Prescribed Performance Tracking Control of Time-Delay Nonlinear Systems With Output Constraints

The problem of prescribed performance tracking control for unknown time-delay nonlinear systems subject to output constraints is dealt with in this paper. In contrast with related works, only the most fundamental requirements, i.e., boundedness and the local Lipschitz condition, are assumed for the allowable time delays. Moreover, we focus on the case where the reference is unknown beforehand, which renders the standard prescribed performance control designs under output constraints infeasible. To conquer these challenges, a novel robust prescribed performance control approach is put forward in this paper.Herein, a reverse tuning function is skillfully constructed and automatically generates a performance envelop for the tracking error. In addition, a unified performance analysis framework based on proof by contradiction and the barrier function is established to reveal the inherent robustness of the control system against the time delays. It turns out that the system output tracks the reference with a preassigned settling time and good accuracy,without constraint violations. A comparative simulation on a two-stage chemical reactor is carried out to illustrate the above theoretical findings.

Book Announcement of L. Celentano, Robust Tracking Controllers Design with Generic References for Continuous and Discrete Uncertain Linear SISO Systems, LAP LAMBERT Academic Publishing, 2012

In this book new results on controller design techniques for the tracking of generic reference inputs are presented. They allow the design of a controller for an uncertain process, either continuous or discrete-time, without zeros, and with measurable state. The controller guarantees that the control system is Type 1 and has the desired constant gain and poles or that the control system tracks, with a specified maximum error and with a specified maximum time constant, a generic reference with bounded derivative (variation in the discrete-time case), also in the presence of a generic disturbance with bounded derivative (variation). In addition, it is considered the case in which the reference is known a priori. The utility and the efficiency of the proposed methods are illustrated with attractive and significant examples of motion control and temperature control. This book is useful for the design of control systems, especially for manufacturing systems, that are versatile, fast, precise and robust.

Model Reference Adaptive Control for Switched Systems with Closed-loop Reference Model Under Arbitrary Switching

This paper explores the model reference adaptive control problem for a class of switched linear systems under arbitrary switching with no need for the measurability of the system state.Based on the state of reference model and the measurable output error, adaptive laws and controllers are designed for switched systems.Each subsystem may have its individual reference model and controller, which increases the design flexibility.The introduction of the closed-loop reference model is to get a better transient performance of the whole switched systems.A numerical example is provided to verify the effectiveness of the main results.

Astronomical relativistic reference systems with multipolar expansion: the global one

With the rapid development of techniques for astronomical observations, the precision of measurements has been significantly increasing. Theories describing astronomical relativistic reference systems, which are the foundation for processing and interpreting these data now and in the future, may require extensions to satisfy the needs of these trends. Besides building a framework compatible with alternative theories of gravity and the pursuit of higher order post-Newtonian approximation, it will also be necessary to make the first order post-Newtonian multipole moments of celestial bodies be explicitly expressed in the astronomical relativistic reference systems. This will bring some convenience into modeling the observations and experiments and make it easier to distinguish different contributions in measurements. As a first step, the global solar system reference system is expressed as a multipolar expansion and the post-Newtonian mass and spin moments are shown explicitly in the metric which describes the coordinates of the system. The full expression of the global metric is given.

Initial alignment for low-cost attitude and heading reference systems

MEMS （micro electro mechanical systems） inertial navigation system ~, Mll＇~3） nas Been WllUly used in robots for its low-cost. The MINS and magnetometers are commonly the component parts of the attitude and heading reference systems （AHRS）, which provide pitch and roll angles relative to the earth gravity vector, and heading angle relative to the north. However, the performance of sen- sors with low cost AHRS is not so good. The gyros are not sensitive enough to observe the earth an- gular velocity, so the traditional technique like alignment algorithm is invalid. The measurements of gyros become useless to determine the initial attitude matrix from navigation frame to body frame. The alignment algorithm is computed by the accelerometers and magnetometers. The process is es- tablished as an optimization problem of finding the maximum eigenvector. Meanwhile the sensitive analysis with respect to the biases of accelerometers is proposed. Then the recursive least squares al- gorithm （RLSA） is introduced. The comparison between the proposed method and RLSA is provid- ed. The results demonstrate its accuracy favorably and verify the feasibility of the proposed algo- rithm.

