Jang Keunwoo, Kim Sanghyun, Park Jaeheung
Graduate School of Convergence Science and Technology, Seoul National University, Seoul 08826, Korea.
Korea Institute of Machinery and Materials (KIMM), Daejeon 34103, Korea.
Sensors (Basel). 2021 Jan 28;21(3):890. doi: 10.3390/s21030890.
This paper introduces a reactive self-collision avoidance algorithm for differentially driven mobile manipulators. The proposed method mainly focuses on self-collision between a manipulator and the mobile robot. We introduce the concept of a distance buffer border (DBB), which is a 3D curved surface enclosing a buffer region of the mobile robot. The region has the thickness equal to buffer distance. When the distance between the manipulator and mobile robot is less than the buffer distance, which means the manipulator lies inside the buffer region of the mobile robot, the proposed strategy is to move the mobile robot away from the manipulator in order for the manipulator to be placed outside the border of the region, the DBB. The strategy is achieved by exerting force on the mobile robot. Therefore, the manipulator can avoid self-collision with the mobile robot without modifying the predefined motion of the manipulator in a world Cartesian coordinate frame. In particular, the direction of the force is determined by considering the non-holonomic constraint of the differentially driven mobile robot. Additionally, the reachability of the manipulator is considered to arrive at a configuration in which the manipulator can be more maneuverable. In this respect, the proposed algorithm has a distinct advantage over existing avoidance methods that do not consider the non-holonomic constraint of the mobile robot and push links away from each other without considering the workspace. To realize the desired force and resulting torque, an avoidance task is constructed by converting them into the accelerations of the mobile robot. The avoidance task is smoothly inserted with a top priority into the controller based on hierarchical quadratic programming. The proposed algorithm was implemented on a differentially driven mobile robot with a 7-DOFs robotic arm and its performance was demonstrated in various experimental scenarios.
本文介绍了一种用于差分驱动移动机械臂的反应式自碰撞避免算法。所提出的方法主要关注机械臂与移动机器人之间的自碰撞。我们引入了距离缓冲边界（DBB）的概念，它是一个包围移动机器人缓冲区域的三维曲面。该区域的厚度等于缓冲距离。当机械臂与移动机器人之间的距离小于缓冲距离时，这意味着机械臂位于移动机器人的缓冲区域内，所提出的策略是将移动机器人移离机械臂，以使机械臂位于该区域（即DBB）的边界之外。该策略通过对移动机器人施加力来实现。因此，机械臂可以避免与移动机器人发生自碰撞，而无需在世界笛卡尔坐标系中修改机械臂的预定义运动。特别地，力的方向是通过考虑差分驱动移动机器人的非完整约束来确定的。此外，还考虑了机械臂的可达性，以达到一种使机械臂更具机动性的配置。在这方面，与现有的不考虑移动机器人非完整约束且不考虑工作空间就将连杆相互推开的避免方法相比，所提出的算法具有明显优势。为了实现所需的力和产生的扭矩，通过将它们转换为移动机器人的加速度来构建一个避免任务。该避免任务基于分层二次规划以最高优先级平滑地插入到控制器中。所提出的算法在一个带有7自由度机械臂的差分驱动移动机器人上实现，并在各种实验场景中展示了其性能。
