Test Set-up to Study the Behavior of a Flexible Instrument in a Bent Tube

Abstract

The continued involvement of flexible endoscopy in carrying out both diagnostic and therapeutic interventions requires complex manipulation of flexible surgical instrument. The instrument is guided through the endoscope. The motion and force are transmitted to the distal end of the instrument by actuating the proximal end. The friction and the clearance between the instrument and the endoscope, together with the limited stiffness of the instrument, induces non-linear dynamic behavior, which jeopardizes the motion and force fidelity of the instrument. In order to study the dynamic behavior of the instrument, simulations were carried out using a flexible multibody model. The simulation results showed stick-slip behavior and motion hysteresis, which depend on a number of parameters such as the shape of the bent tube, friction, and stiffness of the instrument. This paper will discuss the test set-up which was designed to validate the model and simulation results, and also to characterize the instrument behavior inside a bent tube. The design objectives of the set-up are to actuate the instrument tip from the proximal end, to measure the interaction force between the instrument and the bent tube, and to measure the tip motion.