Hybrid Manipulator With Force Estimation for Lower Gastrointestinal Interventions

This letter introduces a novel hybrid manipulator composed of two pneumatically-actuated soft segments and a tendon-driven continuum segment, connected in series. The soft segments enhance the mobility of the tendon-driven manipulator, enabling functionalities such as triangulation while maintaining low tool stiffness, making it suitable for endoluminal surgery in the lower gastrointestinal tract. A key advantage of this design is the implementation of a model-based controller and an observer-based contact force estimation method, which estimates external forces based on the configuration and actuation of the soft segments. This approach is experimentally compared to a tendon tension sensing methodology, known as intrinsic force sensing. The experiments include typical lifting and pushing tasks, along with realistic operations on ex-vivo porcine intestinal tissue. The results demonstrate the feasibility of the proposed approach in surgical applications and its advantages over intrinsic force sensing, achieving an average 15.8% reduction in normalized RMSE among all tasks.