Automatic Contact Force-regulated End-effector Using Pneumatic Actuator for Safe Robotic Ultrasound Imaging

Robotic-assisted ultrasound (US) imaging has demonstrated great promise to address issues such as high physical demands and limited scanning reproducibility in traditional freehand US procedures. Yet, using a robot arm to manipulate the US probe brings a fundamental concern about patient safety. This is because an overwhelming force can be easily produced from the robot joint actuation and exerted onto the patient's body when an electrical force-sensing error exists. Therefore, a mechanism that maintains a more compliant contact force, functioning independently from the robot arm, is needed to mitigate this concern. Here, we introduce a robotic US system with a novel automatic contact force-regulated end-effector. A linear pneumatic actuator is embedded in the end-effector to prevent excessive force from being applied to the patient. Such force compliance can be realized without relying on electrical force sensing and robot joint actuation. We tested the proposed system in US imaging tasks under a phantom-based environment. Results show that the contact force has an adjustable range from 4.10 N to 7.53 N, and can be regulated with ± 0.46 N variation using the automatic contact force-regulated end-effector during scanning, which demonstrates potential clinical applicability.