High-performance decentralized control design for general interconnected systems with applications in cooperative control

This paper deals with the decentralized control of an interconnected system, where each subsystem has models of all other subsystems (subject to uncertainty). A decentralized controller is constructed based on a reference centralized controller. It is shown that when a priori knowledge of each subsystem about the other subsystems’ models is exact, then the decentralized closed-loop system can perform exactly the same as its centralized counterpart. An easy-to-check necessary and sufficient condition for the internal stability of the decentralized closed-loop system is obtained. Moreover, the stability of the closed-loop system in the presence of the perturbation in the parameters of the system is investigated, and it is shown that the decentralized control system is probably more robust than its centralized counterpart. A proper cost function is then defined to evaluate the closeness of the decentralized closed-loop system to the corresponding centralized control system. This enables the designer to obtain the maximum allowable standard deviation for the modelling errors of the subsystems to achieve a satisfactorily small relative performance deviation with a sufficiently high probability. Finally, the proposed method is exploited to design a near-optimal decentralized control law with respect to a quadratic cost function, whose performance can, under certain conditions, be equal to the minimum achievable performance index corresponding to the centralized LQR control law. The effectiveness of the proposed method is demonstrated in three numerical examples.     

Gain-scheduled PID controller design

Gain scheduling (GS) is one of the most popular approaches to nonlinear control design and it is known that GS controllers have a better performance than robust ones. Following the terminology of control engineering, linear parameter-varying (LPV) systems are time-varying plants whose state space matrices are fixed functions of some vector of varying parameters. Our approach is based on considering that the LPV system, scheduling parameters and their derivatives with respect to time lie in a priori given hyper rectangles. To guarantee the performance we use the notion of guaranteed costs. The class of control structure includes centralized, decentralized fixed order output feedbacks like PID controller. Numerical examples illustrate the effectiveness of the proposed approach.     

基于ARM的智能车位锁远程控制系统设计

针对目前普遍存在停车难的问题,运用物联网技术和无线通信技术,构建由服务器、移动终端和控制器组成三级网络结构的智能车位远程管理系统.实现服务器、移动终端、控制器和车位锁之间的互联,并通过GSM与互联网连接,用户可通过移动终端进行预定车位、出租车位等操作.实现对城市停车场车位集中管理,分散控制,车位资源的共享,是物联网技术在创建新型智慧城市方面的应用场景之一.     

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.     

Modelling and decentralized control of a multizone crystal growth furnace

The controller of a crystal growth furnace with 15 heating zones must have a decentralized structure. It is shown that each control station must necessarily satisfy a certain robustness property and that the design of the whole decentralized controller can be replaced by the problem of designing the control stations separately from each other as robust centralized controllers. As a basis for this, it is shown that the model can be considerably reduced. Although the zones are strongly coupled it will be seen here that, owing to structural properties of the plant, the furnace can be described by a model which has regard to only three zones. Experimental results with furnace illustrate the modelling and design methods used.     

The decentralized control of large flexible space structures

The decentralized robust servomechanism problem with constant disturbances/set points is considered in this paper for large flexible space structures (LFSS). It is shown that for LFSS which have colocated, mutually dual sensors and actuators, the decentralized fixed modes [1] of the system are precisely equal to the centralized fixed modes [2] of the system. Simple necessary and sufficient conditions are then obtained for a solution to exist for the robust decentralized servomechanism problem [3] for the system. A controller is demonstrated which, for this class of LFSS systems, eliminates the "spillover problem." A two-hundreth-order numerical example of an LFSS control problem using the Purdue model [4] is included to illustrate the results.     

Fault-tolerant decentralized H-infinity control for multi-channel systems using homotopy method

This paper considers a fault-tolerant decentralized H-infinity control problem for multi-channel linear time-invariant systems. The purpose is to design a decentralized H-infinity output feedback controller to.stabilize the given system and achieve a certain H-infinity performance requirement both in the normal situation and in the situation where any one of the local controllers fails. The designed problem is reduced to a feasibility problem of a set of bilinear matrix inequalities （BMIs）. An algorithm is proposed to solve the BMIs. First, the normal situation is considered where all the local controllers are functioning. The local controllers are obtained from a standard centralized H-infinity controller by using a homotopy method imposing a structural constraint progressively. Secondly, the above case is extended to the one where any one of the local controllers fails. We again use a homotopy method where the coefficient matrices of the failed controller are decreased progressively to zero. The efficiency of the proposed algorithm is demonstrated by an example.     