Robust model-reference control for descriptor linear systems subject to parameter uncertainties

Robust model-reference control for descriptor linear systems with structural parameter uncertainties is investigated. A sufficient condition for existing a model-reference zero-error asymptotic tracking controller is given. It is shown that the robust model reference control problem can be decomposed into two subproblems： a robust state feedback stabilization problem for descriptor systems subject to parameter uncertainties and a robust compensation problem. The latter aims to find three coefficient matrices which satisfy four matrix equations and simultaneously minimize the effect of the uncertainties to the tracking error. Based on a complete parametric solution to a class of generalized Sylvester matrix equations, the robust compensation problem is converted into a minimization problem with quadratic cost and linear constraints. A numerical example shows the effect of the proposed approach.

The Possibility of Detecting our Solar System through Astrometry

Searching for exoplanets with different methods has always been the focus of astronomers over the past few years.Among multiple planet detection techniques,astrometry stands out for its capability to accurately determine the orbital parameters of exoplanets.In this study,we examine the likelihood of extraterrestrial intelligent civilizations detecting planets in our solar system using the astrometry method.By conducting injection-recovery simulations,we investigate the detectability of the four giant planets in our solar system under different observing baselines and observational errors.Our findings indicate that extraterrestrial intelligence could detect and characterize all four giant planets,provided they are observed for a minimum of 90 yr with signal-noise ratios exceeding 1.For individual planets such as Jupiter,Saturn,and Neptune,a baseline that surpasses half of their orbital periods is necessary for detection.However,Uranus requires longer observing baselines since its orbital period is roughly half of that of Neptune.If the astrometry precision is equal to or better than 10μas,all 8707 stars located within30 pc of our solar system possess the potential to detect the four giant planets within 100 yr.Additionally,our prediction suggests that over 300 stars positioned within 10 pc from our solar system could detect our Earth if they achieve an astrometry precision of 0.3μas.

NOETHER’S THEORY FOR NONHOLONOMIC DYNAMICAL SYSTEMS RELATIVE TO NON-INERTIAL REFERENCE FRAME

The new variational principle of Gauss's form of nonlinear nonholonomic nonpotential system relative to non-inertial reference frame is established by constructing generalized inertial potentials. Naether's theorem and Naether's inverse theorem of the system above is presented and proved. Finally, one example is given to illustrate the application.

基于铁路带状北斗CORS的网络RTK测量精度分析

为研究和拓展北斗导航系统在铁路工程测量中的应用,利用BDS系统技术优势解决山区铁路测量定位难题。基于某山区铁路建立带状北斗连续运行参考站系统(以下简称“北斗CORS系统”)和高精度位置服务云平台。采用国产多星多频测量型接收机进行控制点数据采集工作,分别对比基于北斗CORS系统的单BDS、单GPS以及GNSS混合星历网络RTK观测数据以及传统基站形式的RTK观测数据的测量精度。结果表明:(1)铁路带状北斗高精度位置服务云平台网络RTK定位功能稳定可靠;(2)基于北斗CORS系统的网络RTK测量方法仅需进行高程曲面拟合,按3s采集的成果精度即可满足铁路测量规范中网络RTK中线测量、断面测量、施工放样、像控测量的精度要求,测量时应尽量采用同类型的设备并采用同精度观测方法以保证重复测量精度,也可通过增加观测时长、在局部区域利用既有高程控制点做高程校正的方式提高测量精度;(3)基于北斗CORS系统的网络RTK测量平面和高程内符合精度限差可分别设定为1.7 cm和2 cm,外符合精度可分别设定为2.2 cm和5 cm。

一种可调焦离轴两反光学系统精密调校工艺技术研究

针对可调焦离轴两反光学系统的精密装调,提出了一种共基准调校方法,使导轨导向与主镜和次镜光轴均以同一基准进行精确调校,实现导轨运动轴线与主镜和次镜光轴平行。主镜、次镜系统光轴一致性调试采用初调整和精调整两步完成,初调整实现主镜和次镜基本位于理论安装位置,降低装调误差,然后进行计算机辅助装调,实现主镜和次镜光轴一致性精调整,使系统波像差满足要求。实验结果表明:无穷远处系统波像差RMS达到(1/15)λ(λ=632.8 nm),系统衍射分辨率达到0.64″,系统调焦至10 mm处,实测主镜、次镜系统所成焦距为1608 mm,系统分辨率为2.6″,达到设计要求。

