Continuum Robot Wire-Length Control Under Torsional Twist
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Solution Overview
Problem
Continuum robots used in minimally invasive medical procedures face challenges in maintaining control performance due to twisting of their bendable portions, which affects the accuracy of wire length calculation and subsequently the robot's attitude control.
Innovation Solution
A control system that includes a torsional angle acquisition unit and a kinematics calculation unit to accurately calculate the wire length in the bendable portion by dividing it into minute sections and considering bending, turning, and torsional angles, allowing for precise control even when the robot is twisted.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the diameter of the bendable portion is decreased to reach deep portions of the body, then the reachability is improved, but the rigidity of the bendable portion decreases causing twist about the central axis
Solution Approach 1:
The patent changes the parameter of wire path geometry from linear to spiral to account for torsional deformation. By modeling the wire's actual spiral path through the twisted bendable portion, the system accurately calculates wire length despite changes in rigidity and twist, resolving the contradiction between reachability and stability.
2Device complexity
If the wire length is calculated assuming linear movement from proximal end to wire guide, then the calculation simplicity is improved, but the accuracy of wire length calculation deteriorates when the bendable portion is twisted
Solution Approach 1:
The patent segments the bendable portion into multiple sections along its length. For each section, it calculates the wire path considering local torsional angles, then sums these segments to obtain the total wire length. This segmentation approach balances calculation feasibility with accuracy by breaking down the complex spiral path into manageable segments.
Solution Approach 2:
The patent transitions from calculating wire length in a simple linear dimension to accounting for three-dimensional spiral geometry. By incorporating torsional angles and modeling the wire's path through the twisted structure in 3D space, the system achieves accurate length calculation that reflects the actual spatial configuration.
Data Source
AI summary
A control system for a continuum robot includes a kinematics calculation unit configured to calculate a length of a wire in a bendable portion. The kinematics calculation unit includes a wire length calculation unit configured to calculate, for each of a plurality of minute sections obtained by dividing the bendable portion in a longitudinal direction thereof, a length of the wire in the minute section based on a bending angle, a turning angle, and a torsional angle of the minute section, and an addition unit configured to add the lengths of the wire in the plurality of minute sections obtained by the wire length calculation unit to calculate the length of the wire in the bendable portion.