一类未知参数非线性系统的自适应无源控制

对一类含有未知参数的本质非线性系统,通常的Backstepping方法无法应用.为此,提出一种基于状态反馈的自适应无源控制对策,通过对非线性系统进行反馈无源化控制,设计自适应无源镇定控制器和自适应无源输出跟踪控制器.设计中适当调节自适应无源控制器参数,能够保证闭环系统稳定且所有信号全局一致有界,从而解决了此类含有未知参数非线性系统的稳定性和输出跟踪问题.仿真算例验证了提出控制方案的有效性,表明系统具有较强的稳定性和跟踪特性.     

控制量前具有不确定系数的电液伺服系统自适应控制

针对控制输入前具有不确定系数的电液伺服位置系统精确跟踪控制问题, 提出了一种改进的自适应Backstepping控制器设计方法. 该方法通过对系统模型的等价变换和选择合适的Lyapunov函数, 有效解决了系统模型中控制输入前存在不确定系数而导致所设计的控制器存在参数自适应律, 而自适应律中存在控制量造成的嵌套难题. 以驱动连铸结晶器的电液伺服位置系统为例, 进行了控制器的设计和稳定性证明. 仿真研究结果表明, 所提出的改进设计方法是可行的, 设计的控制器具有较强的鲁棒性和良好的跟踪性能.     

不确定轮式移动机器人的任意轨迹跟踪

本文研究参数不确定轮式移动机器人的任意轨迹跟踪统一控制问题.通过引入坐标变换、输入变换和辅助动态,将机器人模型转换为合适的形式;进而运用Lyapunov方法和自适应技术设计了一种自适应统一控制器,该控制器可以保证跟踪误差全局一致最终有界,且最终界大小可以通过调整控制器参数而任意调节.仿真结果验证了控制律的有效性.     

带有未知参数和有界干扰的移动机器人轨迹跟踪控

针对模型参数未知和存在有界干扰的非完整移动机器人的轨迹跟踪控制问题,本文提出了一种鲁棒自适应轨迹跟踪控制器方法.非完整移动机器人的控制难点在于它的运动学系统是欠驱动的.针对这一难点,本文利用横截函数的思想,引入新的辅助控制器,使得非完整移动机器人系统不再是一个欠驱动系统,缩减了控制器设计的难度,进而利用非线性自适应算法和参数映射方法构造李雅谱诺夫函数.通过李雅普诺夫方法设计控制器和参数自适应器,从而使得非完整移动机器人的跟随误差任意小,即可以任意小的误差来跟随任意给定的参考轨迹.仿真结果证明了方法的有效性.     

电液伺服系统自适应逆向递推控制器设计

针对电液伺服系统的精确位置跟踪控制问题,引入虚拟控制量的概念,提出了一种逆向递推控制器的设计方法;同时考虑到实际系统存在内部参数和外负载力的不确定性,采用Lyapunov稳定理论对系统的不确定性进行自适应控制律设计,最终得到了自适应Backstepping控制器,并进行了稳定性分析.仿真结果表明,设计的自适应Backstepping控制器不需要知道内部不确定性参数和外部负载力干扰的边界,与常规PID控制方法相比,具有较强的鲁棒性及良好的位置跟踪性能.     

带有未知参数和有界干扰的移动机器人轨迹跟踪控制

针对模型参数未知和存在有界干扰的非完整移动机器人的轨迹跟踪控制问题,本文提出了一种鲁棒自适应轨迹跟踪控制器方法.非完整移动机器人的控制难点在于它的运动学系统是欠驱动的.针对这一难点,本文利用横截函数的思想,引入新的辅助控制器,使得非完整移动机器人系统不再是一个欠驱动系统,缩减了控制器设计的难度,进而利用非线性自适应算法和参数映射方法构造李雅谱诺夫函数.通过李雅普诺夫方法设计控制器和参数自适应器,从而使得非完整移动机器人的跟随误差任意小,即可以任意小的误差来跟随任意给定的参考轨迹.仿真结果证明了方法的有效性.     

基于参数不确定机械臂系统的自适应轨迹跟踪控制

针对机械臂系统惯性参数及运动学参数不能准确测量进而影响轨迹跟踪性能的问题,提出一种任务空间自适应轨迹跟踪控制方法,通过定义关节角速度参考误差,并将任务空间的轨迹跟踪误差及运动学参数误差反馈给控制器,以改善系统稳定性,设计电机参数传输矩阵及电机参数自适应率,以抵消电机发热引起参数漂移对跟踪性能影响,并给出了稳定性证明.实验结果表明,该方法能够较好地克服电机参数漂移对跟踪控制性能的影响.     

