不确定时变混沌系统的一种自适应无抖振变结构控制

混沌系统的一般变结构控制方法存在高频抖振和需要事先已知系统不确定项的上界等不足，针对这些不足，以一类不确定时变混沌系统为例，提出了自适应无抖振变结构控制（ACFVSC）方法，以控制混沌系统到任意设定轨道.该方法不仅能消除滑模面附近的抖振现象，实现渐近跟踪，而且不需要“不确定项的上界已知”的先验知识.ACFVSC的渐近跟踪分析与仿真结果都表明，只要选择合适的控制器参数，就能在有限时间内达到任意的设定跟踪精度. 关键词： 不确定时变混沌系统 变结构控制 无抖振     

SISO仿射非线性系统自适应变结构BPNN控制

为了更好地消除抖振,提高复杂非线性系统的控制效果,针对一类典型SISO仿射非线性系统,提出了一种新的变结构神经网络自适应控制策略(VSYNC)。其中,对于系统未知非线性函数,将神经网络用作估计器。对控制输入加入连续函数项,其可以根据状态点和滑动切换面之间的距离自适应地调节不连续的控制变量,从而使变结构控制策略得到了显著提高。所提出的控制方法能够有效地抑制周围切换面的抖振,保证了系统地动态性能,同时还能够消除系统的稳态误差。仿真结果表明,该方法具有较高的控制精度和鲁棒性。     

一种提高RS422通信BIT可靠性的设计方法

电动静液作动器是飞机操纵系统的关键部件,要求有较好的速度平稳性。系统内存在泄漏非线性和摩擦非线性等影响速度平稳性的因素。滑模控制可以有效抑制系统内非线性因素的影响,但是由于抖振现象的存在限制了速度平稳性的进一步提升。针对固定切换增益的滑模控制方法的不足,提出一种基于变结构滤波器的自适应滑模控制方法。采用变结构滤波器估计系统状态信息,估计的系统状态信息用于构建滑模面,采用自适应切换增益来导出控制率,有效减小了抖振幅度。仿真结果证明了自适应滑模控制方法的有效性,采用这种方法提高了电动静液作动器的速度平稳性。     

Adaptive Fixed-Time Neural Network Tracking Control of Nonlinear Interconnected Systems

In this article, a novel adaptive fixed-time neural network tracking control scheme for nonlinear interconnected systems is proposed. An adaptive backstepping technique is used to address unknown system uncertainties in the fixed-time settings. Neural networks are used to identify the unknown uncertainties. The study shows that, under the proposed control scheme, each state in the system can converge into small regions near zero with fixed-time convergence time via Lyapunov stability analysis. Finally, the simulation example is presented to demonstrate the effectiveness of the proposed approach. A step-by-step procedure for engineers in industry process applications is proposed.     

基于单驱动变量分数阶混沌同步的参数调制数字通信及硬件实现

通过单驱动变量设计了三维分数阶混沌系统通用的自适应同步控制器.基于参数调制原理, 利用单驱动变量分数阶混沌系统的同步,提出了一种新的通用型数字通信方案,对电路进行了仿真,同时搭建了实际硬件电路,结果显示接收信息和发送信息符合完好,验证了本方案的有效性和可行性.     

非匹配不确定交叉严反馈超混沌系统神经网络反演同步

针对一类具有非匹配不确定性的交叉严反馈超混沌系统,提出一种基于多层前向神经网络的反演自适应同步设计方法.利用神经网络估计系统中的不确定性,运用滑模控制和交叉自适应反演控制处理系统中的非匹配不确定性及神经网络的逼近误差, 当虚拟控制项系数不过零时可保证系统的同步误差趋向于零,过零时可保证同步误差有界. 数值仿真证明了提出的控制方案的有效性.     

Robust adaptive synchronization for a general class of uncertain chaotic systems with application to Chua's circuit

The synchronization problem for a general class of uncertain chaotic systems is addressed. The underlying systems may be perturbed by unknown time-varying parameters, unstructured uncertainties, and external disturbances. Meanwhile, the time-varying parameters and disturbances are neither required to be periodic nor to have known bounds. Assuming the disturbances are L(2) signals, an adaptive control incorporated with H(∞) control technique is employed to construct a robust adaptive synchronization algorithm. Then, removing such assumption, a novel adaptive-based method is developed to achieve the goal of synchronization. In order to demonstrate the effectiveness of the proposed algorithms, such methods are applied to solve the synchronization problem of uncertain chaotic Chua's circuits.     

