SAPM: Self-Adaptive Parallel Manipulator With Pose and Force Adjustment for Robotic Ultrasonography

Robotic ultrasonography potentially acts as an essential aid to medical diagnosis. To overcome the limitations in robotic ultrasonography, in this article, we proposed a novel self-adaptive parallel manipulator (SAPM) that can automatically adjust the ultrasound (US) probe pose to adapt to various contours of scanned areas, provide approximate constant operating forces/torques, achieve mechanical measurement, and cushion undesired produced forces. A novel parallel adjustment mechanism is proposed to attain automatic pose adjustment with 3 degrees of freedom (DOFs). This mechanism enables the US probe to adapt to different scanned areas and to perform the scanning with approximate constant forces and torques. Besides, we present a mechanical measurement and safety protection method that can be integrated into the SAPM and used as operation status monitoring and early warning during scanning procedures by capturing operating forces and torques. Experiments were carried out to calibrate the measurement and buffer units and evaluate the performance of the SAPM. Experimental results show the ability of the SAPM to provide 3 DOFs motion and operating force/torque measurement and automatically adjust the US probe pose to capture US images of equally good quality compared to a manual sonographer scan. Moreover, it has characteristics similar to soft robots that could significantly improve operation safety, and could be extended to some other engineering or medical applications.

I. Introduction

Robotic ultrasonography has become a potentially effective tool in medical applications due to its precision, dexterity, and repeatability [1], [2]. A commercial ultrasound (US) probe is commonly mounted on a robotic arm operated remotely by sonographers in robotic ultrasonography (see Fig. 1). During the scanning procedure, sonographers manipulate the robot system through the following three types of operations: 1)

control the robotic arm and position its end near the target;

2)

adjust the pose of the US probe to achieve satisfactory imaging angles;

3)

control the contact forces and torques between the scanned areas and the US probe within a safe range (especially for the fetal imaging);

Fig. 1.

Diagram of the robotic ultrasonography.