Manipulator-Mounted Force Estimation for Minimally Invasive Instruments
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing minimally invasive medical systems lack accurate force feedback at the instrument tip and access port, necessitating costly and constrained sensors on each instrument and trocar, which are subject to miniaturization and sterilization challenges.
Innovation Solution
A method and system using a 6-DOF force/torque sensor mounted on the manipulator outside the patient, estimating forces at the instrument tip by determining the instrument's position relative to the fulcrum and calculating forces based on measured torque and position, without requiring sensors on the instrument or trocar.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If sensors are mounted on each instrument and trocar to measure force at the instrument tip, then measurement precision is improved, but device complexity and manufacturing cost increase significantly
Solution Approach 1:
The force sensor is extracted from the instrument tip and relocated to the manipulator base. This removes the need for miniaturized sensors on each instrument while maintaining force measurement capability through mathematical calculation based on measured base forces and known instrument geometry.
Solution Approach 2:
A force sensor mounted on the manipulator base serves as an intermediary measurement point. The actual instrument tip forces are not measured directly but are derived through calculation from the intermediary base measurements combined with instrument position and orientation data.
2Measurement precision
If miniaturized sensors are placed on instruments and trocars, then force feedback at the instrument tip is achieved, but ease of manufacture and sterilization are worsened due to miniaturization constraints
Solution Approach 1:
The force sensing capability is extracted from the disposable instrument/trocar components and relocated to the reusable manipulator base. This eliminates the need to miniaturize sensors on instruments that require sterilization, as the sensor remains on the non-sterile manipulator base.
Solution Approach 2:
A single force sensor on the manipulator base serves multiple instruments simultaneously. The same sensor measures forces for different instruments and trocars, eliminating the need for individual sensors on each component and simplifying manufacturing and sterilization protocols.
3Reliability
If multiple sensors are deployed on instruments and trocars, then force measurement reliability is improved, but loss of time for system setup and calibration increases
Solution Approach 1:
Force measurement is extracted from multiple distributed sensor locations and consolidated to a single sensor location on the manipulator base. This reduces the number of sensors requiring calibration and setup while maintaining measurement reliability through mathematical reconstruction of tip forces from base measurements.
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 estimates forces at the instrument tip and fulcrum, enabling cost-effective force feedback and automated safety features in minimally invasive procedures, eliminating the need for dedicated sensors on each instrument and trocar.
Implementation Method 1
measuring by means of a six degrees-of-freedom (6-DOF or 6-axes) force/torque sensor a force and a torque exerted onto the effector unit by the first end of the instrument
Data Source
AI summary
A method of operating a minimally invasive medical system, including positioning a tip of a surgical instrument through an incision into a body cavity, the surgical instrument having an instrument shaft with a longitudinal instrument axis, mounting the surgical instrument to a manipulator, the manipulator including a force/torque sensor, moving the minimally invasive instrument along a first axis and a second axis, each of the first and second axes perpendicular to the instrument axis, until a reaction force along each axis is below a given threshold, and defining and axis coordinates of the external fulcrum at a location where the reaction forces along both axes are below the given threshold, and determining an axis coordinate position of the external fulcrum along the instrument axis by pivoting the instrument with respect to its tip until a sufficient contact force is reached, and determining the axis coordinate position using the lever principle.