FLEXIBLE SPACECRAFT VIBRATION SUPPRESSION USING PWPF MODULATED INPUT COMPONENT COMMAND AND SLIDING MODE CONTROL

This paper presents a dual‐stage control system design method for the rotational maneuver and vibration stabilization of a spacecraft with flexible appendages. In this design approach, attitude control system and vibration suppression were designed separately using lower order model. The design of attitude controller was based on sliding mode control (SMC) theory leading to a discontinuous control law. This controller accomplishes asymptotic attitude maneuvering in the closed‐loop system and is insensitive to the interaction of elastic modes and uncertainty in the system. The shaped command input controller based on component synthesis vibration suppression (CSVS) method is designed for reduction of flexible mode vibration, which only requires information about natural frequency and damping of the closed system. Additionally, to extend the CSVS method to the system with on‐off actuators, pulse‐width pulse‐frequency (PWPF) modulation is employed to control the thruster firing and integrated with the CSVS method. Simulation results have been proven the potential of this technique to control flexible spacecraft.     

具有数据包丢失的网络控制系统主动容错控制

在保证稳定性的前提下,研究具有数据包丢失的网络控制系统主动容错控制问题.基于一类包含马尔可夫丢包过程的网络控制系统模型,考虑了执行器可能失效的情况.利用Lyapunov稳定性理论和线性矩阵不等式方法,获得了系统的保性能被动容错控制器.从控制性能的角度考虑,针对不同的执行器失效模式,得到了丢包网络环境下系统的主动客错控制器的设计方法.数值示例表明,该控制器设计方法是有效的.     

基于风速估计的风力机状态反馈滑模容错控制

针对风力机变桨距执行机构突变故障,提出了基于风速估计的自适应状态反馈滑模容错控制策略.首先,设计了基于自适应状态反馈滑模理论的鲁棒主动容错控制器,并结合全阶补偿器对控制律进行设计;然后,利用基于变速灰狼优化算法的组合径向基函数神经网络实现风速估计,可以改善风速测量精度并提高控制系统可靠性;最后,根据线性矩阵不等式和Lyapunov理论对控制器稳定性进行讨论,并与现有控制策略进行比较.仿真结果表明,在健康/故障的变桨距执行机构条件下,所提容错控制方法均能获得较好的控制效果.     

Vibration control of a flexible aerial refuelling hose with input saturation

In this study, we consider a boundary control problem of a flexible aerial refuelling hose in the presence of input saturation. To provide an accurate and concise representation of the hose's behaviour, the flexible hose is modelled as a distributed parameter system described by partial differential equations (PDEs). By using the backstepping method, a boundary control scheme is proposed based on the original PDEs to regulate the hose's vibration. An auxiliary system based on a smooth hyperbolic function and a Nussbaum function is designed to handle the effect of the input saturation. Then based on Lyapunov's direct method, the state of the system is proven to converge to a small neighbourhood of zero by appropriately choosing design parameters. Finally, the results are illustrated using numerical simulations for control performance verification.     

Adaptive fault-tolerant control for a class of flexible air-breathing hypersonic vehicles

In this paper, a novel adaptive fault-tolerant control (FTC) scheme is proposed for a class of flexible air-breathing hypersonic vehicles with unknown inertial and aerodynamic parameters and even input constraints. The fault model under consideration covers the case that all actuators suffer from unknown time-varying faults. In the controller design and stability analysis, we introduce new Lyapunov functions, some differentiable auxiliary functions, a bound estimation approach, and a Nussbaum function, which help us successfully circumvent the obstacle caused by the faults, input constraints, and flexible modes. In addition to higher reliability, the proposed scheme is able to ensure that all closed-loop signals are globally uniformly bounded and to steer the tracking errors of altitude and velocity into predefined arbitrarily small residual sets. As a result, the tracking accuracy can be designated in advance. Simulation results illustrate the effectiveness of the proposed scheme.     

FAULT TOLERANT CONTROL OF FLEXIBLE SMART STRUCTURES USING ROBUST DECENTRALIZED FAST OUTPUT SAMPLING FEEDBACK TECHNIQUE

This paper presents the modeling, design and simulation of a Robust Decentralized Fast Output Sampling (RDFOS) feedback controller for the vibration control of a smart structure (flexible cantilever beam) when there is actuator failure. The beam is divided into 8 finite elements and the sensors / actuators are placed at finite element positions 2, 4, 6, and 8 as collocated pairs. The smart structure is modeled using the concepts of piezoelectric theory, Euler‐Bernoulli beam theory, Finite Element Method (FEM) techniques and the state space techniques. Four multi‐variable state‐space models of the smart structure plant are obtained when there is a failure of one of the four actuators to function. The effect of failure of one of the piezo actuators to function during the vibration of the beam is observed. The tip displacements, open and closed loop responses with and without the controller are observed. For all of these models, a common stabilizing state feedback gain F is obtained. A robust decentralized fast output sampling feedback gain L which realizes this state feedback gain is obtained using the LMI approach. In this designed control law, the control inputs to each actuator of the multi‐model representation of the smart structure is a function of the output of that corresponding sensor only and the gain matrix has got all off‐diagonal terms zero and this makes the control design a robust decentralized one. Then, the performance of the designed smart system is evaluated for Active Vibration Control (AVC). The robust decentralized FOS controller obtained by the designed method requires only constant gains and hence may be easier to implement in real time.     