Adaptive fuzzy sliding mode control of smart structures

Smart structures are usually designed with a stimulus-response mechanism to mimic the autoregulatory process of living systems. In this work, in order to simulate this natural and self-adjustable behavior, an adaptive fuzzy sliding mode controller is applied to a shape memory two-bar truss. This structural system exhibits both constitutive and geometrical nonlinearities presenting the snap-through behavior and chaotic dynamics. On this basis, a variable structure controller is employed for vibration suppression in the chaotic smart truss. The control scheme is primarily based on sliding mode methodology and enhanced by an adaptive fuzzy inference system to cope with modeling inaccuracies and external disturbances. The robustness of this approach against both structured and unstructured uncertainties enables the adoption of simple constitutive models for control purposes. The overall control system performance is evaluated by means of numerical simulations, promoting vibration reduction and avoiding snap-through behavior.     

Practical time-delay synchronization of a periodically modulated self-excited oscillators with uncertainties

This paper studies time-delay synchronization of a periodically modulated Duffing Van der Pol (DVP) oscillator subjected to uncertainties with emphasis on complete synchronization. A robust adaptive response system is designed to synchronize with the uncertain drive periodically modulated DVP oscillator. Adaptation laws on the upper bounds of uncertainties are proposed to guarantee the boundedness of both the synchronization error and the estimated feedback coupling gains. Numerical results are presented to check the effectiveness of the proposed synchronization scheme. The results suggest that the linear and nonlinear terms in the feedback coupling play a complementary role in increasing the synchronization regime in the parameter space of the synchronization manifold. The proposed method can be successfully applied to a large variety of physical systems.     

Robust synchronization for a class of fractional-order chaotic and hyperchaotic systems

In this paper, the issue of robust synchronization for a class of fractional-order chaotic and hyperchaotic systems with model uncertainties and disturbances is studied. A stability criterion for fractional-order nonlinear dynamic systems is introduced, and an adaptive scheme is contrived to accomplish synchronization of fractional-order chaotic and hyperchaotic systems. The controller contains only a single state variable, which is simple and flexible in implementation. Two corresponding numerical examples are given to confirm the theoretical results of the paper.     

Smooth control of HIV/AIDS infection using a robust adaptive scheme with decoupled sliding mode supervision

In this paper, a robust adaptive controller subject to decoupled sliding mode controller as a supervisory controller has been implemented on the HIV infection dynamic model. A five-state dynamic model of HIV is utilized which the measurement of the CD4+T cells and the viral load counts are necessary to estimate all its parameters. Decoupled sliding mode control is a variable structure controller having significant and appropriate features, such as best tracking and regulation performance and robustness and elevate the performance of the controller. Generally, due to the importance of applied treatment strategy to mitigate viral escape, sliding mode control is utilized in accordance with PI control to deliver necessary control inputs. To achieve the least possible chattering, effectual methods such as the transfer function is used. To update the gains of PI control, an adaptation law is then employed. The results demonstrate the suitable performance of the controller via providing proper tracking performance, and also, elimination of the chattering problem and decrease the time of treatment. The number of infected CD4+ T-cells and the number of free virus particles can be controlled in less than five days. The proposed controller is capable of controlling the dynamic behavior of the virus concentration for different patients with the same control scheme.     

Adaptive Fixed-Time Control of Strict-Feedback High-Order Nonlinear Systems

This paper examines the adaptive control of high-order nonlinear systems with strict-feedback form. An adaptive fixed-time control scheme is designed for nonlinear systems with unknown uncertainties. In the design process of a backstepping controller, the Lyapunov function, an effective controller, and adaptive law are constructed. Combined with the fixed-time Lyapunov stability criterion, it is proved that the proposed control scheme can ensure the stability of the error system in finite time, and the convergence time is independent of the initial condition. Finally, simulation results verify the effectiveness of the proposed control strategy.     

改进的保群算法及其在混沌系统中的应用

混沌系统的跟踪控制是近年来非线性控制领域研究的热点之一. 本文提出了一种基于快速下降控制方法的保群算法, 此方法使受控混沌系统能够快速稳定到相空间的一个不动点; 另外提出一种基于滑模控制方法的保群算法, 此方法使受控混沌系统能够快速跟踪一个确定的运动轨迹. 应用这两种新方法分别对两个经典的混沌系统(Lorenz系统和Duffing系统)进行了相应的数值实验, 实验结果表明这两种方法都具用较高的精度和稳定性.     

