EndoForce: Development of an Intuitive Axial Force Measurement Device for Endoscopic Robotic Systems

TL;DR

This paper introduces EndoForce, a dedicated axial force sensing device for endoscopic robotic systems. By mimicking clinicians’ insertion techniques, EndoForce delivers intuitive force feedback using a compact sensing assembly, an overload limiter for safety, and a detachable, sterilizable gripper, all powered by a commercial load cell for cost-effectiveness. Validation on a ureteroscope-based testbed with straight and curved pathways demonstrates accurate axial-force measurement, achieving RMSEs around 0.4 N and showing that EndoForce readings correspond to the sum of friction and distal-contact forces. The work lays groundwork for real-time haptic feedback and potential automation in endoscopic robotics, with plans to enhance adaptability, motion efficiency for longer scopes, and AI-based noise reduction to further improve reliability in clinical settings.

Abstract

Robotic endoscopic systems provide intuitive control and eliminate radiation exposure, making them a promising alternative to conventional methods. However, the lack of axial force measurement from the robot remains a major challenge, as it can lead to excessive colonic elongation, perforation, or ureteral complications. Although various methods have been proposed in previous studies, limitations such as model dependency, bulkiness, and environmental sensitivity remain challenges that should be addressed before clinical application. In this study, we propose EndoForce, a device designed for intuitive and accurate axial force measurement in endoscopic robotic systems. Inspired by the insertion motion performed by medical doctors during ureteroscopy and gastrointestinal (GI) endoscopy, EndoForce ensures precise force measuring while maintaining compatibility with clinical environments. The device features a streamlined design, allowing for the easy attachment and detachment of a sterile cover, and incorporates a commercial load cell to enhance cost-effectiveness and facilitate practical implementation in real medical applications. To validate the effectiveness of the proposed EndoForce, physical experiments were performed using a testbed that simulates the ureter. We show that the axial force generated during insertion was measured with high accuracy, regardless of whether the pathway was straight or curved, in a testbed simulating the human ureter.

Figures (7)

• Figure 1: An overview of the proposed force feedback device, EndoForce, capable of measuring the axial force from the endoscopic robotic system. The proposed device consists of three main components: a sensing part to measure the axial force; an overload protection part that prevents overload on the load cell; a gripper part for the stable insertion of the insertion tube; and a linear transport part to automate the forward and backward movements of the scope or the endoscopic robotic system.
• Figure 2: (a) Structural components of the sensing part, including the insertion tube holder, force transmission arm, hinge joint, ball tip, load cell, tension spring, and overload limiter; and (b) a simplified kinematic diagram illustrating the operating principle.
• Figure 3: Implementation of the overload limiter within the sensing part to ensure clinical safety. The overload limiter prevents potential damage to the load cell by restricting excessive forces when the endoscopic robotic system interacts with human tissue, such as the kidney or the inner wall of the colon.
• Figure 4: (a) Attachment procedure of the disposable insertion tube holder, designed to maintain sterilization by utilizing a sterile drape and minimizing cross-contamination risks; (b) bistable mechanism of the gripper part, ensuring stable holding of the insertion tube by maintaining the grasped state without continuous actuation.
• Figure 5: Operational principle of the insertion tube's forward and backward translation, along with the grasping and releasing mechanism. The system mechanically replicates the clinical procedure by sequentially grasping, advancing, and releasing the insertion tube. A servo motor and timing belt drive the linear transport part, enabling precise movement of the endoscopic robotic system while simultaneously performing axial force measurement.