Multi-robot task allocation for exploration

The problem of allocating a number of exploration tasks to a team of mobile robots in dynamic environments was studied. The team mission is to visit several distributed targets. The path cost of target is proportional to the distance that a robot has to move to visit the target. The team objective is to minimize the average path cost of target over all targets. Finding an optimal allocation is strongly NP-hard. The proposed algorithm can produce a near-optimal solution to it. The allocation can be cast in terms of a multi-round single-item auction by which robots bid on targets. In each auction round, one target is assigned to a robot that produces the lowest path cost of the target. The allocated targets form a forest where each tree corresponds a robot＇s exploring targets set. Each robot constructs an exploring path through depth-first search in its target tree. The time complexity of the proposed algorithm is polynomial. Simulation experiments show that the allocating method is valid.     

硬脆材料精密小深孔BTA型珩磨工具的加工特性研究

从分析国内外现有工具存在的问题入手,着重解决超硬材料精密小深孔珩磨加工中走偏量较大、圆度误差较大等问题,提出了一种三导向的BTA型珩磨工具结构,使超硬材料精密小深孔加工的质量得到了提高.实验证明 ,采用新型珩磨工具加工出的小深孔可达到走偏量0.001～0.002 mm /1 00 mm,锥度0.005 mm/100 mm,圆度误差0.00 2～0.004 mm,表面粗糙度可达到Ra0.08～0.16 μm(采用W10油石),最高可达Ra0.04～0.08 μm, 尺寸精度可达IT5,可获取以珩代研的效果.     

Fault detection and identification for dead reckoning system of mobile robot based on fuzzy logic particle filter

To deal with fault detection and diagnosis with incomplete model for dead reckoning system of mobile robot, an integrative framework of particle filter detection and fuzzy logic diagnosis was devised. Firstly, an adaptive fault space is designed for recognizing both known faults and unknown faults, in corresponding modes of modeled and model-free. Secondly, the particle filter is utilized to diagnose the modeled faults and detect model-free fault according to the low particle weight and reliability. Especially, the proposed fuzzy logic diagnosis can further analyze model-free modes and identify some soft faults in unknown fault space. The MORCS-1 experimental results show that the fuzzy diagnosis particle filter (FDPF) combinational framework improves fault detection and identification completeness. Specifically speaking, FDPF is feasible to diagnose the modeled faults in known space. Furthermore, the types of model-free soft faults can also be further identified and diagnosed in unknown fault space.     

衬底温度对热丝法生长纳米金刚石膜的影响

采用热丝化学气相沉积法在氩/丙酮/氢气体系中研究衬底温度对纳米金刚石膜生长的影响,使用扫描电子显微镜、X射线衍射仪、拉曼光谱仪对金刚石膜进行检测.结果表明衬底温度对金刚石膜的生长模式、形貌、粒径和生长速率有很大影响.在750℃衬底温度下生长模式为颗粒状生长模式,呈现纳米金刚石结构,生长速率达到8.45μm/h;随着衬底温度的降低,金刚石晶粒粒度逐渐变大,由纳米金刚石向微米金刚石转变,生长模式变为柱状生长模式,生长速率逐渐降低;在600℃衬底温度下变为微米金刚石,生长速率下降到1.95μm/h.     

An adaptive genetic algorithm with diversity-guided mutation and its global convergence property

An adaptive genetic algorithm with diversity-guided mutation, which combines adaptive probabilities of crossover and mutation was proposed. By means of homogeneous finite Markov chains, it is proved that adaptive genetic algorithm with diversity-guided mutation and genetic algorithm with diversity-guided mutation converge to the global optimum if they maintain the best solutions, and the convergence of adaptive genetic algorithms with adaptive probabilities of crossover and mutation was studied. The performances of the above algorithms in optimizing several unimodal and multimodal functions were compared. The results show that for multimodal functions the average convergence generation of the adaptive genetic algorithm with diversity-guided mutation is about 900 less than that of adaptive genetic algorithm with adaptive probabilities and genetic algorithm with diversity-guided mutation, and the adaptive genetic algorithm with diversity-guided mutation does not lead to premature convergence. It is also shown that the better balance between overcoming premature convergence and quickening convergence speed can be gotten.     

