Differential Coaxial Inductive Force Sensor for Surgical Haptics
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Solution Overview
Problem
Existing force sensing technologies in minimally invasive surgical systems lack accuracy and reliability in measuring axial forces applied to end effectors, which affects haptic feedback and surgical precision.
Innovation Solution
A compact differential inductive force sensor system is developed, featuring a rod with a magnet moving within coaxial first and second coils, generating signals associated with linear displacement of a shaft, allowing for precise measurement of axial forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a force sensor is disposed at or near a tool shaft to measure clinical forces, then haptic feedback accuracy is improved, but the device complexity increases
Solution Approach 1:
The patent replaces complex mechanical force sensing mechanisms with an inductive sensing system. A magnet coupled to the shaft moves within coils, generating electrical signals that correspond to shaft displacement and force. This substitution of mechanical sensing with electromagnetic induction simplifies the overall device architecture while maintaining measurement accuracy.
Solution Approach 2:
The patent introduces a magnet as an intermediary element that couples the shaft movement to the coils. The magnet translates mechanical displacement into electrical signals without requiring direct mechanical contact between the shaft and sensing elements, reducing complexity while enabling accurate force measurement.
2Volume of moving object
If a compact sensor design is implemented, then the device size is reduced, but measurement precision may deteriorate
Solution Approach 1:
The patent implements a nested configuration where the magnet is positioned within the coils, and the entire sensor assembly is integrated within the existing tool shaft structure. This nesting approach minimizes the overall volume of the sensor unit while maintaining the functional integrity and measurement precision of the force sensing system.
Solution Approach 2:
The patent merges the force sensing function with the existing shaft structure by coupling the magnet directly to the shaft and positioning the coils within the same assembly. This integration combines multiple functions into a compact unit, reducing size while preserving measurement accuracy through the direct coupling of the sensing elements to the shaft.
3Reliability
If differential inductive sensing is used, then measurement reliability is improved, but device complexity increases
Solution Approach 1:
The patent divides the sensing system into two separate coils positioned at different locations along the shaft. Each coil independently measures displacement, and the differential processing of these two measurements provides reliable force data. This segmentation into multiple sensing elements improves reliability through redundancy and error cancellation.
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
The system provides accurate and reliable measurement of axial forces, enhancing haptic feedback and surgical precision by translating linear displacement into force measurements, while being compact and resistant to cautery interference.
Implementation Method 1
A magnet translates within the first coil and the second coil along a center axis of the rod
Data Source
AI summary
A variety of applications can include apparatus and/or methods that provide an axial force transducer. Two coils wound coaxially with respect to each other can be used with a magnet to determine a distance traveled based on application of an axial force to an instrument component. The two coils and magnet can be configured in a number of ways with respect to the instrument component. In various embodiments, the difference between an inductance associated with one of the two coils along with its relation to the magnet and an inductance associated with the other one of the two coils along with its relation to the magnet can be used to determine the axial force on the component of the instrument associated with the distance travelled. Additional apparatus, systems, and methods are disclosed.