一类非线性时滞系统的保性能控制器设计

针对一类具有非线性控制输入的参数不确定时滞系统和给定的保性能指标,研究了此类系统的保性能控制问题.利用Lyapunov稳定性定理和线性矩阵不等式工具,得到了非线性不确定时滞系统的保性能控制存在的充分条件.与现有结果相比,考虑的保性能控制器是非线性的,并且保性能控制器可由线性矩阵不等式的解给出.得到的保性能控制器不仅保证...     

约束条件下不确定系统的保性能控制

针对一类范数有界不确定连续时间系统，研究在控制输入存在位置约束条件下的状态反馈保性能控制问题。给出约束条件下保性能控制律存在的充分条件，并等价为线性矩阵不等式的求解问题。给出控制器的参数化表示。通过数值仿真验证所得结论的正确性。     

不确定时滞系统的非线性保性能控制

针对一类非线性系统和给定的性能指标,研究其保性能控制问题。基于Lyapunov稳定性理论,采用线性矩阵不等式工具,给出非线性状态反馈保性能控制器存在的一个充分条件,并依据其可行解给出相应保性能控制律的设计方法。建立一个具有线性矩阵不等式约束的凸优化问题,得到非线性系统的最优保性能控制律。仿真示例表明该方法的可行性。     

不确定广义系统的弹性H∞保性能控制

利用线性矩阵不等式(LMI)方法,研究被控对象与控制器同时存在摄动的H∞保性能控制问题.针对控制器存在加法式摄动情形,以线性矩阵不等式约束条件给出了广义系统弹性H∞保性能的充分条件,并以线性矩阵不等式的可行解给出了相应的控制器设计方法.通过求解具有线性矩阵不等式约束的凸优化问题,给出了弹性H∞最优保性能及最优H∞性能控制器的设计方法.仿真表明了方法的可行性.     

不确定系统的网络化保性能控制

本文针对控制网络中存在着随机传输时延和数据包丢失的现象,考虑了网络化控制系统的状态反馈保性能控制器设计问题.首先采用时滞相关方法并引入自由权矩阵,给出了基于矩阵不等式的网络化二次型保性能控制器存在的充分条件,然后基于该充分条件获得了基于线性矩阵不等式的控制器设计方法,相应的网络化保性能控制律可以通过求解线性矩阵不等式来构造,并采用锥互补线性化算法给出了网络化次优保性能控制器的设计方法.最后数值示例演示了所得控制器设计结果的应用方法和有效性,并通过仿真比较了传统保性能控制器和网络化保性能控制器在网络化控制系统中的控制性能.     

不确定广义系统的弹性H∞保性能控制

利用线性矩阵不等式（LMI）方法，研究被控对象与控制器同时存在摄动的H∞保性能控制问题。针对控制器存在加法式摄动情形，以线性矩阵不等式约束条件给出了广义系统弹性H∞保性能的充分条件，并以线性矩阵不等式的可行解给出了相应的控制器设计方法。通过求解具有线性矩阵不等式约束的凸优化问题，给出了弹性H∞最优保性能及最优H∞性能控制器的设计方法。仿真表明了方法的可行性。     

具有非线性扰动的广义系统的鲁棒H∞控制

研究具有非线性结构扰动广义系统的鲁棒H∞控制和鲁棒H∞保性能控制问题,该不确定性为时间和状态的函数.且满足Lipschitz条件.目的是分别设计系统的鲁棒H∞控制器和鲁棒H∞保性能控制器.应用线性矩阵不等式方法,分别给出了系统的鲁棒H∞控制器和鲁棒H∞保性能控制器存在的充分条件.当这些条件可解时,分别给出了鲁棒H∞控制器和鲁棒H∞保性能控制器的表达式.最后通过一个仿真算例说明了所给出方法的应用.     

时变时滞复杂动态网络的非脆弱性同步保性能控制

针对一类时变时滞复杂网络系统,提出了一种非脆弱性同步保性能控制方法。在假设非线性向量函数f(x)可微条件下,通过Jacobi矩阵方法进行线性化处理,余项满足匹配条件,设计具有增益摄动的非脆弱性状态反馈控制器,以确保当控制器的参数发生小的摄动时,仍能保证控制器的有效性。通过构造合适的Lyapunov-Krasovskii泛函,采用积分等式、矩阵分析、Schur补定理等方法,在给定的保性能指标的条件下,得到了该系统非脆弱性同步保性能控制存在的充分条件;并证明了该条件等价于一组线性矩阵不等式(LMI)的可行性问题, 给出了LMI约束条件下的凸优解构造方法,求出了闭环时变时滞系统保性能值的最小值。最后,通过数值算例对比验证了设计方法的可行性。     

