Robotic Surgical Wrist Assemblies Using Differential Cable Drives
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Solution Overview
Problem
Existing surgical robotic systems face challenges in efficiently articulating surgical instruments with precise control over pitch and yaw movements, leading to potential stress and strain on articulation cables due to non-linear motion curves.
Innovation Solution
The implementation of a differential gear mechanism within the surgical instrument's transmission system, which includes a first and second transmission with articulation cables that move at different rates to articulate the end effector relative to the shaft, allowing for precise adjustment of pitch and yaw movements while reducing stress on the cables.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If articulation cables are used to articulate the end effector with pitch and yaw movements, then the end effector can be positioned precisely at the work site, but the cables experience stress and strain due to non-linear motion curves
Solution Approach 1:
A differential mechanism is introduced as an intermediary between the actuation system and the articulation cables. This differential mechanism converts the non-linear motion requirements into linear cable movements, allowing the cables to move in straight lines while still achieving the required pitch and yaw articulation of the end effector, thereby reducing stress and strain on the cables
Solution Approach 2:
The system changes the motion parameters of the articulation cables from non-linear curved paths to linear axial movements. By modifying the cable motion trajectory from complex non-linear curves to simple linear extensions and retraction, the mechanical stress on the cables is significantly reduced while maintaining positioning precision
2Duration of action of stationary object
If a differential gear mechanism is implemented to reduce cable stress, then cable lifespan is extended, but the device complexity increases
Solution Approach 1:
The differential mechanism serves multiple functions simultaneously: it articulates the end effector in pitch and yaw, converts non-linear motion to linear cable movement, and reduces stress on the cables. By combining these functions into a single mechanism, the overall system complexity is managed more effectively than if separate systems were used for each function
3Measurement precision
If the articulation cables move at different rates to articulate the end effector, then precise pitch and yaw control is achieved, but the motion coordination becomes more complex
Solution Approach 1:
The differential mechanism acts as a motion coordination intermediary that automatically manages the complex relationship between cable movements and end effector articulation. It translates simple linear cable movements into the required differential angular movements for pitch and yaw control, eliminating the need for complex active coordination control
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 differential gear mechanism ensures precise and efficient articulation of the end effector, prolonging the lifespan of the articulation cables and enhancing the accuracy of surgical instrument movements.
Implementation Method 1
a first differential gear mechanism operably coupling the first input shaft to the first and second output shafts and the first and second output shafts to one another
Data Source
AI summary
A surgical instrument for use in a robotic surgical system includes an end effector, a housing configured to be operably coupled to an instrument drive unit, a shaft extending distally from the housing, a wrist assembly coupled to a distal end portion of the shaft, articulation cables that adjust the pitch and yaw of the end effector relative to the shaft, and a differential gear mechanism that transfers an input rotation to the articulation cables.