Roll Control for Robotic Surgical Instruments
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Solution Overview
Problem
In robotic surgical systems, controlling the roll axis of surgical instruments to minimize motion at the Remote Center of Motion (RCM) is challenging, especially when combined with pitch and yaw rotations, as it can induce additional stress and discontinuous or multivalued roll-angle offsets, affecting the precision and stability of surgical procedures.
Innovation Solution
A method for controlling roll by specifying a reference frame with a roll-axis-alignment rotation, determining a roll-angle offset, and rotating the device about the roll axis to maintain a specified offset, ensuring continuous and precise alignment of the roll axis with the device's roll axis, even in singularities where pitch and yaw rotations are significant.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If pitch and yaw rotations are applied to control the surgical instrument, then the instrument can reach different orientations, but roll-axis stress and discontinuous roll-angle offsets occur
Solution Approach 1:
The orientation control is segmented into independent components: pitch-yaw rotation for positioning and roll-angle offset control for orientation alignment. This separation allows pitch and yaw to handle spatial positioning while a dedicated roll control mechanism handles orientation, preventing the coupling that causes harmful roll-axis stress.
Solution Approach 2:
The system dynamically adjusts the roll-angle offset parameter based on the current pitch-yaw orientation. By continuously monitoring the device frame orientation and calculating the required roll correction, the system maintains optimal roll alignment across all pitch-yaw configurations, eliminating discontinuities and reducing stress on the patient.
2Adaptability or versatility
If conventional pitch-yaw rotation is used for device orientation, then positioning flexibility is achieved, but roll control precision deteriorates due to discontinuous offsets
Solution Approach 1:
The system continuously monitors the device frame orientation (pitch, yaw, and roll components) and uses this feedback to calculate the required roll-angle offset. This closed-loop control ensures that roll precision is maintained regardless of the pitch-yaw positioning, correcting any orientation drift or discontinuities in real-time.
Solution Approach 2:
The roll-angle offset is dynamically adjusted based on the current pitch-yaw configuration rather than being fixed. This dynamic adaptation allows the system to maintain precise roll control across the entire range of motion, with smooth transitions that eliminate discontinuities and multivalued offsets.
3Manufacturing precision
If roll control is implemented during pitch-yaw operations, then orientation precision improves, but system complexity increases
Solution Approach 1:
The roll control is merged with the existing pitch-yaw control framework by computing the roll-angle offset as a derived parameter from the device frame orientation. Rather than adding an independent complex roll actuator, the system integrates roll correction into the control algorithm that processes pitch-yaw commands, achieving enhanced precision without proportional complexity increase.
Data Source
AI summary
Roll control is provided for a device by controlling the roll-angle offset about the device roll axis in correspondence to a specified rotation of a reference frame for the device. This specified rotation may correspond to a roll-free rotation of the reference frame to align a corresponding reference roll axis with the device roll axis. In applications to robotics generally, the device may be characterized as a robotic element or a robotically-supported instrument. In specific applications to robotic surgery in a computer-assisted medical system, the device may include a spar or cannula that is configured to support a surgical instrument.