一类非线性系统的直接自适应控制器

针对带一类非线性参数系统的状态反馈自适应跟踪控制问题,通过设计一种新的李亚普诺夫函数--加权控制李亚普诺夫函数,由它作用于控制器和参数调整律,使之达到全局渐近跟踪从而满足控制指标。     

具有H∞ 跟踪性能的机器人自适应犘犐犇控制

针对非线性不确定机器人系统的轨迹跟踪控制问题,提出一种鲁棒自适应ＰＩＤ 控制算法．该控制器由主控制器和监督控制器组成．主控制器以常规ＰＩＤ 控制为基础,基于滑模控制思想设计ＰＩＤ 参数的自适应律,根据误差实时修正ＰＩＤ 参数．基于Ｌｙａｐｕｎｏｖ函数设计的监督控制器补偿自适应ＰＩＤ 控制器与理想控制器之间的差异,使系统具有设定的犎∞ 的跟踪性能．最后,两关节机器人的仿真实验结果表明了算法的有效性．     

自由漂浮空间机器人末端轨迹优化自适应控制

惯性参数不确定情况下的自由漂浮空间机器人(FFSR)轨迹跟踪控制是当前FFSR自主控制研究的重点与难点之一.针对该问题,提出一种FFSR末端轨迹优化自适应跟踪控制方法.该方法首先基于离散状态依赖黎卡提方程(DSDRE),设计两级DSDRE优化跟踪控制器,然后在控制器输出基础上,通过求解有约束条件下的非线性优化问题实现FFSR惯性参数的辨识,进而根据辨识结果调整控制器相关参数,实现FFSR末端轨迹的优化自适应跟踪控制.最后,采用平面两连杆FFSR模型进行仿真,验证了所提出方法的有效性.     

Robust adaptive control using a universal approximator for SISOnonlinear systems

This paper deals with the robust adaptive control of a class of nonlinear systems in the presence of parametric uncertainties and dominant uncertain nonlinearities. The proposed controller utilizes the robust adaptive control to guarantee uniform boundedness and convergence of tracking errors. In addition, an adaptive fuzzy logic system is used as a universal approximator to reduce the model uncertainties coming from uncertain nonlinearities and to improve tracking performance. The approach does not require the matching condition imposed on control systems by using the backstepping design procedure, and provides boundedness of tracking errors under poor parameter adaptation. The method can be applied to a class of single-input single-output (SISO) nonlinear systems, transformable to a parametric-strict-feedback form     

Adaptive output tracking of inherently nonlinear systems with nonlinear parameterization

We address the problem of output tracking for a class of nonlinearly parameterized systems with unstabilizable linearization. To achieve practical output tracking globally in the case when both the bound of reference signals and the bound of unknown time-varying parameters are not known a priori, we present a robust adaptive control method that is based on the idea of universal control combined with the new adaptive feedback design method developed recently for controlling uncertain systems with nonlinear parameterization. Continuous adaptive tracking controllers are explicitly constructed in this paper. The proposed adaptive tracking controllers use only the information of a prescribed reference signal but not its derivatives, nor its bound.     

LMI-Based Adaptive Tracking Control for Parametric Strict-Feedback Systems

This paper presents an effective linear matrix inequality (LMI)-based adaptive scheme to design the output tracking controller for parametric strict-feedback systems. In our previous paper, the concepts of virtual desired variables (VDVs) and, in turn, the so-called generalized kinematics are introduced to benefit the tracking design. All the VDVs can be determined without fail from the generalized kinematics via a newly defined recursive procedure if the systems are in strict-feedback form. The proposed adaptive tracking control is investigated for single-input and multi-input systems with unknown parameters. Different from the existent adaptive fuzzy control, our research is an exact approach, compared with the approach using universal approximation. Relative to the adaptive backstepping control, it makes the design procedure more straightforward. Moreover, we propose a new method called balance technique to deal with the infeasibility of LMIs for the specified structure of common positive definite matrix $P$, and adopt an overparameterization technique to make sure that the VDVs can be well-defined. From the numerical simulations, it is shown that the proposed scheme is very powerful with expected satisfactory performance.      

