Robotic Surgery Coordinate System Registration via Gradient Descent
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Solution Overview
Problem
In robotic surgery, there is a challenge in registering the Robot Coordinate System (RCS) with the Tracking Coordinate System (TCS) to accurately control the surgical robot, as existing methods like Iterative Closest Point (ICP) can be slow and prone to local minima convergence.
Innovation Solution
A processor-based system that receives arm-tracking and sensor-tracking signals to derive poses in both coordinate systems, computes transformations, and reregisters them based on distance thresholds, allowing for quick and accurate registration using a single pose or iterative algorithms like gradient descent.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Iterative Closest Point (ICP) algorithm is used for coordinate system registration, then registration accuracy can be improved, but registration speed deteriorates and convergence to local minima occurs
Solution Approach 1:
The patent applies preliminary action by performing gradient descent optimization before the ICP algorithm. The system first computes an initial transformation using gradient descent that minimizes the distance between corresponding points in the two coordinate systems. This preliminary transformation provides a better starting point for ICP, reducing the risk of local minima convergence and accelerating the registration process while maintaining accuracy.
Solution Approach 2:
The patent replaces the purely iterative mechanical optimization approach of traditional ICP with a hybrid method that incorporates gradient descent. Instead of relying solely on iterative point-to-point or point-to-plane minimization, the system uses gradient-based optimization to compute transformation parameters more efficiently, substituting the slow iterative mechanical process with a faster mathematical optimization approach.
2Measurement precision
If full tracking array is attached to the robot for accurate positioning, then positioning accuracy is improved, but device complexity increases
Solution Approach 1:
The patent applies the taking out principle by extracting the essential tracking function from a full tracking array and implementing it through a single marker on the robotic end effector or guide tube. Instead of requiring multiple distributed tracking elements, the system isolates the critical positioning information to a single extracted marker, significantly reducing device complexity while maintaining positioning accuracy through the coordinate system registration approach.
Solution Approach 2:
The patent applies universality by making the single marker serve multiple functions: it provides both the tracking reference for coordinate system registration and the positioning reference for surgical navigation. This multi-functional marker replaces the need for separate tracking arrays and positioning systems, reducing overall system complexity while maintaining full functionality.
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 method enables rapid and precise registration of the RCS and TCS, reducing the risk of local minima convergence and improving the speed of coordinate system alignment, facilitating more accurate control of the surgical robot during procedures.
Implementation Method 1
a first tracking sensor for detecting the current position of a tracking element inside a body relative to a nominal position with respect to the first tracking sensor
Data Source
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AI summary
A method for controlling a robot, which moves an ensemble that includes an arm and a tool, includes receiving from the robot, at one or more times, an arm-tracking signal, which indicates an armpose of the arm relative to a robot coordinate system (RCS) of the robot, deriving, from the arm-tracking signal, respective RCS-poses of at least one portion of the ensemble, relative to the RCS, at the times, receiving, from a tracking system, a sensor-tracking signal, which indicates a sensor-pose of at least one sensor, which belongs to the tracking system and is coupled to the ensemble, relative to a tracking-system coordinate system (TCS) of the tracking system, deriving, from the sensor-tracking signal, respective TCS-poses of the portion of the ensemble, relative to the TCS, at the times, registering the RCS to the TCS based on the RCS-poses and the TCS-poses, and, based on the registering, controlling the robot.