ROBUST STABILIZATING FOR A OLASS OF UNOERTAIN NONLINEAR INTEROONNECTED SYSTEMS USING VARIABLE STRUCTURE CONTROL

The robust stabilizating control problem for a class of uncertain nonlinear large-scale systems is discussed. Based on the theory of both input/output (I/O) linearization and decentralized variable structure control (VSC),two-level and decentralized variable structure control laws for this kind of systems are presented respectively,which achieve asymptotically stabilization despite the uncertainties and disturbances. At last,sirnulation of the disturbed two-pendulum system is given to illustrate the feasibility of proposed technique.

Adaptive Variable Structure Control of MIMO Nonlinear Systems with Time-varying Delays and Unknown Dead-zones

In this paper, adaptive variable structure neural control is presented for a class of uncertain multi-input multi-output （MIMO） nonlinear systems with state time-varying delays and unknown nonlinear dead-zones. The unknown time-varying delay uncer- tainties are compensated for using appropriate Lyapunov-Krasovskii functionals in the design. The approach removes the assumption of linear function outside the deadband without necessarily constructing a dead-zone inverse as an added contribution. By utilizing the integral-type Lyapunov function and introducing an adaptive compensation term for the upper bound of the residual and optimal approximation error as well as the dead-zone disturbance, the closed-loop control system is proved to be semi-globally uniformly ultimately bounded. In addition, a modified adaptive control algorithm is given in order to avoid the high-frequency chattering phenomenon. Simulation results demonstrate the effectiveness of the approach.

Variable structure control with sliding mode prediction for discrete-time nonlinear systems

A new variable structure control algorithm based on sliding mode prediction for a class of discrete-time nonlinear systems is presented. By employing a special model to predict future sliding mode value, and combining feedback correction and receding horizon optimization methods which are extensively applied on predictive control strategy, a discrete-time variable structure control law is constructed. The closed-loop systems are proved to have robustness to uncertainties with unspecified boundaries. Numerical simulation and pendulum experiment results illustrate that the closed-loop systems possess desired performance, such as strong robustness, fast convergence and chattering elimination.

Nonlinear and Variable Structure Excitation Controller for Power System Stability

A new nonlinear variable structure excitation controller is proposed. Its design combines the differential geometry theory and the variable structure controlling theory. The mathematical model in the form of ＂an affme nonlinear system＂ is set up for the control of a large-scale power system. The static and dynamic performances of the nonlinear variable structure controller are simulated. The response of system with the controller proposed is compared to that of the nonlinear optimal controller when the system is subjected to a variety of disturbances. Simulation results show that the nonlinear variable structure excitation controller gives more satisfactorily static and dynamic performance and better robustness.

Adaptive variable structure control for large-scale time-delayed systems with unknown nonlinear dead-zone

The problem of adaptive fuzzy control for a class of large-scale, time-delayed systems with unknown nonlinear dead-zone is discussed here. Based on the principle of variable structure control, a design scheme of adaptive, decentralized, variable structure control is proposed. The approach removes the conditions that the dead-zone slopes and boundaries are equal and symmetric, respectively. In addition, it does not require that the assumptions that all parameters of the nonlinear dead-zone model and the lumped uncertainty are known constants. The adaptive compensation terms of the approximation errors axe adopted to minimize the influence of modeling errors and parameter estimation errors. By theoretical analysis, the closed-loop control system is proved to be semiglobally uniformly ultimately bounded, with tracking errors converging to zero. Simulation results demonstrate the effectiveness of the approach.

PREDICTIVE VARIABLE STRUCTURE CONTROL FOR A CLASS OF NONLINEAR SYSTEM

Nonlinear sliding m ode predictive controller is designed for a class of nonlinear system w ith unm odeled dynam ic characteristics and nonlinear term . The m ethod is based on nonlinear opti- m alpredictive control. The variable structure controllaw m inim izes the quadratic index ofa predic- tive sliding m ode, w hich contains thecostfunction ofcontrolpreventing the controleffectfrom satu- ration for in m ostpracticalim plem entation the controlinputs are bounded by physicalconstraints and energy constraints. According to the im m easurable states, the variable structure observer for nonlin- ear system sisadapted. The variablestructure system m ethod isaptto therealization ofobserverw ith variable param eters and uncertainty. The proofshow s thatthe states ofthe observer asym ptotically convergence to the realstates ofthe system although itisofuncertainty and nonlinear term s. Final- ly, the digitalsim ulation results prove the effectiveness ofthe proposed m ethod.

