Adaptive tree bucking using group-guiding of harvesters: A simulation approach

Abstract

The objective of this study was to test harvester group-guiding methods by comparing how the total log output distribution of independent harvesters differs from the total log output distribution of group-guided harvesters. In this simulation study four harvesters worked in their own stands in the same region for an identical target, given by a sawmill. Group-guiding was done by utilizing other harvesters’ bucking outcomes to fulfil the target log distribution better. Harvesters were combined to form a group in an adapting phase where a new price list was formed. For group-guiding, four different price list adapting methods were developed. There were five different simulations: four with adaptation and one reference simulation without adaptation. Apportionment degree and log/pulpwood proportions were calculated to compare the difference between the methods and reference simulation. With group-guiding, by adapting the price list harvesters reached the target distribution better than working independently. The best group-guiding method fulfilled the target distribution almost 9% better than independently working harvesters. However, the pulpwood proportion increased as a result of using the group-guided method.     

Comparison of two harvesting systems for the production of forest biomass from the thinning of Picea abies plantations

Abstract

This study compares two principally different harvesting systems used for the thinning of Norway spruce [Picea abies (L.) Karst.] plantations in the Alps. The first system was whole-tree harvesting (WTH), producing only whole-tree chips for energy purposes. This system minimizes the production costs by simplifying the harvesting process. The other system was cut-to-length (CTL) mechanical harvesting with an excavator-based harvester. This system maximizes value recovery by producing both short sawlogs and quality fuel chips. Trials were conducted on two similar sites in the Dolomites, in northern Italy, and demonstrated that the CTL system resulted in slightly higher harvesting costs, and also higher revenue. The price differences between the different products determine which system offers the best economic results. If the delivered price of sawlogs does not exceed [euro]25 t^?1, WTH and CTL harvesting offer very similar economic performances, and become profitable only if the delivered price of raw chip wood exceeds [euro]40 t^?1. If the delivered price of sawlogs increases to [euro]50 t^?1, the mechanized CTL system always becomes preferable, and it will turn some profits when the price of raw biomass exceeds [euro]35 t^?1. The CTL system is less sensitive to long extraction and transport distances than the WTH system.     

A comparison between excavator-based harvester productivity in coppiced and planted Eucalyptus grandis compartments in KwaZulu-Natal,South Africa

Due to the labour challenges in South Africa, mechanised forestry equipment has increasingly been required to operate in complex forest conditions – such as coppiced Eucalyptus compartments – where they have not operated before. For this reason, harvesters are either used in certain coppiced compartments with uncertain productivity expectations, or harvesters are not used in these compartments due to a lack of productivity knowledge. This research aimed to determine the influence of tree volume and tree form on the productivity of an excavator-based harvester in coppiced regrowth – with either double or single stems, or planted single stems – in Eucalyptus grandis pulpwood compartments. In addition, the stem felled first and the distance between stems were investigated for coppiced double stems. The stem felled first is whichever stem between the two coppiced double stems the harvester grabbed, felled and processed first. The tree volume was determined; thereafter the trees were classified into different form classes. The tree volume and the cycle time were used to determine productivity. The research results showed that planted trees had the highest productivity across all tree sizes, followed by coppiced single stems and then coppiced double stems. When harvesting a 0.2 m³ tree, the mean harvester productivity was 8.7 m³ per productive machine hour (PMH₀) in coppiced double stems, 13.8 m³ per PMH₀ in coppiced single stems and 16.1 m³ per PMH₀ in planted trees. In coppiced double stems the productivity was significantly influenced by the size of the stem felled first. In coppiced double stems the productivity was not significantly influenced by the distance between stems. The productivity for both coppiced single stems and coppiced double stems was significantly influenced by stem form. The poorly formed trees had lower productivity compared to the trees with good form.     

联合收割机前进速度电控系统设计

以联合收割机的电控系统为研究对象,针对其电控系统工作过程中出现的问题,提出了采用模糊自适应控制方法对其进行自适应控制。针对性地设计了基于单片机的自适应控制的速度控制装置,建立了自适应控制参考模型和模糊控制规则,试验表明,此设计完全满足联合收割机的电控系统设计要求,提高了工作效率。     

基于英语语音识别的水稻收割机控制系统设计

农业机械远高于人工的生产效率,可在较短时间内完成目标作业。精准农业是现代农业的发展方向,对农业机械提出了更高要求。语音识别技术可以赋予机器识别和理解人类语音的能力,在农业机械控制上有着广阔的应用前景。为此,基于英语语音识别技术设计了一种水稻收割机的控制系统,以嵌入式微处理芯片为核心,通过隐马尔科夫(HMM)模型算法识别英语语音并以指令的形式输出,对机械的行驶速度、行驶方向和割台高度进行控制。试验表明:系统具有较好的语音识别准确性和实时性,可以降低收割机的操作难度,提高智能化水平。     

收割机控制中的英语语言理解动态领属研究

稻麦类作物的收割工作量大,依靠人工难以顺利完成,研制收割机械具有重要的意义。我国现有的收割机控制水平不高,限制了机械的适用性。英语语言理解是对英语形式的语言信息进行分析,理解表达的意义内容能够用于机械控制。领属是两个英语名词之间的领有和从属关系,若领属关系发生转移,则属于动态领属。为此,研究了英语语言理解动态领属在收割机行驶速度、割台高度和滚筒转速控制中的作用,列举了代表性的动态领属事件。试验结果表明:英语语言理解可以提高收割机的控制精度,降低操作难度。     

国外联合收割机的最新发展趋势

简要介绍了近期国外联合收割机产品的驱动技术、收获附件的发展、脱粒与分离机构、自动控制技术、秸秆切碎机以及操纵安全性等方面的技术发展新动向和新趋势。     

洋葱收获机械化发展现状综述

我国是世界上洋葱产量最大的国家之一,但洋葱收获还是基本依靠人工。随着人口老 龄化和农村劳动力的减少,利用人工收获洋葱不仅成本高而且工作效率低。采用机械化收获可 以减少洋葱收获及其他人工产生的费用,有效地降低劳动强度,提高劳动效率。因此,探索适合 我国的洋葱机械化收获甚至全程机械化技术很要必要。     

基于专利计量的谷物收割机技术竞争态势分析

针对中国谷物收割机技术难以充分满足购买农机的新型农业经营主体使用需求,农产品国际竞争力受限的现状,采用专利计量的方法,兼顾“质”和“量”2个分析视角,综合技术竞争热点分析、创新主体分析和竞争格局分析3个维度,对不同国家及其微观创新主体在谷物收割机领域的竞争态势进行研究。结果表明：1)谷物收割机技术处于成熟期,技术竞争热点在发展过程中有所偏移;2)相较于其他国家以企业为中心的集中式创新格局,中国更倾向于依赖高校、科研机构且专利申请力量较为分散,主要专利申请力量在产出质量上也有所欠缺;3)作为其他专利申请国的重点布局区域,中国对外布局专利数极少;4)不同国家的微观创新主体在技术重点布局上呈现出集中趋势,并且存在广泛的技术联系。总体上,为发展谷物收割机技术,中国应关注技术竞争热点偏移方向、加快企业为中心的创新格局构建,并采取手段保证技术产出质量、提升自身技术影响力。     

沉水植物收获机械推进器的设计研究

本文主要以沉水植物收获机械明轮推进器的连杆机构为研究对象,确定蹼板入、出水角,最小传动角和偏心距的较优组合,从而提高明轮推进效率。