基于Pro/ENGINEER的伐木机起重臂虚拟样机设计

起重臂作为伐木机的重要工作装置,决定了伐木机的作业能力与作业范围。本研究利用Pro/ENGINEER软件强大的三维实体建模功能和机构运动仿真与分析功能,实现伐木机起重臂从三维模型设计、建模、装配到运动仿真的全过程,完成伐木机起重臂虚拟样机的设计。由运动仿真结果,得出伐木机起重臂作业范围及其最大作业半径(带伐木头)为9 435mm,最大作业半径(不带伐木头)为7 349mm。通过静态与动态干涉检查,最终结果无干涉现象发生,表明设计可靠。整个虚拟样机设计研究过程,有效地避免了实体样机研发过程存在的缺陷,明显缩短产品的研发时间,有效地降低设计成本。     

钻式伐木机的生产现场试验

近几年,日本先后研制了几种自走式采伐机。这些采伐机均为液压剪式。其最大缺点是锯口劈裂严重,木材损失很大。尽管多次组织技术力量改进,但劈裂问题至今尚未解决。于是,开始研究不同于液压剪式的新型采伐装置。1976年研制成功“钻式伐木机”,由沼田营林署进行现场生产试验,考察其作业性能、安全性能及需改进之点。试验报告如下:     

联合采伐机在桉树采伐上的成本分析

桉树是广西主要速生丰产造林树种之一,造林面积已经达到165万hm~2,"十二五"期末将达到200万hm~2,年生产木材3 000万m~3,如此大的采伐量为伐木工作提出了新要求。文章从联合采伐机和油锯的伐木成本进行分析,认为利用联合采伐机可以节约油锯伐木成本的43%,能大大的降低劳动强度,显著提高劳动效率、促进林业现代化建设。     

伐木剪Ⅴ型刀片对树木的劈裂影响

在采伐作业中,劳动成本的提高促进了工业对机械化投资的加强.例如,在采伐方面已经采用在拖拉机上装置伐木剪取代链锯伐木,因为这样能较快地使他们自己更好的适应自动化. 在采伐中一个主要目标是减少伐木作业中,特别是在严寒季节里产生的大量木材劈裂损伤现象;另一个考虑是在设计轻型伐木剪装置的允许设计范围内,减少切削刀.在     

联合采育作业精确进料控制系统开发与测试

为提高林木联合采育机的工作效率,开发测试一种进料辊精准进料控制系统,该控制系统是基于PID控制算法研究林木联合采育机作业机头自动精准进料的控制系统。本文从林木联合采育机作业机头自动精确进料的控制需求出发,结合其控制过程,研究基于增量式PID控制算法在自动精确进料控制上的应用。试验中针对不同的P、I和D参数,分组对进料结果进行了分析,随后提出改进的多段自适应PID控制算法。实验结果表明,通过改进的PID控制算法可以实现林木联合采育机作业机头进料辊自动精确进料,其误差在允许范围之内。此方法适应性强,能够有效提升采育机的作业效率,但仍需在后期作业中,针对不同树种树径、造材长度等特征数据,进行进一步优化。     

自走式联合采伐机

法国制造的新型Sifer204自走式联合采伐机,具有伐木、打枝和造材功能。204型机以一台70—kw Deutz柴油机为动力,有一个850公斤的工作头,打枝直径6～35厘米,伐木直径40厘米。附有电子长度测量装置。疏伐作业生产力每小时平均处理2米长树木60～120株。另一种70～kw 644自走式加工机,是一种小型机械,主要用于30厘米直径木的疏伐作业;725型伐木、打捆机     

基于ST2和ADAMS的圆锯机进料夹紧机构动态仿真与优化

进料夹紧机构是双工位截段圆锯机的关键组成部分,在工作过程中由于工作频繁致使其非常容易损坏.采用ST2建立三维模型导入虚拟样机仿真软件ADAMS对进料夹紧机构进行仿真,以确定进料夹紧机构中弹簧的扭矩及变形曲线,并对弹簧进行优化选择,分析其受力状态及使用寿命,为设计合理的进料夹紧机构提供理论依据.     

