Integrated Navigation Algorithm for Large Concave Obstacles
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摘要:
针对移动机器人导航过程中无法规避大型凹型障碍物问题,该文提出一种多状态的组合导航算法。算法按照不同的运动环境,将移动机器人的运行状态分类为运行态、切换态、避障态,同时定义了基于移动机器人运行速度和运行时间的状态双切换条件。当移动机器人处于运行态时,采用人工势场法(APFM)进行导航,并实时观测毗邻障碍物的几何构型。在遭遇障碍物时,切换态用于判断是否满足状态切换条件,以进入避障态执行避障算法。避障完成后,状态自动切换回运行态继续执行导航任务。多状态的提出,可有效解决传统人工势场法在大型凹形障碍物的避障过程中存在局部震荡的问题。基于运行速度和运行时间的双切换条件判定算法,可实现多状态间的平滑切换。实验结果表明,该算法在解决局部震荡问题的同时,还可降低避障时间,提升导航算法效率。
Abstract:For the problem that mobile robot can not avoid large concave obstacles during navigation, this paper proposes a multi-state integrated navigation algorithm. The algorithm classifies the running state of mobile robot into running state, switching state and obstacle avoidance state according to different moving environment, and defines the state double switching conditions based on the running speed and running time of the mobile robot. The Artificial Potential Field Method (APFM) is used to navigate and observe the geometric configuration of adjacent obstacles in real time. When encountering an obstacle, the switching state is used to determine whether the state switching condition is satisfied, and the obstacle avoidance algorithm is executed to enter the obstacle avoidance state and enter the obstacle avoidance state to implement the obstacle avoidance algorithm. After the obstacle avoidance is completed, the state automatically switches back to the running state to continue the navigation task. The proposal of multi-state can solve the problem of local oscillation of traditional artificial potential field method in the process of avoiding large concave obstacles. Furthermore, the double-switching condition determination algorithm based on running speed and running time can realize smooth switching between states and optimize the path. The experimental results show that the algorithm can not only solve the local oscillation problem, but also reduce the obstacle avoidance time and improve the efficiency of the navigation algorithm.
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表 1 人工势场法符号含义
符号 符号含义 符号 符号含义 ${\rm{obs}}$ 障碍物 ${\bf{X}}{\rm{d}}$ 目标位置 ${U_{{\rm{Xd}}}}(x)$ 引力势能 ${U_{{\rm{obs}}}}(x)$ 斥力势能 ${U_{{\rm{art}}}}(x)$ 总势能 ${{F}}$ 合力 ${{{F}}_{{\rm{Xd}}}}$ 吸引力 ${{F}}_{\rm{obs}}$ 排斥力 $j$ 移动机器人感知到的
周边障碍物的个数表 2 A*算法符号含义
符号 符号含义 符号 符号含义 $g(\cdot )$ 从初始节点到当前移动机器人
所在节点node的启发式评估代价$h(\cdot )$ 从当前移动机器人所在节点node到
目标节点的启发式评估代价$(x_{\rm{start}},y_{\rm{start}})$ 初始节点坐标 $(x_{\rm{goal}},y_{\rm{goal}})$ 目标节点坐标 $(x,y)$ 移动机器人实时位置坐标 表 3 模型描述符号含义
符号 符号含义 符号 符号含义 $O_1$ 障碍物的左端点 $O_2$ 障碍物的右端点 $2\alpha $ 障碍物的长 $\beta $ 障碍物的宽 $v_t$ 移动机器人的实时线速度 $a$ 移动机器人在运行态时的最大速度 $\Delta d$ 移动机器人在某段时间内的移动距离 $S_{\rm{obs}}$ 所有障碍物总面积 $S_{\rm{map}}$ 地图面积 $\rho $ 障碍物密度 表 4 算法性能比较
算法 时间(s) 路径长度(m) A*算法 22.40 1040.69 改进人工势场法[15] 无穷大 无穷大 本文组合算法 10.62 707.09 -
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