Phantom Degrees of Freedom in Robotic Surgical Control
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Solution Overview
Problem
Current robotic surgical systems face challenges in effectively controlling manipulator arms and tools with fewer degrees of freedom than the master controller, leading to overconstrained situations, sluggish responses, and increased complexity when handling tools with different degrees of freedom, resulting in undesirable tool movements and increased costs.
Innovation Solution
A method and system that utilize a kinematic model to generate instructions for controlling mechanical bodies with fewer degrees of freedom, incorporating phantom degrees of freedom to simulate missing degrees of freedom and reduce complexity by using a single computation engine for various instruments, allowing for flexible control of manipulator arms and tools.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a master controller with more degrees of freedom than the manipulator is used, then control flexibility and adaptability are improved, but system complexity and computational burden increase
Solution Approach 1:
A virtual model of the manipulator with phantom degrees of freedom is introduced as an intermediary between the master controller and the actual manipulator. This virtual model absorbs the mismatch in degrees of freedom, allowing the master controller to operate with full 6-DOF freedom while the physical manipulator operates with its limited degrees of freedom through null-space projection
Solution Approach 2:
A virtual copy of the manipulator is created in the control system with additional phantom degrees of freedom that do not physically exist. This virtual copy allows the master controller to manipulate all 6 degrees of freedom while the actual manipulator executes only the necessary movements through null-space projection, eliminating the need for multiple physical controllers
2Measurement precision
If tools with different degrees of freedom are controlled by separate computation engines, then control precision is improved, but system complexity and cost increase
Solution Approach 1:
A single computation engine is designed to universally control all surgical tools regardless of their specific degrees of freedom. The engine uses a virtual manipulator model with phantom degrees of freedom that can be configured to match any tool's kinematic properties, allowing one engine to handle multiple tool types with different DOF requirements through software configuration rather than hardware differentiation
3Device complexity
If the manipulator has fewer degrees of freedom than the master controller, then hardware simplicity is improved, but control responsiveness and accuracy deteriorate due to overconstrained situations
Solution Approach 1:
The control problem is shifted from physical space to virtual space by introducing phantom degrees of freedom in the virtual manipulator model. The master controller operates in this expanded virtual dimension space where all 6 DOF are available, while the null-space projection algorithm translates these virtual movements into valid physical movements for the limited-DOF manipulator, maintaining responsiveness without requiring additional physical actuators
Data Source
AI summary
Methods, apparatus, and systems for controlling the movement of a mechanical body. In accordance with a method, desired movement information is received that identifies a desired motion of a mechanical body, the mechanical body having a first number of degrees of freedom. A plurality of instructions are then generated by applying the received desired movement information to a kinematic model, the kinematic model having a second number of degrees of freedom greater than the first number of degrees of freedom, each of the instructions being configured to control a corresponding one of the second number of degrees of freedom. A subset of the plurality of instructions are then transmitted for use in controlling the first number of degrees of freedom of the mechanical body.