Binary ABR flow control over ATM networks with uncertainty using discrete-time variable structure controller

A binary available bit rate （ABR） scheme based on discrete-time variable structure control （DVSC） theory is proposed to solve the problem of asynchronous transfer mode （ATM） networks congestion in this paper. A discrete-time system model with uncertainty is introduced to depict the time-varying ATM networks. Based on the system model, an asymptotically stable sliding surface is designed by linear matrix inequality （LMI）. In addition, a novel discrete-time reaching law that can obviously reduce chatter is also put forward. The proposed discrete-time variable structure controller can effectively constrain the oscillation of allowed cell rate （ACR） and the queue length in a router. Moreover, the controller is self-adaptive against the uncertainty in the system. Simulations are done in different scenarios. The results demonstrate that the controller has better stability and robustness than the traditional binary flow controller, so it is good for adequately exerting the simplicity of binary flow control mechanisms.     

Discrete-time sliding mode control of flexible rotor-magnetic bearing systems

This paper is concerned with the computer-based sliding mode control of flexible rotor—magnetic bearing systems (FR-MBS). The plant dynamics consisting of actuator dynamics and flexible rotor dynamics are described. The reduced-order model for controller design is given by eliminating higher-order modes of the mechanical and electrical magnetic interaction system. A discrete-time sliding mode controller with a new robust reduced-order variable structure system (VSS) observer is proposed and its robust performance is evaluated with several simulations based on a calculation model. This digital controller is implemented to replace a linear analogue PID compensator. Levitation tests using the proposed digital controller are performed and compared with those of the PID compensator. The unstable modes can be easily controlled with the good stability and the spillover phenomena due to ignored higher-order modes are not generated. It is indicated that the discrete-time sliding mode control has robustness to the model parameter variations and external disturbances. Using the discrete time sliding mode controller with the reduced-order VSS observer, the test rig of the magnetic bearing system can be successfully rotated in a speed range of 0–35 000 rpm, which includes the first critical shaft frequency of the flexible rotor.     

Binary ABR flow control over ATM networks with uncertainty using discrete-time variable structure controller

A binary available bit rate (ABR) scheme based on discrete-time variable structure control (DVSC) theory is proposed to solve the problem of asynchronous transfer mode (ATM) networks congestion in this paper. A discretetime system model with uncertainty is introduced to depict the time-varying ATM networks. Based on the system model, an asymptotically stable sliding surface is designed by linear matrix inequality (LMI). In addition, a novel discrete-time reaching law that can obviously reduce chatter is also put forward. The proposed discrete-time variable structure controller can effectively constrain the oscillation of allowed cell rate (ACR) and the queue length in a router. Moreover, the controller is self-adaptive against the uncertainty in the system. Simulations are done in different scenarios. The results demonstrate that the controller has better stability and robustness than the traditional binary flow controller, so it is good for adequately exerting the simplicity of binary flow control mechanisms.     

一种离散时间系统变结构趋近律

针对一类离散时间系统,提出一种变结构控制设计方法。为了减小离散指数趋近律的抖振现象,本文构造一种趋近律, 利用它设计变结构控制器,能够大幅度削弱抖振,有效地改善控制品质,使系统最终趋于原点,并使系统稳定。给出数值计算和仿真算例。     

Delta 算子不确定系统的滑模变结构控制

研究算子系统滑模变结构控制的综合问题.首先,利用线性矩阵不等式方法给出了切换面存在的充分条件,分析了算子变结构控制系统的到达条件,将连续系统和离散系统统一到算子系统.基于指数趋近律,给出滑模变结构控制一般方法.其次,给出一类算子不确定系统的滑模控制器设计,分析了准滑动模态的渐近稳定性,使得系统具有良好的动态性能.最后,用一个仿真实例说明在采样周期取值非常小的前提下,该方法设计的滑模变结构控制仍具有可行性和有效性.     

