Compact Redundant Inductive Force Sensor for Surgical Instruments
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Solution Overview
Problem
Existing force sensing technologies in minimally invasive surgical instruments face challenges in providing accurate haptic feedback within the spatial constraints of these instruments, requiring improved force-sensing capabilities that can measure axial forces effectively while fitting within the limited space.
Innovation Solution
A compact inductive force sensor unit is designed, comprising two inductive coils and rods with magnets, allowing for axial force measurement by translating the rods within the coils, which generates signals associated with linear displacement, and a microprocessor determines the force from these signals, providing redundancy and reduced height to conserve space.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a force sensor unit is included in the proximal mechanical structure to measure axial forces, then haptic feedback accuracy is improved, but the device complexity increases
Solution Approach 1:
The force sensor unit is nested within the proximal mechanical structure of the instrument. The sensor unit includes a first sensor and a second sensor that are integrated into the mechanical structure, allowing force measurements to be taken without adding external bulk to the instrument shaft. This nesting approach enables accurate force sensing while maintaining the compact form factor required for minimally invasive surgical instruments.
Solution Approach 2:
The force sensing capability is segmented into multiple independent sensors (first sensor and second sensor) rather than using a single complex sensor. Each sensor can independently measure axial forces, and their outputs can be combined or compared to improve measurement accuracy. This segmentation provides redundancy and allows the system to tolerate sensor failure while maintaining measurement precision.
2Reliability
If multiple sensors are used to improve measurement accuracy and provide redundancy, then reliability is improved, but the volume of the force sensor unit increases
Solution Approach 1:
Multiple sensors are nested within the compact proximal mechanical structure rather than being arranged in a linear fashion. The first sensor and second sensor are positioned to share common structural elements and mounting features, allowing them to occupy overlapping or adjacent spatial volumes. This nesting arrangement provides redundant sensing capability while constraining the overall volume increase to a minimum.
Solution Approach 2:
The first sensor and second sensor are merged into a single integrated force sensor unit that is coupled to the proximal mechanical structure. The sensors share common mounting brackets, electrical connection pathways, and structural support elements. This merging approach allows multiple sensing elements to function together within a compact volume, providing both redundancy and improved measurement accuracy without proportionally increasing the overall sensor unit volume.
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 solution enhances force measurement accuracy, provides redundant sensing to ensure operation even if one sensor fails, and fits within the spatial constraints of minimally invasive surgical instruments, improving haptic feedback and instrument performance.
Implementation Method 1
a first inductive coil and a second inductive coil... each inductive coil having an inductance that changes when the rod with the magnet inside moves within the coil
Data Source
AI summary
A medical device includes a mechanical structure and a force sensor unit. The force sensor unit comprises a mounting bracket, a first rod, a second rod, a first magnet, a second magnet, a first coil coupled to the mounting bracket, and a second coil coupled to the mounting bracket. The first rod and the second rod each have a center axis defined between a proximal and distal portion of the respective first and second rods. The center axis of the second rod is noncoaxial with the center axis of the first rod. The first magnet is coupled to the first rod and translates within the first coil along the center axis of the first rod. Similarly, the second magnet is coupled to the second rod and translates within the second coil along the center axis of the second rod.