Safety for physical human-robot interaction (pHRI) is a major concern for all application domains. While current standardization for industrial robot applications provide safety constraints that address the onset of pain in blunt impacts, these impact thresholds are difficult to use on edged or pointed impactors. The most severe injuries occur in constrained contact scenarios, where crushing is possible. Nevertheless, situations potentially resulting in constrained contact only occur in certain areas of a workspace and design or organisational approaches can be used to avoid them. What remains are risks to the human physical integrity caused by unconstrained accidental contacts, which are difficult to avoid while maintaining robot motion efficiency. Nevertheless, the probability and severity of injuries occurring with edged or pointed impacting objects in unconstrained collisions is hardly researched. In this paper, we propose an experimental setup and procedure using two pendulums modeling human hands and arms and robots to understand the injury potential of unconstrained collisions of human hands with edged objects. Pig feet are used as ex vivo surrogate samples - as these closely resemble the physiological characteristics of human hands - to create an initial injury database on the severity of injuries caused by unconstrained edged or pointed impacts. For the effective mass range of typical lightweight robots, the data obtained show low probabilities of injuries such as skin cuts or bone/tendon injuries in unconstrained collisions when the velocity is reduced to < 0.5 m/s. The proposed experimental setups and procedures should be complemented by sufficient human modeling and will eventually lead to a complete understanding of the biomechanical injury potential in pHRI.

翻译：物理人机交互（pHRI）的安全性是所有应用领域的主要关切点。虽然当前工业机器人应用标准提供了针对钝性冲击疼痛阈值的约束条件，但这些冲击阈值难以应用于边缘或尖端冲击体。最严重的损伤发生在约束接触场景中，此时可能发生挤压伤害。然而，仅在某些工作空间区域才会出现可能导致约束接触的情况，且可通过设计或组织方法予以避免。真正难以在保持机器人运动效率的同时完全规避的，是由无约束意外接触导致的人身伤害风险。尽管如此，对于边缘或尖端冲击物体在无约束碰撞中造成损伤的概率和严重程度，目前仍缺乏深入研究。本文提出一种实验装置与流程，通过两个分别模拟人手手臂和机器人的摆锤系统，探究人手与边缘物体发生无约束碰撞时的损伤潜力。采用猪蹄作为离体替代样本——因其生理特性与人手高度相似——构建关于无约束边缘或尖端冲击所致损伤严重程度的初始损伤数据库。在典型轻型机器人有效质量范围内，所获数据表明：当速度降至<0.5 m/s时，无约束碰撞导致皮肤切割或骨骼/肌腱损伤的概率较低。所提出的实验装置与流程应辅以充分的人体建模，最终将实现对pHRI中生物力学损伤潜力的完整认知。