Evaluation and improvement of coastal GNSS reflectometry sea level variations from existing GNSS stations in Taiwan

Global sea level rise due to an increasingly warmer climate has begun to induce hazards, adversely affecting the lives and properties of people residing in low-lying coastal regions and islands. Therefore, it is important to monitor and understand variations in coastal sea level covering offshore regions. Signal-to-noise ratio (SNR) data of Global Navigation Satellite System (GNSS) have been successfully used to robustly derive sea level heights (SLHs). In Taiwan, there are a number of continuously operating GNSS stations, not originally installed for sea level monitoring. They were established in harbors or near coastal regions for monitoring land motion. This study utilizes existing SNR data from three GNSS stations (Kaohsiung, Suao, and TaiCOAST) in Taiwan to compute SLHs with two methods, namely, Lomb–Scargle Periodogram (LSP)-only, and LSP aided with tidal harmonic analysis developed in this study. The results of both methods are compared with co-located or nearby tide gauge records. Due to the poor quality of SNR data, the worst accuracy of SLHs derived from traditional LSP-only method exceeds 1?m at the TaiCOAST station. With our procedure, the standard deviations (STDs) of difference between GNSS-derived SLHs and tide gauge records in Kaohsiung and Suao stations decreased to 10?cm and the results show excellent agreement with tide gauge derived relative sea level records, with STD of differences of 7?cm and correlation coefficient of 0.96. In addition, the absolute GNSS-R sea level trend in Kaohsiung during 2006–2011 agrees well with that derived from satellite altimetry. We conclude that the coastal GNSS stations in Taiwan have the potential of monitoring absolute coastal sea level change accurately when our proposed methodology is used.     

强不确定系统“全系数之和等于1”的实现方法

摘要： 研究强不确定系统“全系数之和等于1”的实现方法，强不确定系统指的是系统的静态增益及其界不完全确知且范围较大.“全系数之和等于1”是吴宏鑫院士20世纪80年代发现的，该原理表明，对于未知连续系统，其离散化系统的系数的和在一定条件下是1.该原理的发现对于解决闭环辨识和自适应控制的瓶颈问题具有关键作用.“全系数之和等于1”是在一定条件下成立的.为了实现系统的“全系数之和等于1”，需要对系统进行一定的变换，以满足所需条件.其中，采用静态增益的标称值的倒数进行输入变换的方法在实际中得到了广泛应用.但是，当系统的不确定性较大时，该变换将带来较大偏差.针对该问题开展了深入研究，明确给出了系统静态增益的不确定性与标称值的比值的关系对于实现“全系数之和等于1”的影响.当不确定性与标称值的比值较小时，可以近似实现“全系数之和等于1”；当比值较大时，进一步给出了通过选取合适的采样周期，近似实现“全系数之和等于1”的方法.本文的研究对于特征模型理论在实际中的应用提供了一定的基础.     

Motion synchronization in a dual redundant HA/EHA system by using a hybrid integrated intelligent control design

This paper presents an integrated fuzzy controller design approach to synchronize a dis-similar redundant actuation system of a hydraulic actuator (HA) and an electro-hydrostatic actu-ator (EHA) with system uncertainties and disturbances. The motion synchronous control system consists of a trajectory generator, an individual position controller for each actuator, and a fuzzy force tracking controller (FFTC) for both actuators. The trajectory generator provides the desired motion dynamics and designing parameters of the trajectory which are taken according to the dynamic characteristics of the EHA. The position controller consists of a feed-forward controller and a fuzzy position tracking controller (FPTC) and acts as a decoupled controller, improving posi-tion tracking performance with the help of the feed-forward controller and the FPTC. The FFTC acts as a coupled controller and takes into account the inherent coupling effect. The simulation results show that the proposed controller not only eliminates initial force fighting by synchronizing the two actuators, but also improves disturbance rejection performance.     

新一代机载悬挂物管理系统需求分析

针对当前悬挂物管理系统的局限性,结合国外先进战机悬挂物管理系统功能,对我国下一代机载悬挂物管理系统需求进行分析,从FC总线技术、开放式系统架构、多挂点混挂技术、悬挂发射装置控制技术、武器数据链技术5个方面进行了具体的描述,为悬挂物管理系统设计指明了方向.     

