Connectability and structural controllability of composite systems

The notion of connectability for multivariable composite systems consisting of a number of subsystems interconnected in an arbitrary way is introduced in this paper. It is shown that connectability plays a fundamental role in composite systems; in particular, it is shown that under certain mild conditions, almost all composite interconnected systems are controllable and observable from any nontrivial input and output if and only if the resultant composite system is connectable. A class of composite systems called general input-output hierarchical systems, which has the property of always being connectable is then defined. Since such systems are almost always controllable, this observation perhaps gives some insight in explaining why so many real world systems have as their basis a hierarchical structure. An application of the previous results is then made to show that a system (C, A, B) is structurally controllable and observable if and only if it is connectable and a certain non-pathological rank condition holds.     

考虑时滞影响的SVC广域附加阻尼控制器设计

本文提出了考虑时滞影响的静止无功补偿器(SVC)广域附加阻尼控制器的设计方法。以含有SVC的新英格兰电力系统为例,通过几何可控/可观度分析选择SVC的附加阻尼控制器的广域输入信号,采用留数法计算得出了其时滞补偿参数,随后采用时滞稳定性判据分析了含有SVC常规附加阻尼控制器的增益与闭环电力系统的时滞稳定裕度的关系,最后根据时滞稳定裕度结果确定了SVC附加阻尼控制器的增益。仿真结果表明,考虑时滞影响的SVC附加阻尼控制器既能够提高系统的阻尼特性,又具有一定的时滞鲁棒性。     

基于遗传禁忌搜索算法的PMU布点配置

将遗传算法GA（Genetic Algorithm）和禁忌搜索算法TS（Tabu search）相结合,提出一种遗传禁忌搜索算法GATS ( Genetic Algorithm & Tabu search)用于相量测量单元优化配置。GATS算法结合了遗传算法的随机搜索能力、并行性和禁忌搜索算法的记忆功能,有效地解决了遗传算法的爬山能力差、早熟的问题,提高了收敛速度及优化质量;同时遗传算法的种群操作,保留了遗传算法的多出发点的优势,弥补了禁忌搜索的单一单操作缺乏并行性的弱点。在约束条件处理时,采用了不可行解启发性修复方法,提高了算法的优化效果。基于图论的深度优先方法用于系统可观性分析。将GATS算法应用于优化相量测量装置安装地点选择,实现了安装地点最少,而整个系统可观的目标。通过算例证明了算法的有效可靠。     

近地小行星仅测角相对导航可观性判据

针对近地小行星仅测角相对导航系统的非线性可观测性分析问题,本文基于非线性系统局部弱可观性理论给出了新的可观测性判据.首先,通过分析非线性系统李导数的共有属性,给出了李导数梯度空间的共有子空间.进一步,利用该共有子空间和非线性系统局部弱可观性定义给出了新的可观性判据.经理论证明,该判据适用于非线性系统任意阶李导数,并且给出的可观性结论可与高阶可观性矩阵秩判据的结论等价.与传统的秩判据相比,该判据具有无需进行高阶李导数运算,无需进行高维矩阵运算的优点.因此该判据适合在轨计算,具有一定的工程价值.最后仿真结果验证了可观性判据的有效性.     

Observability and stabilisability of networked control systems with limited data rates

This paper investigates the observability and stabilisability problem for linear time-invariant systems, where sensors and controllers are geographically separated and connected by a stationary memoryless digital communication channel. The limited information of the plant state is transmitted over such a channel to the controller. We focus on explaining the effect imposed by limited data rates. A new quantisation, coding and control scheme is presented to minimise the required data rate for observability and stabilisability. Different from prior research, our study shows that, the required data rate is determined by the state prediction error. Namely, the smaller prediction error requires the smaller codeword length, which leads to the smaller data rate. It is shown that, there exists a lower bound on the average data rate above which the system is observable and stabilisable. Illustrative examples are given to demonstrate the effectiveness of the proposed quantisation, coding and control scheme.     

Lever Arm Compensation of Autonomous Underwater Vehicle for Fast Transfer Alignment

Transfer alignment is used to initialize SINS (Strapdown Inertial Navigation System) in motion. Lever-arm effect compensation is studied existing in an AUV (Autonomous Underwater Vehicle) before launched from the mother ship. The AUV is equipped with SINS, Doppler Velocity Log, depth sensor and other navigation sensors. The lever arm will cause large error on the transfer alignment between master inertial navigation system and slave inertial navigation system, especially in big ship situations. This paper presents a novel method that can effectively estimate and compensate the flexural lever arm between the main inertial navigation system mounted on the mother ship and the slave inertial navigation system equipped on the AUV. The nonlinear measurement equation of angular rate is derived based on three successive rotations of the body frame of the master inertial navigation system. Nonlinear filter is utilized as the nonlinear estimator for its capability of non-linear approximation. Observability analysis was conducted on the SINS state vector based on singular value decomposition method. State equation of SINS was adopted as the system state equation. Simulation experiments were conducted and results showed that the proposed method can estimate the flexural lever arm more accurately, the precision of transfer alignment was improved and alignment time was shortened accordingly.     

纯方位角目标跟踪及移动平台可观性控制方法

为了解决未知环境下的单目视觉移动机器人目标跟踪问题,提出了一种将目标状态估计与机器人可观性控制相结合的机器人同时定位、地图构建与目标跟踪方法。在状态估计方面,以机器人单目视觉同时定位与地图构建为基础,设计了扩展式卡尔曼滤波框架下的目标跟踪算法;在机器人可观性控制方面,设计了基于目标协方差阵更新最大化的优化控制方法。该方法能够实现机器人在单目视觉条件下对自身状态、环境状态、目标状态的同步估计以及目标跟随。仿真和原型样机实验验证了目标状态估计和机器人控制之间的耦合关系,证明了方法的准确性和有效性,结果表明:机器人将产生螺旋状机动运动轨迹,同时,目标跟踪和机器人定位精度与机器人机动能力成正比例关系。     

On "Over-Sized" High-Gain Practical Observers for Nonlinear Systems

In this paper, it is shown that the performances of a class of high-gain practical observers can be improved by estimating the time derivatives of the output up to an order that is greater than the dimension of the system, which is assumed to be in observability form and, possibly, time-varying. Such an improvement is achieved without increasing the gain of the observers, thus allowing their use in a wide variety of control and identification applications.