Strain Gauge Placement for Surgical Instrument Force Sensing
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Solution Overview
Problem
Current surgical robot systems face challenges in accurately providing force and torque feedback to surgeons during remote manipulation, particularly due to the need to route wires or optic fibers through flexible wrist joints, which complicates the sensing of forces and torques at the instrument tip.
Innovation Solution
The placement of axially oriented strain gauges proximal to the wrist joint on the surgical instrument shaft allows for accurate sensing of forces and torques at the instrument tip, independent of wrist orientation changes and temperature variations, eliminating the need for wires or optic fibers through the wrist joint.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If force sensors are placed distal to the wrist joints, then force sensing at the instrument tip is achieved, but wires or optic fibers must be routed through the flexing wrist joint increasing device complexity
Solution Approach 1:
Instead of placing force sensors distal to the wrist joint (conventional approach), the patent inverts the approach by placing strain gauges proximal to the wrist joint on the instrument shaft. This reversal eliminates the need to route wires through the flexing wrist joint, solving the complexity problem while maintaining force sensing capability through mathematical transformation of the strain measurements.
Solution Approach 2:
The patent replaces the conventional mechanical force sensor with strain gauges that measure deformation of the instrument shaft. By using strain measurements combined with mathematical models, the system substitutes direct mechanical sensing at the tip with indirect sensing through shaft deformation, eliminating the need for complex wire routing through moving joints.
2Measurement precision
If force sensors are placed distal to the wrist joints, then force feedback is provided, but the system requires separate pivot axes for yaw and grip reducing ease of manufacture
Solution Approach 1:
The patent inverts the conventional sensor placement from distal to proximal location. By placing strain gauges on the instrument shaft proximal to the wrist joint, the system eliminates the requirement for separate pivot axes, allowing yaw and grip to share a common pivot axis, thereby simplifying manufacturing while maintaining accurate force feedback through mathematical transformation.
3Measurement precision
If wires are routed through the flexing wrist joint, then force sensing is enabled, but reliability decreases due to potential wire damage from flexing
Solution Approach 1:
The patent extracts the force sensing function from the distal end of the instrument where wires would need to pass through the flexing wrist joint. By relocating the sensing function to strain gauges on the proximal instrument shaft, the system removes the vulnerable wire routing from the flexing joint area, eliminating the reliability issue while preserving force sensing capability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution enhances the accuracy and reliability of force and torque feedback to surgeons, simplifies the instrument design, and reduces the complexity of routing delicate cables, enabling more precise control during surgical procedures.
Implementation Method 1
Groups of axially oriented strain gauges are positioned on or near a distal end of an instrument shaft to sense forces and torques
Data Source
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AI summary
An apparatus, system, and method for improving force and torque sensing and feedback to the surgeon performing a telerobotic surgery are provided. Groups of axially oriented strain gauges are positioned on a distal end of an instrument shaft proximate a moveable wrist of a robotic surgical instrument to sense forces and torques at the distal tip of the instrument. Advantageously, errors due to changes in the configuration of the tip or steady state temperature variations are eliminated. Other advantageous configurations and methods are disclosed.