What is considered safe for a robot operator during physical human-robot collaboration (HRC) is specified in corresponding HRC standards (e.g., ISO/TS 15066). The regime that allows collisions between the moving robot and the operator, called Power and Force Limiting (PFL), restricts the permissible contact forces. Using the same fixed contact thresholds on the entire robot surface results in significant and unnecessary productivity losses, as the robot needs to stop even when impact forces are within limits. Here we present a framework that decides whether the robot should interrupt or continue its motion based on estimated collision force computed individually for different parts of the robot body and dynamically on the fly, based on the effective mass of each robot link and the link velocity. We performed experiments on simulated and real 6-axis collaborative robot arm (UR10e) with sensitive skin (AIRSKIN) for collision detection and isolation. To demonstrate the generality of our method, we added experiments on the simulated KUKA LBR iiwa robot, where collision detection and isolation draws on joint torque sensing. On a mock pick-and-place scenario with both transient and quasi-static collisions, we demonstrate how sensitivity to collisions influences the task performance and number of stops. We show an increase in productivity over 45% from using the standard approach that interrupts the tasks during every collision. While reducing the cycle time and the number of interruptions, our framework also ensures the safety of human operators. The method is applicable to any robot for which the effective mass can be calculated.

翻译：在物理人机协作（HRC）中，机器人操作员的安全要求由相应的HRC标准（如ISO/TS 15066）规定。允许移动机器人与操作员发生碰撞的机制——功率与力限制（PFL）——对允许的接触力进行了限制。若在整个机器人表面采用相同的固定接触阈值，将导致显著且不必要的生产效率损失，因为即使冲击力在限值内，机器人仍需停止运动。本文提出一种框架，该框架基于对机器人身体不同部位单独、动态实时计算的估计碰撞力（依据各机器人连杆的有效质量与连杆速度），决定机器人应中断或继续其运动。我们在配备敏感皮肤（AIRSKIN）用于碰撞检测与隔离的模拟及真实六轴协作机械臂（UR10e）上进行了实验。为证明方法的通用性，我们增加了在模拟KUKA LBR iiwa机器人上的实验，该机器人通过关节力矩传感实现碰撞检测与隔离。在一个包含瞬态与准静态碰撞的模拟拾放场景中，我们展示了碰撞灵敏度如何影响任务性能与停止次数。实验表明，相较于每次碰撞均中断任务的标准方法，本方法使生产效率提升超过45%。在减少循环时间与中断次数的同时，本框架亦确保了操作人员的安全。该方法适用于任何可计算有效质量的机器人。