快速二阶终端滑模控制及其在下肢外骨骼的应用

为了提高传统二阶终端滑模控制的全局收敛性,提出一种快速二阶终端滑模控制算法.设计一种二阶趋近律,将绝对值函数隐藏在积分项里,并增加线性项以提高全局收敛性.当系统状态未到达滑模面时,采用二阶趋近律,并通过调整参数避免奇异问题;当系统状态到达滑模面时,采用不含不连续符号项的指数趋近律,以保证控制误差有限时间收敛.采用Lyapunov直接法证明快速二阶终端滑模控制算法的稳定性,及其比super twisting算法具有更优良的收敛特性.以下肢外骨骼为研究对象,建立动力学模型.在考虑建模误差和外部干扰的情况下,将该算法应用于下肢外骨骼的姿态控制.仿真结果表明,所提出的控制算法能够有效抑制抖振,并且比super twisting算法具有更良好的跟踪性能,验证了该算法的有效性.     

基于参数估计的一类非线性系统故障诊断算法

针对系统模型的不确定性、未知输入扰动和非线性特性, 提出一类非线性系统参数估计的故障诊断算法. 构造系统故障诊断观测器, 采用Lyapunov 稳定性定理验证观测器的稳定性, 通过Barbalat 引理证明满足故障诊断观测器为渐近稳定的表征故障参数的参数估计, 并总结了设计算法流程. 仿真结果表明, 所提出算法具有快速收敛性, 对一类非线性系统诊断效果较好.

     

基于广义扩张状态观测器的干扰不匹配离散系统状态反馈控制

针对一类干扰不匹配的线性离散时间系统, 研究基于广义扩张状态观测器的稳定化状态反馈控制器设计问题. 在经典的自抗扰控制器中, 扩张状态观测器主要针对干扰匹配的积分串联型系统. 然而, 在许多实际系统中往往存在干扰不匹配的情况, 例如存在采样抖动的离散时间控制系统. 针对这一问题, 基于一类存在不匹配干扰的离散时间系统, 提出广义扩张状态观测器和相应的稳定化状态反馈控制器设计方法. 最后通过永磁同步电机调速控制仿真实例验证了所设计的观测器和控制器的有效性.

     

双层自适应快速super twisting控制算法

为提高super twising算法的收敛速度,解决现有算法存在的增益过估计问题,提出了两种自适应增益快速super twisting算法.分别通过快速终端滑模趋近律和增加线性项加快收敛速度.利用基于等效控制的双层自适应律调节增益,保证滑模存在条件的成立,同时使增益尽量的小.采用Lyapunov方法证明了新算法具有更优良的收敛特性,根据有界实引理和Schur补定理分别给出了两种算法的参数整定策略.仿真算例表明,在相同控制参数下,新算法的能耗与原算法接近,并具有更快的收敛速度和更强的鲁棒性.     

基于NDO的ROV变深自适应终端滑模控制器设计

针对ROV的深度控制问题, 提出基于非线性干扰观测器的自适应终端滑模控制方法. 详细叙述了控制器的设计过程, 并利用Lyapunov 稳定性判据, 验证了存在模型参数不确定性和外干扰时, 系统的全局渐近稳定性和跟踪误差的收敛性. 仿真实验表明, 所提出的控制器不仅能够很好地估计并克服外干扰和模型不确定性等因素, 具有很好的鲁棒性能, 而且还可以实现在任意规定时刻变深运动的快速收敛.

     

一类非线性严格反馈系统基于干扰观测器的抗干扰控制

针对一类带有干扰的非线性严格反馈系统, 研究其抗干扰控制问题. 系统干扰满足不匹配条件, 代表一类部分信息已知的干扰. 通过设计非线性干扰观测器, 提出基于非线性干扰观测器和back-stepping 的抗干扰控制方法来补偿干扰, 该方法可以保证闭环系统所有信号是半全局最终一致有界的. 最后, 通过与现有方法的对比验证了所提出方法的正确性和有效性.

     

基于扩张状态观测器的分散模型预测控制

针对复杂关联系统中分散控制方法无法有效解决子系统间的耦合和干扰问题, 提出一种基于扩张状态观测器的分散模型预测控制算法. 首先将复杂关联系统分解为多个状态维数较低、控制变量较少的子系统, 并为每个子系统设计本地预测控制器; 然后, 采用扩张状态观测器对子系统的耦合项以及干扰项进行估计, 进而利用估计值对子系统进行前馈补偿, 从而降低复杂关联系统的计算复杂度, 提高系统的稳定性和抗干扰能力; 最后, 利用液位控制系统验证了所提出算法的有效性.

