Design of a Robotic System Featured With High Operation Transparency for Quantifying Arm Impedance During Ultrasound Scanning

Experienced sonographers can adjust their arm impedance in real-time to obtain high-quality ultrasound (US) images during US scanning. These operational skills can be captured through robot systems with multimodal data collection capabilities (position, force, and impedance). However, low operational transparency between the system (generally, a serial robot with admittance control) and its users will result in significant delays and errors, interfering with the skill acquisition process. The paper proposes a new system that adopts the parallel mechanism (Omega.7) to improve the transparency of the operation. The scanning probe and a 6-axis force sensor are attached to the end of Omega.7. When operating the probe, a zero-force drag effect can be realized through gravity and torque compensations. The arm impedance during the scanning can be measured through the force disturbance method by analyzing external forces on the device. Ultrasonic scans were conducted on phantoms of different hardness, and arm impedance was measured. Statistical analysis reveals that when scanning softer phantoms, arms exhibit higher stiffness. The transparency analysis results show that the equipment designed in this paper has a higher level of transparency than the scheme of serial robot with admittance control. The high operation transparency of the system makes it an ideal skill-acquisition device with broad applications.