Use of nonlinear variable structure control with equivalent term in design of coordinated controls for turbo generators

Presents the coordinated controls of nonlinear variable structure with an equivalent control term designed for turbo generators following the theory of nonlinear variable structure control, which integrates the valve control with the excitation control and reduce the problem of high frequency shiver with conventional variable structure control in addition to a simplified design, and concludes from simulation results that the use of this control can improve the transient of the system.

Nonlinear variable structure excitation and steam valving controllers for power system stability

A set of novel nonlinear variable structure excitation and steam-valving controllers are proposed in this paper. On the basis of the classical dynamic equations of a generator, excitation control and steam valving control are simultaneously considered. Design of these controllers combines the differential geometry theory with the variable structure controlling theory. The mathematical model in the form of ＂an affine nonlinear system＂ is set up for the control design of a large-scale power plant. The dynamic performance of the nonlinear variable structure controllers proposed for a single machine connected to an infinite bus power system is simulated. Simulation results show that the nonlinear variable structure excitation and steam-valving controllers give satisfactory dynamic performance and good robustness.

Adaptive Neural Control for a Class of Low-triangular-structured Nonlinear Systems with H-∞ Performance Analysis

In this paper, a neural-network-based variable structure control scheme is presented for a class of nonlinear systems with a general low triangular structure. The proposed variable structure controller is proved to be Cl, thus can be applied for backstepping design, which has extended the scope of previous nonlinear systems in the form of strict-feedback and pure-feedback. With the help of neural network approximator, H-∞ performance analysis of stability is given. The effectiveness of proposed control law is verified via simulation.

A Variable Structure Model Reference Adaptive Control

A variable structure model reference adaptive control problem for the nonlinear system is studied in this paper. First, according to the relative degree concept of th nonlinear control system an error equation between the outputs of the reference model and the controlled plant is derived. Then, by using the variable structrue control method, an algorithm of variable structure model reference adaptive control is deduced on the basis of a new concept of reaching law. The definition of the SISO system is introduced into the MIMO nonlinear system. Finally, as an example, a pendulum nonlinear control system is simulated to demonstrated the effectiveness of the method. The results show that the method has some advantages: the design is simple, intuitive and easy to be realized in engineering. Besides, it is of practical significance for the synthesis of nonlinear control systems.

Design of Variable Structure Control by Using the L_2 Gain Method

The robust stabilization problem for a family of nonlinear plants with mismatch uncertainties is addressed, and a solution is presented based on variable structure control theory and H∞ control theory. A kind of boundary layer is built near the ideal switch surface which can eliminate chattering in the switch surface. The proposed control method with L2 gain can guarantee exponential stability of a system state with no parameter uncertainty and exter- nal disturbance, while it can guarantee state ultimate boundness if parameter uncertainty and external disturbance exist. In the proposed design method, stability of the closed-loop system is analyzed by adopting the Lyapurtov func- tion approach. Finally the numerical simulation results show that the proposed smooth variable structure controller has good pelformance without chattering in the switch surface.

Adaptive Sliding Mode Control for MIMO Nonlinear Systems Based on Fuzzy Logic Scheme

In this study an indirect adaptive sliding mode control (SMC) based on a fuzzy logic scheme is proposed to strengthen the tracking control performance of a general class of multi-input multi-output (MIMO) nonlinear uncertain systems. Combining reaching law approach and fuzzy universal approximation theorem, the proposed design procedure combines the advantages of fuzzy logic control, adaptive control and sliding mode control. The stability of the control systems is proved in the sense of the Lyapunov second stability theorem. Two simulation studies are presented to demonstrate the effectiveness of our new hybrid control algorithm.

Chattering Reduction in Design of Variable Structure Systems

This paper presents a new method of smoothing control signal in control system of variable structure. Using the relationship between the gain of nonlinear term in the control signal and distance of the system states from the equivalent point, a saturating property with the variable width is adopted. The method not only reduces the chattering of the control signal but also decrees the steady-state error.

