鲁棒低增益变结构模型参考自适应控制

就对象含未建模动态且其建模部分相对阶大于1时的变结构模型参考自适应控制(VS-MRAC)系统,提出了一种鲁棒低增益变结构控制方案,特点是系统变结构律在低增益状态下仍可保证所有辅助误差均在有限时间内收敛到零,从而提高了系统跟踪精度.此外,还研究了平均值滤波器对系统稳定性的影响.     

鲁棒变结构模型参考自适应控制器的分析与设计(Ⅰ)

对含有未建动态ＳＩＳＯ定常线性系统提出了一种控制增益可切换的变结构模型参考自适应控制方案。其主要结果是：解决了当对象建模部分相对阶为１、高频增益符号未知时,确保跟踪误差满足预先给定的过渡过程性能指标（超调量,过渡时间和稳态误差）的问题。     

低增益变结构模型参考自适应控制器设计

就对象相对阶大于1时的变结构模型参考自适应控制（VS－MRAC）系统提出了一种低增益变结构控制方案,主要特点是：1）系统变结构律在低增益状态下仍可保证所有辅助误差在有限时间内收敛到零,从而提高了系统跟踪精度;2）进一步研究了平均值滤波器对系统稳定性的影响。     

具有理想跟踪特性的鲁棒变结构模型参考自适应控制

针对相对阶为1的定常线性被控对象,提出了一种控制增益可切换的鲁棒变结构模型参考自适应控制方案.该方案在对象参数及高频增益符号均未知的情形下,可确保跟踪误差满足预先给定的过渡过程性能指标,即超调量、过渡过程时间和稳态误差.     

具有理想跟踪特性的鲁棒变结构模型参考自适应控制1)

针对相对阶为1的定常线性被控对象,提出了一种控制增益可切换的鲁棒变结构模型参考自适应控制方案.该方案在对象参数及高频增益符号均未知的情形下,可确保跟踪误差满足预先给定的过渡过程性能指标,即超调量、过渡过程时间和稳态误差.     

可具有非严格正实参考模型的变结构鲁棒自适应控制

提出了一种可具有非严格正参考模型的变结构鲁棒自适应的控制方案,可去除变结构模型参考自适应控制中普遍要求参考模型为严格正害或相当对阶大于１时参考模型补偿后严格正实的假设,在此基础上提出的变结构控制律可保保证跟踪误差在相对阶为１时于有限时间内收敛到零,而当相对阶大于１时则可使跟踪误差收敛到一个残差集内。     

具有理想跟踪特性的多变量变结构模型参考自适应控制

考虑一个广义相对阶为1的多变量系统之变结构模型参考自适应控制器(VS-MRAC)设计问题,提出了一种切换控制方案,解决了现有多变量VS-MRAC和多变量模型参考自适应控制(MRAC)中两个尚未解决的问题:1)使系统跟踪误差的每个分量均满足预先给定的性能指标;2)无须假定对象高频增益矩阵满足通常的正定性条件.     

高频增益符号未知时的变结构模型参考自适应控制:任意相对阶的控制律设计

讨论被控对象相对阶大于1且高频增益符号未知时的变结构模型参考自适应控制问题,从而将相对阶为1时的结果推广到任意相对阶.首先对关键信号构造监控函数,并在此基础上提出了一种控制信号切换律.进而证明,当被控对象相对阶大于1、高频增益符号未知时,在监控函数的监测下,相关控制信号经至多有限次切换后将停止切换,跟踪误差将收敛到一个残集内,且该残集可通过减小某些设计参数而变得任意小.特别,本文证明,与相对阶为1时相同,当对象相对阶大于1时,若系统的某些初始条件为零,则至多只需要一次切换.     

高频增益符号未知时的变结构模型参考自适应控制

解决了对象相对阶大于1、高频增益符号未知时的变结构模型参考自适应控制(VS-MRAC)问题．提出了一种基于监控函数的控制信号切换律, 证明只需要对首个辅助误差构造监控函数, 就可决定控制信号的切换时间;进而, 在监控函数的管理下, 控制信号经至多有限次切换后将停止切换, 闭环系统所有信号一致有界, 跟踪误差将收敛到一个残集内, 且该残集可通过减小某些设计参数而变得任意小．特别地, 我们证明, 若系统的某些初始条件为零, 则至多只需要一次切换．     

相对阶n*=3系统的鲁棒直接型模型参考自适应控制

针对相对阶n*=3的具有输入和输出未建模动态的一类系统,设计了可以实现的具有未规范化自适应律的鲁棒直接型模型参考自适应控制器,构造了满足引理1性质的自适应律.通过利用Lyapunov稳定性理论及鲁棒自适应控制分析理论,构造误差系统,严格地分析了闭环系统的稳定性和跟踪性能.     

A robust VS-MRAC using switching scheme for the gain of control variables

A switching scheme for the gain of control variable of a VS-MRAC system was recently presented for plants with relative degree one. In this paper, the scheme is extended to the general case of plants with arbitrary relative degree. By the establishment of the relationship between the tracking error and those auxiliary errors for the case of plants with relative degree greater than one, it is shown that as long as the performance indexes are guaranteed for the auxiliary errors, each of which is in dynamics a subsystem with relative degree one, the tracking error will converge to a small residual set in a prespecified transient time. Furthermore, the influence of averaging filters on the system is analysed and shows that it can be considered as, in a sense, unmodelled dynamics.     