小行星探测器轨道计算的动力学研究

针对中国即将开展的小行星探测活动中面临的轨道计算动力学问题进行研究。分析了小行星探测器轨道计算的需求,并对小行星轨道计算中涉及的时空参考系进行了描述,然后对轨道计算所需考虑的动力学模型进行了讨论,并给出了各类摄动加速度的计算公式。最大的是太阳引力加速度,约为10^(-6)km/s^(2);最小的是小行星本体摄动加速度,约为10^(-12)~10^(-13)km/s^(2)。利用欧空局Rosetta探测器的实测数据对动力学模型精度进行了验证,结果表明4天弧段位置互差约15 m,速度互差约0.44 mm/s,动力学模型精度可靠。本研究可以为中国小行星探测活动轨道计算提供参考。

SNARC效应的空间参照机制

SNARC效应是人脑处理和解释数字信息时,数字信息与空间属性产生的一种联结现象。该效应自被发现以来,就成为认知心理学的研究热点之一。然而,关于该效应产生的空间机制仍存在争议。从SNARC效应的自我空间参照和非自我空间参照两个角度进行梳理,并基于空间参照的层级系统和内外系统两种假设,深入分析SNARC效应空间参照的组织系统。未来可在深入探讨SNARC效应在垂直方向上的空间参照机制和组织系统的基础上,进一步研究SNARC效应在水平与垂直两个方向的空间参照行为与神经机制的特点及相互关系。

九轴MEMS微型AHRS设计及其在矢量水听器中的应用

为了精确测量矢量水听器的姿态,设计了一种体积为20 mm×20 mm×5 mm、重量为1.8 g的微型航姿参考系统(AHRS)。利用微机电系统(MEMS)陀螺仪测定角速度,用四元数等效旋转矢量算法求解姿态角;采用扩展卡尔曼滤波器对姿态角估计值进行修正,并估计出MEMS陀螺仪的角速度漂移量。测试结果表明,所提AHRS的俯仰、横滚和航向角误差均方根值分别为0.04°、0.04°和0.34°。最后,将AHRS集成到矢量水听器中,并在加窗直方图统计波达方向估计算法中加入姿态修正。海上实验结果表明,对于航速为8 kn的目标船,经AHRS修正后的单矢量水听器方位角误差均方根值约为3.8°,减小了平台运动导致的方位测量误差。

基于模型参考自适应的水肥一体化控制系统设计

针对水肥混合过程中水肥EC值精准控制的问题,设计一个基于模型参考自适应的水肥一体化决策和控制系统。建立母液动态调控模型,并通过该模型设计模型参考自适应控制器。仿真试验结果显示,模型参考自适应控制相较于模糊PID控制,在跟踪试验中超调量降低1.2%,调整时间减少12.6 s,阶跃试验中超调量降低14.4%,调整时间减少超过2 s,抗干扰能力优于模糊PID控制。通过3种方式进行田间试验,对比模糊PID控制和人工灌溉方式,采用模型参考自适应控制能够使番茄株高分别提高15.7%和35.6%,茎粗分别增长11.1%和18.6%,产量分别提升23.3%和48.1%,结果表明,模型参考自适应控制优于模糊PID控制和人工灌溉方式,从而验证模型参考自适应控制的有效性,为精准施肥灌溉提供技术支持。

一阶系统模型参考自适应辨识及位置控制

针对新建系统或负载变化导致的模型参数不确定问题,对交流伺服系统进行研究,提出模型参考自适应辨识(model reference adaptive identification,MRAI)算法,对一阶系统模型参数进行在线辨识。首先对一阶系统进行数学模型构建,然后根据李雅普诺夫(Lyapunov)稳定理论选择参考模型,并设计自适应控制律,在此基础上对一阶系统进行模型参数在线辨识。当参数收敛后,根据系统要求的自然频率和阻尼比,在线设计位置控制器参数,并进行跟踪定位控制。仿真和实验结果表明,模型参考自适应在线辨识算法能快速精准地辨识出系统模型参数,通过在线设计控制器参数实现了对参考信号的快速跟踪。

