Fuzzy variable structure delay control algorithms and their applications to AQM

This paper analyzes the fuzzy variable structure control algorithms for delay systems and describes the compensation mechanism of the integral factor to the effect of the delay. Based on the linearized model of the congestion-avoidance flow-control mode of transmission control protocol (TCP), we present delay control algorithms for active queue management (AQM) and discuss the parameter tuning of the algorithms. The NS (network simulator) simulation results show that the proposed control scheme for the nonlinear TCP/AQM model has good performance and robustness with respect to the uncertainties of the round-trip time (RTT) and the number of active TCP sessions. Compared to other similar schemes, our algorithms perform better in terms of packet loss ratio, throughput and butter fluctuation.

Compensation for secondary uncertainty in electro-hydraulic servo system by gain adaptive sliding mode variable structure control

Based on consideration of the differential relations between the immeasurable variables and measurable variables in electro-hydraulic servo system,adaptive dynamic recurrent fuzzy neural networks(ADRFNNs) were employed to identify the primary uncertainty and the mathematic model of the system was turned into an equivalent linear model with terms of secondary uncertainty.At the same time,gain adaptive sliding mode variable structure control(GASMVSC) was employed to synthesize the control effort.The results show that the unrealization problem caused by some system's immeasurable state variables in traditional fuzzy neural networks(TFNN) taking all state variables as its inputs is overcome.On the other hand,the identification by the ADRFNNs online with high accuracy and the adaptive function of the correction term's gain in the GASMVSC make the system possess strong robustness and improved steady accuracy,and the chattering phenomenon of the control effort is also suppressed effectively.

Fuzzy variable structure algorithms for active queue management with delay compensation

Based on the linearized model of the TCP connections through the congested routers, this paper puts forward an active queue management algorithm (FVS-T). The algorithm utilizes the fuzzy variable structure control algorithm with delay factor to compensate time varying round-trip times (RTT) and uncertainties with respect to the number of active TCP sessions. By analyzing the robustness and performance of the control scheme for the nonlinear TCP/AQM model, we show that the proposed design has good performance and robustness, which are central to the notion of AQM. Implementation issues were discussed and ns simulations were provided to validate the design and compare its performance to other peer schemes in different scenarios. The results show that the proposed design significantly outperforms the other congestion schemes in terms of packet loss ratio, throughput and buffer fluctuation.

Independent modal variable structure fuzzy active vibration control of thin plates laminated with photostrictive actuators

Photostrictive actuators can produce photodeformation strains under illumination of ultraviolet lights. They can realize non-contact micro-actuation and vibration control for elastic plate structures. Considering the switching actuation and nonlinear dynamic characteristics of photostrictive actuators, a variable structure fuzzy active control scheme is presented to control the light intensity applied to the actuators. Firstly, independent modal vibration control equations of photoelectric laminated plates are established based on modal analysis techniques. Then, the optimal light switching function is derived to increase the range of sliding modal area, and the light intensity self-adjusting fuzzy active controller is designed. Meanwhile, a continuous function is applied to replace a sign function to reduce the variable structure control （VSC） chattering. Finally, numerical simulation is carried out, and simulation results indicate that the proposed control strategy provides better performance and control effect to plate actuation and control than velocity feedback control, and suppresses vibration effectively.

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.

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.

Research on Robust Control of Nonlinear Fuzzy VSS for Spacecraft

The nonlinear dynamic system of spacecraft with uncertainty and coupling is analyzed and its general dynamical equation is given.The decoupling-ability and controllability are proved.Aiming at this system,a new nonlinear decoupling controlling method is put forward by synthetically using the variable structure and fuzzy theory.The simulation results show that this method is effective in tracking performances under the existence of uncertainty and outer disturbance.

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.