广东日化:进攻才是最好的防守

2004年中国日化市场竞争异常激烈,残酷的“洗牌”时代揭开序幕。国际日化品牌全线进攻,本土日化巨头强势出击：高空轰炸,传播策略大转身;地面席卷,渠道价格全渗透;广东日化的市场份额不断被蚕食,面临严峻的生存挑战,是坐以待毙还是奋起直追,出路在何方?     

高应变率加载下复合泡沫塑料的吸能特性及失效机理研究

通过SHPB冲击实验装置对空心玻璃微球填充聚氨酯复合泡沫塑料进行了动态压缩实验,获得了不同密度复合泡沫塑料在高应变率加载条件下的应力-应变曲线,研究了材料的动态力学性能。基于所获得的应力-应变曲线,进一步分析和讨论了复合泡沫塑料的能量吸收特性,发现材料最佳吸能点的包络线是同一直线。此外,通过动态变形试件的扫描电镜分析,还研究了这类新材料的动态失效问题。     

硬质合金金刚石涂层的残余应力分析

采用有限元方法分析硬质合金金刚石涂层的热残余应力,采用轴对称二维几何模型和自由边界条件,考虑了涂层厚度及不同基体对应力场的影响。分析表明,在多晶金刚石涂层中存在压应力,在基体中出现了拉应力,这种应力结构分布对材料性能的影响是有利的。在明锐界面出现了大的剪切应力(415MPa),应力奇异场出现在明锐界面靠近自由边界处。涂层压应力随基体中钴含量的增加而增加,随涂层厚度的增加而减小。因此可以借助这两个因素来适当控制和调节材料中的应力场以得到性能优良的产品。     

A New Series of Mo-free 215Cr-35Ni-xW-02N Economical Duplex Stainless Steels

A new series of economical Mo-free duplex stainless steels 21.5Cr-3.5Ni-xW-0.2N(x=1.8-3.0,mass%) have been developed.The effects of W on mechanical properties and corrosion resistance were investigated,and the microstructures were analyzed by optical microscopy,X-ray diffraction,transmission electron microscopy and electron backscatter diffraction.The designed steels have a balanced ferrite-austenite relation and are free of sigma phase after solution treatment at 750-1 300℃for 30min followed by water-quenching,whereas a small number of Cr23 C6 precipitates were found after solution treatment at 750℃.After solution treatment at 1 050℃,the steel with 1.8%(mass percent)W exhibits the highest room temperature tensile strength due to the strongest work hardening effect, while the steel with 3.0%(mass percent)W exhibits the highest fracture elongation owing to the transformation-induced plasticity(TRIP)effect.The ductile-brittle transition(DBT)and martensite transformation are respectively found in the ferrite and austenite,which deteriorates the impact properties of the steels with the increase of W content.The corrosion resistance of the designed steels is improved with the increase of W content.The pitting resistance of austenite is obviously better than that of ferrite for the designed alloys.Among the designed steels,the steel with 1.8%(mass percent)W is found to be an optimum steel with excellent comprehensive properties and lowest production cost.     

关键块体系统锚固法在加固边坡危岩中的应用

基于Goodman-Shi的块体理论和A.R.Yarahmadi Bafg hi的关键块体群理论,提出确定危岩边坡关键块体和关键块体系统的几何分析法和矢量分析法,建立边坡危岩的地质模型和力学模型,分析危岩体破坏机理,针对不同变形破坏机理的关键块体系统提出合理、安全和经济的危岩边坡加固新方法--关键块体系统锚固法(KSA法).通过建立集丹公路K49+790 m-K55+550 m段危岩边坡的地质模型和力学模型,结合其坡体及岩体结构特征,分析边坡危岩体变形破坏机理和锚固机理,提出顶部危岩清除,碎裂结构坡面喷射混凝土,块裂结构坡面挂网和块状岩体锚固的清-喷-网-锚联合锚固的系统锚固方案,加固该段危岩体.运用该法锚固方案较传统方法节省锚杆35%、SNS网32%及腰梁19%.