An alternative approach to robot safety

Robotic technology has made significant progresses in the past years. Robots are now common in large manufacturing plants and other industrial settings, safely confined in closed work cells. But to be even more helpful, robots need the capability of interacting physically with humans, and with unstructured environments. This poses new challenges in the design of safe robotic systems. In this article we addressed this problem by proposing a novel design for the joints of the iCub robot. The new design provides the robot with an overload protection mechanism. The overload protection acts as a “passive” torque saturator, which is intrinsically safe. We constructed a prototype of a robotic joint that implements this approach. We first show that our solution is effective in a typical impact scenario. We then evaluate the possible problems arising when the device is controlled with a position control loop. We show that a conventional feedback control loop can trigger positive feedback and instability. Operating the actuator in these conditions is dangerous and can lead to severe failures. We therefore propose the implementation of a relatively simple control strategy that allows to avoid this situation by monitoring slippage, without additional sensors. The quantitative evaluations in the paper demonstrate that our approach is effective and can improve the robustness and safety of complex robotic systems. Indeed these aspects are particularly critical in the case of humaniod robots that are systems prone to severe whole-body impacts in unstructured environments (e.g. falling).