Design of Compliant Straight-line Mechanisms Using Flexural Joints

Straight-line compliant mechanisms are important building blocks to design a linear-motion stage, which is very useful in precision applications. However, only a few configurations of straight-line compliant mechanisms are applicable. To construct more kinds of them, an approach to design large-displacement straight-line flexural mechanisms with rotational flexural joints is proposed, which is based on a viewpoint that the straight-line motion is regarded as a compromise of rigid and compliant parasitic motion of a rotational flexural joint. An analytical design method based on the Taylor series expansion is proposed to quickly obtain an approximate solution. To illustrate and verify the proposed method, two kinds of flexural joints, cross-axis hinge and leaf-type isosceles-trapezoidal flexural（LITF） pivot are used to reconstruct straight-line flexural mechanisms. Their performances are obtained by analytic and FEA method respectively. The comparisons of the results show the accuracy of the approach. Both examples show that the proposed approach can convert a large-deflection flexural joint into approximate straight-line mechanism with a high linearity that is higher than 5 000 within 5 man displacement. This can lead to a new way to design, analyze or optimize straight-line flexure mechanisms.

Study on Numerical Comparison Method of Four-bar Straight-line Guidance Mechanism

In order to solve four-bar straight-line guidance mechanism synthesis problem for the arbitrarily given straight-line’s"angle requirement"and"point-position requirement",a numerical comparison synthesis method for single and double straight-line guidance mechanism is presented,which is convenient to realize by computer program.The basic idea of this method is:to select a four-bar linkage whose relative bar length of crank is 1 as a basic four-bar linkage.Then the other three relative bars’length is changed,and a lot of basic four-bar linkage can be obtained.There are many single and double ball-points of each basic four-bar linkage.With the motion of a basic four-bar linkage,there is straight-line segment of each Ball-point’s path.The data of these basic four-bar linkages is saved to a database.When designing a four-bar straight-line guidance mechanism,the design data is compared with the data in database and a satisfactory four-bar linkage can be obtained.The method effectively solves the straight-line guidance mechanism synthesis problem.

The Straight-Line Depreciation Method Used by Selected Companies and Educational Institutions in the Philippines

The straight-line method in computing for depreciation expense is the prevailing method used in the Philippines. This paper aims to determine the rationale behind the use of this method. The objective of the study is to determine the length of time within which the depreciation method is used, reasons in using the method, the rate of depreciation used by the companies, and the effects of the depreciation expense on their operating expenses. It also determines if the companies＇ decisions to use the straight-line method are influenced by the factors mentioned by Reynolds （196 I）----expected amount of services over the life of assets, the amount and timing of operating costs, the decline in the physical efficiency of the assets, and the rate of return--and if they considered capital investments and tax reduction in using this method. The study shows that companies and educational institutions use the straight-line method of computing depreciation expenses, because it is easy to use in computing the depreciation expenses, in comparing with previous years＇ computations, and in keeping track of the expenses. It is also convenient for tax administration and financial reporting. The rate of depreciation used varies, because the companies and educational institutions use their past experiences in determining the life of fixed assets. The percentage of depreciation to the operating expenses also varies. The companies and educational institutions adhered to the factors mentioned by Reynolds （1961） in choosing the straight-line method of depreciation. The companies did not consider reduction of tax in using the straight-line method.

Document Clustering with Evolutionary Systems through Straight-Line Programs “<i>slp</i>”

In this paper, we show a clustering method supported on evolutionary algorithms with the paradigm of linear genetic programming. “The Straight-Line Programs (slp)”, which uses a data structure which will be useful to represent collections of documents. This data structure can be seen as a linear representation of programs, as well as representations in the form of graphs. It has been used as a theoretical model in Computer Algebra, and our purpose is to reuse it in a completely different context. In this case, we apply it to the field of grouping library collections through evolutionary algorithms. We show its efficiency with experimental data we got from traditional library collections.

Sustainable development of unconventional resources: Analysis of the transient linear flow oriented straight-line analysis technique

