Design and control of a novel gastroscope intervention mechanism with circumferentially pneumatic-driven clamping function

Background: Robot-assisted manipulation is promising for solving problems such as understaffing and the risk of infection in gastro-intestinal endoscopy. However, the commonly used friction rollers in few existing systems have a potential risk of deforming flexible endoscopes for non-uniform clamping. Methods: This paper presents a robotic system for a standard flexible endoscope and focuses on a novel gastroscope intervention mechanism (GIM), which provides circumferentially uniform clamping with an airbag. The GIM works with a relay-on mechanism in a way similar to manual operation. The shear stiffness of airbag and the critical slipping force (CSF) were analyzed to determine the parameters of the airbag. A fuzzy PID controller was employed to realize a fast response and high accuracy of pneumatic actuation. Experiments were performed to evaluate the accuracy, stiffness and CSF. In vitro and in vivo animal experiments were also carried out. Results: The GIM realized an accuracy of 0.025±0.2mm and –0.03±0.25° for push–pull and rotation without delivery resistance. Under <10N delivery resistance, the error caused by the airbag stiffness was <0.24mm. A quadratic polynomial could be used to describe the relationship between the CSF and pneumatic pressure. Conclusions: The novel GIM could effectively deliver gastroscopes. The pneumatic-driven clamping method proposed could protect the gastroscope by circumferentially uniform clamping force and the CSF could be properly controlled to guarantee operating safety.