干式铣削Al-50wt%Si高硅铝合金刀具磨损与表面粗糙度评价

本文以Al-50wt%Si高硅铝合金为研究对象，采用单因素试验方法进行无涂层硬质合金刀具干式铣削试验，分析切削参数对刀具磨损和表面粗糙度的影响。结果表明：表面粗糙度受每齿进给量的影响最显著，随每齿进给量的增加而增加，当每齿进给量从0.07 mm/z增加到0.16 mm/z时，表面粗糙度增加2倍；刀具磨损受切削速度的影响最显著，随切削速度的增加而增加，当切削速度从140 m/min增加到260 m/min时，切削总长度降低3倍，而刀具后刀面磨损量仅是260 m/min速度下的0.8倍；表面粗糙度随刀具磨损的增加呈现先增加后降低的变化趋势，切削长度从350 mm增加到1 750 mm，刀具磨损量平均增加4.5倍，而表面粗糙度却下降2倍；硬质合金刀具主要的磨损形式为磨粒磨损、崩刃。     

Improving performance of macro electrolyte jet machining of TC4 titanium alloy: Experimental and numerical studies

Electrolyte jet machining (EJM) is a promising method for shaping titanium alloys due to its lack of tool wear, thermal and residual stress, and cracks and burrs. Recently, macro-EJM has attracted increasing attention for its high efficiency in machining wide grooves or planes. However, macro-EJM generates large amounts of electrolytic products, thereby increasing the difficulty of rapid product removal with a standard tool and reducing the surface quality. Therefore, for enhanced product transport, a novel tool with a back inclined end face was proposed for macro-EJM of TC4 titanium alloy. For comparison, also proposed were ones with a standard flat end face, a front inclined end face, and both front and back inclined end faces. The flow field distributions of all proposed tools were simulated numerically, and experiments were also conducted to validate the simulation results. The results show that one with a 5° back inclined end face can decrease the low-velocity flow zone in the machining area and increase the high-velocity flow zone at the back end of tool, thereby promoting rapid product removal. A relatively smooth bright-white groove surface was obtained. The same tool also resulted in the highest machining depth and material removal rate among the tested ones. In addition, rapid product removal was beneficial to the subsequent processing. Because of its rapid product removal, the machining depth and material removal rate during deep groove machining using the tool with a 5° back inclined end face were respectively 7% and 14% higher than those produced using a standard one. Moreover, the lowest bottom height difference of 0.027 mm can be obtained when the step-over value was 8.2 mm, and a plane with a depth of 0.285 mm and a bottom height difference of 0.03 mm was fabricated using the tool with a 5° back inclined end face.     

弱全局信息下月面超远距离保通行性移动规划

针对月面超远距离移动规划任务因缺乏精确全局信息而导致的规划路径可通行性不足问题，提出了月面道路拓扑网的构建设想及相应路径规划技术，凭借复杂道路网络的连通能力确保巡视器超远距离规划路径的可通行性。首先进行月面道路拓扑网的设计方法研究，分别提出了基于滑动最优泊松采样算法的网络节点设计方法和基于均匀领邻网络拓扑模型网络结构设计方法，使月面道路网网络节点分布均匀、密度适中且覆盖完整，网络连接合理且各路径尽量远离障碍区域。然后进行基于月面道路拓扑网的超远距离移动规划研究，分析了基于月面道路拓扑网路径规划技术的概率完备性和整体可通行概率，并提出了基于月面道路拓扑网的K优路径规划方法，通过道路网的连通性来提高超远距离移动探测任务的整体可通行概率。最后以阿波罗两次登月任务的着陆点之间进行超远距离转移任务为仿真场景，验证了本方法的有效性。     

基于状态改变的机器人路径规划算法

为了解决目前机器人路径规划中时效性低、避障解算量大的问题,借鉴直流电路中理想电感元件两端电压能够从感抗状态恢复到稳定状态的现象,提出了一种利用机器人状态检测量对机器人状态实时检测,从而实现避障的机器人路径规划算法.首先对绕行单个固定障碍物的机器人进行深入分析,然后采用状态叠加的方法,生成任意位置多障碍物同时存在的避障路径.同时对斥力系数进行改进,以确保机器人能够有效到达目标点.为了验证算法在多障碍物环境下的路径规划能力,进行了数值仿真模拟实验.仿真结果表明,使用该算法规划机器人路径时,能够在避免局部极小值点和目标不可达问题的前提下,在较短时间内规划出机器人由起始点到目标点的路径.