Off-Axis Drive Rod Compensation for Surgical Robot Wrists
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Solution Overview
Problem
Surgical robotic systems face unintended movement of end effectors due to the actuation of push-pull rods when the drive rod is positioned off-axis relative to the wrist joint, causing misalignment during pivoting or articulation.
Innovation Solution
A software algorithm calculates a compensation distance based on the bend radius of the off-axis drive rod, adjusting its longitudinal position to account for pitch and yaw articulation, ensuring precise actuation by commanding the instrument drive unit to advance the drive rod by the calculated compensation distance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the drive rod is positioned off-axis relative to the wrist joint, then routing of other components through the end effector is enabled, but unintended movement of the end effector occurs during articulation
Solution Approach 1:
The system dynamically changes the actuation distance parameter based on the drive rod's position. The controller calculates a compensation distance based on the drive rod's offset position and articulation angle, then adjusts the actuation distance accordingly to maintain accurate end effector positioning despite the off-axis configuration
Solution Approach 2:
The system uses feedback from articulation angle sensors and drive rod position detection to continuously adjust the actuation distance. The controller receives real-time data on the drive rod's position and articulation state, then computes compensation values to maintain precise control of the end effector throughout the articulation range
2Stability of the object's composition
If the drive rod is disposed along the neutral axis of the wrist joint, then the path of the drive rod remains unchanged during pivoting, but design flexibility is reduced due to component routing constraints
Solution Approach 1:
The system dynamically adjusts the actuation distance parameter based on the drive rod's position. The controller calculates a compensation distance based on the drive rod's offset position and articulation angle, then adjusts the actuation distance accordingly to maintain accurate end effector positioning despite the off-axis configuration
Solution Approach 2:
The system transitions from a static mechanical alignment to a dynamic computational adjustment. Instead of relying on fixed geometric alignment to maintain drive rod path stability, the system uses real-time calculations based on drive rod position and articulation angle to compensate for path changes, enabling flexible component routing while maintaining control stability
3Length of moving object
If the drive rod is bent further due to off-axis positioning, then the travel distance is lengthened, but the actuation precision is reduced
Solution Approach 1:
The system dynamically changes the actuation distance parameter to compensate for the increased travel distance caused by the bent drive rod. The controller calculates the compensation distance based on the drive rod's bend radius and articulation angle, then adjusts the actuation distance to maintain precise actuation of the end effector despite the lengthened travel path
Data Source
AI summary
A surgical robotic system includes a surgeon console configured to receive user input and a robotic arm configured to hold an instrument drive unit and an instrument coupled to the instrument drive unit. The instrument is controllable in response to the user input and includes an elongate shaft and an end effector coupled to the elongate shaft at a joint. The end effector is configured to pivot about at least one pivot axis relative to the elongate shaft. The instrument also includes a flexible drive rod configured to move longitudinally through the joint and to actuate at least one function of the end effector. The flexible drive rod is disposed off-axis relative to at least one pivot axis of the joint. The system also includes a controller configured to calculate a bend radius of the flexible drive rod during pivoting of the end effector; calculate a compensation distance based on the bend radius; and command the instrument drive TJ, TM, TN, TR, TT, TZ, UA, UG, US, UZ, VC, VN, WS, ZA, ZM, ZW.