An Active Strategy for Safe Human–Robot Interaction Based on Visual–Tactile Perception

Ensuring safety is crucial for robots collaborating with humans in a shared workspace. Current human–robot interaction (HRI) safety strategies focus on either precollision motion replanning or postcollision force control, using unimodal perception. In this article, we present an active safety strategy that combines precollision and postcollision strategies using a hierarchical control architecture, making it possible to ensure safety throughout the entire HRI process. The inner loop utilizes a whole-body compliance controller to reduce multicontact forces throughout the robot's body. The outer loop involves velocity scaling that anticipates collisions based on visual perception and decelerates the robot's velocity before a collision occurs. This deceleration also simplifies the inner force control law to a computationally efficient linear model. Furthermore, to relieve the communication load of large-scale tactile systems and enable real-time control, we propose the vision assisted event-driven mechanism. It selectively transmits tactile information from potential collision areas. We have constructed a humanoid robotic platform called the visual–tactile humanoid robot and conducted four experiments. Our results demonstrate that our proposed strategy actively ensures safety in the whole process of HRI. The comparison study also confirms that the strategy can both reduce the impact forces at the beginning of the collisions and dissipate the subsequent continuous contact forces compared with existing works. This active strategy promises safety for various scenarios where humans and robots require close and frequent physical contacts.