一种基于EPLL技术的自适应正交解调技术研究

针对过零检测实现的全数字锁相环不仅锁相速度慢, 而且过零点的扰动会 直接影响锁相精度以及适合模拟电路实现的相干解调技术,在数字电路中实现则需要设 计高阶数字低通滤波器,将占用大量数字电路资源并且会显著增加系统功耗等问题,在 设计一种新型全数字锁相环(All-digital Enhanced Phase-lock Loop,EPLL)的基础上,结合自 适应正交解调技术,提出了一种基于EPLL 技术的自适应正交解调技术方案,并对该方 案进行了研究与仿真。仿真得到了满意的结果,验证了基于EPLL 技术的自适应正交解 调技术方案的可行性,并研究验证了算法的参数变化对其性能的影响,为今后算法在数 字系统中的实现以及其在各领域的应用研究奠定了坚实的基础。     

基于Kalman滤波的变体飞行器T-S模糊控制

针对变体飞行器的跟踪控制问题,提出了一种基于Kalman滤波的T-S模糊控制方法。考虑飞行器系统状态不可测,引入惯导数据作为辅助信息,利用Kalman滤波算法融合飞控信息与惯导信息实现状态估计。由于变体飞行器在不同变形结构下气动特性变化较大,为便于控制器设计,采用小扰动线性化方法得到飞行器在不同平衡点处的局部线性模型,并通过状态反馈方法设计局部控制器,局部线性模型和局部控制器通过模糊集和模糊规则聚合成一个连续光滑的全局T-S模糊模型和T-S模糊控制器。通过综合Kalman滤波器与T-S模糊控制器得到一个基于Kalman滤波的T-S模糊控制器。仿真结果表明,该控制器在变形过程中能够实现状态估计,保证飞机的跟踪性能。     

可重复使用热防护材料应用与研究进展

可重复使用热防护系统是为高速重复使用飞行器而发展的关键性技术,涵盖了地球大气环境及非地球大气环境下的弹道式再入、高马赫数巡航等应用场景。根据现有高马赫数飞行器热防护现状,对高马赫数飞行器的主要热防护系统类型、特点和使用场景进行了简要介绍。在此基础上,结合国外里程碑式可重复使用飞行器（X-15、SR-71、航天飞机、X-33、X-37B、Spaceliner等）,梳理了可重复使用热防护材料的应用与研究进展,论述了代表性可重复使用热防护材料的发展、性能、研制进度、特点及应用前景。对国外在可重复使用热防护材料研制中的设计及发展思路,以及所存在的主要问题进行了总结归纳,为可重复使用热防护材料未来的发展提供了思路。     

A null frame for spacetime positioning by means of pulsating sources

We introduce an operational approach to the use of pulsating sources, located at spatial infinity, for defining a relativistic positioning and navigation system, based on the use of four-dimensional bases of null four-vectors, in flat spacetime. As a prototypical case, we show how pulsars can be used to define such a positioning system. The reception of the pulses for a set of different sources whose positions in the sky and periods are assumed to be known allows the determination of the user’s coordinates and spacetime trajectory, in the reference frame where the sources are at rest. We describe our approach in flat Minkowski spacetime, and discuss the validity of this and other approximations we have considered.     

用于直升机现场计量的低频振动校准技术

本文面向直升机健康与使用监测系统(HUMS)的现场计量保障需求,针对其中振动传感器在低频段尚无法实现现场校准的现状,提出了基于直线电机驱动技术的便携式低频振动校准技术方案。该方案利用高精度直线电机构造低频标准振动源,采用稳定性高的石英挠性加速度计作为标准加速度计,具有体积小、精度高、现场环境适应性好的特点,非常适用直升机HUMS的现场计量保障。根据不确定度评估结果,该方案能够实现0.5Hz～20Hz频率范围,0.01m/s~2～20m/s~2加速度范围内不超过1%的校准不确定度(k=2)。     

Shock protection of penetrator-based instrumentation via a sublimation approach

It is often necessary for space-borne instrumentation to cope with substantial levels of shock acceleration both in the initial launch phase, as well as during entry, descent and landing in the case of planetary exploration. Current plans for a new generation of penetrator-based space missions will subject the associated on-board instrumentation to far greater levels of shock, and ways must therefore be found to either ruggedize or else protect any sensitive components during the impact phase. In this paper, we present an innovative method of shock protection that is suited for use in a number of planetary environments, based upon the temporary encapsulation of said components within a waxy solid which may then be sublimated to return the instrument back to its normal operation. We have tested this method experimentally using micromachined silicon suspensions under applied shock loads of up to 15,000g, and found that these were able to survive without incurring damage. Furthermore, quality factor measurements undertaken on these suspensions indicate that their mechanical performance remains unaffected by the encapsulation and subsequent sublimation process.