Grip Force Normalization in Teleoperated Surgical Instruments
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Solution Overview
Problem
Teleoperated surgical instruments face challenges in maintaining a consistent gripping force throughout the range of motion of their end effectors, leading to variations in grip torque that can be detrimental during surgical procedures.
Innovation Solution
A method and system that adjust the grip force of surgical instrument end effectors based on their mechanical advantage, using a combination of processor-controlled servomechanisms and input devices to apply a force that remains substantially linear throughout the range of motion, by modifying the proportional gain and commanded position limits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional force transmission mechanisms are used in teleoperated surgical instruments, then the instrument can perform surgical procedures, but the grip force varies throughout the range of motion of the end effector
Solution Approach 1:
The patent applies dynamics by making the mechanical advantage variable rather than fixed. The transmission mechanism is designed to dynamically adjust the mechanical advantage ratio as the end effector moves through its range of motion, ensuring that the grip force remains substantially linear and consistent regardless of the end effector's position. This dynamic adjustment resolves the contradiction by adapting the force transmission characteristics to maintain operational consistency throughout the full range of motion.
2Device complexity
If the mechanical advantage of the end effector varies throughout its range of motion, then the instrument structure can be simplified, but the grip force becomes non-linear and inconsistent
Solution Approach 1:
The patent applies parameter changes by modifying the mechanical advantage parameter as a function of the end effector's position or actuation state. Rather than maintaining a constant mechanical advantage ratio, the system intentionally varies this parameter throughout the range of motion to compensate for geometric changes in the transmission mechanism. This ensures that the product of mechanical advantage and actuation force remains constant, producing linear grip force while allowing the physical structure to remain relatively simple.
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 approach ensures a consistent grip force across the range of motion, reducing the risk of tissue damage and enhancing the precision and safety of surgical procedures by maintaining grip strength when needed while minimizing excessive force.
Implementation Method 1
outputting an actuation signal in response to receiving the first input signal and second input signals to apply a grip force with the first and second gripping elements, the grip force based at least in part on a mechanical advantage of the surgical instrument end effector
Data Source
AI summary
A teleoperated surgical system includes a surgical instrument with an end effector and a master input device. A servomechanism may be operatively coupled to the end effector to apply a force to the end effector, and at least one processor may operatively couple the servomechanism to the master input device to apply a grip force with the first and second gripping elements in response to input at the master input device. The applied grip force may be based at least in part on a mechanical advantage of the surgical instrument end effector.