基于时变内流的柔性立管自适应边界控制

针对具有系统结构参数不确定的海洋柔性立管不确定性系统,为了提高其振动控制效果和品质,通过对立管结构参数进行估计,采用自适应控制技术和Lyapunov综合法,设计了自适应边界控制算法对耦合内流动力学的立管振动进行控制.所设计的自适应控制器能补偿系统参数不确定性,以及避免了控制溢出,并能保证系统的稳定性和一致有界性.仿真结果进一步验证了该控制算法对抑制立管振动的有效性.     

具有量化输入和边界扰动的柔性臂边界振动滑模控制

本文针对量化输入和有界扰动下柔性臂系统的振动抑制和边界滑模控制器设计问题开展研究. 柔性臂的动态特性由偏微分方程表示的分布参数模型描述. 对于具有未知有界干扰的柔性臂系统, 其主要控制目标是减小干扰的影响, 使柔性臂到达期望角度并同时抑制系统的振动. 首先, 利用边界输出信号构造滑模函数和滑模面. 其次, 结合所构造的滑模面, 设计一种边界滑模控制器, 并利用算子半群理论证明了闭环系统的适定性. 所提出的边界滑模控制策略保证了系统状态能够在有限时间内到达滑模面, 并且系统状态在滑模面上是指数收敛的. 最后, 通过物理实验验证了所提出控制策略的有效性.     

线性系统相容指标约束下的容错控制新方法

针对一类具有范数有界不确定性不满足匹配条件的线性连续系统,对易于失效的执行器进行容错控制设计,重新研究了圆域极点指标、H∞指标和H2指标约束下的满意容错控制器的设计问题.基于线性系统的极点配置理论和H2/H∞控制理论,利用线性矩阵不等式( LMI)方法,在假设失效执行器的输出为任意能量有界信号的情况下,分析了这3类指标在相容情况下的取值范围,并在相容指标约束下得到了新的满意容错控制器的设计方法,给出了满意容错控制器的具体设计步骤.所设计的满意容错控制器使闭环系统的极点在一个给定的圆域内,并且保持着系统给定的H2/H∞性能要求.     

Physiological hemostasis based intelligent integrated cooperative controller for precise fault-tolerant control of redundant parallel manipulator

This paper focuses on precise fault-tolerant control for actual redundant parallel manipulator. Based on kinematic redundancy, some unnoticed influences such as mechanical clearance have been considered to design a more precise and intelligent fault-tolerant plan for actual plants. According to regulation principles in human hemostasis system, a bio-inspired intelligent integrated cooperative controller (BIICC) is developed including system structure, algorithm and step in parameter tuning. The proposed BIICC optimises partial error signal and improves control performance in each sub-channel. Moreover, the new controller transfers and disposes cooperative control signals among different sub-channels to achieve an intelligent integrated fault-tolerant system. The proposed BIICC is applied to an actual 2-DOF (degrees of freedom) redundant parallel manipulator where the feasibility of the new controller is demonstrated. The BIICC is beneficial to control precision and fault-tolerant capability of redundant plant. The improvements are more obvious in cases where extra actuators of redundant manipulator are broken.     

Vibration damping of a flexible car body structure using piezo-stack actuators

Active vibration damping of a railway car body is accomplished by actuator forces acting directly on the flexible car body structure. In this work piezo-stack actuators mounted in consoles are utilized to introduce bending moments into the flexible structure, thus achieving a significant increase in ride comfort. For a heavy metro vehicle the complete design of the active vibration damping system is presented. Analytic modeling, system identification, and robust controller design are presented. The excellent performance of the proposed method is documented by both extensive experimental results and co-simulation studies.     

Direct tip regulation of a single-link flexible manipulator by adaptive variable structure control

Direct tip position regulation of flexible manipulators is one of the most challenging control tasks. There are mainly three problems to be addressed in order to achieve good performance. The first two control problems arise owing to the unstable zeros and complex poles in the system nominal part which is dominated by a transfer function. The third problem is the existence of unstructured uncertainties owing to the truncation of high-order resonance modes and system nonlinearities. Because of the above difficulties and in particular the non-minimum-phase nature, tip regulation task of flexible manipulators is usually solved indirectly: direct control of joint angle and suppression of the flexible link vibration. The aim of this study is to investigate the direct approach for tip regulation. Since the tip transfer function contains unstable zeros and the first few dominant flexible modes (complex poles), a reference model of the same order is selected which does not have any finite zero but all negative real poles. In order to force the system to follow the reference model in the presence of the unstructured uncertainties, a variable structure controller is adopted in which the switching surface is derived from the reference model. When in sliding mode, the system performs as the reference model. Hence there will be no vibration and the tip position regulation can be achieved when the system approaches steady state. To improve the system responses further, an adaptation law with dead-zone scheme is combined with the variable structure controller. Simulation results show that link vibrations have been eliminated and the control profile is fairly smooth.     

