Torque Saturation Limiter for Robotic Surgical End Effectors
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Solution Overview
Problem
Robotic surgical gripping instruments experience reduced gripping torque over time due to cable stretching or instrument compression, limiting the application of maximum force during surgical procedures.
Innovation Solution
A control system that includes a torque saturation limiter, a torque to current converter, and a motor to drive end effectors to maximum torque limits, ensuring the input disks continue to rotate and adjust grip compliance to maintain maximum torque throughout the tool's life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the input disk is limited to a predetermined position limit, then the wires or cables are protected from overload, but the maximum torque cannot be reached resulting in reduced gripping force
Solution Approach 1:
The position limit of the input disk is changed from a fixed predetermined value to a dynamic value that is adjusted based on the actual condition of the cables. The control system monitors cable tension and instrument compression, then automatically modifies the position limit to maintain maximum torque while preventing cable overload, allowing the system to adapt to aging and wear over time
Solution Approach 2:
The system changes the parameter of the position limit from a static predetermined value to a variable parameter that is continuously adjusted based on feedback from sensors monitoring cable condition and instrument compression. This parameter change enables the system to compensate for cable stretching and compression, maintaining optimal gripping force throughout the instrument's lifetime
2Force
If the position limit is adjusted to compensate for cable stretch, then maximum torque can be maintained, but the system complexity increases
Solution Approach 1:
The control system incorporates feedback mechanisms that monitor cable tension and instrument compression levels, then use this information to automatically adjust the position limit of the input disk. This closed-loop feedback system maintains maximum gripping torque without requiring complex manual calibration or adjustment procedures
Solution Approach 2:
The system performs self-adjustment of the position limit based on sensor feedback about cable condition and instrument compression. The control system automatically compensates for wear and aging without requiring external intervention or complex calibration procedures, maintaining optimal performance throughout the instrument's lifetime
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
This solution ensures consistent maximum gripping force is applied to tissue throughout the life of the robotic surgical tool, regardless of cable stretch or instrument compression, enhancing the effectiveness of robotic surgical procedures.
Implementation Method 1
a motor to drive end effectors to maximum torque limits
Data Source
AI summary
In one embodiment of the invention, a control system for a robotic surgical instrument is provided including a torque saturation limiter, a torque to current converter coupled to the torque saturation limiter, and a motor coupled to the torque to current converter. The torque saturation limiter receives a desired torque signal for one or more end effectors and limits the desired torque to a range between an upper torque limit and a lower torque limit generating a bounded torque signal. The torque to current converter transforms a torque signal into a current signal. The motor drives an end effector of one or more end effectors to the bounded torque signal in response to the first current signal.