压电驱动快速反射镜的自适应反演滑模控制

由压电驱动器驱动的快速反射镜(FSM)广泛应用于各种精密稳定跟踪系统,FSM的控制精度决定了系统的跟踪精度。但压电驱动器具有严重的迟滞非线性干扰,针对这一缺点,应用自适应径向基RBF神经网络对迟滞干扰进行非线性逼近,并在此基础上结合滑模控制和反演法,设计了自适应反演滑模(ABSM)控制器。仿真实验表明,相对于滑模控制器,ABSM控制器的最大跟踪误差和均方根误差为分别降低了57.26%和52.53%,提高了FSM的控制精度。     

Optimal tracking control with zero steady-state error for time-delay systems with sinusoidal disturbances

The problem of optimal tracking control with zero steady-state error for linear time-delay systems with sinusoidal disturbances is considered. Based on the internal model principle, a disturbance compensator is constructed such that the system with external sinusoidal disturbances is transformed into an augmented system without disturbances. By introducing a sensitivity parameter and expanding power series around it, the optimal tracking control problem can be simplified into the problem of solving an infinite sum of linear optimal control series without time-delay and disturbance. The obtained optimal tracking control law with zero steady-state error consists of accurate linear state feedback terms and a time-delay compensating term, which is an infinite sum of an adjoint vector series. The accurate linear terms can be obtained by solving a Riccati matrix equation and a Sylvester equation, respectively. The compensation term can be approximately obtained through a recursive algorithm. A numerical simulation shows that the algorithm is effective and easily implemented, and the designed tracking controller is robust with respect to the sinusoidal disturbances.     

Observation of zero creep in piezoelectric actuators

Piezoelectric actuators are frequently used nowadays in a wide variety of positioning devices. Although very suitable for small displacements in the range of nm to several hundreds of μm, the actuators always suffer from hysteresis and creep between the input voltage and resulting displacements. In scanning applications, the input voltage is often used as an indicator of the induced displacement. This procedure can result in a large position error depending on the amount of hysteresis and creep. In order to describe and control hysteretic systems various models for hysteresis have been published but little is known about relaxation and creep in piezo materials. In this paper we present detailed studies of the hysteretic behavior and piezo relaxation and creep. We have identified certain locations on the hysteresis loop that exhibit zero creep. From this observation, a more fundamental relation between the amount of creep and the local slope of the hysteresis loop and the virgin curve is presented. This observation could be useful in both open-loop and closed-loop position control, since it allows quantification of the creep. Futhermore, the experimentally observed relation between the creep and the hysteresis suggests a reduction of the creep for non-hysteretic transfers. First measurements on a system with reduced hysteresis support this hypothesis. Received: 15 February 1999 / Accepted: 16 February 1999 / Published online: 28 April 1999     

混沌系统自适应追踪控制新方法

提出一种混沌系统自适应追踪控制任意参考信号的新方法.该方法是通过预先设计出补偿控制器将混沌系统状态变量对参考信号的追踪控制问题转化为同结构混沌系统状态变量的自适应同步问题,再通过设计出自适应控制器,使同结构混沌系统全局渐近达到同步,追踪控制器为补偿控制器和自适应控制器的代数和.基于Lyapunov稳定性原理,理论上严格证明了利用本方法所设计追踪控制器的正确性.最后,以超混沌Chen系统为控制对象,利用本方法设计出追踪控制器完成了对不动点,正、余弦信号,同结构混沌系统状态变量,异结构混沌系统状态变量的追踪控 关键词： 自适应追踪控制 补偿控制器 自适应控制器 追踪控制器     

混沌系统的非线性连续预测变结构控制与同步

在连续时间混沌系统的控制与同步问题统一处理的基础上,给出一种可实现两个相同或不同连续时间混沌系统的控制与同步的预测变结构控制方法.其控制器由针对对象标称非线性模型设计的连续预测控制器和针对对象不确定性设计的滑模变结构控制器组成.所提出的方案具有变结构控制鲁棒性强的优点,实现了系统对参考信号的追踪控制.数值仿真表明了本方法的有效性 关键词： 混沌同步 预测控制 滑模 变结构 鲁棒性     

