了无抖振改进,验证了所提出方法的有效性。     

不确定离散时间系统的变结构控制设计

讨论了利用离散趋近律设计不确定离散时间系统的变结构控制问题,分析了离散趋 近律系数造成系统颤振的原因,给出了改进的离散趋近律,并利用它设计了变结构控制律,对 不确定部分建立灰色估计模型,估计出参数值.仿真结果表明该方法是可行的,有效地防止了 系统的颤振和不确定因素的影响.     

不确定系统离散变结构控制及在位置伺服系统中的应用

研究有界不确定离散时间系统的变结构控制设计问题.对利用传统离散趋近律设计变结构控制器时出现的稳态抖振现象进行分析,提出一种能有效减弱抖振的控制策略,并将研究结果用于设计某位置伺服系统变结构控制器.理论分析及仿真结果表明,所设计的控制器可以有效减弱抖振,并使伺服系统具有良好的跟踪能力和很强的鲁棒性.     

基于隐式积分的广义离散趋近律

针对传统基于前向欧拉近似的离散趋近律存在数值抖振的问题,首先,提出一种衍生于后向欧拉积分的广义离散趋近律,该广义离散趋近律具有全局无抖振收敛特性,并释放更多的参数设计自由度;然后,揭示趋近律参数对滑模变量收敛速率的影响关系,为参数整定提供理论依据;最后,在考虑系统不确定性时,给出滑模面最终的边界层,验证所设计的趋近律可同时确保系统的快速瞬态响应和高精度控制.数值仿真验证了所提出算法的有效性.     

On 2 types of robust reaching laws

The reaching law is an important part of a sliding‐mode controller, which guarantees the existence of sliding motion in finite time. Fast access to sliding motion with a weak chattering phenomenon in control input is always desired. In this paper, 2 different types of reaching laws are proposed, which guarantee finite‐time convergence to the sliding manifold. Moreover, the reaching time is robust to initial conditions and can be designed by the user. Some useful discussions on the design of parameters are also presented to weaken the chattering phenomenon. A careful simulation study is finally provided to verify the effectiveness and efficiency of the proposed methods.