Development of Real-Time Contact Force Control of a Collaborative Robot for Automated Ultrasound Scanning

For treating liver cancer, ablation is a minimally invasive treatment option, though it relies on image guidance such as ultrasound. There is a general continuing interest in automating medical ultrasound image acquisition due to it being widely used, lower cost and more portable compared to other imaging modalities. Earlier interest in using robots for automating sonography revolve around remote ultrasonography i.e. teleimaging. More recently there is increasing interest in semi-automated or fully automated image robotic image acquisition. In this work we envisage automated robot assisted ultrasound imaging for liver ablation surgery. We propose the use of a collaborative robot arm from Universal RobotsTM (UR) which also have been increasingly popular in a variety of applications. In this work we show a preliminary proof of concept of a real-time force control system to control the contact force applied across a small angular range by the robot with respect to the surface a torso phantom. This is intended to represent the range of contact angles during ultrasound imaging. We use the Robot Operating System (ROS) and the UR Real-Time Data Exchange (UR-RTDE) interface to control the robot. We show that the contact force can be maintained around 9 N albeit with deviations due to the actual contact angle and surface deformation. The result will guide further development of automation of ultrasound scanning.