     

基于动态学习策略的群集蜘蛛优化算法

为了提高群集蜘蛛优化(SSO) 算法的性能, 提出一种基于动态学习策略的群集蜘蛛优化(DSSO) 算法. 该算法通过群体协作过程中学习因子的动态选择, 平衡算法的搜索能力和勘探能力; 采用随机交叉策略和云模型改进协作过程个体更新方式, 在维持种群多样性的同时尽量提高收敛速度. 基于标准测试函数的仿真实验表明, DSSO 算法可有效避免早熟收敛, 在收敛速度和收敛精度上较标准SSO 算法和其余4 种较具代表性的优化算法均有显著提高.

     

晃动基座下捷联惯导的抗干扰自对准算法

针对捷联惯导(SINS) 晃动基座下, SINS 难以快速实现自对准的问题, 提出SINS 的抗干扰自对准算法. 该算法通过将初始对准问题转化为Wahba 求解问题来消除角运动干扰的影响; 利用惯性坐标系重力矢量和晃动干扰加速度的频率特点, 通过设计低通滤波器对比力在惯性坐标下的投影进行滤波来消除线振动干扰的影响. 仿真结果表明, 该算法不需要进行粗对准, 能够在角运动干扰和线振动干扰同时存在的情况下快速实现自对准.

     

多目标资源优化分配问题的Memetic 算法

针对传统算法求解多目标资源优化分配问题收敛慢、Pareto解不能有效分布在Pareto 前沿面的问题, 提出一种新的Memetic 算法. 在遗传算法的交叉算子中引入模拟退火算法, 加强了遗传算法的局部搜索能力, 加快了收敛速度. 为了使Pareto 最优解均匀分布在Pareto 前沿面, 在染色体编码中引入禁忌表, 增加了种群的多样性, 避免了传统遗传算法后期Pareto 解集过于集中的缺点. 通过与已有的遗传算法、蚁群算法、粒子群算法进行比较, 仿真实验表明了所提出算法的有效性, 并分析了禁忌表长度和模拟退火参数对算法收敛性的影响.

     

飞翼布局无人机分数阶积分滑模姿态控制

针对存在复合干扰的飞翼布局无人机(UAV)姿态控制问题,提出了一种基于分数阶积分滑模与双幂次趋近律的姿态跟踪控制方案.结合分数阶微积分及滑模变结构控制理论,设计了分数阶积分滑模面.为解决传统趋近律收敛时间长和抖振严重等不足,提出一种具有二阶滑模特性且有限时间收敛的双幂次趋近律.在名义控制律的基础上,设计super twisting滑模干扰观测器,实现对复合干扰的估计和补偿,增强内外环控制器应对复合干扰的鲁棒性.为充分利用冗余操纵面与解决非线性舵效问题,在飞行控制系统中引入了非线性控制分配环节.仿真结果验证了所提方案的有效性.     

Adaptive disturbance observer‐based finite‐time continuous fault‐tolerant control for reentry RLV

The control effectors of reusable launch vehicle (RLV) can produce significant perturbations and faults in reentry phase. Such a challenge imposes tight requirements to enhance the robustness of vehicle autopilot. Focusing on this problem, a novel finite‐time fault‐tolerant control strategy is proposed for reentry RLV in this paper. The key of this strategy is to design an adaptive‐gain multivariable finite‐time disturbance observer (FDO) to estimate the synthetical perturbation with unknown bounds, which is composed of model uncertainty, external disturbance, and actuator fault considered as the partial loss of actuator effectiveness in this work. Then, combined with the finite‐time high‐order observer and differentiator, a continuous homogeneous second‐order sliding mode controller based on the terminal sliding mode and super‐twisting algorithm is designed to achieve a fast and accurate RLV attitude tracking with chattering attenuation. The main features of the integrated control strategy are that the adaptation algorithm of FDO can achieve non‐overestimating values of the observer gains and the second‐order super‐twisting sliding mode approach can obtain a more elegant solution in finite time. Finally, simulation results of classical RLV (X‐33) are provided to verify the effectiveness and robustness of the proposed fault‐tolerant controller in tracking the guidance commands. Copyright © 2017 John Wiley & Sons, Ltd.     