具有非线性扰动的离散奇异时滞系统的保性能控制

为了设计系统的保性能控制器，使得闭环系统是正则、具有因果关系且稳定和性能指标有一上界，研究了扰动是满足Lipschitz条件的一类非线性离散奇异时滞系统的保性能控制问题．应用线性矩阵不等式方法，给出了系统的保性能控制器存在的充分条件，并在这些条件可解时．给出了保性能控制器的表达式．最后通过仿真实例表明了所给方法的有效性。     

一类时滞广义非线性系统H_∞可靠跟踪控制

讨论一类Lipschitz时滞非线性广义系统的H∞可靠跟踪控制问题.分别给出了执行器失效和传感器失效两种模型下可靠控制器存在的充分条件,使得闭环系统正则无脉冲并且指数稳定,同时系统输出跟踪预先给定的可测参考模型的输出,且满足H∞性能指标,并利用线性矩阵不等式技巧给出了可靠控制器的设计方法.最后给出了一个数值例子,说明了本文所给出方法的有效性.     

Input-output linearizing control of constrained nonlinear processes

An input-output linearization strategy for constrained nonlinear processes is proposed. The system may have constraints on both the manipulated input and the controlled output. The nonlinear control system is comprised of: (i) an input-output linearizing controller that compensates for processes nonlinearities; (ii) a constraint mapping algorithm that transforms the original input constraints into constraints on the manipulated input of the feedback linearized system; (iii) a linear model predictive controller that regulates the resulting constrained linear system; and (iv) a disturbance model that ensures offset-free setpoint tracking. As a result of these features, the approach combines the computational simplicity of input output linearization and the constraint handling capability of model predictive control. Simulation results for a continuous stirred tank reactor demonstrate the superior performance of the proposed strategy as compared to conventional input-output linearizing control and model predictive control techniques.     

Virtual control strategy and conditioning technique for tracking and learning controls under input restrictions

The virtual control strategy for mechanical systems has been recently proposed (Gnucci and Marino, 2021) in the context of under-actuated mechanical systems. Such a strategy views and represents an under-actuated mechanical system as a fully actuated system with virtually added inputs and outputs having to satisfy, through a suitable choice of the virtual output reference signals, the virtual input zero-equality constraint: the related adaptive tracking control problem is then solved through standard design techniques. This paper exhibits a twofold aim. The first one is: to enlarge the concept of zero-input constraint and thus naturally adapt the virtual control approach to the case in which an actuator fault can occur. The second aim is: to show how the application and transposition of such an adaptation to two well-known classes of nonlinear systems (special systems in multi-variable tracking form with two inputs and outputs under actuator faults; one-relative-degree, single-input, single-output systems in output feedback form under input saturation) not only own strong connections with the conditioning technique, originally conceived in the context of anti-windup problems under input constraints, but they also gain original results.     

Robust Control System Design for an Uncertain Nonlinear System Using Minimax LQG Design Method

A systematic approach to design a nonlinear controller using minimax linear quadratic Gaussian regulator (LQG) control is proposed for a class of multi‐input multi‐output nonlinear uncertain systems. In this approach, a robust feedback linearization method and a notion of uncertain diffeomorphism are used to obtain an uncertain linearized model for the corresponding uncertain nonlinear system. A robust minimax LQG controller is then proposed for reference command tracking and stabilization of the nonlinear system in the presence of uncertain parameters. The uncertainties are assumed to satisfy a certain integral quadratic constraint condition. In this method, conventional feedback linearization is used to cancel nominal nonlinear terms and the uncertain nonlinear terms are linearized in a robust way. To demonstrate the effectiveness of the proposed approach, a minimax LQG‐based robust controller is designed for a nonlinear uncertain model of an air‐breathing hypersonic flight vehicle (AHFV) with flexibility and input coupling. Here, the problem of constructing a guaranteed cost controller which minimizes a guaranteed cost bound has been considered and the tracking of velocity and altitude is achieved under inertial and aerodynamic uncertainties.     

一类不稳定时滞过程的最优控制

本文对控制能量存在约束条件下一类不稳定时滞过程的最优控制问题进行了探讨. 首先基于不稳定过程的互质分解, 由敏感度函数和控制敏感度函数定义了一个包含跟踪误差和控制能量在内的性能指标, 然后应用谱分解最小化该性能指标, 从而为一类不稳定时滞过程导出了一种最优的控制器设计方法, 可使系统在控制能量存在约束时获得最优的控制性能. 仿真研究进一步说明了该方法的有效性.     

