High-Curvature Consecutive Tip Steering of a Soft Growing Robot for Improved Target Reachability

Over the years, soft growing robots that allow the feeding of new materials at their tips have attracted considerable attention owing to their unique locomotion characteristics. However, accessing targets over highly curved passages by steering compliant continuum bodies remains challenging. To this end, this study proposes a new tip steering mechanism that imparts soft growing robots with consecutive high-curvature steering ability. We place a hyper-redundant rolling contact joint and twisted string actuator (TSA) at the tip of a soft growing robot to provide high-curvature continuous steering with a smaller scale factor, allowing consecutive turns. The proposed small form factor continuous curvature tip steering mechanism allows the steering mechanism to stay at the tip during steering, improving accessibility by enabling consecutive turns. The improved accessibility of the proposed mechanism is demonstrated based on better confined space reachability compared with that of conventional whole-body steering soft growing robots, along with a consecutive high-curvature pipe navigation demonstration.