最优滑模飞行控制系统的设计与仿真

针对机动飞机按时标分离原则可分为快慢两个子系统而形成两环控制结构的特点，提出了最优滑模飞控系统的设计。外环控制器的设计采用基于依赖状态的Riccati方程最优控制器，用以产生最优滑模面，以保证整个飞控系统具有一定的性能鲁棒。内环控制器设计时采用滑动模控制以减小飞控系统对参数变化、模型误差、外部干扰敏感，具有一定的稳定鲁棒性。最后对机动飞机作大机动仿真，仿真结果表明该飞控系统是有效的。     

Adaptive filtering with bandwidth constraints in the feedback path

This paper introduces a new, adaptive-filter-based controller that shows advantageous properties from the viewpoint of its communication requirement. The algorithm is called signed-error filtered-x LMS (SE-FxLMS). Its novelty is characterized by the fact that it makes possible data compression in the feedback path of adaptive-filter-based control loops in a very simple way. This feature is especially useful in such closed-loop systems where the feedback signals are transmitted over a low-bandwidth communication channel. This is a typical case in so-called networked control systems (NCS), where the communication is carried out over a shared communication channel, e.g., using a wireless sensor network. The paper introduces an analysis of the algorithm as well.     

信道噪声对无线远程迭代学习控制系统的影响

无线远程控制系统的主要特征是信号通过无线网络在传感器与控制器,控制器与执行器之间传输,但信号无线传输过程中受到的信道噪声干扰会严重影响系统的控制性能。针对一类控制器采用迭代学习控制方式的无线远程控制系统,首先得到系统输出误差和信道噪声在迭代域内的关系表达式,然后在此基础上就信道噪声对输出误差信号 范数平方期望收敛性能的影响进行分析。由分析可知,该期望是关于信道噪声方差和系统参数的函数,并将随迭代次数的增加收敛于一个有限的误差值。在系统参数一定的情况下,该误差值将随信道噪声方差的增大而增大,即信道噪声方差越大,其对系统跟踪性能的影响越明显。最后,通过仿真实验证明了分析结果的正确性。      

Design and calibration of 3D printed soft deformation sensors for soft actuator control

Soft actuators made from compliant materials are superior to conventional rigid robots in terms of flexibility, adaptability and safety. However, an inherent drawback of soft actuator is the low actuation precision. Implementing closed loop control is a possible solution, but the soft actuator shape can hardly be measured directly by commercially available sensors, which either are too stiff for integration or cause performance degradation of the actuator. Although 3D printing has been applied to print bendable sensors from conductive materials, they either have larger stiffness than the soft actuator or are made from specially designed materials that are difficult to reproduce. In this study, easily accessible commercial soft conductive material is applied to directly 3D print soft sensors on soft actuators. Different configurations of the printed sensors are studied to investigate how the sensor design affects the performance. The best sensor configuration is selected to provide shape feedback using its changing resistance during deformation. Compared with a commercial flexible bending sensor, the printed sensor has less influences on the soft actuator performance and enjoys higher shape estimation accuracy. Closed loop shape control of the actuator using feedback from the 3D printed sensor is then designed, implemented and compared with the control results using image feedback. A gripper consisting of three individually controlled soft actuators demonstrates the applications of the soft sensor.     

拒绝服务攻击下的弹性事件触发负荷频率控制

针对互联电力系统负荷频率控制通信网络带宽受限及易遭受恶意网络攻击的问题,文中研究了拒绝服务攻击下弹性事件触发机制和负荷频率控制器的联合设计问题。在拒绝服务攻击参数已知的情况下,提出了一种既能缓解通信带宽压力,又可同时消除拒绝服务攻击影响的弹性事件触发机制。文中构建了一种基于弹性事件触发机制及拒绝服务攻击的负荷频率控制时滞切换系统模型。应用分段李亚普洛夫函数对切换系统稳定性进行了分析,并进行了触发参数和控制器的联合设计。最后,通过一个两区域互联电力系统仿真验证了所提方法的有效性。     

不同驱动方式下网络控制系统的建模与分析

控制回路通过实时网络闭环而成的反馈控制系统称为网络控制系统.文中介绍了时间驱动和事件驱动的异同,建立了节点在不同驱动方式下网络控制系统的数学模型.由分析可知在设计网络控制系统时要对传感器、控制器、执行器选择合适的触发方式.     

Investigation of Sliding-Surface Design on the Performance of Sliding Mode Controller in Antilock Braking Systems

Sliding mode control (SMC) has widely been employed in the development of a wheel-slip controller because of its effectiveness in applications for nonlinear systems as well as its performance robustness on parametric and modeling uncertainties. The design of a sliding surface strongly influences the overall behavior of the SMC system due to the discontinuous switching of control force in the vicinity of a sliding surface that produces chattering. This paper investigates the effects of sliding-surface design on the performance of an SMC-based antilock braking system (ABS), including a brake-torque limitation, an actuator time delay, and a tire-force buildup. Different sliding-surface designs commonly used in ABS were compared, and an alternative sliding-surface design that improves convergence speed and oscillation damping around the target slip has been proposed. An 8-degree-of-freedom (dof) nonlinear vehicle model was developed for this paper, and the effects of brake-system parameter variations, such as a brake actuator time constant, target slip ratios, an abrupt road friction change, and road friction noises, were also assessed.     