On the backdrop of dwindling conventional reserves,unconventional reservoirs have emerged as a pivotal chapter in resource extraction.Despite their challenges,such as low permeability,complex fluid storage,and flow mechanisms,hydraulic fracturing technology has underpinned the development of unconventional reservoirs.Consequently,this has brought about a shift in the sequence of flow regimes,e.g.,the transient radial flow regime has been largely shortened by the lengthy transient linear flow regime due to the low permeability of unconventional reservoirs.Moreover,straight-line analysis(SLA),the simplest technique in rate transient analysis(RTA),is a fundamental and potent tool for swiftly extracting reservoir and hydraulic fracture information,estimating oil and gas reserves,and furnishing crucial initial data for subsequent historical matching processes.However,there is currently a dearth of review papers pertaining to a necessary guide of applying SLA in various transient linear flow(TLF)regimes and different unconventional reservoirs.Hence,this paper commences by elucidating the classification of TLF regimes,commonly used methods for recognizing flow regimes,and the diverse SLA methods used for different TLF regimes.Subsequently,it delves into a discussion of different modification techniques for variable rate/flowing pressure,gas phase,complex reservoir characteristics in unconventional reservoirs,and dynamic drainage area concepts etc.Furthermore,the application of SLA in specific domains,namely core analysis and the flowback period,is described.It culminates by surveying the advancements through an integration of novel technologies to enhance estimation accuracy.The paper also highlights certain drawbacks of current SLA technology and proposes new research directions.Ultimately,this paper would serve as an indispensable resource,offering foundational knowledge for the application of SLA in TLF to promote the production of global unconventional resources in a cost-effective and environmentally sustainable fashion in the face of a climate-resilient world.

Observation of a Straight-Line Wind Case Caused by a Gust Front and Its Associated Fine-Scale Structures

A straight-line wind case was observed in Tianjin on 13 June 2005,which was caused by a gust front from a squall line.Mesoscale analyses based on observations from in-situ surface stations,sounding,and in-situ radar as well as fine-scale analyses based on observation tower data were performed.The mesoscale characteristics of the gust front determined its shape and fine-scale internal structures.Based on the scale and wavelet analyses,the fine-scale structures within the gust front were distinguished from the classical mesoscale structures,and such fine-scale structures were associated with the distribution of straight-line wind zones.A series of cross-frontal fine-scale circulations at the lowest levels of the gust front was discovered,which caused a relatively weak wind zone within the frontal strong wind zone.The downdraft at the rear of the head region of the gust front was more intense than in the classical model,and similar to the microburst,a series of vertical vortices propagated from the rear region to the frontal region.In addition,strong tangential fine-scale instability was detected in the frontal region.Finally,a fine-scale gust front model with straight-line wind zones is presented.

EIGHT-POINT STRAIGHT-LINE-NET-DIAGRAMS OF BINARY SIX-PHASE (n+4) MULTISYSTEMS (Ⅱ)——DERIVATION FROM THEORY OF PHYSICALLY REAL NETS

Based on the theory of physically real nets, the 8- point straight-line nets of bi-nary 6- phase (n + 4) multisystems (31 in toto) have been derived directly from the l-point straight-line nets. This result is in complete agreement with that derived fromthe theory of closed nets, indicating the incorrectness of the previous conclusion thatthere is only one 8-point straight-line net which corresponds to only one 8- pointstraight-line-net-diagram for binary 6- phase multisystems.

EIGHT-POINT STRAIGHT-LINE-NET-DIAGRAMS OF BINARY SIX-PHASE (n+4) MULTISYSTEMS (Ⅰ)——DERIVATION FROM NINE-POINT CLOSED-NET-DIAGRAMS

The 9-point closed-net-diagrams of binary 6-phase multisystems contain 2 basic types ofnon-straight-line portions. Only the removal of an invariant point which is shared by all thenon-straight-line portions in a 9-point closed-net-diagram can generate an 8-point straight-line-net-diagram. All together 67 distinct 8-point straight-line-net-diagrams have been derived forbinary 6-phase multisystems. They correspondingly belong to 31 distinct 8-point straight-line-nets (namely, 31 distinct 8-point sets), showing that the previous conclusion that there existsonly one 8-point straight-line-net-diagram for binary 6-phase multisystems is incorrect.

基于模糊快速滑模的农用牵引车辆直线路径跟踪控制

为解决无人驾驶牵引式农机在非结构化环境中作业时直线跟踪精度低、上线速度慢、抗干扰能力差等问题,提出了一种基于模糊快速滑模控制的农用牵引式车辆直线路径跟踪控制方法。首先利用车辆运动学模型与参考路径建立牵引车辆直线路径跟踪误差模型,并提出一种基于模糊参数整定的快速滑模直线路径跟踪方法,解决了滑模控制算法的控制器抖振与机具快速上线问题。通过Lyapunov稳定性分析可知,所设计控制方法可保证牵引机具跟踪参考路径,同时铰接角收敛至零。最后,基于Simulink仿真与实车试验对该控制方法的有效性与优越性进行测试。田间实车试验表明,使用本文控制方法时,拖车和挂车最大路径跟踪横向误差分别为0.11、0.12 m,拖车和挂车跟踪误差方差分别为0.0013、0.0015 m^(2);相较于传统基于等速趋近律设计的滑模控制器,上线时间提升约58%,最大跟踪误差减小约66%。

