Two-degree-of-freedom haptic device of the colonoscopy training simulator

Abstract

This thesis presents a new 2-DOF haptic device for a colonoscopy training simulator. The 2-DOF haptic device includes three parts, a translation motion part, a roll motion part, and folding guides. A wire-driven mechanism is used for translational force reflection. Roll torque is generated by a timing belt mechanism. These two mechanisms implement force and torque reflections large enough for the colonoscopy simulation. The folding guides keep the endoscope tube straight. The folding guides fold and spread like a curtain. This mechanism helps transmit forces and torques from the endoscope tip to the user. The specifications of 2-DOF haptic device such as continuous and maximum exertable forces and torques; workspace; sensitivity; and inertia in each direction are evaluated. The force bandwidth of the device is also evaluated through frequency response tests. The force bandwidth is suitable for simulation of colonoscopy. The 2-DOF mechanism is decoupled, so that Jacobian matrix has only diagonal elements. A closed-loop PD controller using a 6-DOF force/torque sensor is designed to reduce the friction and inertial effects. The user``s maneuvering forces are measured in real-time, and compensated for including the effects of coulomb and viscous friction. This provides the users with better transparent sensation of the simulation. A questionnaire test is conducted to evaluate the 2-DOF haptic device. The result of the questionnaire is analyzed by using a statistical method.