An Efficient Online Trajectory Generation Method Based on Kinodynamic Path Search and Trajectory Optimization for Human-Robot Interaction Safety

With the rapid development of robot perception and planning technology, robots are gradually getting rid of fixed fences and working closely with humans in shared workspaces. The safety of human-robot coexistence has become critical. Traditional motion planning methods perform poorly in dynamic environments where obstacles motion is highly uncertain. In this paper, we propose an efficient online trajectory generation method to help manipulator autonomous planning in dynamic environments. Our approach starts with an efficient kinodynamic path search algorithm that considers the links constraints and finds a safe and feasible initial trajectory with minimal control effort and time. To increase the clearance between the trajectory and obstacles and improve the smoothness, a trajectory optimization method using the B-spline convex hull property is adopted to minimize the penalty of collision cost, smoothness, and dynamical feasibility. To avoid the collisions between the links and obstacles and the collisions of the links themselves, a constraint-relaxed links collision avoidance method is developed by solving a quadratic programming problem. Compared with the existing state-of-the-art planning method for dynamic environments and advanced trajectory optimization method, our method can generate a smoother, collision-free trajectory in less time with a higher success rate. Detailed simulation comparison experiments, as well as real-world experiments, are reported to verify the effectiveness of our method.     

轮式移动教育机器人避障方法的研究

对一种轮式移动教育机器人进行了研究,在实验中采用传统的红外传感器使机器人具有避障功能,另外使用新颖的机械式胡须对机器人进行避障设计,达到了预期的避障效果。以胡须避障为例,讨论并解决了避障过程中的卡死问题,并给出了利用BASIC语言编写控制程序的方法。     

汽车防撞系统高速激光脉冲收发回路的实验研究

针对汽车防撞系统中的激光测距技术,提出了利用数字脉冲调制大功率窄脉冲半导体激光二极管(PLD),模拟开关拉升调制电平,以及电容充放电储能回路驱动PLD的方法,在车载12 V电源电压下,实验实现了波长1.55 μm、脉宽10 ns、周期为1.6 μs的激光脉冲发射,峰值功率大于3 W.激光脉冲的光学收发装置采用了准值光路和双回转扫描技术,实现目标的二维扫描和同一性判断,同时用高灵敏积分器对信号进行数据采集实现测距.实验研究得到,该光电收发回路降低了激光发射电路的电源功率,减小了收发过程的测量误差,解决了对光脉冲窄脉宽测量的精度问题,并且有良好的电光特性.     

关于七元统计量模式避免Fishburn排列的计数

Fishburn 排列与许多重要组合结构包括区间序存在双射. 在这篇论文中, 我们利用生成树的方法, 得到两类模式避免Fishburn排列的关于7元经典统计量的生成函数.我们考虑的类别是避免 (321,312) 和 (321,4123) 模式的 Fishburn 排列.我们关注的统计量包括升序数、降序数、逆序数、从右到左的极大值、从右到左的极小值、从左到右的极大值和从左到右的极小值。我们的结果推广了 Egge 的一个结论.     

A differential game of evasion with delays

A game of evasion (or contact avoidance problem) described by a system of differential equations containing delays in state and control is considered. There is given a sufficient condition for the existence of a strategy which ensures the contact avoidance. A method of constructing such a strategy is presented.     

退化椭圆型障碍问题弱解的边界正则性

本文研究包含于R~N的有Lipschitz边界的有界区域Ω上涉及到 p-Laplacian算子的退化椭圆障碍问题弱解的边界正则性,得到了C_(loc)~(1,α)边界正则性。     

基于蚁群算法的无人船平滑路径规划

为解决无人驾驶船舶在复杂环境中规划路径时存在的转向角度大、路径拐点多、航行能耗高等问题,文中提出一种基于改进蚁群算法的平滑路径规划方法。该方法采用栅格法进行环境建模,通过在启发函数中引入路径平滑度、距离启发因子以及在路径转移概率中引入障碍物启发因素,提高路径寻优和静态避障能力。结合启发因素改进信息素更新标准,设置可调节信息素挥发因子增加算法的自适应性。提取输出的最优路径关键节点并对其进行平滑处理,进一步保证路径平滑度和安全性。根据不同栅格环境下的避障仿真结果可知,与传统算法相比,文中改进蚁群算法的路径寻优速度提高了45%～62%,转向次数减少了25%～44%,平滑处理后的路径安全性和可行性得到了提升,较好地实现了不同环境下无人船自主路径规划。     

Systematic review of congestion handling techniques for 802.11 wireless networks

IEEE 802.11 is a matured standard for wireless local area networks (WLANs). The cellular network providers had made every possible effort to offload their traffic over WLANs whenever it was possible, owing to the benefits that this technology provides. IEEE 802.11 is gaining greater prominence with the arrival of 802.11ax standard, which is backed by the Wi‐Fi alliance by branding as Wi‐Fi 6. The issue of congestion has been studied well for various networks. Particularly, in wireless networks, it needs to be tackled in a peculiar manner owing to the uncertain nature of the wireless medium. This study explores and evaluates the improvements done at various protocol layers to handle the problem of congestion in 802.11‐based wireless networks. An attempt is made to understand the implication of different parameters and the significance of cross‐layer interaction. Further, an endeavor is made to assess the influence on congestion control mechanisms in the different architectures of 802.11 networks. Lastly, the challenges that might be confronted at different protocol layers, while dealing with the issue of congestion, are classified.     

基于模糊贝叶斯网络算法的智能轮椅避障

对传统BP神经网络模糊逻辑的智能轮椅避障方法在训练过程中存在的过拟合和避障路径不够优化的问题,提出了一种模糊贝叶斯网络避障算法以降低神经网络的复杂度。该算法利用模糊神经网络对隶属度函数的参数进行自主学习调整,同时为增强神经网络的泛化能力和计算能力,在网络目标函数中加入权衰减项,利用贝叶斯原理优化神经网络的结构和权值。仿真和实机实验表明,该算法在训练结果和避障效果上均优于传统BP神经网络,提高了智能轮椅避障的实时性,优化了避障路径,可满足用户对智能轮椅安全性和舒适性的需求。化了避障路径,可满足用户对智能轮椅安全性和舒适性的需求。     

Modified Rayleigh conjecture method and its applications

The Rayleigh conjecture about convergence up to the boundary of the series representing the scattered field in the exterior of an obstacle D$D$ is widely used by engineers in applications. However this conjecture is false for some obstacles. AGR introduced the Modified Rayleigh Conjecture (MRC), which is an exact mathematical result. In this paper we present the theoretical basis for the MRC method for 2D and 3D obstacle scattering problems, for static problems, and for scattering by periodic structures. We also present successful numerical algorithms based on the MRC for various scattering problems. The MRC method is easy to implement for both simple and complex geometries. It is shown to be a viable alternative for other obstacle scattering methods. Various direct and inverse scattering problems require finding global minima of functions of several variables. The Stability Index Method (SIM) combines stochastic and deterministic method to accomplish such a minimization.