网络控制系统的鲁棒L1跟踪控制

将L1性能约束引入网络控制系统中,研究具有时延和不确定性的网络控制系统的模型参考输出跟踪问题。基于线性矩阵不等式方法推出了该网络控制系统的稳定性和控制器设计的充分条件,并将控制器的设计转化为一个凸优化的求解问题。所设计的控制器能够保证相对于所有峰值有界的外界扰动信号,网络控制系统具有L1性能约束水平。仿真实例证实了该设计方法的有效性。     

Multi-objective optimal trajectory design and tracking with non-periodic tracking-transition switching for non-minimum phase linear systems

In this paper, the problem of trajectory design and tracking of non-periodic tracking-transition switching for non-minimum phase linear systems is considered. Such a problem exists in various applications, where the output trajectory consists of application-dependent tracking sessions and to-be-designed transition sessions. The challenge arises when multiple control objectives are considered, including the smooth transition from one output tracking session to the next one without large oscillations during the transition, smooth tracking-transition switching without inducing pre- and/or post-switching oscillations, input-energy minimisation without saturation under amplitude constraint, and furthermore, minimisation of the overall transition time. The proposed approach extends the previous work that attained smooth output transition and smooth tracking-transition switching to further achieve amplitude-constrained input-energy minimisation and transition time minimisation. First, the constrained input optimisation problem is converted to an unconstrained input minimisation problem. Then, the optimal output and input are obtained by using an improved conjugate gradient method. Finally, the total transition time is further minimised via one-dimensional search. The proposed approach is illustrated through a simulation example in probe-based nanomanipulation utilising a piezoelectric actuator.     

Adaptive finite‐time fault‐tolerant tracking control for a class of MIMO nonlinear systems with output constraints

In this work, we present a novel adaptive finite‐time fault‐tolerant control algorithm for a class of multi‐input multi‐output nonlinear systems with constraint requirement on the system output tracking error. Both parametric and nonparametric system uncertainties can be effectively dealt with by the proposed control scheme. The gain functions of the nonlinear systems under discussion, especially the control input gain function, can be not fully known and state‐dependent. Backstepping design with a tan‐type barrier Lyapunov function and a new structure of stabilizing function is presented. We show that under the proposed control scheme, finite‐time convergence of the output tracking error into a small set around zero is guaranteed, while the constraint requirement on the system output tracking error will not be violated during operation. An illustrative example on a robot manipulator model is presented in the end to further demonstrate the effectiveness of the proposed control scheme. Copyright © 2016 John Wiley & Sons, Ltd.     

On real-time robust model predictive control

High-speed applications impose a hard real-time constraint on the solution of a model predictive control (MPC) problem, which generally prevents the computation of the optimal control input. As a result, in most MPC implementations guarantees on feasibility and stability are sacrificed in order to achieve a real-time setting. In this paper we develop a real-time MPC approach for linear systems that provides these guarantees for arbitrary time constraints, allowing one to trade off computation time vs. performance. Stability is guaranteed by means of a constraint, enforcing that the resulting suboptimal MPC cost is a Lyapunov function. The key is then to guarantee feasibility in real-time, which is achieved by the proposed algorithm through a warm-starting technique in combination with robust MPC design. We address both regulation and tracking of piecewise constant references. As a main contribution of this paper, a new warm-start procedure together with a Lyapunov function for real-time tracking is presented. In addition to providing strong theoretical guarantees, the proposed method can be implemented at high sampling rates. Simulation examples demonstrate the effectiveness of the real-time scheme and show that computation times in the millisecond range can be achieved.     

带不确定时滞的中立型系统之鲁棒非脆弱保性能控制

针对一类动态不确定时滞中立型系统,研究了非脆弱鲁棒保性能控制器设计问题.考虑的中立型系统和状态反馈控制器均具有不确定性.在适当的假设下利用Lyapunov稳定性方法,以线性矩阵不等式的形式,给出了使该动态时滞不确定中立型系统二次稳定及非脆弱鲁棒保性能状态反馈控制器存在的充分条件.通过求解相应的线性矩阵不等式就可得到系统的非脆弱鲁棒保性能控制器,同时也能保证二次性能函数不超过一个确定的界.最后,用数值仿真验证了所给方法的可行性.     

Practical time-varying formation tracking for high-order nonlinear multi-agent systems based on the distributed extended state observer

Practical time-varying formation tracking analysis and design problems for high-order nonlinear multi-agent systems are investigated, where the time-varying formation tracking error is controlled within an arbitrarily small bound. The states of followers form a predefined time-varying formation while tracking the state of the leader with unknown control input. Besides, the dynamics of each agent has heterogeneous nonlinearity and disturbance. First, a distributed extended state observer is constructed to estimate the follower's nonlinearity and disturbance, and the leader's unknown control input simultaneously. A protocol based on the distributed extended state observer is proposed. Second, sufficient conditions for the multi-agent systems to achieve the practical time-varying formation tracking under the protocol are presented by using the Lyapunov stability theory. Third, an approach is derived to design the proposed protocol by solving a linear matrix inequality. Finally, numerical simulation results are given to illustrate the effectiveness of the theoretical results.