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Multi-Axis Force Sensing in Robotic Minimally Invasive Surgery With No Instrument Modification

A. H. Hadi-Hosseinabadi, S. E. Salcudean

TL;DR

The paper tackles the lack of haptic feedback in RAMIS by introducing a proximal 6-axis optical force sensor and a two-tube cannula overcoat that filters body forces, enabling multi-axis force sensing without altering clinical instruments. It presents both model-based and data-driven calibration approaches, showing that lateral forces, moments, and axial torque can be resolved with high accuracy, while axial force remains more challenging due to frictional effects. The design is compact, high-bandwidth, and adaptable to different instruments, supporting real-time control and potential vibrotactile haptics. The work demonstrates robust filtering of body forces and evaluates the impact of wrist articulation, highlighting practical steps toward improved tactile feedback in RAMIS and outlining future calibration and design refinements.

Abstract

This paper presents a novel multi-axis force-sensing approach in robotic minimally invasive surgery with no modification to the surgical instrument. Thus, it is adaptable to different surgical instruments. A novel 6-axis optical force sensor, with local signal conditioning and digital electronics, was mounted onto the proximal shaft of a da Vinci EndoWrist instrument. A new cannula design comprising an inner tube and an outer tube was proposed. The inner tube is attached to the cannula interface to the robot base through a compliant leaf spring with adjustable stiffness. It allows bending of the instrument shaft due to the tip forces. The outer tube mechanically filters out the body forces from affecting the instrument bending behavior. A mathematical model of the sensing principle was developed and used for model-based calibration. A data-driven calibration based on a shallow neural network architecture comprising a single 5-nodes hidden layer and a 5x1 output layer is discussed. Extensive testing was conducted to validate that the sensor can successfully measure the lateral forces and moments and the axial torque applied to the instruments distal end within the desired resolution, accuracy, and range requirements.

Multi-Axis Force Sensing in Robotic Minimally Invasive Surgery With No Instrument Modification

TL;DR

The paper tackles the lack of haptic feedback in RAMIS by introducing a proximal 6-axis optical force sensor and a two-tube cannula overcoat that filters body forces, enabling multi-axis force sensing without altering clinical instruments. It presents both model-based and data-driven calibration approaches, showing that lateral forces, moments, and axial torque can be resolved with high accuracy, while axial force remains more challenging due to frictional effects. The design is compact, high-bandwidth, and adaptable to different instruments, supporting real-time control and potential vibrotactile haptics. The work demonstrates robust filtering of body forces and evaluates the impact of wrist articulation, highlighting practical steps toward improved tactile feedback in RAMIS and outlining future calibration and design refinements.

Abstract

This paper presents a novel multi-axis force-sensing approach in robotic minimally invasive surgery with no modification to the surgical instrument. Thus, it is adaptable to different surgical instruments. A novel 6-axis optical force sensor, with local signal conditioning and digital electronics, was mounted onto the proximal shaft of a da Vinci EndoWrist instrument. A new cannula design comprising an inner tube and an outer tube was proposed. The inner tube is attached to the cannula interface to the robot base through a compliant leaf spring with adjustable stiffness. It allows bending of the instrument shaft due to the tip forces. The outer tube mechanically filters out the body forces from affecting the instrument bending behavior. A mathematical model of the sensing principle was developed and used for model-based calibration. A data-driven calibration based on a shallow neural network architecture comprising a single 5-nodes hidden layer and a 5x1 output layer is discussed. Extensive testing was conducted to validate that the sensor can successfully measure the lateral forces and moments and the axial torque applied to the instruments distal end within the desired resolution, accuracy, and range requirements.

Paper Structure

This paper contains 13 sections, 9 equations, 14 figures, 1 table.

Table of Contents

  1. Introduction
  2. Introduction
  3. Background
  4. Motivation
  5. Sensing Approach
  6. Modeling
  7. Calibration
  8. Model-based
  9. Data-driven
  10. Design Evaluation
  11. Overcoat Test
  12. Wrist Maneuver Test
  13. Discussion and Conclusion

Figures (14)

  • Figure 1: Transduction concept. The motion of the slit w.r.t the LED-bicell pair modulates the light on the bicell's active areas.
  • Figure 2: The exploded (a) and assembled (b) views of the 6-axis F/T sensor
  • Figure 3: Schematics of the proposed force sensing approach. The 6-axis optical force sensor is mounted onto the proximal shaft. The cannula is modified to have an outer tube as an overcoat.
  • Figure 4: The schematic for development of the instrument's bending model.
  • Figure 5: The schematic for calculating the equivalent stiffness at the distal end of the inner tube as a function of the leaf-spring's parameters.
  • ...and 9 more figures