虚拟样机技术在联合采伐机设计中的应用研究

介绍了虚拟样机技术的内涵、特点及其应用,并结合联合采伐机工作臂的设计,指出了虚拟样机技术及其动态仿真在机械设计中的优越性,探讨了虚拟样机技术在林业机械设计中的发展趋势。     

日本小型伐木造材联合机性能

林野厅研制成功小型伐木造材联合机。这种联合机是在轮式拖拉机上安装伐木和造材装置,这样,一台机械即可以完成立木的采伐和造材。联合机采伐最大树木的直径为40厘米,这就解决了用油锯采伐的振动问题,同时,由于伐木装置为液压链锯,所以不存在液压剪伐木的木材劈裂问题。     

基于Hypermesh联合LS-DYNA的小径木采伐机构动力学分析

介绍了一种新型履带式小径木择伐采伐机,采用Solid Works软件对该机进行三维建模,并进行了各部件的结构设计,如推倒机构、切口铣削机构、横切机构等。基于有限元方法,利用Hypermesh联合LS-DYNA对综合采伐机的主要工作部件横切机构的双圆锯片及推倒机构进行了工作过程的动力学分析显示。结果表明,在双圆锯片转速为5 000 r/min、进给速度为0.5 km/h的工况下,小径木最大等效应力发生在最先锯切处,其值为2.854 MPa;推倒机构弧形筋板接触应力的最大值为34.91 MPa,此时弹簧钢丝位移为58.1 mm。在此工况下可使小径木的倒向得到有效控制,符合该小径木综采机的工况需求。     

Fibre losses during debranching and debarking of Eucalyptus pulp logs using a single-grip harvester

Mechanised harvesting operations are becoming more prevalent in South Africa, with the realisation that motor- manual and manual harvesting operations pose significant health and safety risks to workers. However, the potential damage caused by single-grip harvester feed rollers and delimbing knives on the log surface during debranching and debarking of eucalypts pulp logs may negatively affect fibre recovery as opposed to manually debarked logs, which show little or no log surface damage. Compared with manual debarking, this study investi- gated the influence of two mechanised debarking treatments on wood fibre loss on eucalypt log assortments debarked by harvester head feed rollers and delimbing knives. The two mechanised debarking treatments consisted of three and five feed roller passes along the stem surface. In addition to quantifying the magnitude of this fibre loss, a financial evaluation was done to calculate the value of these losses. The three- and five-pass debarking treatments caused significant fibre losses of 1.425 green tonnes per hectare (gt ha?1) and 2.275 gt ha?1, respec- tively, as opposed to manually debarked logs, which produced no fibre losses. Wood fibre losses in terms of total potential (or available) wood mass for three- and five-pass mechanically debarked trees were 1.06% and 1.70%, respectively. These represent a fibre value loss of R441.75 ha?1 and R705.25 ha?1 for three- and five-pass operations, respectively. For the 6.48 million gt y?1 currently mechanically debarked for the South African pulp and paper industry, this equates to fibre value losses of R21.36 million and R34.10 million annually for three- and five-pass operations, respectively.     

