Continuum Robot Curvature Control With Modified Kinematic Model
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Solution Overview
Problem
The existing kinematic models for continuum robots do not effectively account for modeling errors such as friction and twisting, leading to reduced precision in shape control, and the installation of magnetic sensors is challenging, especially in narrow-diameter robots, limiting their application.
Innovation Solution
A control method and kinematic model modification that consider the continuity between curvable sections, using a control unit to control driving wires based on a modified kinematic model, which includes a curve target value achieved by the sum of curved amounts of adjacent sections, and an optimization technique to reduce errors between target and actual positions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional kinematic model is used for continuum robot control, then the control system is simple, but positioning precision deteriorates due to modeling errors such as friction and twisting
Solution Approach 1:
The patent introduces feedback control by measuring the actual curvature of curvable sections using sensors (such as magnetic sensors or strain gauges) and comparing it with the target curvature. The control unit then adjusts the actuator driving amounts based on the curvature error to achieve precise positioning. This feedback mechanism compensates for modeling errors including friction and twisting effects.
Solution Approach 2:
The patent modifies the kinematic model parameters by introducing correction factors that account for friction and twisting. Instead of using a simple rigid-link kinematic model, the patent adjusts the model to include nonlinear parameters representing flexible deformation, friction coefficients, and twisting moments, thereby improving positioning accuracy while maintaining computational feasibility.
2Measurement precision
If magnetic sensors are installed in narrow-diameter continuum robot, then curvature detection precision is improved, but installation difficulty increases
Solution Approach 1:
The patent integrates magnetic sensors directly into the structure of curvable sections by nesting them within the hollow cylindrical segments. The sensors are positioned concentrically within the tube walls, allowing curvature measurement without adding external bulk. This nested arrangement enables precise curvature detection while maintaining the narrow diameter and flexibility of the continuum robot.
Solution Approach 2:
The patent replaces complex mechanical curvature sensing mechanisms with magnetic field-based sensing. Instead of using mechanical linkages or contact-based sensors that would require complex installation, the patent employs magnetic sensors that detect curvature through magnetic field changes, simplifying the installation process while maintaining high measurement precision.
3Adaptability or versatility
If the continuum robot uses flexible structure with infinite degree of freedom, then adaptability to narrow spaces is improved, but derivation of kinematic model becomes difficult
Solution Approach 1:
The patent divides the continuum robot into discrete curvable sections or segments, each with defined geometric parameters. By segmenting the flexible structure into manageable units with localized curvature control, the patent reduces the complexity of deriving the overall kinematic model. Each segment can be modeled independently, and the complete robot kinematics is obtained by composing the segment transformations.
Solution Approach 2:
The patent transitions from a static rigid-link model to a dynamic flexible structure model that accounts for continuous deformation. The kinematic model incorporates time-varying curvature parameters and differential equations describing the flexible behavior of each curvable section, enabling accurate representation of the infinite degree of freedom while maintaining computational tractability through numerical methods.
Data Source
AI summary
A continuum robot includes a curvable first curvable portion, a curvable second curvable portion provided adjacent to the first curvable portion, a first wire connected to the first curvable portion, a second wire connected to the second curvable portion, and a control unit which controls curves of the first curvable portion and the second curvable portion by controlling driving of the first wire and the second wire. The control unit controls driving of the first wire and the second wire on the basis of a kinematic model in consideration of a curve of the second curvable portion accompanying driving the first wire and a curve of the first curvable portion accompanying driving of the second wire. Alternatively, the control unit controls driving of the first wire and the second wire so that a curve target value of the first curvable portion is achieved by the sum of curved amounts of the first curvable portion and the second curvable portion.