Controller design for a class of nonlinear multi-input systems using modified sliding mode

A modified sliding mode controller with continuous switching is proposed for a class of nonlinear multi-input systems. The control design consists of first choosing a set of suitable sliding sectors, instead of conventional sliding surfaces, then constructing a continuous switching controller. It is shown that the global attractiveness and stability of the sliding sectors are guaranteed with the continuous switching control strategy. While retaining the robustness property of general sliding mode control, the modified sliding mode controller provides much smoother control signals. Trajectory control of a two-link robot and set point control of a nonlinear two-input system are investigated to show the effectiveness of the new method.     

基于情感神经网络的有源电力滤波器智能终端滑模控制

为了增强有源电力滤波器的电流跟踪控制性能,提出一种基于连续径向基情感神经网络的递归终端滑模控制方案.首先介绍包括集总不确定的有源电力滤波器数学模型;然后构造递归终端滑模面,该滑模面由快速非奇异终端滑模面和递归积分终端滑模面组成,不仅可确保跟踪误差在有限时间内收敛到零,而且可通过为滑模面参数设置适当的初始值消除滑模面的到达模态.为了有效克服系统不确定因素的影响,采用连续径向基情感神经网络逼近系统不确定参数,并运用Lyapunov方法对其进行稳定性和收敛性分析.所设计的连续径向基情感神经网络,不仅结构简单、响应速度快,而且具备参数在线调节能力.仿真和实验结果均表明,该控制方案具有优异的电流跟踪能力以及抗干扰能力.     

An improved continuous sliding mode controller for flexible air‐breathing hypersonic vehicle

An improved continuous sliding mode control algorithm is proposed for a flexible air‐breathing hypersonic vehicle (FAHV), including nonsingular fast fixed‐time sliding surface (NFFS) and dual‐layer adaptive continuous twisting reaching law (DACTL). Firstly, the nonlinear control‐oriented model of FAHV is processed using input/output feedback linearization method with the significant flexible effects modeling as unknown matched disturbances. Secondly, a novel NFFS is improved from conventional fixed‐time sliding surface by adjusting power exponent to accelerate convergence rate. In the meanwhile, in order to avoid singularity aroused by fractional power term, an exponential convergent sliding surface is switched when tracking error approaches zero. Thirdly, a DACTL is proposed to realize finite‐time convergence of sliding mode variable with higher convergence precision and less chattering. Dual‐layer adaptive law is utilized to adjust the gain in DACTL based on equivalent control concept so as to enhance robustness automatically and avoid overestimation of control gain. Meanwhile, disturbances can be compensated without knowledge of Lipschitz constants. Ultimately, simulations on longitudinal control of FAHV demonstrate the control algorithm proposed is superior to conventional quasi‐continuous sliding mode controller in the aspect of convergence accuracy and chattering suppression.     

一种连续非奇异快速终端滑模控制方法

为解决现有终端滑模控制算法在收敛速度和抖振方面的问题, 提出一种连续非奇异快速终端滑模控制方法. 采用变系数双幂次趋近率和非奇异快速终端滑模面相结合的设计方式, 提高系统状态在趋近和滑动阶段的收敛速度. 通过Lyapunov 稳定性方法证明所提出的控制率可使得状态轨迹在扰动存在的情况下, 在有限时间内快速收敛到一个区域. 与传统方法相比, 所提出的控制率是连续的, 因此抑制了抖振, 拥有更高的控制精度. 将所提出的方法应用于光电稳定平台, 仿真结果验证了算法的有效性.

     

基于模糊双线性模型的连续搅拌反应釜滑模控制

主要对连续搅拌反应釜系统(CSTR)的滑模控制问题进行研究;该系统的模型可由Takagi-Sugeno (T-S)模糊双线性模型进行描述,基于该模糊双线性模型,给出滑模控制方法;在之前学者的研究成果上对线性滑模面进行改进,构造积分滑模面,由此设计出的等效控制量与切换控制量,可以保证系统的控制精度;通过对其进行稳定性研究,得到全局稳定的充分条件,并求出滑模面的控制器参数;同时,构造7条模糊规则,采用模糊化方法对切换增益项进行模糊推理,使整体控制量平滑化,也避免系统状态出现抖振现象,实现实际可操作性;最后,连续搅拌反应釜的仿真验证了控制方法的有效性.     

一类多执行机构系的滑模控制设计及其应用

针对一类具有多执行机构的非线性系统,利用滑模控制和backstepping技术,研究了输出跟踪问题.针对执行机构的不同特点,利用离散执行机构实现滑模控制中的不连续控制量,利用连续执行机构实现滑模控制中的连续控制量.然后利用backstepping技术实现连续执行机构的输出对滑模控制中的连续控制量的有限时间收敛.将提出的设计方法应用于导弹直接侧向力与气动力复合控制系统设计,并进行了仿真验证.     

On sliding mode control of single input Markovian jump systems

In this paper, an equivalent control based sliding mode control is proposed for single input linear Markovian jump systems which guarantees the asymptotical stability. Furthermore, by using the stochastic system theory, a multi-step state transition conditional probability function is introduced for the continuous Markovian process, which is used to define the reaching and sliding probabilities. Furthermore, the formulas for calculating reaching and sliding probabilities are derived for situations where the control force may not be strong enough to ensure the fully asymptotical stability. Extensive simulations are conducted to validate the theoretical results and show the relationship between the control force and reaching and sliding probabilities.     

On Discretization of Continuous-Time Terminal Sliding Mode

In terminal sliding-mode control, the system states are brought to the origin in finite time using the concept of sliding-mode control. Though the theory of terminal sliding mode is well studied for continuous time systems, a discrete-time terminal sliding mode concept has not been investigated. This note analyses the applicability of terminal sliding-mode control in the discrete-time framework and discusses the problems involved in the discretization of continuous-time terminal sliding mode. The note also suggests a method to approach the discrete-time terminal sliding-mode control problem.     

Continuous Sliding Mode Controller with Disturbance Observer for Hypersonic Vehicles

In this paper, a continuous sliding mode controller with disturbance observer is proposed for the tracking control of hypersonic vehicles to suppress the chattering. The finite time disturbance observer is involved to make that the continuous sliding mode controller has the property of disturbance rejection. Due to continuous terms replacing the discontinuous term of traditional sliding mode control, switching modes of velocity and altitude firstly arrive at small regions with respect to disturbance observation errors. Switching modes keep zero and velocity and altitude asymptotically converge to their reference commands after disturbance observation errors disappear. Simulation results have proved the proposed method can guarantee the tracking of velocity and altitude with continuous sliding mode control laws, and also has the fast convergence rate and robustness.      

Sliding mode control approaches to the robust regulation of linear multivariable fractional‐order dynamics

Sliding mode control approaches are developed to stabilize a class of linear uncertain fractional‐order dynamics. After making a suitable transformation that simplifies the sliding manifold design, two sliding mode control schemes are presented. The first one is based on the conventional discontinuous first‐order sliding mode control technique. The second scheme is based on the chattering‐free second‐order sliding mode approach that leads to the same robust performance but using a continuous control action. Simple controller tuning formulas are constructively developed along the paper by Lyapunov analysis. The simulation results confirm the expected performance. Copyright © 2010 John Wiley & Sons, Ltd.