规范状态空间系统辨识方法

因为状态空间模型既包含了未知状态,又包含了未知参数,且二者是非线性乘积关系,使得辨识问题变得复杂.针对这一问题,详细研究了规范状态空间系统的状态与参数联合估计方法.采用交互估计理论,即采用递推方法或迭代方法实现系统状态与参数的交互估计.基本思路是在计算参数估计时,辨识算法信息向量中的未知状态用其估计值代替,然后利用获得的参数估计,设计基于参数估计的状态观测器或基于参数估计的Kalman滤波算法估计系统的状态,二者形成一个交互计算过程(递阶计算过程).沿着这条思路,分别从递推方案和迭代方案,研究和提出了基于状态观测器和基于Kalman滤波状态估计的随机梯度辨识算法、递推最小二乘辨识算法、多新息随机梯度辨识算法、多新息最小二乘辨识算法,以及模型分解的辨识算法,并给出了几个典型算法的计算步骤、流程图和计算量.     

Assessing the suitability of commercial fisheries data for local-scale marine spatial planning in South Africa

This study integrates fisheries logbook data with observer and vessel monitoring system (VMS) data in order to assess the accuracy of reported data and to develop high-resolution spatial data suitable for use in local-scale marine spatial planning analyses. Spatial assessments were conducted on five nearshore commercial fisheries to provide baseline information to inform spatial management and conservation planning in Algoa Bay, South Africa. Clear spatial patterns in the distribution of fishing effort were apparent for the linefishery, chokka-squid and inshore demersal trawl sectors. Observer and VMS data confirmed the broad spatial distribution of resource-use patterns of logbook data. Combining these data sources allowed higher-resolution spatial indices of fishing effort to be developed, which are suitable for systematic spatial planning on a local scale and can be used for future spatial management and conservation.     

A critical examination of worldwide guidelines for minimising the disturbance to marine mammals during seismic surveys

Marine seismic exploration has potentially detrimental effects upon marine life and marine mammals in particular. Potential effects range from disturbance that may lead to displacement from feeding or breeding areas, to auditory damage and potential mortality. Nations including the USA, Canada and Brazil have followed the example set by the United Kingdom by introducing guidelines to minimise acoustic disturbance to marine mammals. This paper describes the mitigation measures central to the guidelines currently in place, and identifies the similarities, differences and deficiencies within them. A need for further review by some nations is identified, with a recommendation that an international standard should be produced, benefiting both the geophysical exploration industry and the conservation community.     

Autocyclic behaviour of fan deltas: an analogue experimental study

Fan deltas are excellent recorders of fan‐building processes because of their high sedimentation rate, particularly in tectonically active settings. Although previous research focuses mainly on allogenic controls, there is clear evidence for autogenically produced storage and release of sediment by flume and numerical modelling that demands further definition of characteristics and significance of autogenically forced facies and stratigraphy. Analogue experiments were performed on fan deltas with constant extrinsic variables (discharge, sediment supply, sea‐level and basin relief) to demonstrate that fan‐delta evolution consists of prominent cyclic alternations of channellized flow and sheet flow. The channellized flow is initiated by slope‐induced scouring and subsequent headward erosion to form a channel that connected with the valley, while the removed sediment is deposited in a rapidly prograding delta lobe. The resulting decrease in channel gradient causes a reduction in flow strength, mouth‐bar formation, flow bifurcation and progressive backfilling of the channel. In the final stage of channel filling, sheet flow coexists for a while with channellized flow (semi‐confined flow), although in cycle 1 this phase of semi‐confined flow was absent. Subsequent autocyclic incisions are very similar in morphology and gradient. However, they erode deeper into the delta plain and, as a result, take more time to backfill. The duration of the semi‐confined flow increases with each subsequent cycle. During the period of sheet flow, the delta plain aggrades up to the ‘critical’ gradient required for the initiation of autocyclic incision. This critical gradient is dependent on the sediment transport capacity, defined by the input conditions. These autogenic cycles of erosion and aggradation confirm earlier findings that storage and release of sediment and associated slope variation play an important role in fan‐delta evolution. The erosional surfaces produced by the autocyclic incisions are well‐preserved by the backfilling process in the deposits of the fan deltas. These erosional surfaces can easily be misinterpreted as climate, sea‐level or tectonically produced bounding surfaces.     

基于角加速度的航空遥感平台稳定控制研究

针对航空遥感用三轴惯性稳定平台由于质量不平衡、摩擦等干扰力矩影响,易导致稳定精度下降,难以满足高分辨率载荷成像要求的问题,文章提出一种基于角加速度信息融合估计的航空遥感惯性稳定平台干扰观测器:在控制系统稳定回路中,基于速率陀螺测得框架相对惯性空间的角速度信息,同时采用卡尔曼滤波与跟踪-微分器对框架角加速度信息进行估计,并进行融合获得更为精确的角加速度输出,该角加速度作为干扰观测器的输入以获得补偿电流,通过将补偿电流加到电流环的输入端实现对干扰力矩的补偿。实验结果表明该方法能有效抑制干扰力矩,提高航空遥感惯性稳定平台的稳定精度。     

Path following control of fully-actuated autonomous underwater vehicle in presence of fast-varying disturbances

This paper presents an improved active disturbances rejecter control (ADRC) for path following control of autonomous underwater vehicles under significant fast-varying disturbances caused by waves and sea currents. Two significant and efficient improvements are introduced to the traditional ADRC in order to accomplish this task. First, a generalized ESO (GESO) and Harmonic ESO (HESO) were designed to achieve a high disturbances estimation quality. Secondly, two AUV path following controllers based on ADRC-GESO and ADRC-HESO were designed to ensure a high performance tracking in presence of periodic-type disturbances. Finally, numerical simulations were performed and the obtained results showed very significant enhancements of robustness and tracking accuracy by the proposed methods compared to conventional ADRC.     

Comparative review of marine mammal guidance implemented during naval exercises

This article reviews the types and effectiveness of marine mammal mitigation measures used during some naval activities worldwide. The three main standard methods used to mitigate the potential impacts of naval sonar sound on marine mammals are (1) time/area planning (of exercises/active sonar use) to avoid marine mammals; (2) implementation of operational procedures (e.g. ‘soft start’ - where sound levels are gradually increased over time); and (3) monitoring of animals for the purpose of maintaining an ‘exclusion zone’ around the sound source. Suggestions towards a minimum worldwide mitigation standard are made.     

水下机器人-机械臂系统的滑模自抗扰控制

针对水下机器人机械臂系统的强耦合、强非线性、复杂海洋多源干扰等因素影响,提出了滑模自抗扰控制器,将复杂系统模型转变为简单的积分串联系统,将内部参数不确定性、测量误差、建模误差和海洋多源干扰等扰动归结为总扰动,并采用线性扩张观测器对其进行估计并抵消。利用滑模控制器提高系统对参数摄动的不敏感性,增强控制系统的抗干扰性能,通过李雅普诺夫理论分析了控制系统的有界稳定性。仿真结果表明滑模自抗扰与传统滑模控制和自抗扰控制相比,能使水下机器人机械臂实现更好的轨迹跟踪,且系统具有更好的抗干扰能力。     

非线性微分-代数子系统的初始化高增益观测器设计

针对一类大系统中的非线性微分-代数子系统,研究其状态观测问题,提出了一种初始化高增益观测器设计方案.首先,通过一个非线性微分同胚变换,实现了系统的等价变换;然后针对等价系统,给出了初始化状态观测器设计,使得观测误差是指数收敛的;最后,给出一个数值仿真算例.仿真结果验证了该方法的有效性.