A new approach to control design with overlapping information structure constraints

In this paper, a new strategy is proposed for decentralized state feedback design with overlapping information structure constraints. The method combines linear matrix inequalities and the inclusion principle in a way that eliminates controllability problems that are inherent to standard decentralized control design in the expanded space. This approach can be extended to include an important class of uncertain nonlinearities, and its validity is demonstrated through applications to strings of moving vehicles.     

Fault-tolerant decentralized H-infinity control for multi-channel systems using homotopy method

This paper considers a fault-tolerant decentralized H-infinity control problem for multi-channel linear time-invariant systems. The purpose is to design a decentralized H-infinity output feedback controller to stabilize the given system and achieve a certain H-infinity performance requirement both in the normal situation and in the situation where any one of the local controllers fails. The designed problem is reduced to a feasibility problem of a set of bilinear matrix inequalities (BMIs). An algorithm is proposed to solve the BMIs. First, the normal situation is considered where all the local controllers are functioning. The local controllers are obtained from a standard centralized H-infinity controller by using a homotopy method imposing a structural constraint progressively. Secondly, the above case is extended to the one where any one of the local controllers fails. We again use a homotopy method where the coefficient matrices of the failed controller are decreased rogressively to zero. The efficiency of the proposed algorithm is demonstrated by an example.     

滞后关联分布参数系统的分散变结构控制

针对滞后分布参数关联大系统的变结构控制进行了讨论,采用M-矩阵理论,Lp-估 计及Liapunov方法,给出了完全分散的滑动流形和变结构控制器的设计方案.此外,还给出 了系统轨线达到滑动流形的时间估计.     

Independent design of robust partially decentralized controllers

An independent design method for robust partially decentralized controllers is developed. In the proposed design method, the partially decentralized control system is first expanded to the nonsquare decentralized structure. Using the Internal Model Control parametrization, the independent design procedure for robust nonsquare decentralized controllers can then be applied directly to the expanded system. Two examples, including a nonlinear stirred mixing tank, are used to illustrate the developed design method and a comparison to a decentralized controller is made.     

一种基于操作空间的操作器分散自适应控制方法

本文提出了一种操作器分散自适应阻力控制方法．这种方法不要求知道操作器动态模型的结构和参数，采用分散控制的形式，可以对各自由度单独进行控制，因此计算简单有效，具有一定的容错能力，控制系统有较好的暂态性能，由于控制律以操作空间坐标形式描述，适合于具有冗余自由度的操作器的控制．计算机仿真表明了该方法的良好的控制效果     

Structural modification of systems using discretization and generalized sampled-data hold functions

This paper investigates the decentralized control of LTI continuous-time plants using generalized sampled-data hold functions (GSHF). GSHFs can be used to modify the structure of the digraph of the resultant discrete plant, by removing certain interconnections in the discrete-time equivalent model to form a hierarchical system model of the plant. This is a new application of discretization and has, as its motivation, the design of decentralized controllers using centralized methods.     

Overlapping control design for multi-channel systems

This paper deals with the decentralized overlapping control of interconnected systems. The notion of a quotient overlapping fixed mode (QOFM) is first introduced and it is shown that a mode of an interconnected linear time-invariant system can be shifted by means of a general decentralized overlapping controller if and only if it is not a QOFM. It is then asserted that any interconnected system with no unstable QOFM can be stabilized by using an appropriate finite-dimensional linear time-varying controller. It is also shown how the existing results aiming at designing a decentralized controller of a certain type such as generalized sampled-data hold function, finite-dimensional linear time-varying, and sampled-data can be utilized to design a decentralized overlapping controller of a desired form, in order to achieve any design specification. The efficacy of the results is elucidated through two numerical examples.     