基于混沌控制的采摘机器人防碰撞系统设计

针对采摘机器人在作业过程中遇到障碍物导致路径规划出现混沌现象的问题,基于混沌控制对采摘机器人防碰撞系统进行设计,并采用模糊自适应控制算法和滑模变结构控制算法结构的方式对系统进行控制。为了验证防碰撞系统的有效性,对采摘机器人进行了防碰撞和采摘仿真试验,结果表明:采摘机器人在作业过程中可以避开障碍物,按照规划路线到达预设位置,完成果蔬的采摘。

融合反步法的无人驾驶汽车轨迹跟踪控制方法

为了解决无人驾驶汽车轨迹跟踪控制的准确性、稳定性和快速性问题,将反步法分别融合滑模变结构控制和模糊自适应控制.建立车辆三自由度运动学位姿误差微分方程,推导了基于反步法的车速和横摆角速度控制律,结合Lyapunov稳定性判据验证了系统稳定性.分别建立融合反步法的滑模变结构和模糊自适应轨迹跟踪控制方法,结合轨迹跟踪稳态误差、超调量和调整时间,验证、比较了控制方法准确性、稳定性和快速性3种性能的优劣.结果表明:融合反步法的滑模变结构轨迹跟踪控制的稳定性最好,轨迹跟踪超调量接近于0;融合反步法的模糊自适应轨迹跟踪控制快速性最好,轨迹跟踪调整时间相对于反步法缩短了18.2%.

基于神经网络优化直/气复合控制导弹迅捷转弯

空空导弹迅捷转弯控制是在保证导弹稳定飞行的前提下,在尽可能短的时间内完成整个机动过程。为实现上述战术指标,考虑到导弹迅捷转弯的快时变性、强非线性和大干扰性,设计基于滑模变结构控制和模糊逻辑的直/气复合控制器。针对实际飞行中可能出现的初值不确定和外界干扰过大等现象,引入固定时间收敛理论和扩张状态观测器,有效避免干扰带来的控制输入抖振并保证导弹姿态角能在固定时间内快速稳定收敛。利用神经网络对滑模变结构控制的设计参数进行优化,在保证导弹迅捷转弯的同时减轻导弹侧向发动机的质量。通过仿真验证新提出的控制和分配方案的有效性。研究结果表明,所设计的控制器在存在模型不确定性和外部干扰等复杂情况下具一定的鲁棒性、稳定平滑的控制效果、较强的抗干扰能力以及优异的姿态跟踪性能,同时参数优化后的控制算法跟踪效果更优,在降低了原收敛时间的12.6%的同时,降低了原最大控制力的9.6%。

基于模糊控制的永磁同步电机协同控制

多电机协同控制系统中存在变量多、耦合程度高等问题,使得系统的同步误差较大、启动时间久。基于传统自抗扰控制方案,提出用滑模变结构控制策略优化自抗扰控制,提高了单电机的跟踪精度;设计模糊自调整控制方案优化同步误差。在MATLAB/SIMULINK下搭建两台电机交叉耦合控制模型,并与传统固定增益的相邻交叉耦合方案进行对比,结果显示:该方案可以有效提高控制精度,在面对扰动影响时能够快速恢复稳定,且恢复稳定所用时间显著缩短。

汽车ABS模糊变结构控制设计

针对汽车制动过程中防抱死制动系统(ABS)存在的难以充分利用地面附着系数和高度非线性的问题,提出了一种基于路面识别的ABS模糊变结构控制策略。利用Burckhardt轮胎模型设计路面识别算法,并通过模糊变结构控制调节路面识别算法识别出的最优滑移率。仿真实验结果表明,路面识别算法响应速度快、准确率高;在跃变路面条件下,模糊变结构控制比变结构控制的制动时间减少7%,制动距离缩短6%,控制器输出的抖振幅度得到有效削弱.

模糊神经网络滑模控制在高压电极热水锅炉液位控制系统中的应用

针对某公司生产的高压电极热水锅炉在工作过程中的高阶性、非线性及强耦合等特性以及用户对高压电极热水锅炉在电网侧调频调峰应用中的功率稳定性、响应快速性的严苛要求,而现有的控制策略难以满足精确控制(主要指功率)要求的实际情况,提出了一种将模糊神经网络控制与滑模变结构控制相结合的先进PID控制器,使其应用在高压电极热水锅炉的液位控制系统中。实验结果显示,将该控制器应用到高压电极热水锅炉的液位控制系统中,可有效克服上述系统的不良特性且有较好的稳定性和响应快速性,能够满足电网侧对电极锅炉在调频调峰中功率稳定性、响应快速性的要求。