Boundary control for a vibrating string with asymmetrically constrained outputs

In this paper, vibration control and output constraint are addressed for a flexible string system. A boundary controller is designed to suppress vibrations and asymmetrically constrain endpoint displacement by adopting tangent functions into a barrier Lyapunov function. With the proposed boundary control law, the closed‐loop system is stabilized asymptotically and even uniform boundedness is achieved. Simulation results aim to prove the effectiveness of the designed boundary control scheme.     

Adaptive actuator fault compensation control for a rigid-flexible manipulator with ODEs-PDEs model

In this paper, the actuator fault problem is studied for a two-link rigid-flexible manipulator system in the presence of boundary disturbance and state constraint. The system consists of a rigid beam, a flexible beam and a payload at the end, which are described by hybrid ordinary differential equations–partial differential equations. The novel controller includes a proportional-derivative feedback structure, a disturbance observer and a fault-tolerant algorithm, which can regulate the joint positions and eliminate vibration of flexible beam, on circumstance of boundary disturbance and actuator fault. With the help of Barrier Lyapunov Function, the states will not be violated. It is proved that the closed-loop system has asymptotic stability by LaSalle Invariance Principle. Simulations are provided to demonstrate the effectiveness of the proposed controller.     

Quantized H ∞ fault-tolerant control for networked control systems

Quantized H_∞ fault-tolerant control for networked control systems (NCSs) with partial actuator fault with respect to actuators is concerned in this paper. Considering transmission delay, packet dropout and quantization, a synthesis model with partial actuator fault is established. The piecewise constant controller is adopted to model NCS with the transmission delay and packet dropout. Due to data transmitted in practical NCSs should be quantized before they are sent to the next network node, the logarithmic static and time-invariant quantizers at the sensor and controller sides are proposed in the paper. For the established model, an appropriate type of Lyapunov functions is provided to investigate the delay-dependent H_∞ control problem. According to an optimal problem, the controller that makes the system achieve the best performance is designed. Finally, an illustrative example is given to demonstrate the effectiveness of the proposed approach.     

Adaptive fault-tolerant vibration control of a wind turbine blade with actuator stuck

ABSTRACT

This paper proposes an adaptive fault-tolerant boundary vibration control method designed to resolve unknown failure and stuck actuator problems in the wind turbine blade control process. The blade is modelled as a distributed parameter system described by two coupled partial differential equations. The proposed boundary control achieved the fact that the vibration of the blade can still be suppressed even when the actuator fails, and the bending and torsional deformation is eventually reduced to zero. Based on the Lyapunov direct method, a fact has been confirmed that the stability of the system is guaranteed under the boundary controller. The effectiveness of the controllers is demonstrated by numerical simulations.     

基于内流动力学的海洋输油柔性立管鲁棒边界控制

海洋输油柔性立管的振动是引起立管疲劳破坏的主要原因,对其研究边界控制是消除振动疲劳、减少断裂的有效方法.本文引入内流动力学,完善了立管原始无穷维分布参数模型,更好地表达了柔性立管的动力学响应.为抑制柔性立管在内外流激励下的振动奠下基础,本文用Lyapunov直接法对柔性立管系统的稳定性和状态一致有界性进行了证明,设计了边界控制器调节柔性立管的振动,其中控制器使用了符号函数来消除不确定性环境扰动对振动控制效果的影响,提高了系统的鲁棒性.仿真实验表明本文所设计的控制算法有效地减少了柔性立管的振动偏移量.     

Fault-tolerant control systems design via subdivision of parameter region

This paper presents a linear matrix inequality （LMI） approach to solve the fault-tolerant control （FTC） problem of actuator faults. The range of actuator faults is considered as a parameter region and subdivided into several subregions to achieve a certain desired performance specification. Based on the integral quadratic constraint （IQC） approach, a passive fault-tolerant controller for the whole fault region and multiple fault-tolerant controllers for each fault subregion are designed for guaranteeing stability and improving performance of the FTC system, respectively. According to the estimation of parameters by FDI process, the corresponding subregion controller is chosen for the stability and optimal performance of closed-loop systems when the fault occurs. The case of incorrect estimation is also considered by comparing the performance index between the switched controller and the passive fault-tolerant controller. The proposed design technique is finally evaluated in the light of a simulation example.     

一类分布参数系统的有限维变结构控制

本文研究了一类非线性分布参数系统的有限维变结构控制问题，首先采用Ｇａｌｅｒｋｉｎ近拟法给出了系统的有限维近似模型；进而给出了使近似系统具有良好动态品质的有限维变结构控制器的设计方法；最后分析了闭环系统的渐近性态，给出了近似阶次一定的情况下，原系统具有良好渐近性态的充分条件。