A Smooth Velocity Transition Framework Based on Hierarchical Proximity Sensing for Safe Human-Robot Interaction

With the rapid technology development pushing the introduction of the fifth industrial revolution, Industry 5.0, robots are getting rid of fences and sharing the workspace with humans. In such a context, ensuring the safety of humans and robots is a critical demand. One of the effective methods for this is proximity sensing, among which capacitive sensors are widely used to detect the proximity of humans. However, the capacitive sensor cannot get accurate distance information since the capacitance varies with the characteristics of obstacles. This work develops a capacitive robot skin, seamlessly integrated into the proposed smooth velocity transition framework to deal with this challenge. The robot skin is customized to cover a large area on the exterior of a 6-DOF robot arm. A hierarchical proximity perception approach is used to grade the sensing state. Based on this, distance reduction and collision avoidance velocity generation methods are used to reach a smooth and quick decay of the velocity. The control strategy is applied in a pick-and-place scenery for verification. Compared to the traditional threshold trigger method, the proposed smooth velocity transition framework can greatly reduce the absolute value of the local maximum acceleration, which can enable a flexible and natural human-robot interaction while ensuring human safety.