Force and thermal tactile sensing can recognize contact with different materials and contact with the human body. Robots could benefit from skin with both force and thermal sensing, such as when manipulating objects in human environments. However, designing thermal sensing skin for robots presents a number of challenges, including heating the sensors, achieving a fast response time, and distributing the sensors to make contact.
We present a novel fabric-based skin for robots that combines force and thermal sensing. The skin's stretchable fabric-based design adds a layer of compliance to the robot's exterior and enables it to cover curved surfaces on a robot and conform to manipulated objects to improve sensing. The design incorporates small self-heated temperature sensors on the surface of the skin that directly make contact with objects, thereby improving the sensors' response time.
To evaluate the design, we conducted tests in which a robot arm used a cylindrical end effector covered with skin to slide and press on objects made from four different materials and make contact with two locations on the arms of 10 human participants. The system could detect the onset of contact via the force sensors and then use the active thermal sensors to distinguish contact with different materials, and the force and active and passive thermal sensors to distinguish contact between humans and non-human objects.
In our evaluation of the skin, with 2 s of contact, the active thermal sensors enabled binary classification accuracy over 90% for the majority of material pairs. For discrimination between humans vs. objects, the skin's force and active and passive thermal sensing modalities allowed for 93% classification accuracy with 0.5 s of contact. Overall, our results suggest that the skin design could enable robots to recognize contact with distinct task-relevant materials and humans while performing manipulation tasks.