Hybrid force/impedance control method for ultrasound robot based on three-dimensional modeling

Abstract

The ultrasound robot not only needs to be able to maintain stable contact forces in the direction of the scan check normal in unknown or complex environments, but also needs to maintain safe human-robot interaction forces in other directions, and at the same time needs to satisfied the constraints of avoiding joint limits. In response to the above control requirements, this paper proposes a hybrid force/impedance control method for ultrasound robots based on three-dimensional modeling, which performs indirect force impedance control in the scan tangential direction of the ultrasound robot, and direct force control in the scan normal direction maintains stable contact forces between the ultrasound probe and human tissue, and introducing environmental three-dimensional point cloud information for scan normal position compensation. This improves the force control performance of the ultrasound robot in unknown environments. The tangential impedance control reduces the tangential contact force generated by the scanning motion of the robot and prevents the physical injury to the patient. The weighted minimum parametric number is also introduced into the hybrid force/impedance control to optimize the motion of the null space of the ultrasound robot and avoid the ultrasound robot from entering the joint limit in the contact interaction control. Finally the effectiveness and reliability of the proposed method is verified by ultrasound robot experiments.