Surgical Instrument Velocity Control for Stable Stapling Force
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Solution Overview
Problem
Minimally invasive surgical instruments with small end effectors face challenges in maintaining stiffness and stability during procedures like stapling, leading to flexing and splaying due to limited torque and force, resulting in failed operations and irregular velocity profiles.
Innovation Solution
A surgical instrument system with a computer-assisted medical device that sets a velocity set point for the actuator, monitors force or torque, and adjusts the operation based on predefined conditions to maintain optimal force and torque levels, pausing or adjusting the actuator's movement to ensure smooth and effective stapling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the end effector size is kept small for minimally invasive procedures, then the invasiveness is reduced, but the stiffness and stability during stapling operations deteriorate
Solution Approach 1:
The system dynamically adjusts the velocity of the actuator based on real-time force feedback. When force exceeds a threshold during stapling, the velocity is automatically reduced to prevent tissue damage and maintain stable operation, resolving the contradiction between small size and stability.
Solution Approach 2:
The system incorporates force sensors that continuously monitor the force applied during stapling operations. This feedback mechanism allows the control system to detect when force thresholds are exceeded and adjust actuator velocity accordingly, maintaining stability despite the small end effector size.
2Productivity
If the actuator velocity is increased to improve productivity, then the stapling speed is improved, but the force control precision deteriorates leading to tissue damage
Solution Approach 1:
The system employs dynamic velocity adjustment where the actuator velocity is not fixed but varies based on real-time force measurements. When force approaches critical thresholds, velocity is automatically reduced, allowing high-speed operation during safe phases and precise control during critical phases.
Solution Approach 2:
The system changes the velocity parameter dynamically based on force feedback. The velocity setpoint is adjusted in real-time according to the measured force, allowing the system to optimize both productivity and precision by adapting parameters to current operating conditions.
3Productivity
If the force limit is set high to maintain productivity, then the stapling efficiency is improved, but the risk of tissue damage increases
Solution Approach 1:
The system uses force feedback to continuously monitor tissue response during stapling. When the measured force approaches the safety threshold, the system automatically reduces velocity to prevent tissue damage, while allowing higher velocities when force levels are safe, thus maintaining both efficiency and safety.
Solution Approach 2:
The system establishes force thresholds beforehand that serve as safety cushions. These pre-defined limits trigger velocity reduction before tissue damage can occur, providing a protective mechanism that maintains productivity while preventing harmful effects.
Data Source
AI summary
A system and method of variable velocity control of an instrument by a computer-assisted device includes a computer-assisted device that includes an actuator and one or more processors. To perform an operation with an instrument coupled to the computer-assisted device, the one or more processors are configured to set a velocity set point of the actuator to an initial velocity, monitor force or torque applied by the actuator to actuate the instrument, when the applied force or torque is above a first force or torque limit, determine whether a total duration of a set of pauses occurring during the operation of the instrument is below a maximum pause threshold, and in response to determining that the total duration is below the maximum pause threshold, pause the operation of the instrument.