一类不确定广义系统的鲁棒可靠H∞控制

针对一类存在参数不确定性、外部扰动的广义系统,讨论了系统控制器失效情形下鲁棒可靠H∞控制问题,通过求解一组矩阵不等式获得了使系统鲁棒可靠H∞控制问题可解的充分条件和控制器的形式.     

一类含不确定因素的非线性系统鲁棒跟踪

讨论了在木材工业计算机集成制造系统中抽象出的一类含不确定因素的非线性系统的鲁棒渐进跟踪问题，其中的未知参变量是时变的，且取值于一紧集Ω上。当未知参变量以线性和非线性形式出现时。给出了鲁棒渐进跟踪问题的自校正控制器的设计。     

非线性系统鲁棒渐进跟踪

本文讨论了在木材工业计算机集成制造系统中，抽象出的一类含不确定因素的非线性系统的鲁棒渐进跟踪问题，其中的未知参变量是时变的，且取值于一紧集Ω上。当未知参变量以线性和非线性形式出现时，给出了静态自校正控制器的设计。     

一类非线性系统的鲁棒自校控制器设计

本文讨论了在木材工业计算机集成制造系统中，抽象出的一类含不确定因素的非线性系统的鲁棒渐进跟踪问题，其中的未知参变量是时变的，且取位于一聚集Ω上。当未知参变量以线性和非线性形式出现时，给出了静态自校正控制器的设计。     

基于无刷直流电机EPS H∞控制的研究

为验证鲁棒控制理论是否适用于无刷直流电机控制的EPS系统,本文针对EPS系统非线性多输入多输出的系统特点,在应用无刷直流电机的基础上,采用H∞控制方法设计其控制器。首先根据EPS系统动力学模型,进行不确定性分析;然后建立EPS系统的状态空间方程和增广被控对象矩阵,将其描述成标准H∞问题求解;利用H∞方法极小化系统中各种干扰对被控输出的不确定性影响。计算机运算结果表明：应用鲁棒控制理论所设计的EPS控制器有良好的鲁棒性能。     

基于自适应遗传算法整定的刨花板热压系统PID控制

刨花板热压控制系统存在着迟滞、非线性、时变性以及模型参数的不确定性,针对此问题,提出了基于遗传算法的自适应PID智能控制策略,通过自适应控制与遗传算法相结合,实现对PID参数的在线自整定,使其具有更大的灵活性和适应性,完善了PID控制器的性能。在Matlab7.0环境下进行仿真,结果表明:与常规PID控制器相比较,该控制器明显地提高了热压位置伺服控制系统的动态性能和静态性能,抗干扰的能力也明显增强,兼具更好的鲁棒性能。     

基于Q参数化方法的水轮发电机组鲁棒控制器设计

提出一种新的水轮发电机组控制器设计方法,并将其应用到一个高阶、非最小相位的水轮发电机组中。该方法的主要特点是被控对象的所有稳定控制器均可用一个独立的Q参数来描述。以我国某水电站的真实数据对所设计的控制器进行计算机仿真。仿真结果表明：在系统参数发生变化的情况下,在参考频率和负载发生改变时,提出的控制策略都能保证水轮机调节系统获得鲁棒稳定性和良好的动态性能。     

基于改进分数阶积分滑模的MDF电液伺服系统自抗扰控制北大核心

提出一种基于改进分数阶积分滑模的中密度纤维板(MDF)连续热压电液伺服系统自抗扰控制策略,以消除复杂外干扰和系统未建模动态对中密度纤维板板坯厚度的影响。利用扩张状态观测器(Extended State Observer,ESO),将系统未建模动态和复合干扰扩张成一个新的状态,通过前馈通道返回控制器进行补偿,以保证系统的稳定。将分数阶积分滑模控制(Fractional-Order Integration Sliding Mode Control,FOISMC)引入自抗扰控制(Active Disturbance Rejection Control,ADRC),通过建立滑模面与非线性鲁棒项,提高系统的鲁棒性与抗扰动能力;同时构造分数阶积分滑模切换项减少抖振的影响,使系统对高频未建模动态失稳具有更好的动态性能。仿真结果表明,所设计的控制器能够使MDF获得良好的板厚控制精度。     

免疫PID控制器在木材干燥控制系统中的应用研究

通过免疫系统与控制系统类比,借鉴免疫响应调节机理,提出免疫PID控制器的设计方法,并讨论了免疫PID控制器与传统PID的结合方式及其免疫参数在调节过程中的作用.对木材干燥系统进行了仿真研究,结果表明,当工况变化和存在扰动时,免疫PID控制器也能获得满意的效果.     