Nonlinear control of three‐dimensional underactuated vehicles

This paper presents the derivation of robust trajectory‐tracking nonlinear control laws for general three‐dimensional vehicle models with one degree of underactuation where all of the state tracking errors are stabilized. The method is based on a novel transformation of the trajectory tracking problem into a reduced‐order error dynamics. Two traditional nonlinear controllers based on sliding mode and backstepping approaches are developed and shown to stabilize the trajectory tracking errors in presence of modeling uncertainties and bounded disturbances. The performance of the two controllers are compared in absence and presence of disturbances.     

Terminal sliding mode fault-tolerant control for aviation redundant hydraulic actuation system based on robust fault reconstruction

This paper investigates the fault-tolerant control problem for a dual-redundant hydraulic actuation system on active/active (A/A) mode subject to servovalve leakage and disturbances. The change in system dynamics caused by servovalve leakage is modeled as an additive time-varying fault. Then, an enhanced iterative learning observer with improved robustness against abrupt unknown input is designed for fault reconstruction. In view of the high relative degree of the plant, an auxiliary variable is adopted to facilitate the controller design. Combined with the fault reconstruction results, an adaptive continuous nonsingular fast terminal sliding mode (NFTSM) fault-tolerant controller is developed, in which an NFTSM manifold is constructed based on the auxiliary variable to achieve fast convergence of trajectory tracking errors. An adaptive continuous reaching law with less chattering is designed to compensate for the influence of the lumped disturbance. Lyapunov stability analysis demonstrates that this method can ensure finite-time convergence of sliding variable and can guarantee the trajectory tracking errors converge to the neighborhood of the origin exponentially. Finally, the effectiveness of the proposed method is verified through a comparative simulation study.     

Saturated Adaptive Output-Constrained Control of Cooperative Spacecraft Rendezvous and Docking

This paper investigates the robust relative pose control for spacecraft rendezvous and docking with constrained relative pose and saturated control inputs. A barrier Lyapunov function is used to ensure the constraints of states, so that the computational singularity of the inverse matrix in control command can be avoided, while a linear auxiliary system is introduced to handle with the adverse effect of actuator saturation. The tuning rules for designing parameters in control command and auxiliary system are derived based on the stability analysis of the closed-loop system. It is proved that all closed-loop signals always keep bounded, the prescribed constraints of relative pose tracking errors are never violated, and the pose tracking errors ultimately converge to small neighborhoods of zero. Simulation experiments validate the performance of the proposed robust saturated control strategy.      

任意相对阶下非线性切换系统的事件触发漏斗控制

针对一类具有任意相对阶且带有部分非输入到状态稳定逆动态的非线性切换系统, 提出一种动态事件触 发漏斗跟踪控制方案. 首先, 引入一个虚拟输出将任意相对阶的非线性切换系统转换为相对阶为一的非线性切换系 统. 其次, 设计各子系统的事件触发漏斗控制器和切换的动态事件触发机制, 解决候选事件触发漏斗控制器和子系 统之间的异步切换问题, 所提方案消除已有文献中为所有子系统设计共同控制器带来的保守性. 在一类具有平均驻 留时间切换信号的作用下, 保证切换闭环系统的所有信号都是有界的, 且跟踪误差一直在预设的漏斗内演化, 并排 除采样中的奇诺现象. 最后, 一个仿真例子验证方案的实用性和有效性.     

Adaptive output feedback control of uncertain nonlinear systems using single-hidden-layer neural networks

We consider adaptive output feedback control of uncertain nonlinear systems, in which both the dynamics and the dimension of the regulated system may be unknown. However, the relative degree of the regulated output is assumed to be known. Given a smooth reference trajectory, the problem is to design a controller that forces the system measurement to track it with bounded errors. The classical approach requires a state observer. Finding a good observer for an uncertain nonlinear system is not an obvious task. We argue that it is sufficient to build an observer for the output tracking error. Ultimate boundedness of the error signals is shown through Lyapunov's direct method. The theoretical results are illustrated in the design of a controller for a fourth-order nonlinear system of relative degree two and a high-bandwidth attitude command system for a model R-50 helicopter.     

Feedback linearisation control of an induction machine augmented by single-hidden layer neural networks

We consider adaptive output feedback control methodology of highly uncertain nonlinear systems with both parametric uncertainties and unmodelled dynamics. The approach is also applicable to systems of unknown, but bounded dimension. However, the relative degree of the regulated output is assumed to be known. This new control strategy is proposed to address the tracking problem of an induction motor based on a modified field-oriented control method. The obtained controller is then augmented by an online neural network that serves as an approximator for the neglected dynamics and modelling errors. The network weight adaptation rule is derived from the Lyapunov stability analysis, that guarantees boundedness of all the error signals of the closed-loop system. Computer simulations of an output feedback controlled induction machine, augmented via single-hidden-layer neural networks, demonstrate the practical potential of the proposed control algorithm.