河南地矿CORS省域地面沉降监测与机理分析

为了进一步研究省域尺度范围地面沉降,分析河南地矿CORS省域地面沉降的监测方法与其形成机理:针对河南省地面沉降分布特征,采用河南省地质信息连续采集运行系统(HNGICS)的62个基准站数据,时间序列为2012—2019年,获得国际地球参考框架下无净旋转条件的河南省三维速度场;然后分解三维速度场获得河南垂直速度场,发现河南省地面沉降呈现“西稳东沉”的现象,开封附近出现沉降漏斗;最后将河南省地质图、河南省耕地面积占比、河南省年均降雨量与沉降等值线对比分析。结果表明:不同地质条件下,河南省地面沉降分布于豫东地区的第四系冲积层,而相同地质条件下,耕地占比和区域年均降雨量是地表差异性沉降的主要原因,如豫东地区耕地约占总面积的70%,地下水用于农业灌溉是豫东平原出现沉降漏斗的主要原因。

湖南省卫星导航定位基准站网服务体系建设及思考

卫星导航定位基准站网是重要的国家空间基础设施,对国家安全和国民经济建设具有重要意义。湖南省卫星导航定位基准站网(HNCORS)经过多年发展,其网型结构不断优化,用户并发服务能力得到提升,服务领域不断拓展。随着数字中国建设和数字经济的蓬勃发展,高精度位置服务需求日益旺盛,HNCORS迎来了新的发展机遇,同时也面临新的挑战,如在监管机制、基础设施、自主创新和共享融合等方面存在不足。为了解决这些问题,湖南开展了卫星导航定位基准站网服务体系建设。本文首先描述了HNCORS服务体系建设背景;然后从管理机制、基础设施和核心技术三个方面阐述建设过程,总结出在服务模式、应用领域和共享融合方面取得的成效;最后对其未来发展进行展望,并从要素保障、自主创新、发展与安全三个方面提出针对性建议,可为卫星导航产业的发展和相关部门政策制定提供参考。

茶叶感官国家标准样品的研制和展望

随着我国茶产业标准化建设工作的推进,我国已基本建立了完善的茶叶文字标准体系,但与文字标准相协同配套的标准样品研制工作还相对薄弱。文章介绍了茶叶领域国家标准样品研制现状,总结了茶叶感官分级标准样品研制过程中的主要技术和存在的问题,并对未来工作进行了展望。

应用于运动平台光电跟瞄系统的惯性参考单元研究综述

目标的变化和任务的拓展对光电跟瞄系统提出了快速机动的要求,从地基平台到车载、船载、机载、星载等运动平台是光电跟瞄系统的重要发展趋势。基于惯性参考单元(Inertial Reference Unit,IRU)的视轴稳定方式是克服运动平台高频扰动,实现光电跟瞄系统微弧度甚至亚微弧度级跟瞄的主要技术手段。针对运动平台光电跟瞄系统精确指向对载体基座扰动抑制的需求,分析和对比了IRU的各种技术方案,特别介绍了利用低噪声、宽频带惯性传感器敏感角扰动,并通过反馈控制实现视轴惯性稳定的系统方案。从此类IRU系统的工作原理出发,阐述了系统的两种工作模式及功能特点,建立了系统数学模型。然后,介绍了IRU的国内外研究进展及发展方向,指出惯性传感、支承结构和控制系统是决定IRU稳定能力的关键因素,梳理了三项关键技术的研究动态。最后,总结了IRU的空间应用情况,并结合目前的应用需求对其未来应用领域进行了探讨。

海洋科学数据共享标准体系框架研究

本文调研了国内外相关领域标准体系的建设和应用现状,介绍了标准体系的构建原则、方法与技术路线,提出了由标准类型、标准类别和共享生命周期三个维度组成的参考模型,以及由基础标准、数据组织、汇交与整合、数据存储、发布与服务、数据利用、评估评价和数据安全8个大类、26个小类组成的海洋科学数据共享标准体系框架,全面覆盖了共享生命周期的关键业务节点,并从统筹构建标准明细表、加强全生命周期关键节点标准规范编制,以及标准宣贯和试点应用等方面提出下一步工作建议。