Planetary Differential Handle Mechanism for Surgical Cable Tension
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Solution Overview
Problem
Pulley-cable mechanisms in robotic-assisted minimally invasive surgical instruments are prone to cable slack and complex assembly, leading to inconsistent and unpredictable performance.
Innovation Solution
A degree-of-freedom regulating mechanism featuring a handle, a drive unit group, and a differential mechanism with a planetary gear train, allowing the mechanism to switch between locked and released states to maintain cable tension across varying operating conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a pulley-cable mechanism is used to drive the end effector, then the end effector can be rotated to a specified position, but the mechanism is prone to cable slack and complicated assembly under different operating conditions
Solution Approach 1:
The patent employs a differential mechanism that dynamically adjusts the degree of freedom based on operating conditions. The mechanism transitions between locked and released states, allowing the cable system to adapt its tension characteristics dynamically rather than relying on static cable tensioning, thereby eliminating cable slack while maintaining operational flexibility
Solution Approach 2:
The patent changes the degree of freedom parameter of the drive mechanism from fixed to variable. By using a differential mechanism with switchable states (locked/released), the system can alter its kinematic parameters to maintain optimal cable tension across different operating conditions, preventing cable slack without compromising the ability to position the end effector
2Ease of operation
If a pulley-cable mechanism is used to drive the end effector, then the end effector can be rotated to a specified position, but the assembly becomes complicated under different operating conditions
Solution Approach 1:
The differential mechanism serves multiple functions: it provides the drive connection between the drive unit and end effector, maintains cable tension across different operating conditions, and enables dynamic degree of freedom adjustment. This multi-functionality reduces the need for separate tensioning mechanisms and simplifies the overall assembly compared to traditional pulley-cable systems
3Reliability
If the degree of freedom is reduced to N−1 in locked state, then cable tension is maintained, but the flexibility of the surgical instrument is reduced
Solution Approach 1:
The mechanism dynamically switches between locked state (N−1 degree of freedom) for cable tension maintenance and released state (N degree of freedom) for flexible positioning. This dynamic state transition allows the system to maintain reliability when needed while preserving adaptability during surgical operations, resolving the contradiction between tension consistency and operational flexibility
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
Ensures that the cable remains tensioned under any operating condition, enhancing the precision and reliability of the surgical instrument's performance by compensating for cable slack and simplifying the structural complexity.
Implementation Method 1
The differential mechanism comprises a first planetary gear train and a corresponding rotating mechanism; any two gears of the first planetary gear train are configured to independently rotate and are respectively coupled to one of the drive units
Data Source
AI summary
A degree-of-freedom regulating mechanism and a surgical instrument. The degree-of-freedom regulating mechanism comprises a handle, a drive unit group, and a differential mechanism. The differential mechanism comprises a first planetary gear train and a corresponding rotating mechanism. Any two gears of the first planetary gear train are configured to independently rotate and are respectively coupled to a drive unit, and the differential mechanism can be switched between a locked state and a released state. When in a locked state, a driven wheel of the first planetary gear train and the corresponding rotating mechanism are fixed to each other in the rotation direction, such that the degree of freedom of the degree-of-freedom regulating mechanism is N−1. When in a released state, the driven wheel and the corresponding rotating mechanism can rotate independently, such that the degree of freedom of the degree-of-freedom regulating mechanism is N.