Resonance-Based Object Sensing System for Soft Robotic Skin in Human Cooperative Robots

This article presents a resonance-based object sensing system (ROSS) for soft robotic skin applications to enhance human safety in human cooperative robots (HCRs). The proposed system utilizes the single-conductor power transfer (SCPT) methodology, enabling the ROSS coil to be integrated into the soft skin of robotic arm end effectors or fingers while operating with minimal power consumption (-16 to -56 dBm). The ROSS coil provides passive voltage gain due to its high quality factor (Q > 550). During human interaction with the soft skin of ROSS, it operates at 1.4 MHz and functions at its self-resonant frequency (SRF) in the radio frequency (RF) band. The DC output from the passive RF-to-DC converter circuit remains sufficiently high after conversion losses and can be directly interfaced with a microcontroller unit (MCU) for real-time testing of the ROSS. The ROSS responds by varying its DC output voltage depending on the type of object in contact, including insulating and conducting materials, as well as humans. It also differentiates the nature of interaction, such as gentle human touch and higher applied force (≥21 N) exerted by the human hand on the soft skin of the ROSS. This design shows the potential to enhance both safety and selectivity when integrated into the soft skin of robotic arm end effectors or fingers for future industrial HCR applications.