Nonlinear control of spacecraft formation flying with disturbance rejection and collision avoidance

A nonlinear controller for disturbances rejection and collision avoidance is proposed for spacecraft formation flying.The formation flying is described by a nonlinear model with the J_2 perturbation and atmospheric drag. Based on the theory of the state-dependent Riccati equation(SDRE), a finite time nonlinear control law is developed for the nonlinear dynamics involved in formation flying. Then, a compensative internal mode(IM) control law is added to eliminate disturbances.These two control laws compose a finite time nonlinear tracking controller with disturbances rejection. Moreover, taking safety requirements into account, the repulsive control law is incorporated in the composite controller to perform collision avoidance manoeuvres. A numerical simulation is presented to demonstrate the effectiveness of the proposed method.Compared to the conventional control method, the proposed method provides better performance in the presence of the obstacles and external disturbances.     

"量子相干性跟踪控制"的鲁棒性分析

文献[Quantum Information and Computation,2005,5(4):350-363]提出量子相干性跟踪控制策略以保持量子位的相干性,该策略本质是开环控制,而开环控制的缺陷就是严重依赖于精确地了解系统的初始条件和模型参数。然而,我们对于系统的知识总是存在不确定性的。本文从鲁棒性的角度分析了量子相干性跟踪控制策略的局限性。首先,我们对该方法的鲁棒性进行了理论分析;接着用仿真实例定量说明了:量子初始条件和模型参数的精度对保持相干性的影响。根据相干性的精度要求,我们可以利用仿真分析的手段,来确定对模型参数和初始状态必须满足的精度条件。总之,我们在应用中必须谨慎采用量子相干性跟踪控制策略。     

Chaos control via a simple fractional-order controller

In this Letter, we propose a fractional-order controller to stabilize the unstable fixed points of an unstable open-loop system. Also, we show that this controller has strong ability to eliminate chaotic oscillations or reduce them to regular oscillations in the chaotic systems. This controller has simple structure and is designed very easily. To determine the control parameters, one needs only a little knowledge about the plant and therefore, the proposed controller is a suitable choice in the control of uncertain chaotic systems.     

雷达天线控制系统频域辨识与仿真方法研究

雷达天线控制系统仿真是雷达系统目标跟踪动态仿真中一个重要环节。为解决雷达天线控制系统仿真中滞后误差大、动态效果差等问题,依据某雷达天线控制系统性能实际测试结果,以典型系统模型作为研究对象,利用频域最小二乘法完成模型参数辨识,建立系统模型,并对辨识模型进行验证。在此基础上,采用基于时域的增广矩阵法对系统进行了数字快速仿真分析。结果表明,辨识模型满足精度,且增广矩阵法能够有效快速地完成系统数字仿真,对天线控制系统建模以及快速动态仿真研究具有一定的参考价值。     

自适应光学中的控制算法设计与仿真

对自适应光学系统中的控制算法设计进行了整体研究。首先对自适应光学系统各模块的物理特性进行了分析,并在此基础上建立了系统整体的数学模型。针对传统处理含有纯滞后环节系统近似方法的不足,文章采用直接求解系统传递函数幅频和相频解析函数的方法来对系统特性进行分析,通过比较系统的开环特性、闭环特性、误差和噪声传递特性等对三种控制方法（积分控制、PI控制和Smith控制）的控制品质进行了分析。分析和仿真结果表明,Smith控制方法对自适应光学系统能够达到较好的控制效果,为实际系统的设计提供了理论指导。     

Motion planning and actuator specialization in the control of active-flexible link robots

