A method of constructing an inspiration library driven by user-perceived preference evaluation data for biologically inspired design

Biologically inspired design (BID) is one of the common methods for product design. To solve the problem of inaccurate acquisition of inspirational creatures due to the lack of user perception preference analysis, a data-driven intelligent service model for BID considering user perception needs is proposed based on Kansei engineering. Firstly, by extracting the perceptual features of creatures from the semantic source elements of products through mapping and encodes them, we proposed a data acquisition method based on intuitionistic fuzzy sets considering different customer preference distributions, bridging the gap caused by the asymmetry between designers and users. Secondly, the functional relationship between biometric features and user-perceived attributes is identified and predicted, and a predictive model of biodata considering user preferences is obtained by multiple linear regression analysis. Finally, based on the data clustering and reorganization theory to understand the organization and dynamics of the database, the construction of a BID library was completed, and the design resources in the library were used as analyzed knowledge for designers to plan design activities. Taking the bionic design of a UAV product as an example, a prototype of a computer-aided design service system was developed based on the theory proposed in the article, and the analyzed knowledge was used to improve the efficiency and science of the design, effectively verifying the usefulness of this study for design. To a certain extent, this study addresses the problem of cognitive limitations of designers and cognitive differences between designers and users, promotes the application of bioinspiration in product design, and improves the marketability of design solutions.     

Development of a small DMFC bipolar plate stack for portable applications

The direct methanol fuel cell (DMFC) is regarded as a promising candidate in portable electronic power applications. Bipolar plate stacks were systematically studied by controlling the operating conditions, and by adjusting the stack structure design parameters, to develop more commercial DMFCs. The findings indicate that the peak power of the stack is influenced more strongly by the flow rate of air than by that of the methanol solution. Notably, the stack performance remains constant even as the channel depth is decreased from 1.0 to 0.6 mm, without loss of the performance in each cell. Furthermore, the specific power density of the stack was increased greatly from ∼60 to ∼100 W l⁻¹ for stacks of 10 and 18 cells, respectively. The current status of the work indicates that the power output of an 18-cell short stack reaches 33 W in air at 70 °C. The outer dimensions of this 18-cell short stack are only 80 mm × 80 mm × 51 mm, which are suitable for practical applications in 10–20 W DMFC portable systems.     

Hybrid active/passive force control strategy for grinding marks suppression and profile accuracy enhancement in robotic belt grinding of turbine blade

Grinding marks and traces, as well as the over- and under-cutting phenomenon are the severe challenges in robotic abrasive belt grinding of turbine blades and it greatly limits the further application of robotic machining technology in the thin-walled blade fields. In the paper, an active force control method consisting of force/positon and PI/PD controller based on six-dimensional force/torque sensor is introduced to eliminate the grinding marks and traces, and a passive force control method including PID controller based on one-dimensional force sensor is proposed to reduce the over- and under-cutting phenomenon in robotic machining system. Then the Kalman filter information fusion methodology is adopted to combine the active and passive force control methods which could improve the controlled force accuracy and efficiency, as well as avoid the control interference. Finally both the test workpiece and turbine blade are employed to examine and verify the reliability and practicality of the proposed hybrid force control method by achieving the desired surface quality and higher profile precision.     

Online stiffness estimation for robotic tasks with force observers

In this paper we propose an online stiffness estimation technique for robotic tasks based only on force data, therefore, not requiring contact position information. This allows estimations to be obtained in robotic tasks involving interactions with unstructured and unknown environments where geometrical data is unavailable or unreliable. Our technique – the Candidate Observer Based Algorithm (COBA) – uses two force observers, configured with different candidate stiffnesses, to estimate online the actual target object stiffness. COBA is embedded in a force control architecture with computed torque in the task space. The theoretical presentation of the algorithm, as well as simulation tests and experimental results with a lightweight robot arm are also presented.     

A new force-depth model for robotic abrasive belt grinding and confirmation by grinding of the Inconel 718 alloy

Robotic abrasive belt grinding has been successfully applied to the grinding and polishing of aerospace parts. However, due to the flexible characteristics of robotic abrasive belt grinding and the time-varying characteristics of the polishing contact force, as well as the plastic and difficult-to-machine material properties of Inconel 718 alloy, it is very difficult to control the actual removal depth and force of the polished surface, which brings great challenges to robot automatic polishing. Therefore, the relationship between the grinding force and the grinding depth in the robotic abrasive belt grinding is analyzed in detail, the robot machining pose error model considering the deformation of the grinding head is established, and the Inconel 718 alloy machining experiment of the robotic abrasive belt grinding is designed. The mapping relationship between the grinding force and the grinding depth is obtained, and the grinding force ratio in the downgrinding and upgrinding mode is discussed. The experimental and theoretical comparisons results show that with the increase of the grinding depress depth, both the grinding depth and the grinding force show an irregular increasing trend, and the increasing trend of the grinding force (increases by about 344.44%–445.45%) is obviously greater than that of the grinding depth (increases by about 52.94%). When the grinding depress depth is large (greater than 3 mm), the feed direction force and the normal force appear obvious secondary pressure peaks at the beginning and end of grinding, which has not been seen in previous studies. In addition, regardless of whether it is downgrinding or upgrinding, the grinding force ratio decreases with the increase of the depress depth, and the grinding force ratio of downgrinding (average 0.668) is smaller than that of upgrinding (average 0.724). This study provides a reference for robotic abrasive belt grinding, and the surface quality of Inconel 718 alloy of robotic abrasive belt grinding can be further improved through the optimization of force and depth.     