大柔性飞机降落抗震动方法研究与仿真

研究大柔性飞机降落中震动的优化控制问题。大柔性飞机在起落过程中,柔性结构决定了缓冲支撑点结构刚度低、内阻小、间距较大,降落时会产生较大震动,引起建立的飞机抗震模型阶数较高。传统的飞机震动控制方法都是以建立的抗震动力学模型为基础的,一旦模型阶数较高,将产生飞机缓冲系数过小,从而降低抗震模型的精度。提出一种独立模态抗震法直接针对大柔性飞机的高阶动力模型设计,采用柔性压电结构振动模态控制技术,准确地设计大柔性飞机抗震控制器的控制律,可以防止控制溢出被有效抑制,减小飞机降落的振幅幅度。仿真结果表明:改进方法对大柔性飞机的振动模态进行独立控制,起落过程振动抑制效果非常显著,降低了震动强度。     

LMI solutions for H-two and H-infinity decentralized controllers applied to an aerothermic process

In this paper, we present a linear matrix inequality (LMI)-based solution to implement H-two and Hinfinity decentralized robust control strategies. Appropriate parametrization of optimal H-two and H-infinity controllers is used. The general formulation of the decentralized control design leads to the optimal determination of both the state feedback gains and the observer gains of the decentralized controllers. This formulation is two folds: first, a centralized controller is obtained, and then, a simplified decentralized solution is derived by optimizing only the observer gains. The mathematical determination of these gains is formulated as an LMI optimization problem that can be easily solved using LMI solvers. As an experimental evaluation of these controllers, a real time application to an aerothermic process is carried out. A continuous-time model of the process obtained with a suitable direct continuous-time identification approach is elaborated. Results illustrating the real performance obtained from the H-two and H-infinity decentralized controllers are discussed and compared with the centralized ones.     

A precise robust fuzzy control of robots using voltage control strategy

Fuzzy control of robot manipulators with a decentralized structure is facing a serious challenge. The state-space model of a robotic system including the robot manipulator and motors is in non-companion form, multivariable, highly nonlinear, and heavily coupled with a variable input gain matrix. Considering the problem, causes and solutions, we use voltage control strategy and convergence analysis to design a novel precise robust fuzzy control (PRFC) approach for electrically driven robot manipulators. The proposed fuzzy controller is Mamdani type and has a decentralized structure with guaranteed stability. In order to obtain a precise response, we regulate a fuzzy rule which governs the origin of the tracking space. The proposed design is verified by stability analysis. Simulations illustrate the superiority of the PRFC over a proprotional derivative like (PD-like) fuzzy controller applied on a selective compliant assembly robot arm (SCARA) driven by permanent magnet DC motors.     

基于H∞//μ鲁棒控制原来和使用ATMD的高楼主动振动控制策略研究

对使用主动脉调频质量块ＡＴＭＤ（ＡｃｉｔｖｅＴｕｎｅｄＭａｓｓＤａｍｐｅｒ）的具有ｎ阶自由度的柔性大楼结构建立了全阶模型,并由此将得到的结构降价模型用于设计ＡＴＭＤ的控制器,通过分析,大楼结构的位置和速度可被列为控制器的输出反馈变量,将等效两端口模型应用于带ＡＴＭＤ的大楼结构上,使用Ｈ∞／μ频域定型综合理论,设计出ＡＴＭＤ的鲁棒控制器,通过模拟分析,可见该控制算法是非常有效的,ＡＴＭＤ中的小质量决     

大型柔性空间结构的极小化主动控制

大型柔性空间结构的运动会引起混沌现象的发生,混沌控制方法的选择对航天飞行器的设计起了很在的作用,本注记利用ＳｍｉｔｈＭＪ等人提出的方法,对大型柔性空间结构进行极小化主动控制,以避免混沌现象的发生。     

Centralized/decentralized indirect robust adaptive control for spacecraft attitude and robotics

The diffuse presence of robotic subsystems in new space mission concepts introduces variations and uncertainties in system mass and inertia, imposing stringent constraints to orbital and attitude control. The required performance can be achieved through several paradigms like robust or adaptive controllers and sometimes a combination of the two. In this work, a novel indirect controller, belonging to the robust-adaptive controllers class, is developed, with the core idea of requiring just one adaptive gain with consequent lower sensitivity and easier tunability. The algorithm is developed both in centralized and decentralized formulation and tested for reliability and parameter sensitivity.