基于ACS进化算法的控制规则最优型模糊PID控制器设计

以ACS(Ant colony system)进化算法和模糊逻辑控制为基础,提出了一种新的可适应各种不同控制对象的通用型最优模糊PID控制器的设计方法.这种方法的核心是以ITAE中性能准则为目标函数,采用ACS算法去调整和优化模糊PID控制器的量化因子和比例因子,以获得最优的控制规则,进而获得最优的模糊PID控制器.所设计的这种控制器称为Fuzzy-ACS PID控制器.对四种典型的控制对象所进行的计算机仿真实验表明,Fuzzy-ACS PID控制器具有良好的控制性能和鲁棒性能.与采用微分进化算法、实值编码遗传算以及模拟退火算法设计的其它三种最优PID控制器相比,Fuzzy-ACS PID控制器具有最小的ITAE性能指标值,其动态性能和稳态性能更好.此外,计算机仿真实验的结果还证实,ACS算法在搜寻最优量化因子和比例因子时,收敛速度快,解的波动范围小,动态收敛性能好.     

Conceptual Development of a Eucalypt Canopy Condition Index Using High Resolution Spatial and Spectral Remote Sensing Imagery

Abstract

Recent advances in remote sensing technologies and image analysis provide a realistic opportunity to develop a reliable, robust indicator of forest health for Australian eucalypt forests. Using these technologies we present the development of a conceptual framework for a new indicator based on eucalypt canopy condition. The indicator, termed the Eucalypt Canopy Condition Index (ECCI), is derived from an assumed hierarchy of canopy decline symptoms, both physiological and structural. Our objective is to identify and discuss possible combinations of spectral, radiometric and spatial (scale) features from remotely sensed data that theoretically and practically correlate with each hierarchical phase of severity in canopy decline. Some of the issues associated with the development and application of the ECCI are discussed, and finally, how the ECCI could be integrated into existing or future operational systems is illustrated.     

Adopting robust decision-making to forest management under climate change

Key message

Multi-objective robust decision making is a promising decision-making method in forest management under climate change as it adequately considers deep uncertainties and handles the long-term, inflexible, and multi-objective character of decisions. This paper provides guidance for application and recommendation on the design.

Context

Recent studies have promoted the application of robust decision-making approaches to adequately consider deep uncertainties in natural resource management. Yet, applications have until now hardly addressed the forest management context.

Aims

This paper seeks to (i) assemble different definitions of uncertainty and draw recommendation to deal with the different levels in decision making, (ii) outline those applications that adequately deal with deep uncertainty, and (iii) systematically review the applications to natural resources management in order to (iv) propose adoption in forest management.

Methods

We conducted a systematic literature review of robust decision-making approaches and their applications in natural resource management. Different levels of uncertainty were categorized depending on available knowledge in order to provide recommendations on dealing with deep uncertainty. Robust decision-making approaches and their applications to natural resources management were evaluated based on different analysis steps. A simplified application to a hypothetical tree species selection problem illustrates that distinct robustness formulations may lead to different conclusions. Finally, robust decision-making applications to forest management under climate change uncertainty were evaluated and recommendations drawn.

Results

Deep uncertainty is not adequately considered in the forest management literature. Yet, the comparison of robust decision-making approaches and their applications to natural resource management provide guidance on applying robust decision making in forest management regarding decision contexts, decision variables, robustness metrics, and how uncertainty is depicted.

Conclusion

As forest management is characterized by long decision horizons, inflexible systems, and multiple objectives, and is subject to deeply uncertain climate change, the application of a robust decision-making framework using a global, so-called satisficing robustness metric is recommended. Further recommendations are distinguished depending on the decision context.

     

The behaviour of the species mingling index<Emphasis Type="Italic"> M</Emphasis><Subscript><Emphasis Type="Italic">sp</Emphasis></Subscript> in relation to species dominance and dispersion

Ecosystem conservation plays an increasingly important role in forest management. The value for such conservation has been directly linked to high diversity of species and structure within systems. In the past, forestry inventory practices have concentrated on aspects that were primarily required for timber management. Now, however, much interest has arisen in measures that will indicate higher or lower diversity. The interspersion of trees of different species reflects diversity at a local level and may serve as an important indicator for the simplification of a forest or woodland system. This article shows that the mingling index M_sp is robust in describing the spatial dispersion of plants; some guidelines for interpreting M_sp are provided.     

Use of Smartphone Technology for Small-Scale Silviculture: A Test of Low-Cost Technology in Eastern Ontario

This study examined the potential use of low-cost consumer-grade smartphone technology to perform and improve field data collection in support of small-scale forest management. This proof-of-concept exercise for day-to-day forester operations focused on the effectiveness of the smartphone platform (form factor and functionality) rather than any particular smartphone software. An electronic data acquisition system for a smartphone was developed that combined a simple custom timber cruise application and mobile commercial mapping software to record and process forest stand and geospatial information, and transfer these to a small-scale operator’s existing desktop geographic information system. Workflow efficiency and system performance of the smartphone system was then measured and compared with paper-based methods presently being used in the managed forest. The smartphone greatly increased workflow efficiency by reducing data transfer and processing times, and eliminated the need to carry separate global positioning system (GPS) device, map, paper forms and digital camera. The GPS accuracy of the smartphone was more than adequate to meet operational requirements, and provided a capacity to map forest features on an ad hoc basis that is not easily done through the paper-based process. However, initial data entry using the smartphone takes longer than using paper-based notes, there is a greater chance of data entry error through inadvertent keypad touches on the small screen, and there is the potential for a device malfunction. Overall, it is concluded that smartphones offer an opportunity for small-scale operators to create electronic field data management systems that are affordable, operationally robust, compatible with existing management systems, capable of increasing data management efficiency and, in particular, expanding the types of data that can be collected during silvicultural operations.     