Trajectory planning is a well-known open-loop control strategy to minimize residual vibrations in point-to-point tasks of systems featuring mechanical flexibility. However, the major drawback of open-loop control is its limitation in coping with modeling uncertainty. In this paper a novel approach to trajectory planning based on LQR theory is proposed and applied to a single flexible link robot. To improve performance under parameter uncertainty the strategy is combined with collocated vibration control through piezoelectric actuation of the link. This combination raises the issue of the roles and the contribution of each actuator type to the overall performance of the maneuver. An actuator specialization is proposed where the joint controller is responsible for the gross vibrationless motion of the link, while the link actuators are expected to deal only with residual vibrations that may arise from modeling errors. Simulation and experimental results validate the trajectory planning methodology and the combination of the open-loop strategy with collocated vibration control.     

Micropositioning using shape memory alloy actuators

Shape memory alloys (SMA) can be used to generate motion or force in electromechanical devices and micro-machines, although their accuracy is severely limited by their highly nonlinear and hysteretical stimulus-response characteristics. In this work we present some results regarding a nonlinear control method suitable for SMA-based positioning applications. In particular, we show how the hysteresis effects can be compensated using an inverse hysteresis model generated by a neural network, trained using experimental data. The control strategy, experimented on a laboratory SMA actuator, uses the inverse model inserted in a proportional-integral with antiwindup control loop. It is found that neural networks successfully improve the closed-loop response, leading to position accuracies close to a micrometer.     

Robust tracking control of a piezodriven monolithic flexure-hinge stage

This study presents the controller design and tests of a new piezodriven two degree-of freedom (DOF) monolithic stage for precision motion. The computer-controlled system is developed, designed and employed for better displacement error compensation by proportional-integral-derivative (PID) controller based on Internal Model Control (IMC), Iterative Learning Control (ILC) and Disturbance Observer (DO). Experimental results show that stage positioning is precisely controlled (error ≈ 1.42%) for tracking sinusoidal waveforms by IMC and P-type ILC with repeatable disturbance. With additional DO, experiment tests perform error ≈ 0.5% with non-repeatable disturbance up to 16% of the maximum traveling length in roughly 5 iterations. This is close to the hardware reproducibility level. Experimental results show the piezo-stage controlled system can be potentially used for nano technology applications for precision engineering in industrial systems.     

室内环境中脑控轮椅的路径跟踪控制

为了实现室内环境中脑控轮椅的自主导航,提出了一种简单有效的路径跟踪控制方法。给定的路径通常被表示为一系列离散点,根据这一特点,提出了分段直线路径跟踪方法,即依次跟踪由前后两个路径点构成的直线路径到达目标点。基于预瞄点技术并结合模糊算法和传统的PID控制方法设计控制器,完成各分段直线路径的跟踪,并给出了有效的切换条件。实验结果表明,本文提出的路径跟踪控制方法能够使脑控轮椅在室内环境中精确地跟踪给定路径。     

Information-theoretic approach to the study of control systems

We propose an information-theoretic framework for analyzing control systems based on the close relationship of controllers to communication channels. A communication channel takes an input state and transforms it into an output state. A controller, similarly, takes the initial state of a system to be controlled and transforms it into a target state. In this sense, a controller can be thought of as an actuation channel that acts on inputs to produce desired outputs. In this transformation process, two different control strategies can be adopted: (i) the controller applies an actuation dynamics that is independent of the state of the system to be controlled (open-loop control); or (ii) the controller enacts an actuation dynamics that is based on some information about the state of the controlled system (closed-loop control). Using this communication channel model of control, we provide necessary and sufficient conditions for a system to be perfectly controllable and perfectly observable in terms of information and entropy. In addition, we derive a quantitative trade-off between the amount of information gathered by a closed-loop controller and its relative performance advantage over an open-loop controller in stabilizing a system. This work supplements earlier results (Phys. Rev. Lett. 84 (2000) 1156) by providing new derivations of the advantage afforded by closed-loop control and by proposing an information-based optimality criterion for control systems. New applications of this approach pertaining to proportional controllers, and the control of chaotic maps are also presented.     