Simple adaptive synchronization of chaotic systems with random components

Practical systems usually possess random components. Random components often affect the robustness of synchronism and must be taken into consideration in the design of synchronization. In the present study, we assume that the system satisfies the Lipschitz condition, and the random component is uniformly bounded. By the partial stability theory, we are able to prove that two simple adaptive variable structure controllers achieve synchronization of chaotic systems. Moreover, we discuss how the controllers can be modified to eliminate the undesired phenomenon of chattering. The Duffing two-well system and the Chua circuit system are simulated to illustrate the theoretical analysis.     

Robust fuzzy control for chaotic dynamics in Lorenz systems with uncertainties

This paper deals with the robust fuzzy control for chaotic systems in the presence of parametric uncertainties. An uncertain Takagi--Sugeno fuzzy model for a Lorenz chaotic system is first constructed. Then a robust fuzzy state feedback control scheme ensures the control for stable operations under bounded parametric uncertainties. For a chaotic system with known uncertainty bounds, a robust fuzzy regulator is designed by choosing the control parameters satisfying the linear matrix inequality. To verify the validity and effectiveness of the proposed controller design method, an analysis technique is suggested and applied to the control of an uncertain Lorenz chaotic system.     

Adaptive control and synchronization for chaotic systems with parametric uncertainties

An adaptive control scheme using only part of the system states for the stabilization of one chaotic system and the synchronization of two chaotic systems is presented. The system parameters are allowed to have a large range of time varying uncertainties around their fixed unknown nominal values both in the stabilization and the synchronization control problems. Simulation results also illustrate the effectiveness of the proposed control scheme.     

基于滑模变结构控制及预测跟踪的光电吊舱控制方法北大核心CSCD

光电吊舱在稳像和目标跟踪过程中存在摩擦力矩、不平衡力矩等干扰力矩,从而影响速度环响应精度;另一方面,吊舱视频跟踪器图像传输和处理造成的延迟也会造成跟踪滞后,因此必须进行延时补偿。提出基于预测跟踪的滑模变结构控制方法,采用微分预测跟踪器实现对视频跟踪器的延迟补偿,采用预测跟踪器估计出的目标运动角速率构成自适应补偿参数,以调整滑模变结构控制量,改进的滑模控制算法在补偿干扰力矩的同时抑制了抖振现象。仿真及实验结果表明:改进的控制方法能够有效补偿干扰力矩和跟踪器延迟造成的误差,相对于传统PID控制,其跟踪误差减小为原来的1/3,并且该算法已经在相关系统上得到应用。     

SCARA机器人的模糊自适应滑模控制

为了提高SCARA机器人的轨迹跟踪控制性能,提出一种双模糊自适应滑模控制。采用一自适应模糊控制器,根据滑模到达条件对滑模切换增益进行估算,消除滑模控制中输出力矩的抖振现象,增强其对不确定性因素的适应能力。采用另一自适应模糊控制器对指数趋近律系数进行修正,改善由于大范围初始位姿产生的偏差而引起的大力矩和速度跳变问题。基于Lyapunov方法进行了稳定性证明,保证控制系统的稳定性与收敛性。仿真实验结果表明,该方法应用于SCARA机器人,跟踪效果良好并产生了平滑的力矩输出和速度输出。     

Finite-time sliding mode synchronization of chaotic systems

A new finite-time sliding mode control approach is presented for synchronizing two different topological structure chaotic systems. With the help of the Lyapunov method, the convergence property of the proposed control strategy is discussed in a rigorous manner. Furthermore, it is mathematically proved that our control strategy has a faster convergence speed than the conventional finite-time sliding mode control scheme. In addition, the proposed control strategy can ensure the finite-time synchronization between the master and the slave chaotic systems under internal uncertainties and external disturbances. Simulation results are provided to show the speediness and robustness of the proposed scheme. It is worth noticing that the proposed control scheme is applicable for secure communications.     

基于扩张状态观测器的永磁同步电机混沌系统自适应滑模控制

针对部分状态不可测的永磁同步电机混沌系统, 结合自适应滑模控制和扩张状态观测器理论, 提出一种基于扩张状态观测器的永磁同步电机自适应混沌控制方法, 取消了系统所有状态完全可测的限制. 通过坐标变换, 将永磁同步电机混沌模型变为更适宜控制器设计的Brunovsky标准形式. 在系统部分状态和非线性不确定项上界均未知的情况下, 基于扩张状态观测器估计系统未知状态及不确定项, 并设计自适应滑模控制器, 保证系统状态快速稳定收敛至零点. 仿真结果表明, 该控制器能够改善滑模控制的抖振问题以及提高系统鲁棒性. 关键词： 永磁同步电机 混沌控制 扩张状态观测器 自适应滑模