离散时间系统变结构拟滑模控制改进算法

传统的离散时间变结构控制律均是以等效控制为基础,长期的应用表明这种没计思想欠合理.针对该问题,设计了离散时间系统变结构滑模控制的一种新算法.算法针对前人所提出的控制算法不足之处,对离散时间滑模控制量设计进行了改进.理论分析表明,所提出的控制算法满足离散时间变结构系统到达条件的要求,通过选择合适的滑模切换函数以及控制律参数,保证系统的轨线快速落在滑模面上,有效地缩短了系统状态到达滑动模态的时间,且抖振小.仿真结果表明,使用改进控制算法的系统输出响应优于未改进算法情况,响应速度较快,证明了所提出的算法是可行的、有效的.     

不确定线性2-D离散系统的鲁棒滑模控制

针对不确定线性离散二维（2-D）系统,研究了其鲁棒稳定性、鲁棒镇定和鲁棒滑模控制问题.基于线性矩阵不等式的方法推导了该系统鲁棒渐近稳定的充分条件,并给出了系统状态反馈镇定器和理想滑动模态存在的充分条件.改进了离散时间滑模控制系统的趋近律方法,使得状态能够到达滑模面上产生理想的滑动模态,并将其推广应用到2-D离散系统中,综合了一类滑模控制器保证闭环系统鲁棒渐近稳定.仿真实例证实了该设计方法的有效性.     

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.     

Approximation law for discrete-time variable structure control systems

Two approximation laws of sliding mode for discrete-time variable structure control systems are proposed to overcome the limitations of the exponential approximation law and the variable rate approximation law. By applying the proposed approximation laws of sliding mode to discrete-time variable structure control systems, the stability of origin can be guaranteed, and the chattering along the switching surface caused by discrete-time variable structure control can be restrained effectively. In designing of approximation laws, the problem that the system control input is restricted is also considered, which is very important in practical systems. Finally a simulation example shows the effectiveness of the two approximation laws proposed.     

Approximation law for discrete-time variable structure control systems

Two approximation laws of sliding mode for discrete-time variable structure control systems are proposed to overcome the limitations of the exponential approximation law and the variable rate approximation law. By applying the proposed approximation laws of sliding mode to discrete-time variable structure control systems, the stability of origin can be guaranteed, and the chattering along the switching surface caused by discrete-time variable structure control can be restrained effectively. In designing of approximation laws, the problem that the system control input is restricted is also considered, which is very important in practical systems. Finally a simulation example shows the effectiveness of the two approximation laws proposed.     

Discrete-time sliding mode control for uncertain systems with state and input delays

This article presents a discrete-time sliding mode control method for the robust stabilisation of linear uncertain multi-input discrete-time systems with state and input delays. The systems are assumed to have structured mismatched time-varying parameter uncertainties. A specified switching surface is proposed and a sliding mode controller is derived to ensure the existence of the quasi-sliding mode. Based on the improved Lyapunov function and linear matrix inequality technique, delay-independent sufficient conditions for the design of a stable switching surface are given and the stability of the overall closed-loop system is guaranteed. Neither chattering phenomenon will occur nor the knowledge of upper bound of uncertainties is required. Finally, simulation results demonstrate the efficacy of the proposed control methodology.     

基于滑模变结构的轮式机器人运动误差控制器设计

面对当前使用的基于黎卡提微分方程、综合位姿误差控制优化仿真方法受到不确定性因素干扰,导致控制误差较大的问题,提出了基于滑模变结构的轮式机器人运动误差控制器设计。使用双框架陀螺仪,为控制器提供电力。采用FB900C/E 角位变送器,将交流信号转换为角位移输出。使用TMS320F2812的DSP控制器,负责控制整个控制器的数据传输以及电平转换。充分考虑相变量输入的n阶线形数据,设计滑模变结构控制律,计算滑模变结构控制滑动面。在滑模变结构模态控制阶段,构建滑模变结构模态控制阶段的运动方程矩阵。对滑模切换面强制状态点运动,通过控制目标实现稳定控制。对DSP程序控制流程进行设计,将基于滑模变结构的误差控制结果传递到电位器上,并将运行数据发送到主机,由此完成轮式机器人运动误差控制。由实验结果可知,该控制器通过自适应调整参数后,滑模抖振得到明显消除,且最大控制误差为0.01rad,具有精准控制效果。     

不确定离散切换系统的滑模控制

研究一类不确定离散切换系统的鲁棒滑模控制问题.针对传统变结构控制应用于离散系统时易失去其鲁棒性的问题,提出一种采用带调整参数递归式滑模函数的离散滑模控制策略,改进了离散时间滑模控制系统的趋近律方法,并针对不确定因素的影响设计了无须知道扰动上界的估计器.应用Lyapunov函数给出了离散切换系统的滑动模态可达条件,并设计了离散切换规则.仿真结果表明了所提出设计方法的有效性.     