A Harmonic Disturbance Suppression Method For Frequency Time-variable Systems

为抑制谐波扰动对控制系统的影响，对频率时变的谐波扰动进行分析，提出两种针对频率时变的谐波扰动的抑制方法：线性反馈方法与基于非线性干扰观测器的方法。线性反馈方法依据于线性矩阵不等式理论，将频率变化的谐波扰动分解为频率固定的谐波扰动与非线性不确定项，采用一般的干扰观测方法对固定频率扰动进行观测，并采用线性反馈方法对非线性不确定项进行抑制。基于非线性干扰观测器的方法直接对谐波扰动进行观测，并采用鲁棒控制器进行干扰补偿。采用李亚普诺夫理论来验证扰动抑制方法的稳定性。将两种扰动抑制方法应用于磁悬浮飞轮电机控制系统，通过仿真与实验结果表明，两种方法具有很好的扰动抑制能力。基于非线性干扰观测器的扰动抑制方法依据扰动的特性设计，具有更好的动态、稳态特性与鲁棒性。

Attitude tracking control for variable structure near space vehicles based on switched nonlinear systems

An adaptive robust attitude tracking control law based on switched nonlinear systems is presented for a variable structure near space vehicle （VSNSV） in the presence of uncertainties and disturbances. The adaptive fuzzy systems are employed for approximating unknown functions in the flight dynamic model and their parameters are updated online. To improve the flight robust performance, robust controllers with adaptive gains are designed to compensate for the approximation errors and thus they have less design conservation. Moreover, a systematic procedure is developed for the synthesis of adaptive fuzzy dynamic surface control （DSC） approach. According to the common Lyapunov function theory, it is proved that all signals of the closed-loop system are uniformly ultimately bounded by the continuous controller. The simulation results demonstrate the effectiveness and robustness of the proposed control scheme.

A kind of fuzzy control for chaotic systems

With a T-S fuzzy dynamic model approximating to a non-linear system,the nonlinear system can be decomposed into some local linear models.A variable structure controller based on Lyapunov theories is designed to guarantee the global stability of the T-S fuzzy model.The controlling problems of a nonlinear system can be solved by means of consisting of linear system variable structure control and fuzzy control.The validity of the control method based on the simulating result of two kinds of chaotic systems is shown here.

音圈直线电机滑模变结构控制方法

为了消除音圈直线电机的非线性摩擦特性对系统定位精度的影响,利用机理建模方法建立线性模型描述音圈直线电机系统的幅频及相频特性并采用最小二乘法辨识模型参数。此外,采用摩擦力测试和牛顿第二定律得到系统的等效非线性项参数,利用辨识得到的线性模型与等效非线性项参数,设计了一种含有等效非线性控制项的滑模变结构控制器。实验结果表明,提出的控制方法能够改善音圈直线电机的定位精度,并提升了系统的动态性能。

Variable Structure Control of Catastrophic Course in Airdropping Heavy Cargo

The mathematical model of a transport aircraft would be subjected to a sudden change when heavy cargo is dropped off in airdropping, which exerts serious influences upon the safety of the aircraft. A variable structure controller is specially designed for handling the airdrop process. The nonlinear system is linearized by input-output feedback linearization using differential geometry theories. On this basis, an inner loop system for velocity and attitude tracking control is designed by using the exponentially approaching rule of the variable structure theory. The whole flight control system is integrated with the outer loop flight altitude control. Digital simulation evidences the applicability of the system to potentially catastrophic course in airdropping heavy cargo and provides robustness against system parameter perturbation.

Boost变换器精确反馈线性化滑模变结构控制

利用非线性系统的微分几何理论,在Boost变换器仿射非线性模型基础上,推导出对应的非线性坐标变换矩阵和状态反馈表达式,得到Boost变换器状态反馈精确线性化模型。在此线性化模型基础上,选取线性切换函数和指数趋近律,设计滑模变结构控制器。研究对比表明,所提出的精确反馈线性化滑模变结构控制策略具有良好的动态响应调节和稳态误差调节特性,同时克服了现有精确反馈线性化控制策略固有的对精确数学模型依赖性的缺点,表现出更强的鲁棒性,从而具有一般性理论和实际意义。

基于最优化的坦克稳定器滑动模态变结构控制

以坦克水平向稳定器为例研究坦克稳定器滑动模态变结构控制 ( VSC)技术。用优化方法确定切换函数 ,用到达条件确定变结构控制律。仿真表明该设计方法大大优于传统设计 ,为稳定器设计提供了一种切实可行的新方法。