Some Key Issues Concerning Current Poplar Production and Future Marketing in the United Kingdom

This paper presents survey evidence concerning the UK poplar (Populus spp.) plantation with particular emphasis applied to production systems, markets, and trends. Our results are based on primary data and information that were sourced from a survey of poplar growers in summer 2000. The results show a growing interest in planting poplars throughout the 1990s. Between 1989 and 1998, poplar plantations were established mainly on land previously used for arable purposes and pastureland, and to a lesser extent, on other lands. Growers perceive that a robust value-added market for poplar products may be developed providing poplar cultivars are properly managed. The most common interamericana clones planted are the varieties Beaupré and Boelare. Specifically, plantation sites are currently using the polyclonal system and are growing on sites that have a diversity (mixture) of other forest species. Loss of resistance to disease organisms (e.g., rust fungi of the genus Melampsora) appears to be one of the main current threats to successful poplar exploitation.     

Price integration for domestic and imported sawlogs and pulpwood in Finland: an update

This paper provides an analysis on the integration of prices for imported coniferous pulpwood and sawlogs, and respective domestic stumpage prices in the Finnish wood market. Eight real price series were investigated during 2002–2014 using monthly observations. The bounds testing approach by Pesaran et al. [(2001) Bounds testing approaches to the analysis of level relationships. J Appl Econom. 16: 289–326. doi:10.1002/jae.616], indicates there are long-run relationships between prices of domestic and imported wood. For more detailed information, the vector error correction model (VECM) approach was used. Estimation of a system with all eight prices with interpretable results did not succeed; therefore, we estimated models for prices of sawlogs and for pulpwood separately. For sawlogs, two co-integrating vectors, one for pine and one for spruce, were found. For pulpwood prices, one co-integrating vector was identified. The estimated VECMs confirm the results of bounds testing approach, suggesting that causation in the Finnish wood market runs from domestic prices to prices of imported wood. We conclude that prices of domestic and imported coniferous logs and pulpwood are closely connected. The question of full integration remains open, as border prices and stumpage prices by definition differ, at least, by logging and transportation costs.     

Hydraulic responses to environmental perturbations in Tsuga canadensis and Betula lenta

Eastern hemlock (Tsuga canadensis (L). Carr.) is a late-successional species found across the northeastern United States of America that is currently threatened by the exotic pest, hemlock woolly adelgid (Adelges tsugae Annand). Because whole-tree physiological characteristics may scale to influence ecosystem processes, we considered whole-tree hydraulic controls in eastern hemlock and the replacement species black birch (Betula lenta L.). Through a series of misting perturbations, whole-tree resistances (R), capacitances (C) and time constants (tau) were determined from time series sap flux data in eastern hemlock and black birch. Black birch trees responded more rapidly to environmental perturbations than eastern hemlock. Utilizing the step function after applied treatments, whole-tree tau ranged between 9.4 and 24.8 min in eastern hemlock trees compared with 5.9 to 10.5 min in black birch. Species was not a significant predictor of R or C when controlling for tree size. In both species, R decreased with sapwood area and C increased. Our tau results indicate that the loss and replacement of eastern hemlock by black birch will decrease the lag between transpiration and absorption of water from the soil and potentially alter the diurnal pattern of carbon and water uptake.     

四倍体刺槐组培瓶苗生根培养及生根苗移栽研究

四倍体刺槐是从韩国和匈牙利引进的大叶速生刺槐人工诱变的四倍体树种，具有速生、叶大、条粗、枝密、抗性强等特点，生长速度是普通刺槐的2倍以上。利用不同质量的组培瓶苗为材料，选取最佳生根状态的组培瓶苗进行生根培养和生根苗移栽试验，成功地筛选出生根培养基激素和生根苗移栽基质的最佳组合，建立了四倍体刺槐的再生系统。     

地震扰动区生态修复的概念与四拗

分析提出地震扰动区生态修复的概念,就是在重力侵蚀造成的植被破损处打＂补丁＂。进而分析了植被重建的土、水、树木种苗和当地人四要素的基本特性,分别为土碎、水漫、籽拗、羊狠,均具有执拗特质,合称＂四拗＂,是生态修复的难点所在,均具成败与否的决定性作用。