面向狭窄场景的鲁棒多视角配准方法

多视角点云配准是逆向工程中的关键步骤之一,具有重要的研究意义和工程应用价值。而对于狭窄场景(如口腔或机械结构内部)获取的点云数据,多视角配准算法的精度直接影响重建精度的好坏。为了提升狭窄场景多视角点云配准的速度和鲁棒性,提出一种基于位姿图优化的增量式多视角点云配准方法。首先针对相邻视角的点云,结合迭代最近点法(ICP)和基于特征的配准方法,提出一种多策略融合的成对点云配准算法,用于求解相邻视角点云的配准结果;然后在增量式相邻视角点云配准的基础上,进一步提出一种基于距离约束的回环检测方法,并依据相邻视角点云的配准结果和回环检测的结果构建位姿图;最后采用实时优化策略对位姿图进行优化,消除累计误差,实现鲁棒的多视角配准。实验结果表明,提出的多策略融合配准算法和基于距离约束的回环检测方法是有效的。经典ICP算法和基于FPFH特征的配准算法在实验中存在失效的现象,而提出的多策略融合配准算法并无失效。基于距离筛选的回环检测方法较常规的回环检测方法效率提高。提出的多视角配准算法在配准牙齿模型数据时精度可达到0.0357 mm。为了验证算法的普适性,采用多个狭窄场景下连续采集的模型点云进行验证,结果表明:提出的算法取得了不错的效果,表明该方法是一种有效的狭窄场景多视角配准方法。     

基于网络资源流量的链路预测方法

在复杂网络中,现有基于结构相似性的链路预测方法较少考虑全局和局部拓扑信息之间平衡性、准确度和复杂度之间平衡性以及网络资源动态流动的问题。将网络资源流量作为相似性判断依据,提出一种准局部链路预测方法。根据网络中节点重要性的不同来为它们分配对应的资源,以保证资源分配的合理性。针对网络资源提出一种动态流动机制,将节点对双向流动的资源之和作为相似程度的量化指标。引入节点对之间中间路径节点的概念,分析中间路径节点在资源流动过程中的稀释作用。在此基础上,计算初始资源量和稀释作用量从而得到网络资源流量方法的性能评估指标值。在Jazz、NS等11个真实世界的网络中进行实验,对比该方法与CN、Salton等常见基准方法在准确度和鲁棒性方面的性能表现,结果表明,所提方法能够充分利用准局部信息,既能考虑资源流动性又能解决平衡性问题,可有效提高链路预测性能。     

The influence of corrosion on the life of steel ropes and prediction of their decommissioning

Operation of steel wire ropes brings a number of risks that affect their lifetime. During operation of steel ropes the one of the most adverse effects is the effect of corrosion. Manufacturers are working hard to eliminate the effect of corrosion by lubricating cables, surface protection of wires and alike, but these methods are not able eliminate corrosion rise and propagation totally. To examine the process of degradation of the mechanical properties of the steel ropes in the corrosive environment, we conducted research on a rope sample as a whole and on the samples of individual wires. The samples were exposed to the saline solution for a period of total duration of 64 days. The monitoring of the degradation was carried out at 16-day intervals when the samples were subjected to mechanical tests. The rope sample as a whole was subjected to the tensile test. The individual wire samples were subjected to the tensile test, alternating bend test and torsion test. The criteria according to the standard EN 12927-6 and the Slovak Mining Office Regulation (SBU) No. 50/1989 Coll. were used to evaluate the results of the degradation of the mechanical properties. These were then confronted with the criteria used in maritime shipping. Based on the results of the mechanical tests, the trend of the degradation of the mechanical properties in the saline solution and marginal values for the rope decommissioning were determined. Gradually, with an increase of the impact of corrosion on the rope samples, the impact on rope rotation resistivity was also registered, besides the mechanical properties changes.     

Load transfer of graphene/carbon nanotube/polyethylene hybrid nanocomposite by molecular dynamics simulation

Load transfer of the graphene/carbon nanotube (CNT)/polyethylene hybrid nanocomposite is studied here from molecular dynamics (MD) simulations. Simulations of this composite material under uniaxial tension were conducted by varying CNT’s position and diameter in the polymer matrix. The obtained results show that: (1) The peak strength of stress and strain evolution in the polymer matrix is lower than the peak strength of the graphene/graphene and graphene/polymer interfaces. Hence, the damage zone is always located in the polymer matrix. (2) Agglomerated two-layer graphenes do not possess an increased value in the peak strength compared with single-layer graphene-reinforced polymer nanocomposite (PNC), while two separate layers of graphene show slightly higher peak strength. (3) The largest peak strength is observed before CNT moves to the center of the polymer matrix. The damage location moves from the upper to the lower part of CNT when the CNT is located at the centre of polymer matrix. (4) The influence of the CNT diameter on the peak strength is not obvious, while the damage location and shape in the polymer matrix changes with respect to varying CNT diameters. In addition, the damage zone always falls outside the interphase zone.     

The effect of Stone–Thrower–Wales defects on mechanical properties of graphene sheets – A molecular dynamics study

The mechanical properties of graphene may be strongly affected by defects. In our work, the effects of the orientation and tilting angles of Stone–Thrower–Wales (STW, 5-7-7-5) defects on the mechanical properties of graphene have been investigated based on molecular dynamics simulations. When there is one centred STW defect including STW-1 defect and STW-2 defect, our study reveals that the orientation with respect to the chirality governs the mechanical properties of graphene. For STW-1 defective graphene, the strength of the armchair direction is much lower than that of zigzag direction. While the circumstance for STW-2 defective graphene is opposite, the strength of the armchair direction is much higher than the strength of the zigzag direction. Furthermore, when there is more than one STW defect, the mechanical properties of graphene depends on the tilting angle of STW defects. The breaking strength of graphene decreases with the increasing tilting angle. Our present work could provide significant insights into the effect of STW defects on the mechanical properties of graphene.