Surgical Cable Guide Alignment for Accurate Shaft Force Sensing
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Solution Overview
Problem
In teleoperated surgical systems, extraneous forces from twisting control cables within the shaft introduce errors in clinical force measurements, as they are not isolated from the interaction between the end effector and patient tissue.
Innovation Solution
A surgical instrument with a force sensor aligned coaxially within the shaft, featuring proximal and distal anchors with cable guide holes that maintain control cables parallel to the shaft center axis, isolating clinical forces from extraneous mechanical forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If control cables extend freely within the shaft, then the instrument structure is simpler, but extraneous forces from cable twisting introduce errors in force measurements
Solution Approach 1:
A cable guide structure acts as an intermediary component between the control cables and the force sensor. This cable guide includes a guide channel that constrains cable movement and prevents twisting, while allowing the cables to transmit actuation forces to the end effector. The guide channel effectively mediates between the need for simple cable routing and the need for accurate force measurements by isolating clinical forces from extraneous cable forces.
2Adaptability or versatility
If the shaft rolls around its longitudinal axis during operation, then the instrument has greater operational flexibility, but control cables twist and introduce measurement errors
Solution Approach 1:
The shaft internal structure is segmented into distinct functional zones: a cable guide portion with a guide channel that allows shaft rotation while constraining cable movement, and a force sensor portion that remains isolated from cable twisting. This segmentation enables the shaft to roll around its longitudinal axis for operational flexibility while the cable guide channel prevents cable twisting that would otherwise introduce measurement errors.
3Measurement precision
If a force sensor is placed within the shaft, then clinical forces can be measured, but extraneous forces from control cables contaminate the measurements
Solution Approach 1:
The cable guide structure extracts and isolates the extraneous forces from the force sensor by providing a separate pathway for control cables. The guide channel confines cables to a specific trajectory that prevents them from exerting lateral forces on the sensor beam, effectively removing the harmful twisting forces from the measurement zone while preserving the sensor's ability to detect clinical forces at the end effector.
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
Accurately measures clinical forces by isolating them from extraneous mechanical forces, ensuring precise haptic feedback to the surgeon.
Implementation Method 1
The force sensor comprises a beam and one or more strain gauges on the beam
Data Source
AI summary
Control cables in a surgical instrument are kept parallel to the instrument's longitudinal axis to prevent transverse forces from the cables being sensed by a transverse force sensor in the instrument. A surgical instrument includes an elongated hollow shaft having a longitudinal center axis. Multiple cables extend within the shaft. A force sensor includes a beam disposed within the shaft and one or more strain gauges disposed on the beam. A proximal anchor is disposed within the shaft and in contact with a proximal end of the beam. A distal anchor is at the distal end of the shaft and in contact with a distal end of the beam. A cable guide is disposed within the shaft to constrain portions of the multiple cables disposed alongside the beam to movement parallel to the center axis, and so prevent force from the moving cables causing transverse force on the beam.