The impact of mechanical log surface damage on chip size uniformity during debranching and debarking Eucalyptus pulpwood logs using a single-grip harvester

Mechanised harvesting operations are becoming more prevalent in South Africa with the realisation that motormanual and manual harvesting operations pose significant health and safety risks to workers. The damage inflicted by single-grip harvester feed rollers and delimbing knives on log surfaces during debranching and debarking eucalypts, may affect eventual chip quality. Chip quality influences pulp quality and recovery in the kraft pulping process. This study investigates the influence of two mechanised debranching and debarking treatments on Eucalyptus pulp logs (threeand five-feed roller passes along the stem surface) by feed rollers and delimbing knives on chip uniformity, size and purity. The two mechanised treatments to three log classes (base, middle and top logs) were compared with chips produced from manually debarked logs. Manually debarked logs produced significantly less undesirable-sized chips than both three and five-pass processed logs. The volume of undesirablesized chips produced during chipping also increased with decreasing log size. Manually debarked logs produced chips with significantly less bark than three-pass-processed logs (0.008% vs 0.062%), and five-pass-processed logs produced chips with significantly less bark than three-pass-processed logs (0.018% vs 0.062%). Middle logs also produced chips with significantly less bark than base logs (0.016% vs 0.056%), and top logs produced chips with significantly less bark than base logs (0.017% vs 0.056%). In all cases the bark content on logs was considerably less than the maximum of 1.0% generally specified by kraft pulp mills.     

The impact of log surface damage caused by harvester Eucalyptus debarking on pulp value recovery

Mechanised harvesting operations are growing in popularity in South Africa, as motor-manual and manual harvesting operations pose significant health and safety risks to workers. Potential damage inflicted by single-grip harvester feed rollers and delimbing knives on the log surface during debranching and debarking of eucalypts may affect chip size distributions during chip production. Chip size is important as it influences pulp quality and recovery in the kraft pulping process. The study investigated the influence of two mechanised debarking treatments in eucalypts (three feed roller passes and five feed roller passes along the stem surface) with feed-roller-induced log surface damage on pulp value recovery. The two mechanised treatments were compared against chips produced from manually debarked logs with no surface damage. In addition, the effect of two log drying periods (one week and two weeks) and three log classes (base, middle and top logs) on chip quality were also analysed. An economic evaluation was conducted to quantify potential recoverable pulp value losses associated with debarking treatments and log drying periods. Logs subject to manual debarking produced significantly less undesired sized chips than both three-pass and five-pass mechanically debarked logs and therefore had significantly greater pulp value recovery. Mechanically debarked logs had a projected pulp value recovery of R62, R86 and R123 less per bone dry tonne of chips produced from base, middle and top logs, respectively, when compared with manually debarked logs with no log surface damage after a one-week log drying period. Mechanically debarked logs also had a projected pulp value recovery of R77, R40 and R59 less per bone dry tonne of chips produced from base, middle and top logs, respectively, when compared with manually debarked logs with no log surface damage after a two-week log drying period. Logs dried for two weeks also produced significantly less under-sized chips than chips produced from one-week-dried logs and therefore had greater pulp value recovery. However, two-week-dried logs produced wood chips with significantly more over-thick chips than logs dried for one week. The volume of undesirable-sized chips produced during chipping increased with decreasing log size.     

YP2.0-A遥控跑车减速机构动态特性分析与仿真

以YP2.0-A遥控跑车的减速机构为研究对象,应用Solidworks软件对增速箱齿轮系统进行总体参数化建模。通过合理假设,简化复杂机构并对各零部件进行精确装配。合理设置仿真参数,结合动力学软件ADAMS领先的“功能化数字样机”技术,对遥控跑车传动机构的齿轮实体造型、数学建模、动力学及其他动态特性进行仿真分析。采用这样的仿真分析方法可以从根本上解决传统设计模式中的漏洞,避免多次试制物理样机的同时也提高了设计质量。     

Productivity and cost of whole‑tree harvesting without debarking in a Eucalyptus nitens plantation in Tasmania,Australia