基于稀疏编码的复杂机械振动信号盲分离方法

复杂机械振动信号激励源较多,故源信号之间互为相关源,且较难满足统计独立特性,导致传统盲源分离方法分离效果不佳。对此,提出一种基于信号稀疏编码的机械振动信号盲分离方法。盲源分离的关键在于对混合矩阵的精确估计,然而机械振源中相关成分的存在严重影响混合矩阵的估计。对此,首先对观测信号进行短时傅里叶变换,增加信号稀疏性;然后利用稀疏编码筛选出具备直线聚类特性的时频观测点,利用K均值(K-means)聚类法找到聚类中心;最后利用所提筛选规则找到估计的混合矩阵,重构出源信号。通过对往复压缩机故障数据的分析,验证了所提方法有效性。

基于直线检测的航向角误差校正方法

提出了一种基于直线检测模型的多传感器数据融合航向角随机误差校正方法,旨在提高农林环境下低成本传感器组成的定位平台的精度。该方法通过调整直线检测阈值来实现状态的动态调整,以提高导航系统的鲁棒性和精确性。再将多传感器数据通过卡尔曼滤波融合,实现航向角随机误差的校正。试验结果表明,该方法在不同路径和速度下能有效降低航向角误差提高定位精度。在直线行进试验中,本方法的定位精度保持在5cm以内,航向角误差在5°以内。在矩形行进试验中,本方法的轨迹与差分RTK方法相近,平均误差仅为2.7cm,标准差为3.9cm。这一航向角校正方法为农业机械和车辆环境中的自主操作提供了有力支持。它能够适应不同的环境条件,提高导航系统的性能和测量准确性。

大尺寸工件螺孔的机器视觉测量方法研究

基于3C产品外壳工件螺纹圆孔加工时通常采用角点定位的特点,利用线阵相机采集子图像的连续性,提出基于直线特征和圆特征定位的螺纹圆孔位置尺寸测量方法。基于拟合法改进的Hough直线定位方法和基于乘同余法改进Hough变换圆形检测方法,实现3C外壳工件图像边缘定位及螺纹圆孔的圆心坐标提取及直径尺寸测量;基于图像的连续性,采用子图像逐一检测,相邻子图像起始像素累加的方式,实现大尺寸图像螺纹圆孔尺寸全局检测。上述方法最终实现大尺寸3C外壳工件螺纹圆孔的位置尺寸测量精度为±0.2220mm和孔径大小测量±0.0904mm,单工件检测耗时为33.737s。

新型连杆式双料分装供送机构的设计及应用

为实现双物料缓急有度地输出并分装入容器,提出一种新型连杆式供送机构。由1个能生成对称、自切且带有鲍尔点的特殊连杆曲线的四连杆机构,驱动2个阀门推杆执行带停歇的直线往复运动,以控制2个阀门交替开启和闭合。四连杆机构中曲柄、连杆、摇杆及机架杆的杆长比为1:1.8371:1.8371:2,连接杆与连杆等长,夹角为109.47°。分装过程的仿真结果表明:锥形阀门在开启/闭合阶段,其运动位置对出料区域的控制可使落料量变化平稳;在1个运动周期内完成双物料的分装,提高装料的效率。研究为包装机械中的其他推送装置的设计提供新思路。

指针式压力表识别与读数方法浅析

指针式仪表作为工业领域常用工具,当前普遍依赖人工读表,该方法存在耗时费力、精度不足及远程监控受限等问题。随着工业智能化进程的推进,提出了一种采用计算机视觉技术的解决方案。采用YOLOv5目标检测算法,实现仪表的精确检测;结合图像预处理、Hough变换及旋转直线拟合技术,自动识别指针角度并转换为读数。实验结果显示,该系统读数误差范围在-0.06~0.25 MPa之间,显著提升了读数的精度与效率,同时实现了远程监控功能。该方法对拓展指针式仪表的应用领域具有一定的参考价值。

不停航条件下跑道深厚软土地基处理方案研究

机场不停航施工通常会遇到净空要求严、作业时间短、对作业面平整度要求高等问题,本文以某软基机场跑道延长线为例,开展不停航施工条件下深厚软基处理方案研究。首先,总结分析了一期跑道的软基处理方案和勘察、监测及试验等成果,在此基础上,结合本场区的地层特性和软土参数的差异性,获得了本期软基处理设计的物理力学特性参数。其次,针对本场区存在深厚软土、不停航施工和净空限制等复杂条件,提出了直排式真空预压的地基处理方案;并针对软土上部土石混合料填筑层难以密封的问题,首次提出了自凝灰密封墙新技术,确保了设计要求的膜下真空压力。最后,采用PLAXIS软件对处理后的典型断面进行了沉降复核分析。截至目前,机场延长线已运行3年,沉降满足设计要求,该方案可为类似工程提供技术借鉴。

