Geared Rod-Driven Continuum Robot With Woodpecker-Inspired Extension Mechanism and IMU-Based Force Sensing.

Continuum robot arms that can access confined spaces are useful in many applications, such as invasive surgery, search and rescue, and inspection. However, their reach is often limited because their extension mechanism relies on elastic deformation or folding structures. To address this challenge, we propose a continuum robot with a novel extension mechanism inspired by the impressive ability of woodpeckers to extend and bend their long tongues to catch insects in tree holes. The proposed mechanism can change the effective length of the robot from almost zero to any length by moving the robot's body back and forth. Our prototype robot demonstrated a maximum extension of 450 mm and a minimum bending radius of 125 mm. In addition, we developed a Gaussian process regression model to predict an external force applied to the robot's tip using inertial measurement units. This enabled us to determine the magnitude and direction of the force with an error rate of 4.8 percent and 11.1 percent, even when the robot's length was varied between the training and test data. The unrestricted extension capability of the proposed approach has the potential to increase the application prospects of continuum robots.