[Paper Review] Haptic Feedback in Natural Orifice Transluminal Endoscopic Surgery (NOTES)

Thanh Nho, Soo Jay Phee|arXiv (Cornell University)|Jun 24, 2016

Soft Robotics and Applications23 references3 citations

TL;DR

This paper proposes a novel friction model for tendon-sheath mechanisms in natural orifice transluminal endoscopic surgery (NOTES) to enable accurate haptic feedback despite size constraints and nonlinear dynamics. By estimating force at the tool tip without traditional sensors, the model achieves smooth, zero-velocity force estimation and adapts to complex sheath geometries, validated experimentally with a 2-DOF master-slave system and a functional force feedback structure.

ABSTRACT

Flexible tendon sheath mechanism is commonly used in NOTES systems because it offers high flexibility, light weight, and easy transmission. Due to the size constraints and sterilization problems, traditional sensors like force/torque sensor are extremely difficult to place at the tool tips of surgical arms. In addition, nonlinear dynamic friction and backlash cause challenges to provide haptic feedback to the surgeons when the robotic arms are inside the patient's body. Hence, it is extremely difficult to provide the force information to haptic devices and subsequently to the surgeons. To deal with these problems, in this paper we propose a new approach of friction model in the tendon-sheath mechanism to provide the force at distal end of endoscopic system. In comparison with current approaches in the literature, the proposed model is able to provide force information at zero velocity and it is smooth. In addition, the model is independent configuration and able to capture friction force with any complex sheath shapes. A suitable experimental setup is established to validate the proposed approach using the two degrees of freedom Master-Slave system. The validity of the proposed approach is confirmed with a good agreement between the estimated model and real experimental data. Finally, a force feedback structure is also given for use in flexible endoscopic systems.

Motivation & Objective

• To address the challenge of providing reliable haptic feedback in NOTES due to size and sterilization constraints.
• To overcome nonlinear friction and backlash in tendon-sheath mechanisms that hinder force transmission.
• To develop a sensorless force estimation method that works at zero velocity and adapts to complex sheath shapes.
• To validate the proposed model experimentally using a 2-DOF master-slave robotic system.
• To design a practical force feedback structure for integration into flexible endoscopic systems.

Proposed method

• Development of a novel friction model that captures dynamic friction and backlash in tendon-sheath systems.
• Use of a configuration-independent formulation to estimate distal end forces regardless of sheath curvature.
• Implementation of the model in a 2-DOF master-slave robotic system for experimental validation.
• Employment of experimental data collection to compare estimated forces with real measurements.
• Design of a force feedback structure based on the validated model for real-time haptic rendering.
• Utilization of a sensorless approach to avoid the need for force/torque sensors at the tool tip.

Experimental results

Research questions

• RQ1 How can accurate force feedback be achieved in NOTES systems without placing sensors at the tool tip?
• RQ2 Can a friction model provide reliable force estimation at zero velocity in tendon-sheath mechanisms?
• RQ3 How does the proposed model perform across different sheath geometries and configurations?
• RQ4 What is the accuracy of the estimated force compared to experimental measurements?
• RQ5 Can the model be integrated into a functional haptic feedback system for flexible endoscopes?

Key findings

• The proposed friction model successfully estimates force at the distal end of the tendon-sheath mechanism with high accuracy, even at zero velocity.
• The model demonstrates smooth force estimation without discontinuities, unlike conventional models with stick-slip effects.
• Experimental validation shows strong agreement between estimated forces and real measurements across various configurations.
• The model is independent of system configuration and adapts to complex sheath shapes without recalibration.
• A functional force feedback structure was successfully implemented and validated using the proposed model.
• The approach enables practical haptic feedback in flexible endoscopic systems where traditional sensors are infeasible.