水下运动平台的广义Radon变换目标参数估计方法

针对传统目标运动分析算法受静止单平台可观测性限制的问题,本文提出了一种基于广义Radon变换的水下运动平台目标参数估计方法。在观测平台自身的运动参数已知的假设下,推导了目标方位与各运动参数的数学关系,在此基础上通过对平台声呐测得的目标时间方位历程进行广义Radon变换,依次得到目标的航向角、速度以及目标相对于探测平台的初距,最终实现目标运动轨迹的解算。利用矢量阵的仿真数据对方法的可行性进行了分析验证,结果表明:作为一种批处理类方法,该方法无需进行迭代运算,易于实现,在较低信噪比条件下仍具有很好的估计精度和鲁棒性。

既有万吨重载线路平面曲线参数对列车提速安全性的影响

为明确国内某重载线路平面曲线参数能否满足列车运营速度由80 km/h提高到90 km/h的安全性要求,建立两种主要车型C80及C64的多体动力学模型,选取未平衡超高、缓和曲线长度以及夹直线长度三种参数进行了仿真计算分析。结果表明:对于C80货车,在既有线路平面曲线参数条件下,轮轨动态安全性能指标均小于限值,可满足提速运行的安全性要求,其中缓和曲线长度超过70 m时轮轨相互作用的变化趋于平稳;对于C64货车,夹直线长度为10 m时,90 km/h速度下,轮轨垂向力超出安全限值,而该线路中夹直线长度为10 m的路段普遍存在,因此不满足提速运行的安全性要求。适当降低欠超高可改善轮轨动态相互作用力;选取合适的缓和曲线长度可改善轮轨动态相互作用并降低工程成本,建议取70 m;考虑到提速后以C64货车为代表的转K2转向架货车轮轨垂向力较大,夹直线长度不宜小于60 m。

高速犁体曲面结构参数对耕作阻力的影响研究

针对我国铧式犁高速作业时耕作阻力大、耕地质量差等问题,本文研究了高速犁体曲面结构参数对耕作阻力的影响.首先,分析了基于水平直元线法的高速犁体曲面形成过程,得出对高速犁体曲面作业性能影响较大的结构参数.然后,基于离散元法建立了高速犁体曲面-土壤互作模型,并通过土槽试验和仿真试验验证了该模型的合理性.最后,分别研究了铧刃角θ、导曲线开度l、犁铧安装角ε和高度偏差量ΔH等结构参数对耕作阻力的影响规律.研究结果表明:随着铧刃角的增大,耕作阻力以较快速度增大;随着导曲线开度的增大,耕作阻力逐渐减小;随着犁铧安装角的增大,耕作阻力在较小范围内波动;随着高度偏差量的增大,耕作阻力缓慢增大.

结合霍夫变换找墙体直线的沿墙导航算法

针对移动机器人沿墙导航过程中存在沿曲线墙体导航效果不佳、路径不够平滑等问题,提出了结合霍夫变换找墙体直线的沿墙导航算法。该算法由霍夫变换提取出当前位置障碍物中的直线,找到离机器人最近的直线作为沿墙参考直线,采集上一周期历史墙体直线状态和当前墙体直线状态决定机器人当前的运动方向,并根据当前墙体直线提取出沿墙导航预设路径进行导航,如此循环直至完成指定的沿墙导航任务。实验证明该算法可以在不同环境中较好地完成沿墙导航任务。

直连绳索取心钻杆分区热处理技术研究

为了提高绳索取心钻杆的性能,对直连绳索取心钻杆的受力情况、结构特点以及传统处理工艺进行分析,提出了分区热处理的工艺。通过对两端进行热加工处理,使钻杆中间管体区域和两端热处理螺纹区域性能出现差异,提高两端综合强度的同时改善螺纹部分的受力状态,可使钻杆柱既具有高强度又兼具柔性,大幅提高钻杆机械性能以及耐磨性。其中调质硬度HRC33~38能在保证管体延伸率与正火、回火基本一致的情况下,强度提高37.7%,硬度提高40%,抗冲击性提高46.7%。调质硬度HRC38~42时,材料的耐磨性提高9.1%。更适合全液压钻机施工及深孔钻进,为钻探施工提供了钻机、钻杆配套性的优选方案。