基于跟踪微分器的离散滑模控制器

利用跟踪微分器设计了一种新的离散滑模控制器,可以从不连续的指令信号中合理提取连续信号及微分信号,且不需要利用线性外推的方法预测指令信号下一时刻的值及其微分．与基于趋近律的离散滑模控制器进行的对比仿真表明,所设计的控制器在保持传统滑模控制固有强鲁棒性的同时,控制器的输出几乎不存在抖振现象,而且在跟踪不连续的指令信号时,系统表现出良好的动态品质．     

不确定奇异系统的变结构控制

针对一类不确定奇异线性系统,利用线性矩阵不等式(LMI)方法获得了滑模运动渐近稳定的充分条件,给出了变结构控制器的设计方法,该方法保证系统状态轨线经有限时间到达滑模面,并在其上实现滑模运动。滑模运动正则、无脉冲模、渐近稳定。     

广义系统的有限时间滑模变结构控制

研究了一类广义系统的有限时间滑模变结构控制问题。通过非奇异线性变换把广义系统变换成受限等价形式,利用Lyapunov函数的方法,提出了一种新型的有限时间滑模变结构控制策略,给出了特殊的开关型滑模面,设计了相应的滑模变结构控制器,使得闭环系统渐进稳定,实现了滑模运动,保证了在滑模面上系统状态变量在有限时间内到达平衡点。给出了可行性算例,说明了设计的有效性。     

Sliding mode control for a class of nonlinear discrete-time networked systems with multiple stochastic communication delays

In this article, a sliding mode control problem is studied for a class of uncertain nonlinear networked systems with multiple communication delays. A sequence of stochastic variables obeying Bernoulli distribution is applied in the system model to describe the randomly occurring communication delays. The discrete-time system considered is also subject to parameter uncertainties and state-dependent stochastic disturbances. A novel discrete switching function is proposed to facilitate the sliding mode controller design. The sufficient conditions are derived by means of the linear matrix inequality (LMI) approach. It is shown that the system dynamics in the specified sliding surface is robustly exponentially stable in the mean square if two LMIs with an equality constraint are feasible. A discrete-time SMC controller is designed that is capable of guaranteeing the discrete-time sliding-mode reaching condition of the specified sliding surface. Finally, a simulation example is given to show the effectiveness of the proposed method.     

Adaptive Variable Structure Control Design for Uncertain Time-Delayed Systems with Nonlinear Input

This paper presents a new robust control for uncertain dynamic time-delayed systems with series nonlinearities. It is implemented by using variable structure control. The proposed variable structure controller ensures the global reaching condition of the sliding mode of the uncertain time-delayed system. However, in the sliding mode, the investigated uncertain time-delayed system still bears the insensitivity to the uncertainties and disturbances as the systems with linear input. Furthermore, the proposed controller is achieved through adaptive variable structure control without the limitation of knowing the bounds of the uncertainties and perturbations in advance.     

Discrete-time adaptive sliding mode control of a linear system in statespace form

A discrete-time adaptive sliding mode controller for linear systems represented by the state space is presented. The controller is developed using the delta operator, which is better for approximating continuous-time systems than the shift operator. The use of the delta model allows the selection of the sliding surface to be similar to that for the continuous-time case. It is shown that the adaptive control algorithm leads to a stable closed-loop system. Simulation results are presented to illustrate the features of the proposed control scheme.     

机器人离散滑模变结构—PI控制器

本文采用离散滑模变结构控制方法，针对机器人提出了一种滑模变结构——ＰＩ控制方案，给出了该控制方案滑模存在条件及控制器设计方案。该控制器将离散滑模变结构控制和ＰＩ控制两者的优点有机地结合起来，理论分析和仿真结果表明该控制器能使机器人在各种复杂非线性动力学情况下具有良好的性能指标。这种控制器输出切换小，可以投入应用。