Surgical End Effector Control Under Tissue Resistance
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Solution Overview
Problem
Existing surgical robotic systems face challenges in precisely controlling surgical instruments due to insufficient response to external forces during surgical procedures, particularly in scenarios like blunt dissection where tissue resistance hinders the desired movement of end effectors.
Innovation Solution
A control system that transforms surgeon input device commands into control signals using a first control relationship for normal conditions and switches to a second relationship when external forces are detected, adjusting the opening angle of end effector elements to counteract these forces, ensuring precise instrument movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a fixed control relationship is used to map surgeon input to end effector movement, then the control system is simple and responsive, but it cannot compensate for external forces like tissue resistance during procedures such as blunt dissection
Solution Approach 1:
The control system dynamically switches between different control relationships (first and second control relationships) based on detected external forces. When external forces are detected exceeding a threshold, the system transitions from a standard control relationship to an adaptive control relationship that compensates for these forces, enabling the end effector to maintain desired movement despite tissue resistance during blunt dissection procedures
Solution Approach 2:
The system incorporates force sensing to detect external forces applied to the end effector and uses this feedback information to determine when to switch control relationships. The force sensor continuously monitors the surgical environment, and when forces exceed a predetermined threshold, the control system adjusts its behavior accordingly, creating a closed-loop adaptive control system
2Force
If the control system uses a single control relationship for all conditions, then the system is simple to implement, but it fails to provide sufficient force to overcome external forces during procedures like blunt dissection
Solution Approach 1:
The control system changes the control parameters (control relationship) based on the surgical condition. When external forces are detected, the system switches to a second control relationship that modifies the mapping between surgeon input and end effector output, effectively changing the gain or response characteristics to provide sufficient force to overcome tissue resistance during blunt dissection
3Reliability
If the system switches control relationships based on force thresholds, then it can compensate for external forces, but the control system becomes more complex with multiple control relationships
Solution Approach 1:
The control system segments the operational range into different modes based on force conditions. A first control relationship is used when external forces are below a threshold, and a second control relationship is used when forces exceed the threshold. This segmentation allows the system to handle different surgical conditions with appropriately optimized control parameters, improving reliability while keeping each individual control relationship relatively simple
Data Source
AI summary
A control system for controlling manipulation of a surgical instrument in response to manipulation of a remote surgeon input device. The surgical instrument comprises opposable first and second end effector elements connected to a shaft by an articulated coupling. The control system: transforms commands from the surgeon input device to alter the opening angle between the first and second end effector elements according to a first control relationship to drive signals to drive the first and second end effector elements to rotate; receives sensed forces applied to the first and second end effector elements, and compares the sensed forces to a threshold force; and upon determining that the threshold force has been exceeded, transforms subsequent commands from the surgeon input device to alter the opening angle between the first and second end effector elements according to a second control relationship to drive signals to drive the first and second end effector elements to rotate, wherein the second control relationship is different to the first control relationship.