减重支持系统的实现

介绍了康复机器人减重支持系统的构成。利用直线执行器作为支持系统的主要部件,采用H桥驱动直线执行器。利用双闭环反馈控制作为该系统的控制器,其中电流控制器作为内环控制器,速度反馈控制器作为外环控制器,并均采用PID控制器来实现,PID参数采用遗传算法进行整定。同时,利用延迟采样的策略保证了电流控制器参数的正确性。从实际效果上看,双闭环反馈控制基本使减重支持系统达到了恒力输出的要求。     

Compensation voltage control in dynamic voltage restorers by use of feed forward and state feedback scheme

This paper discusses the control of the compensation voltages in dynamic voltage restorers (DVR). It first analyzes the power circuit of a DVR system in order to come up with appropriate control limitations and control targets for the compensation voltage control. Based on this power stage analysis, a combined feed forward and state feedback control structure for the compensation voltages of DVRs is developed. This paper also discusses the time delay problems inherent in the digital control system of a DVR. Digital control systems normally have control delay from the sampling period, the switching frequency of the inverter, the sensor transmission time, etc. The control delay increases the dimension of the system transfer function. This makes the control system more unstable. This paper analyzes the control performance related with the control delay, closed loop damping factor, and the output filter parameters in DVR systems. Based on the control system analysis, design guidelines are proposed for the control gains and the inverter switching frequency of DVRs. The proposed theory is verified by an experimental DVR system with a full digital controller.     

BTO/PDMS/C柔性复合薄膜的制备及压电性能研究

针对压电陶瓷在实现微纳运动中普遍存在的不确定非线性因素,提出了一种新型的非线性鲁棒控制器。该控制器利用非奇异终端滑模控制实现了控制器的鲁棒性,采用时延估计技术实现了对未知项的实时补偿和无模型控制,有利于工程应用,并用鲁棒精密微分器实现对全状态的估计。运用Lyapunov稳定性理论证明了系统的闭环稳定性。半物理仿真实验表明,该控制器能够控制压电陶瓷实现亚微米精度的运动控制。理论分析和实践证明,提出的控制策略具有无模型、高精度和鲁棒性强的控制效果,工程应用性强,能有效应用于压电陶瓷驱动的微纳操作系统中。     

压电微动平台的极点配置PID控制

为提高压电微动平台的位移输出精度,设计极点配置比例、积分、微分(PID)控制器对其进行控制。首先,在对压电执行器进行电学特性、机电特性分析的基础上,建立了压电执行器的数学模型;其次,在对平台进行受力分析、运动分析的基础上,建立了平台的动力学模型;然后,在保持平台极点虚部不变,且将系统闭环阻尼比取为1的情况下,将平台极点沿着平行于实轴的方向平移,设计出平台的PID反馈控制器;最后,实验验证了所设计控制器的有效性。实验结果表明,所设计的控制器可使平台具有较快的响应,在不考虑传感器噪声水平的情况下,平台在控制系统作用下的定位误差基本为0。     

Robustness evaluation of fractional order control for varying time delay processes

In this paper, we investigate the robustness of a methodology to design fractional order PI controllers combined with Smith Predictors, for varying time delay processes. To overcome the drawback of possible instability associated with Smith Predictor control structures, mainly due to the changes in the time delay, the design focuses on ensuring robustness of the closed loop system against time delay uncertainties. The proposed method is based on time-domain performance specifications??more accessible to the process engineer, rather than the more abstract notions related to the frequency domain. A second advantage of the proposed method relies on additional robustness to plant uncertainties, achieved by maximizing open-loop gain margin. The convergence problems associated with optimization techniques, previously used in fractional order controller designs, are eliminated by an iterative procedure in computing the gain margin. The simulation example provided demonstrates the efficiency of the proposed method, in comparison to classical integer order PI controller.     

A Survey of Recent Results in Networked Control Systems

Networked control systems (NCSs) are spatially distributed systems for which the communication between sensors, actuators, and controllers is supported by a shared communication network. We review several recent results on estimation, analysis, and controller synthesis for NCSs. The results surveyed address channel limitations in terms of packet-rates, sampling, network delay, and packet dropouts. The results are presented in a tutorial fashion, comparing alternative methodologies     

Improving Component-Swapping Modularity Using Bidirectional Communication in Networked Control Systems

Availability of low-cost electronics has led to a new breed of control system components, so-called smart components, which can perform control actions in the actuator and sensor components as well as in the controller. ldquoSmartrdquo components can communicate bidirectionally in networked control systems (NCSs). One can improve control system performance and design due to the decentralized, yet more connected, nature of these systems. Current research on NCSs primarily focuses on communication loss and delay. This paper investigates the potential benefits of bidirectional communication in a feedback control loop, which is at the heart of so many applications. First, a definition and quantification of component-swapping modularity is presented. Next, an optimal design formulation is presented for an NCS that maximizes component-swapping modularity. The approach is then demonstrated with an example of driveshaft speed control with a dc motor.     

