Surgical Instrument Velocity Control for End Effector Flexing
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Solution Overview
Problem
Minimally invasive surgical instruments with small end effectors face issues of flexing and splaying due to limited stiffness, leading to failed operations and ragged velocity profiles during procedures like grasping, clamping, and stapling, especially when encountering tissue variations.
Innovation Solution
A computer-assisted surgical instrument system that adjusts the velocity set point of the actuator based on applied force or torque thresholds, using a state machine to transition between different operational states to maintain consistent performance and prevent excessive flexing or splaying.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the end effector is kept small for minimally invasive procedures, then the invasiveness is reduced, but the stiffness is limited causing flexing and splaying
Solution Approach 1:
The patent implements dynamic velocity adjustment based on real-time torque monitoring. When torque exceeds thresholds indicating flexing or splaying, the system automatically reduces velocity to prevent damage. This dynamic control allows the small end effector to operate safely despite limited stiffness, resolving the contradiction between small size and structural strength.
2Productivity
If the velocity is kept high for efficient operation, then the productivity is improved, but the instrument may experience excessive flexing or splaying
Solution Approach 1:
The system continuously monitors torque at the proximal end of the shaft and uses this feedback to adjust velocity in real-time. Multiple torque thresholds trigger different velocity responses, creating a feedback control loop that maintains both high productivity and instrument reliability by adapting velocity to actual loading conditions.
Solution Approach 2:
The patent changes the velocity parameter dynamically based on torque conditions. Instead of maintaining constant high velocity, the system adjusts velocity as a variable parameter responsive to torque measurements, allowing efficient operation during normal conditions while preventing excessive flexing or splaying when torque exceeds thresholds.
3Adaptability or versatility
If the end effector encounters tissue variations during operation, then the adaptability is improved, but the velocity profile becomes ragged and operations may fail
Solution Approach 1:
The system dynamically adapts velocity based on real-time torque feedback when encountering tissue variations. Rather than maintaining a fixed velocity profile that becomes ragged with tissue variations, the controller continuously adjusts velocity to maintain smooth, reliable operation across different tissue conditions while preserving adaptability to tissue variations.
Data Source
AI summary
A computer-assisted device includes an actuator and one or more processors. The computer-assisted device is configured to support an instrument having an end effector located at a distal end. To perform an operation with the instrument, the one or more processors are configured to operate the end effector according to a state machine having a first state and a second state. In the first state a velocity set point of the actuator is set to a first velocity. In the second state the velocity set point of the actuator is set to a second velocity lower than the first velocity. The state machine transitions from the first state to the second state when a force or torque applied by the actuator is above a first threshold and transitions from the second state to the first state when the force or torque applied by the actuator is below a second threshold.