Smooth control of HIV/AIDS infection using a robust adaptive scheme with decoupled sliding mode supervision

In this paper, a robust adaptive controller subject to decoupled sliding mode controller as a supervisory controller has been implemented on the HIV infection dynamic model. A five-state dynamic model of HIV is utilized which the measurement of the CD4+T cells and the viral load counts are necessary to estimate all its parameters. Decoupled sliding mode control is a variable structure controller having significant and appropriate features, such as best tracking and regulation performance and robustness and elevate the performance of the controller. Generally, due to the importance of applied treatment strategy to mitigate viral escape, sliding mode control is utilized in accordance with PI control to deliver necessary control inputs. To achieve the least possible chattering, effectual methods such as the transfer function is used. To update the gains of PI control, an adaptation law is then employed. The results demonstrate the suitable performance of the controller via providing proper tracking performance, and also, elimination of the chattering problem and decrease the time of treatment. The number of infected CD4+ T-cells and the number of free virus particles can be controlled in less than five days. The proposed controller is capable of controlling the dynamic behavior of the virus concentration for different patients with the same control scheme.     

多移动机器人轨迹跟踪控制系统设计与实现

针对轮式移动机器人的轨迹跟踪控制问题,在分析了机器人运动学模型的基础上,构建多机器人的领航-追随模型。采用跟踪微分器在输入输出两端安排过渡过程,设计了一种基于多变量解耦的非线性PID轨迹跟踪控制器。搭建以Arduino Mega 1280控制板为核心的移动机器人实验平台,采用速度PID控制器以满足机器人驱动电机的实时调速要求,基于ROS提出一种结构化和模块化的多机器人控制系统。在此基础上进行实验,并将实验结果与传统PID方法控制的实验结果进行对比。实验结果验证了本文所提算法的有效性,控制器易于实现且具有一定的鲁棒性。     

水下目标多平台协同定位和跟踪方法

提出了一种融合多平台方位观测数据的水下声学目标定位跟踪方法。该方法采用多级多假设跟踪对目标状态进行滤波和关联,第一级基于每个平台波束域检测结果独立使用多假设跟踪方法对目标方位角进行初级跟踪;第二级首先通过多平台联合似然概率估计多目标初始位置,再用多假设跟踪方法对不同平台初级跟踪的方位角航迹进行关联,最后通过关联的角度值和扩展卡尔曼滤波对多目标位置进行序贯估计。仿真结果证明,该方法能以更少计算量实现更优定位性能,优于单级多假设跟踪方法.海试数据处理结果表明,存在较多干扰的情况下,单级方法跟踪过程中丢失目标,而多级方法实现了对目标的全程跟踪,且收敛后定位误差在70m内。该方法可降低噪声干扰对数据关联及目标定位的影响,并通过多平台协同消除线阵的方位模糊,适用于移动多平台声学目标定位和跟踪场景。      

超声振动系统频率自动跟踪的模糊控制算法研究

针对大功率超声应用中,工作频带窄、频率跟踪速度要求快的特点,提出将模糊控制智能算法（Fuzzy Control）和数字频率直接合成技术（DDS）相结合的频率自动跟踪方案,依据经验归纳制定模糊控制器来快速跟踪工作频率,将驱动频率调节至谐振频率附近;随后只采用DDS进行频率的微调节,使得电源频率工作在超声换能器的谐振频率点上。最后,通过在MATLAB软件中对控制算法进行验证,表明本文算法具有可行性,能够实现对大功率超声波电源的频率自动跟踪。     

基于追踪控制的混沌异结构同步

针对连续混沌系统，提出一种混沌异结构同步追踪控制方案.利用Lyapunov方法证明了当受控系统满足Lipchitz条件时，即可使其状态输出指数收敛到任意给定的参考信号.设计的控制器结构对不同的混沌系统具有统一的形式，可实现任意混沌系统之间的异结构同步.数值仿真进一步表明了该方法的有效性. 关键词： 混沌系统 追踪控制 同步