Aiming at the problem that parallel flexible mechanisms applied in micro/nano-positioning fields struggle to decouple rotational motion from other degrees of freedom to form independent actuation units,the rotational motion decoupling mechanism based on orthogonal arrangements of reed-beam parallelogram mechanisms is extended.By replacing reed beams with arc beams,a series of flexible rotational nano-motion decoupling mechanisms based on arc beams are designed,and their compliance modeling and performance testing are conducted.Firstly,the configurations of flexible decoupling mechanisms with different arc beam heights were introduced.Each mechanism was composed of two identical orthogonal upper and lower parts,which fully utilized the compliance characteristics of arc beams in various degrees of freedom,enabling decoupling among multiple coupled degrees of freedom,including translational motions.Then,theoretical modeling of the flexible decoupling mechanisms was performed based on the compliance matrix method to determine their dimensional parameters and derive their output compliance.Finally,the accuracy of the theoretical compliance models was validated by combining finite element analysis with experiments,and the decoupling capabilities of different mechanisms were compared.The results showed that the relative errors between the finite element analysis and experimental results and the theoretical calculation results of each flexible decoupling mechanism's compliance were within 10%,and its decoupling performance was positively correlated with the height of arc beams on both sides.This type of flexible decoupling mechanism can be applied to the flexible mechanism design for multi-degree-of-freedom parallel micro/nano-positioning platforms,which has certain practical value.
Hierarchical Bayes, or E-Bayes, is frequently used to estimate the failure probability when solving a zero-failure reliability evaluation model; however, the accuracy of the reliability estimation using these methods is not very good in practice. Due to this, a novel double-modified hierarchical Bayes (DMH-Bayes) is proposed for Weibull characteristic data in this study to enhance failure probability estimation and improve reliability point estimation accuracy. Meanwhile, in order to guarantee the preservation of the assessment findings' consistency and confidence level, the parametric Bootstrap method (P-Bootstrap) and the L-moment estimation method based on point estimation are introduced to obtain reliability confidence interval estimates. Based on Monte-Carlo simulation testing and analysis of a gyroscope bearing, the new model is confirmed to have better applicability and robustness while improving the accuracy of reliability assessment.
针对异型零件具有众多复杂的相交特征,加工特征难以自动识别,进而影响其高效、高质量自动编程设计的问题,提出了一种基于图和体分解的加工特征识别方法.首先,以STEP中性文件作为输入,获取异型零件的几何、拓扑信息,以构造其毛坯特征和体积特征;同时,采用布尔减运算得到异型零件的加工体积特征,并将其分解为只含凸边关系的单一特征.然后,设计了一种基于特征面关系的几何特征矩阵(geometric feature matrix,GFM)和拓扑特征矩阵(topological feature matrix,TFM)构建方法,其中GFM侧重描述零件模型中面与面之间的位置关系,TFM侧重描述零件模型中面与面之间相邻的凹凸性,该方法较好地解决了传统属性邻接矩阵(attribute adjacency matrix,AAM)易出现无法准确表达零件加工特征的问题.最后,将异型零件的GFM和TFM与加工特征库进行匹配,以实现其加工特征的识别.在Visual Studio 2019平台中开发基于图和体分解的异型零件加工特征识别系统并开展验证实验.结果表明,所提出的方法能准确识别异型零件的所有加工特征,这可为异型零件加工工艺的自动编制和智能制造提供理论依据.
为了解决目前布放回收自主水下机器人(autonomous underwater vehicle,AUV)自动化水平低、工作效率低、危险性高等问题,研制了一款基于无人水面船(unmanned surface vessel,USV)的AUV自主布放回收系统.首先,通过分析国内外常用AUV布放回收方式和布放回收系统,设计了AUV布放回收系统,并对其工作原理进行分析;其次,分别从力学分析、数值仿真等角度研究了布放回收系统的动力学、静力学及接触碰撞问题;最后,搭建了系统原理样机并进行了陆上实验和湖上实验,通过实验验证了所设计的布放回收系统稳定可靠、操作简单、通用性好,可以有效提高AUV自主布放回收的效率.所设计的基于USV的AUV布放回收系统具有良好的应用前景.
为了解决传统环模模孔疏通中疏通效率低、自动化程度低、易损伤等问题,研发了环模智能定孔疏通装置.设计开发了定孔疏通机械手、下位机软硬件和上位机软.利用高磁导体的铁磁性及漏磁检测原理,将模孔定位疏通模块与霍尔效应检测算法相结合,实现了对堵塞模孔的自动化检测及疏通,提高了模孔定位精度.实验表明,采用环模智能定孔疏通装置,疏通效率可达1260个/h,模孔刮伤率低于0.15%,装置运行稳定,实现了堵塞环模的自动化定孔疏通.研究结果对金属模孔探测及疏通技术的发展具有一定的参考价值.
