Differential Mechanism Decouples Surgical Shaft Roll from Actuation
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Solution Overview
Problem
Existing minimally invasive telesurgical robotic systems face limitations in decoupling instrument shaft roll and end effector actuation, leading to reduced range of motion and unintended rotation of main shafts during surgical procedures, which can impact the precision and effectiveness of surgical instruments.
Innovation Solution
The implementation of a differential mechanism that combines instrument shaft rotation with input motions to generate output motions for end effector actuation, effectively decoupling instrument shaft roll from end effector actuation, and the use of counteracting torques to prevent unintended rotation of main shafts during high actuation torque transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a surgical instrument shaft is rotationally coupled to support an end effector, then the end effector can be positioned and oriented at the distal end of the shaft, but rotation of the shaft causes unintended rotation of the drive shaft and end effector mechanism, reducing surgical precision
Solution Approach 1:
A differential mechanism is introduced as an intermediary between the instrument shaft and the drive shaft. The differential receives rotational input from the shaft and combines it with actuation input to produce controlled output to the end effector mechanism. This intermediary decouples the direct rotational coupling, allowing the shaft to rotate for positioning while the differential controls the end effector's actuation independently, preventing unintended rotation and improving surgical precision.
2Adaptability or versatility
If the instrument shaft is allowed to rotate freely for positioning, then the range of motion is increased, but this rotation couples with the drive shaft causing loss of motion control
Solution Approach 1:
The differential mechanism serves as a mediator that accepts rotational motion from the instrument shaft and combines it with actuation motion. By using the differential's inherent motion combination capability, the system allows free shaft rotation for positioning (increasing range of motion) while the differential controls the net output to the end effector, maintaining reliable motion control and preventing the coupling problems of direct drive systems.
3Power
If high actuation torque is transmitted to the end effector mechanism, then the end effector can perform surgical tasks effectively, but this causes unintended rotation of the main shaft
Solution Approach 1:
The differential mechanism provides a counterbalancing effect where the actuation torque applied to the end effector mechanism is offset by the differential's motion combination. The differential receives the high torque input and combines it with the shaft rotation input, effectively canceling out the unintended shaft rotation that would otherwise occur during high-power actuation. This allows effective surgical task performance while maintaining shaft rotation control.
Data Source
AI summary
Surgical assemblies and related methods are disclosed that provide for decoupling of instrument shaft roll and end effector actuation. A surgical assembly includes a base, an instrument shaft rotationally mounted to the base, an end effector supported at a distal end of the instrument shaft and including an actuation mechanism driven by a rotational motion, a drive shaft rotationally coupled with the actuation mechanism and configured to provide the rotational motion to the actuation mechanism, and a differential rotationally coupled to the drive shaft and receiving a first input motion and a second input motion. The differential combines the first and second input motions to generate an output motion that rotates the drive shaft. The first input motion is rotationally coupleable to an actuation source. The second input motion is coupled to rotation of the instrument shaft relative to the base.