基于扩张状态观测器的UCAV自适应滑模控制

针对固定翼UCAV（Unmanned Combat Aerial Vehicle）系统中存在的不确定性和外部扰动，设计了一种基于扩张状态观测器的自适应超扭曲滑模控制器用来抑制系统扰动，从而提高对于UCAV的控制性能。建立固定翼UCAV的六自由度非线性模型，针对姿态控制和速度控制分别设计扩张状态观测器对模型中难以精确测量的状态量和外部扰动进行估计，依据奇异摄动原理分别对姿态和速度设计自适应超扭曲滑模控制器，实现对UCAV的姿态和速度的跟踪控制。采用某型固定翼UCAV非线性模型对所设计的控制器进行仿真验证，并且与传统的自抗扰滑模控制方法进行了对比，仿真结果表明，基于扩张状态观测器的自适应超扭曲滑模控制器具有更小的超调量和稳态误差。     

A Fast Convergence Super‐Twisting Observer Design for an Autonomous Airship

Airships are often under the risk of external disturbances, for example, the wind. The accurate external disturbance of the airship are hard to acquire. Typically, the super‐twisting observer can track the states for mechanical systems and could be used as an external disturbance tracker. However, the convergence rate of the traditional super‐twisting observer is very slow and the observed states often oscillate heavily. We modified the traditional super‐twisting observer by adding more variables to the sliding surface, and adding parameters to the newly added variables. Simulation results illustrates that the new proposed observer is able to reduce the convergence time and reduce overshoot greatly, improving the performance of the observer.     

Continuous Fixed‐Time Convergent Super‐Twisting Algorithm in Case of Unknown State and Disturbance Initial Conditions

This paper presents a fixed‐time convergent super‐twisting‐like algorithm designed to provide a direct extension, without any additional terms, of the conventional super‐twisting control system, whose state initial condition is unknown and the disturbance initial condition is bounded by a known constant or even completely unknown. The fixed‐time convergent super‐twisting‐like algorithm is first designed for a scalar system and then generalized to a multivariable one. An upper estimate of its convergence (settling) time is calculated in each case. Several examples are provided to illustrate the obtained theoretical results.     

A New Finite Time Convergence Condition for Super‐Twisting Observer Based on Lyapunov Analysis

A new convergence condition is proposed for the super‐twisting sliding mode observer in this paper, where Lyapunov stability analysis is used as the main method to get the new convergence condition. The super‐twisting sliding mode observer is designed to obtain unknown system states of the second order nonlinear system with bounded uncertainties and disturbances. By involving a quadratic Lyapunov function, the Lyapunov approach is applied to the stability analysis of the super‐twisting observer, from which a new convergence condition is obtained to guarantee the finite time convergence of the observer. Simulation results of a pendulum and a rigid manipulator are included to demonstrate the effectiveness of the new convergence condition.     

基于滑模的二阶多智能体快速抗扰一致性

针对带有外部未知扰动的二阶多智能体系统的领导—跟随有限时间一致性问题，本文设计出一种带有时变增益的有限时间干扰观测器，用以实现对每个跟随智能体中未知扰动的快速估计，在此基础上，本文结合超螺旋积分滑模控制方法并利用邻居智能体的位置和速度信息设计一种快速抗扰一致性协议，该协议能够保证存在非线性动态的多智能体系统有限时间一致性控制并能抑制抖振现象.同时，利用李亚普诺夫函数进行了稳定性的证明.最后，通过Matlab数值仿真进一步验证了所提出协议的可行性.     

Heterogeneous consensus of higher‐order multi‐agent systems with mismatched uncertainties using sliding mode control

A robust consensus controller is proposed for heterogeneous higher‐order nonlinear multi‐agent systems, when the agent dynamics are involved with mismatched uncertainties. A distributed consensus protocol based on a time‐varying nonhomogeneous finite‐time disturbance observer and sliding mode control is designed to realize the network consensus of higher‐order multi‐agent systems. The time‐varying finite‐time disturbance observer overcomes the problem of peaking value near the initial time caused by the constant gain one and is designed to estimate the uncertainties and to mitigate the effect of mismatched uncertainties during the sliding mode. To eliminate the chattering phenomenon and ensure finite‐time convergence to the sliding surface, the control law is designed by using the super twisting algorithm. Finally numerical simulations are given to illustrate the validity of the proposed method. Copyright © 2016 John Wiley & Sons, Ltd.