Surgical Robot Velocity Limiting Near the Remote Center of Motion
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Solution Overview
Problem
Surgical robotic systems experience undesirable impacts on internal tissue due to unexpected amplification of force and speed during rotation and pivoting of surgical instruments, necessitating velocity limits to prevent tissue damage.
Innovation Solution
A surgical robotic system with a controller that applies velocity limits through a hand pose transform algorithm, velocity limiting function, and motion integrator algorithm to regulate the movement of surgical instruments, ensuring safe and controlled operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the surgical instrument is actuated near the remote center of motion point, then the surgical instrument can perform minimally invasive procedures with precise positioning, but rotation and pivoting cause unexpected amplification of force and speed that impacts internal tissue
Solution Approach 1:
The system dynamically adjusts velocity limits based on the surgical instrument's proximity to the remote center of motion point. As the instrument approaches this critical point, the controller automatically reduces the maximum allowable velocity to prevent harmful amplification effects, while maintaining positioning precision through adaptive control parameters.
Solution Approach 2:
The controller modifies operational parameters (velocity limits) based on the instrument's position relative to the remote center of motion. By changing the velocity parameter dynamically rather than maintaining a fixed limit, the system prevents tissue damage while preserving the ability to perform precise minimally invasive procedures.
2Object-affected harmful factors
If velocity limits are applied to the surgical instrument, then tissue damage from force amplification is prevented, but the surgical procedure efficiency may be reduced
Solution Approach 1:
Rather than applying a static velocity limit that would uniformly reduce surgical efficiency, the system uses dynamic velocity limiting that adapts to the instrument's position. Velocity limits are relaxed when the instrument is far from the remote center of motion (where no amplification occurs) and tightened only when approaching the critical zone, thereby maintaining efficiency while preventing tissue damage.
Solution Approach 2:
The velocity limiting is applied locally and selectively only in the specific region near the remote center of motion where harmful amplification occurs. The rest of the surgical workspace maintains normal velocity capabilities, ensuring that efficiency is preserved in areas where it is safe while protection is provided where needed.
3Reliability
If the controller processes command pose through multiple algorithms including velocity limiting, then safety and precision are enhanced, but system complexity increases
Solution Approach 1:
The velocity limiting function serves as an intermediary processing layer between the hand pose transform algorithm and the motion integrator. This modular intermediary takes the desired delta pose command, applies velocity constraints based on position, and outputs a limited command that preserves the safety and precision benefits while organizing system complexity into manageable, independent functional blocks.
Data Source
AI summary
A surgical robotic system including a robotic arm and a surgical console. The robotic arm having a plurality of joints and a surgical instrument. The surgical console includes at least one interface device and a controller. The interface device configured to receive a user input. The controller configured to output a command pose based on the user input, wherein the robot arm is configured to move in response to the command pose; process the command pose through a hand pose transform algorithm to generate a desired pose and a previous desired pose; determine a desired delta pose command based on the desired pose, the previous desired pose, and a previous command pose; and process the desired delta pose command through a velocity limiting function to apply at least one velocity limit on the desired delta pose command.