A discrete-time parameter estimation based adaptive actuator failure compensation control scheme

This article studies discrete-time adaptive failure compensation control of systems with uncertain actuator failures, using an indirect adaptive control method. A discrete-time model of a continuous-time linear system with actuator failures is derived and its key features are clarified. A new discrete-time adaptive actuator failure compensation control scheme is developed, which consists of a total parametrisation of the system with parameter and failure uncertainties, a stable adaptive parameter estimation algorithm, and an on-line design procedure for feedback control. This work provides a new design of direct adaptive compensation of uncertain actuator failures, using an indirect adaptive control method. Such an adaptive design ensures desired closed-loop system stability and tracking properties despite uncertain actuator failures. Simulation results are presented to show the desired adaptive actuator failure compensation performance.     

Robust tracking enhancement of robot systems including motordynamics: a fuzzy-based dynamic game approach

A robust tracking control design of robot systems including motor dynamics with parameter perturbation and external disturbance is proposed in this study via adaptive fuzzy cancellation technique. A minimax controller equipped with a fuzzy-based scheme is used to enhance the tracking performance in spite of system uncertainties and external disturbance. The design procedure is divided into three steps. At first, a linear nominal robotic control design is obtained via model reference tracking with desired eigenvalue assignment. Next, a fuzzy logic system is constructed and then tuned to eliminate the nonlinear uncertainties as possibly as it can to enhance the tracking robustness. Finally, a minimax control scheme is specified to optimally attenuate the worst-case effect of both the residue due to fuzzy cancellation and external disturbance to achieve a minimax tracking performance. In addition, an adaptive fuzzy-based dynamic game theory is introduced to solve the minimax tracking problem. The proposed method is appropriate for the robust tracking design of robotic systems with large parameter perturbation and external disturbance. A simulation example of a two-link robotic manipulator driven by DC motors is also given to demonstrate the effectiveness of proposed design method's tracking performance     

电液伺服系统的多滑模鲁棒自适应控制

针对一类参数与外负载非匹配不确定的非线性高阶系统,提出了一种基于逐步递推方法的多滑模鲁棒自适应控制策略.应用逐步递推的多滑模控制方法简化了高阶系统的控制问题,同时在自适应控制中加入鲁棒控制的方法,以消除不确定性对控制性能的影响.首先利用逐步递推方法与状态反馈精确线性化理论,得出确定系统的多滑模控制器设计方法;然后基于Lyapunov稳定性分析方法,给出不确定系统的参数自适应律,及鲁棒自适应控制器的设计方法.本文把该控制策略应用到电液伺服系统的位置跟踪控制中,仿真结果显示,该控制方法具有较强的鲁棒性及良好的跟踪效果.     

Adaptive tracking of switched nonlinear systems with prescribed performance using a reference-dependent reparametrisation approach

In this paper, adaptive tracking control of switched nonlinear systems in the parametric strict-feedback form is investigated. After defining a reparametrisation lemma in the presence of a non-zero reference signal, we propose a new adaptive backstepping design of the virtual controllers that can handle the extra terms arising from the reparametrisation (and that the state-of-the-art backstepping designs cannot dominate). The proposed adaptive design guarantees, under arbitrarily fast switching, an a priori bound for the steady-state performance of the tracking error and a tunable bound for the transient error. Finally, the proposed method, by overcoming the need for subsystems with common sign of the input vector field, enlarges the class of uncertain switched nonlinear systems for which the adaptive tracking problem can be solved. A numerical example is provided to illustrate the proposed control scheme.     

具有不确定噪声的随机非线性系统的鲁棒自适应跟踪

研究了一类随机非线性系统的鲁棒自适应跟踪问题.文中利用随机控制Lyapunov设计方法,对于受方差不确定Wiener噪声干扰的参数严格反馈形式的系统,给出了参数自适应律和控制律,使得跟踪误差在4次均方意义下收敛到一个小范围内.     

一种非线性系统的模糊自适应控制

针对一类非线性系统提出一种模糊自适应控制方案，设计中用模糊逻辑系统逼近非线性函数，骨于滑模原理及Ｌｙａｐｕｎｏｖ函数方法给出了闭环系统的稳定性分析。     

An optimal adaptive H-infinity tracking control design via wavelet network

In this paper, an optimal adaptive H-infinity tracking control design method via wavelet network for a class of uncertain nonlinear systems with external disturbances is proposed to achieve H-infinity tracking performance. First, an alternate tracking error and a performance index with respect to the tracking error and the control effort are introduced in order to obtain better performance, especially, in reducing the cost of the control effort in the case of small attenuation levels. Next, H-infinity tracking performance, which attenuates the influence of both wavelet network approximation error and external disturbances on the modified tracking error, is formulated. Our results indicate that a small attenuation level does not lead to a large control signal. The proposed method insures an optimal trade-off between the amplitude of control signals and the performance of tracking errors. An example is given to illustrate the design efficiency.