Planning and Compliant Control for Laparoscopic Ultrasound Scanning System

Laparoscopic ultrasound (LUS) serves as a critical technology in intraoperative surgeries, particularly for guiding complex procedures in liver diseases. However, the development of robotic systems for LUS examination remains hindered by challenges such as high costs and the absence of force feedback capabilities. In this study, we develop an 8-degree-of-freedom (DOF) LUS scanning system, which integrates a flexible manipulator and a force-sensing probe fixture to achieve precise position adjustment and real-time force feedback. A geometry-based coordinate alignment method is proposed under remote centre of motion (RCM) constraints to ensure safe operational execution. In addition, in accordance with the estimated contact force from a neural network, a compliant force controller is designed to achieve high-quality ultrasound imaging. Experimental results validate the motion planning under the RCM constraint, yielding a maximum root mean square error (RMSE) of 0.767 mm, whereas contact force tracking achieved a maximum RMSE of 0.037 N. Furthermore, experiments on phantom models confirmed the effectiveness of the proposed approach, which was further validated on in vitro porcine liver to demonstrate its clinical potential.