基于模糊变结构补偿的机械臂运动路径避障规划算法

机械臂的活动范围可以自由调整,其准确的运动规律较难获取,导致机械臂运动路径避障规划存在规划效果差、规划路径长以及规划耗时长的问题,为此提出基于模糊变结构补偿的机械臂运动路径避障规划算法。该算法首先对机械臂进行相关动力学分析,将分析结果与模糊变结构相结合对机械臂力矩进行补偿控制;然后使用Q-learning算法计算补偿控制结果,获取路径最佳规划策略;最后通过该策略完成机械臂避障路径的规划。实验结果表明,使用该算法进行路径规划时的规划结果较为准确,规划路径短且规划耗时短。

基于模糊变结构的机械臂控制

现有的机械臂模糊变结构控制方法大都计算复杂或需要检测滑模面的微分信号.本文将机械臂模型分为确定部分和不确定部分进行研究,对确定部分采用一般反馈控制,对不确定部分采用变结构集中补偿控制,为了消除变结构控制器的抖震引入模糊控制方法,将滑模面作为模糊控制器的输入,补偿控制器权值作为输出.本方案不仅不需要检测滑模面微分信号,而且计算简单,易于实现.仿真结果表明,在存在模型误差和外部扰动的情况下,该方案既能达到快速跟踪,又能很好的消除控制器的抖震.

不确定参数电动舵机滑模变结构控制

针对电动舵机系统要求在有限时间内无误差跟踪目标的问题,研究了Terminal滑模控制方法。针对常规Terminal滑模控制需要知道不确性的上界且容易产生高频抖振的问题,采用模糊技术对电动舵机的不确定性进行估计,并将其与常规Terminal滑模控制结合起来,提出了模糊Terminal滑模控制技术。建立了电动舵机的模糊Terminal滑模控制系统结构,给出了控制器的设计方法。实验与仿真结果表明,与常规Terminal滑模控制器相比,模糊Terminal滑模控制器能有效降低抖振,改善了控制器的动态品质。

同步发电机混沌振荡的模糊滑模变结构控制

为消除周期性扰动下同步发电机中的混沌振荡,使系统输出跟踪给定信号,采用模糊滑模变结构控制方法,设计混沌控制器。采用指数趋近律方法,设计切换控制律,使系统能克服扰动影响,快速到达切换面;在滑动模态,采用模糊控制规则,抑制控制中的高频抖振。仿真结果显示:加入传统滑模变结构控制器后,大约需要12.5 s,系统跟踪上给定信号,在渐近跟踪过程中,控制中出现高频振荡;加入模糊滑模变结构控制器后,在1 s内,系统跟踪上给定信号,在渐近跟踪过程中,控制中无振荡现象。

四轮驱动混合动力汽车驱动防滑控制策略的研究

本文中以具有发动机、ISG电机和轮毂电机多个动力源的四轮驱动混合动力汽车为研究对象,依据驱动轮的滑模变结构控制算法,制定了目标驱动转矩控制策略。同时,基于模糊控制算法制定了各动力源的转矩协调分配控制策略,并对模糊推理器输出的各转矩进行了修正。在Matlab/Simulink环境下对所设计的控制策略进行了离线仿真。结果表明,在棋盘路面工况下,所设计的控制策略能有效抑制各驱动轮过度滑转,提高了混合动力汽车的动力性和行驶稳定性,改善其燃油经济性。

新型模糊PID控制及在HVAC系统的应用

为了推广模糊控制器在非线性系统中的应用,提出一种利用PID控制器的参数优化和调节模糊控制器的新型设计方法.通过模糊控制器的结构分析建立与PID控制之间的精确解析关系之后提出基于PID控制增益因子的模糊控制器设计算法,然后利用改进的变论域思想进一步优化模糊控制器设计参数.将其应用于暖通空调(HVAC)系统的节能控制中并与常规PID控制器相比较,仿真和实验结果表明这种模糊控制器具有超调量小、跟踪迅速、鲁棒性强等优越的控制性能.