There is increasing interest worldwide in using tree harvesting biomass as an energy source. Bark retained on logs is commonly used as an energy source, but is generally removed from eucalypt logs during harvest. In order to evaluate the potential use of eucalypt bark as fuel, there is a need for information on the productivity and cost implications of retaining eucalypt bark during harvest operations. The study examined the impact of retaining bark on logs on the productivity and costs of a whole?tree to roadside harvesting system in a short?rotation Eucalyptus nitens plantation in Australia being harvested for pulp logs. Trees were felled and bunched with a feller?buncher in spring, then left infield for four weeks to promote bark adhesion and reduce bark loss. A skidder extracted the trees to roadside where a processor processed them to predominantly 10?m logs. Machine productivities were calculated from estimated tree and log volumes and cycle times recorded from video recordings. The feller?buncher's productivity (65 m3 PMH₀^?1) was less than expected as it appeared to be underpowered to handle the larger trees on the study site. The skidder's productivity (56 m3 PMH₀^?1) was comparable to those reported in studies under similar conditions and with bark retained. The roadside processor's productivity (25 m3 PMH₀^?1) was lower than expected. This was believed to result from the operator separately stacking 10?m and 5?m logs, and the lower feed speed resulting from slippage due to the reduced feed roller pressure used in the study to reduce bark loss. Future research could identify feed rollers that increase feed speed while retaining bark. Harvest system costs (AUD18 GMt^?1) were similar to those reported for a eucalypt roadside processing trial where bark was removed. These results suggest that retaining bark on the logs at roadside did not affect the harvesting system's productivity or costs.     

基于联合仿真的林业采育作业模拟系统研究

为解决大型林业装备操作训练复杂的问题,优化驾驶与作业,提高森林资源利用率,本文提出基于分布式系统,对采育作业环境进行视景模拟的虚拟现实作业操作模拟器。系统利用虚拟现实软件Unity3D系统,能够模拟车辆行驶与工作的动力学模型,实时运动仿真包括底盘系统与地面的交互作用,机械臂作业运动以及伐木头作业操作运动,使操作人员能够更快地适应熟悉驾驶和采育作业,减少安全隐患和装备损耗,提高装备作业安全性及效率。     

一种等高齿螺旋锥齿轮齿面方程的简化方法

本文依据结构特性,提出了一种简化等高齿螺旋锥齿轮齿面方程的方法,大幅度简化了齿轮参数化设计过程。实验验证,该简化方法无不良影响,方便实用。     

An investigation of the influence of harvesting practice on the development of blue-stain in Corsican pine logs

In September 1991, at Thetford, East Anglia and at Inverness,north-east Scotland, a comparison was initiated between blue-staindevelopment in Corsican pine logs from trees felled and processedby harvesting machine and similar logs from trees felled andtrimmed out by chain-saw. Blue-stain was assessed in discs from batches of logs destructivelysampled at 2-week intervals after felling. At the more southerlysite of Thetford, stain was first observed after 4 weeks. Themaximum recorded area was 10 per cent of the wood surface ina sample analysed after 10weeks. In contrast, stain never exceeded,1.1 per cent of the wood surface at Inverness. Amounts of stainwere significantly greater with machine-harvested logs thanwith chainsaw-harvested logs and were correlated with the amountof bark removed or loosened during harvesting. The use of spikedrollers resulted in more stain than did the use of rubber rollers. The fungi isolated from stained wood included Sphaeropsis sapinea,Potebniamyces coniferarum and Ceratocystis coerulescens. Theseare species adapted to the colonization of wood exposed throughdamage to the overlying bark     

拨簧-吸送式沙棘果实采收机的研制

在沙棘果实采收作业中通常采用的传统剪枝法对沙棘树木破坏极大,沙棘采收已成为沙棘产业发展的瓶颈。介绍一种根据沙棘生物学特性而研制的用于沙棘果实采收的机器,分析其工作原理、配套动力选型、主要结构及创新点,并进行了生产试验。     

新型自走式割灌机结构分析

介绍了一种新型自走式割灌机.该机由行走、割灌、驾驶台及排障四个核心部分组成,可以锯切直径为10～80 mm的灌木.本文对其行走部分和驾驶台进行了系统介绍,并对其主要部件进行了参数设计.