Toward an automatic diagnostic scanning robotic system using ultrasound images

Ultrasonography is widely used for the diagnosis of various diseases. To obtain a clear view of the ultrasound image, an examiner needs to press the ultrasound (US) probe with a constant press and move smoothly and continuously. To mitigate the workload and prepare the remote treatment, there has been a demand for an automatic diagnostic scanning robotic system (ADSRS) using US images. For the complete ADSRS, the target localization, path planning, robot control, and US image analysis need to be addressed. This paper explains mainly the robot control part as the preliminary research toward ADSRS. A simple path was selected within a predefined inspection area as the preliminary work and the selected path was converted from the camera coordinates into the robot coordinates. Both the position and orientation of the US probe were used as the desired path. For the robot control, hybrid force- positon control was implemented to guarantee the quality of US images and the safety of patients. For the position control, the built-in Cartesian impedance control and null space control were utilized to control the 7-degree-of-freedom (7-DOF) manipulator. For the force control, the basic proportional control was implemented, and it was integrated with the aforementioned position control system. The experimental evaluation was conducted by using a 7-DOF manipulator with a joint torque sensor at each joint after attaching a US probe and a 3-dimensional (3-D) camera to an end-effector. The simple path over the surface of the skin of the patient was generated successfully, and the desired force during movement was set to 5N. The error is measured to 0.3144 +/- 0.4853 N. The proposed system shows sufficient performance in the robot control part and the path planning part.