Real time implementation of fractional order PID controllers for a magnetic levitation plant

Fractional calculus has been a topic of great interest for the last few decades. The applications of fractional calculus can be found in the area of viscoelastic and chaotic systems, whose dynamics is expressed in the form of fractional differential equations. The ongoing research work is based on the design of 1-Degree of Freedom (1-DOF) and 2-Degrees of Freedom (2-DOF) Fractional Order PID (FOPID) controllers for a Magnetic levitation (Maglev) plant and the performance has been compared with that of 1-DOF and 2-DOF Integer Order PID (IOPID) controllers in both simulation and real time. The Degree of Freedom (DOF) represents the number of feed-forward control loops in a closed loop system. A 2-DOF controller configuration comprises of a serial compensator and a feed-forward compensator in a closed loop structure. An FOPID controller has a structure similar to that of a conventional IOPID controller, except that its derivative and integral orders are fractional numbers. The design of such a controller requires the determination of five parameters: K_p, K_i, K_d, α and β, where α and β are the derivative and integral orders of the FOPID controller. The controller design problem has been framed as an optimization problem, in which the cost function is formulated from the characteristic equation of the closed loop system at dominant poles that are identified from the given performance specifications. The closed loop response shows that the proposed2-DOF FOPID controller exhibits superior response and robustness with respect to its integer order counterpart.     

An energy efficient and QoS aware routing protocol for wireless sensor and actuator networks

Wireless sensor and actuator networks are composed of sensor and actuator nodes interconnected via wireless links. The actuators are responsible for taking prompt decisions and react accordingly to the data gathered by sensor nodes. In order to ensure efficient actions in such networks, we propose a new routing protocol that provides QoS in terms of delay and energy consumption. The network is organized in clusters supervised by CHs (Cluster-Heads), elected according to important metrics, namely the energy capability, the riches of connectivity, which is used to select the CH with high node density, and the accessibility degree regarding all the actuators. The latter metric is the distance in number of hops of sensor nodes relative to the actuator nodes. This metric enhances more the network reliability by reducing the communication delay when alerting the actuator nodes, and hence, reducing the energy consumption. To reach efficiently the actuator nodes, we design a delay and energy sensitive routing protocol based on-demand routing approach. Our protocol incurs less delay and is energy efficient. We perform an evaluation of our approach through simulations. The obtained results show out performance of our approach while providing effective gain in terms of communication delay and energy consumption.     

自适应模糊滑模控制器设计

针对传统滑模控制的抖振问题,利用线性化反馈技术,将模糊自适应和滑模控制相结合,设计一种新型的模糊滑模控制器。通过模糊推理和基于Lyapunov函数的稳定性分析,获得模糊控制规则的自适应律,构成自适应模糊滑模控制器,有效解决了传统滑模控制中,需要确定参数摄动和外部干扰上确界不确定性问题,倒立摆上的运行结果表明该方法的有效性。     

智能电动阀门控制器的设计与实现

为了保障阀门工作的安全性和可靠性,智能控制系统由控制器和执行器两部分组成。控制器作为智能化控制的核心组成部分,它以AVRmega系列的mega128和mega16单片机为基础,利用霍尔传感器监控阀门位移,并与预定值进行比较实现阀门位移的闭环控制,同时通过应力传感器和温度传感器实现三相电机的过力矩保护和过温保护。系统三相电源自动相序检测和纠正功能,可以使电机运行不受电源接线的影响。在比较危险或者需要远程控制的场合,系统的最终目标生成的控制信号,能够保证控制器安全有效的运行。     

Design and implementation of a fault tolerant controller for EMS systems

Conventional EMS (electromagnetic suspension) systems are susceptible to instability problems, and could even break down upon failures of the air-gap sensor or the accelerometer. Therefore, in order to improve EMS performance, a fault tolerant controller and a fault detection and isolation (FDI) algorithm are presented in this work. The fault tolerant controller is an extended version of the linear fault tolerant controller designed for known actuator or sensor failures, and it adopts the LMI-based H_∞ control for a class of nonlinear systems. The fault detection algorithm employs fuzzy inference. The merits of the proposed control scheme have been verified by the experiments with a single-axis two-magnet suspension system subjected to failures of the actuator or the sensors.     

模型预测控制在网络闭环控制中的应用研究

在基于Internet的远程控制系统中,通过Internet进行信息传输的时间延时的不确定性对实时闭环控制系统的设计带来较大的困难.研究了网络传输延时对网络闭环控制系统的影响,提出了通过基于神经网络的预测控制方法解决存在网络随机延时的控制系统闭环控制的可行性.仿真结果表明该方法能够反映并预测该测量数据所代表的网络路径之间的时延特性,并能在基于Internet的闭环控制系统的设计中有效地替代实际网络进行研究;而所用的方法具有快速、准确的特点,能用于在线学习网络模型并对网络的时延值进行预测,为基于Internet的远程闭环控制提供了新的思路.