Robust tracking control for operator-based uncertain micro-hand actuator with Prandtl–Ishlinskii hysteresis

Since the hysteresis property inherently exists in the rubber material, it is necessary to deal with the control issues for the micro-hand by considering the hysteresis property. Therefore, in this paper, the robust tracking control for the micro-hand systems is discussed from the aspect of the Prandtl–Ishlinskii hysteresis property which is more applicable for the real applications. Firstly, a new model is obtained by combining the dynamic model of the micro-hand with Prandtl–Ishlinskii hysteresis property. Secondly, a new stability condition based on bounded input and bounded output stability is proposed for the Prandtl–Ishlinskii hysteresis modeled micro-hand system from two different cases. Thirdly, by designing the robust controllers based on the internal model control method, the tracking performance can be improved by eliminating the effect from the disturbance. Finally, simulation is used to further demonstrate the effectiveness of the proposed design scheme.     

一种增强型PTP光纤级联精细时频同步方法

该文提出了一种增强型PTP光纤级联精细时频同步方法,该方法以PTP同步技术为基础,结合同步以太网时钟传递技术和基于数字双混频时差法的多级级联精细时钟同步技术,对PTP技术进行改进和增强,然后基于该方法,通过多级时频设备光纤级联的形式实现多节点、大跨度、网络化的时频信号传递与同步输出,并解决多级级联情况下同步精度会逐级恶化的问题,实现ns量级的系统时间同步精度,保证系统各环节在高度统一的时间尺度下进行高效同步与联动工作。通过设计、试验,验证了该方法的可行性和有效性。     

Chatter detection for milling using novel p-leader multifractal features

Journal of Intelligent Manufacturing - Chatter in machining results in poor workpiece surface quality and short tool life. An accurate and reliable chatter detection method is needed before its...     

A novel cause analysis approach of grey reasoning Petri net based on matrix operations

Cause analysis makes great contributions to identifying the priorities of the causes in fault diagnosis system. A fuzzy Petri net (FPN) is a preferable model for knowledge representation and reasoning and has become an effective fault diagnosis tool. However, the existing FPN has some limitations in cause analysis. It is criticized for the inability to fully consider incomplete and unknown knowledge in uncertain situations. In this paper, an enhanced grey reasoning Petri net (EGRPN) based on matrix operations is presented to address the limitations and improves the flexibility of the existing FPN. The proposed EGRPN model uses grey numbers to handle the greyness and inaccuracy of uncertain knowledge. Then, the EGRPN inference algorithm is executed based on the matrix operations, which can express the relevance of uncertain events in the form of grey numbers and improve the reliability of the knowledge reasoning process. Finally, industrial examples of cause diagnosis are used to illustrate the feasibility and reliability of the EGRPN model. The experimental results show that the new EGRPN model is promising for cause analysis.

     

基于YOLOv5增强模型的口罩佩戴检测方法研究

人脸口罩佩戴检测是公共场所疫情防控中极为重要的措施,智能、高效地检测口罩佩戴情况对实现疫情防控的自动化和数字化具有重要意义。使用卷积类深度神经网络实现端到端的人脸口罩佩戴检测具有可行性,但卷积类神经网络具有结构复杂、参数量和浮点计算量庞大的特点,从而产生较高的计算开销和内存需求,极大地限制了其在资源有限的终端设备上的应用。为了使人脸口罩佩戴监督功能更易获取,并实现多尺度条件下的模型压缩和加速检测,提出一种基于改进YOLOv5的轻量化增强网络模型。设计参数量和计算量更小的GhostBottleneckCSP和ShuffleConv模块并替换原YOLOv5网络中的C3及部分Conv模块,以降低特征通道融合过程中的计算量并增强特征表达能力。实验结果表明,该模型的识别精度达95%以上,模型在精度近乎无损失的前提下,参数量和计算量分别仅为原YOLOv5网络的34.24%和33.54%,且在GPU和CPU上的运行速度分别提升13.64%和28.25%,降低了模型对内存存储及计算能力的要求,更适用于在资源有限的移动端部署。     

热轧工艺对20%B4C/Al复合材料显微组织及缺陷的影响

采用热等静压烧结与热轧相结合的方法制备了20%B_4C/Al(质量分数,下同)复合材料,采用排水法及SEM、EDS等手段研究了热轧工艺(道次变形量、总变形量)对复合材料缺陷及显微组织的影响。研究结果表明,热等静压制备的B_4C/Al复合材料坯体密度可达2.66g/cm3(相对密度100%),B_4C颗粒分布均匀且与Al界面处结合紧密;B_4C/Al复合材料轧制道次变形量应控制在10%以内,进一步增加道次变形量复合材料内出现宏观裂纹。复合材料经热轧后,B_4C颗粒仍分布较为均匀,且与Al基体结合紧密,复合材料内部未观察到明显的显微缺陷。     

Highly enhanced photocatalytic degradation of dye rhodamine B on the biogenic hierarchical porous TiO<Subscript>2</Subscript>/SiO<Subscript>2</Subscript> with 1D/3D-chain

A hybrid photocatalyst consisting of TiO₂ and nonporous SiO₂ (TiO₂/CS-RH) is prepared by loading TiO₂ sol on one-dimensional/three-dimensional chain (1D/3D-chain) which is synthesized from rice husk. The products are characterized by X-ray diffraction, N₂-adsorption–desorption analysis and scanning electron microscopy. Meanwhile, the corresponding photocatalytic activity is evaluated by measuring the photocatalytic oxidation of rhodamine B (RhB). The results reveal that TiO₂/CS-RH displays a hierarchical porous structure from micrometer to nanometer scale with high BET surface area (574.7–719.4 cm²/g). Meanwhile, the activity of TiO₂/CS-RH for the photocatalytic degradation of RhB in aqueous slurry is significantly higher than that of the unsupported TiO₂. The optimal TiO₂ loaded on the support was two times and then treated at 600 °C for 120 min to complete the conversion of RhB. In contrast, the unsupported TiO₂ photocatalyst could convert only 20% of RhB in the same irradiation time and condition.