Surgical Tool Compliance Mechanism for Stable Force Sensing
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Solution Overview
Problem
Admittance-control robotic systems face errors when surgical tools abruptly contact the surgical site due to unforeseen environmental stiffness, leading to non-optimal performance as the force/torque sensor is overly stiff and fails to absorb displacement.
Innovation Solution
Incorporation of a compliance mechanism with a stationary, moveable, and flexible portion between the robotic manipulator and surgical tool, along with a mechanically isolated force/torque sensor to sense user input, allowing the tool to move relative to the manipulator in response to external forces/torques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a stiff force/torque sensor is used to stably support the surgical tool, then the sensor can accurately detect user input forces, but the sensor cannot absorb displacement from abrupt contact with the surgical site
Solution Approach 1:
The system is segmented into a robotic manipulator portion and an end effector portion with a compliance mechanism in between. This segmentation allows the force/torque sensor to be located in the manipulator where it experiences only user input forces, while the compliance mechanism absorbs contact forces at the surgical site, preventing them from reaching the sensor.
Solution Approach 2:
The compliance mechanism acts as an intermediary between the robotic manipulator and the surgical tool. It mechanically isolates the force/torque sensor from external contact forces while still allowing controlled compliance, thus protecting the sensor from displacement caused by abrupt contact with the surgical site.
2Manufacturing precision
If the surgical tool is commanded to a precise position, then the tool can reach the commanded position accurately, but the tool may abruptly contact the surgical site due to unforeseen environmental stiffness
Solution Approach 1:
The compliance mechanism provides beforehand cushioning by being pre-configured with flexible elements that can absorb unexpected contact forces. When the surgical tool abruptly contacts the surgical site, the compliance mechanism cushions the impact, preventing the hard contact from causing errors in the force/torque sensor readings.
Solution Approach 2:
The compliance mechanism changes the mechanical impedance parameters between the robotic manipulator and surgical tool. By introducing compliance (reducing stiffness) in this interface, the system allows controlled movement to absorb contact forces, preventing the harmful effect of abrupt contact while maintaining positioning accuracy through sensor isolation.
3Reliability
If the force/torque sensor is made compliant to absorb displacement, then the sensor can handle contact forces, but the sensor cannot stably support the surgical tool during movement
Solution Approach 1:
The system segments the support function and compliance function into different components. The robotic manipulator provides stable support for the surgical tool during movement, while the separate compliance mechanism provides compliance to absorb contact forces. This segmentation allows each component to optimize its specific function without compromising the other.
Solution Approach 2:
The compliance mechanism serves as an intermediary that provides compliance without compromising the stability of the surgical tool support. It is positioned between the manipulator and tool, allowing it to absorb contact forces while the manipulator maintains stable support, thus resolving the contradiction between compliance and stability.
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
Enhances the stability and accuracy of surgical tool movement by isolating the force/torque sensor from external forces, enabling controlled movement based on user input while absorbing displacement, thus improving surgical precision.
Implementation Method 1
a flexible portion disposed between the stationary portion and the moveable portion
Data Source
AI summary
A surgical system includes a robotic manipulator and an end effector supported by the robotic manipulator. The end effector includes a surgical tool to interact with an anatomy and a compliance mechanism. The compliance mechanism enables the surgical tool to move relative to the robotic manipulator in response to external forces/torques applied to the surgical tool by the anatomy. The compliance mechanism has a stationary portion coupled to the robotic manipulator, a moveable portion coupled to the surgical tool, and a flexible portion disposed between the stationary portion and the moveable portion. An input device has a force/torque sensor that senses a force/torque applied to the input device by a user. The force/torque sensor is mechanically isolated from the external forces/torques applied to the surgical tool.