Area-Based Total Length Estimation for Position Control in Soft Growing Robots

Recently, the use of eversion-based movement in robotics has gained popularity. Eversion mechanisms enable objects to turn inside out, similar to flipping a sock, allowing them to move through narrow spaces without making direct force on the environment. This type of movement can be used for medical devices such as catheters and endoscopes [1]. For instance, an autonomous colonoscope must navigate through tight and curved spaces in the colon. Eversion movement is a suitable solution that allows the colonoscope to move more safely. Furthermore, the implementation of feedback control enhances the accuracy and efficiency of the examination process. The total length of the eversion portion (𝐿) is typically controlled by a reel mechanism [2]. The reel mechanism consists of a spool wrapped tightly with plastic tubing connected to a motor. The system calculates the total length by counting the number of motor rotations. However, the diameter of the reel mechanism varies depending on the layers of material around the roller, making it difficult to calculate the total length from the standard roller model [3], [4]. This paper introduces a method for calculating the total length of the everted portion based on area. The model was validated using an optical tracking camera and compared with four other methods for calculating the total length in roller mechanisms.