Continuum Robot Wire Tension Control for Precise Back Drivability
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Solution Overview
Problem
Existing continuum robots face challenges in achieving high positioning performance without requiring complex operator interactions, particularly in scenarios involving narrow paths with branches or gentle and steep paths, where back drivability and positioning accuracy are compromised.
Innovation Solution
A control system for a continuum robot that includes a curvable unit driven by a wire and a driving unit, with a position control unit to manage target wire tension and a force control unit to compensate for tension errors, implemented in a double-loop control system for enhanced back drivability and positioning precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If back drivability is enabled for insertion operation, then ease of insertion is improved, but positioning performance and operational safety deteriorate due to inability to operate curving unit during insertion
Solution Approach 1:
The control unit dynamically switches between two operational modes: insertion operation mode with back drivability enabled for easy insertion, and operation control mode with back drivability disabled for precise positioning and safety. This dynamic reconfiguration resolves the contradiction by adapting system behavior to operational context.
Solution Approach 2:
The system changes the back drivability parameter (control gain) based on operational phase. During insertion, high back drivability allows passive following of load forces. During positioning operations, low back drivability ensures precise control and prevents erroneous movements, thus resolving the contradiction between ease of insertion and positioning performance.
2Ease of operation
If curving operation is disabled during insertion mode, then operational simplicity is improved, but safety and precision deteriorate when navigating complex paths
Solution Approach 1:
The system dynamically adjusts operational modes based on task requirements. During insertion phases, curving is disabled for simplicity. During navigation of complex paths (branches, gentle/steep transitions), the system switches to operation control mode enabling curving for safe and precise maneuvering, thus resolving the contradiction between simplicity and safety.
Solution Approach 2:
The control unit preliminarily determines the operational phase and configures appropriate control parameters before execution. By anticipating the need for curving in complex path scenarios, the system prepares the operation control mode in advance, ensuring safety and precision are maintained when navigating branches or terrain variations.
3Ease of operation
If high gain is applied in force control loop, then back drivability is improved, but stability deteriorates due to potential oscillations
Solution Approach 1:
The control gain parameter in the force control loop is adjusted based on operational context. During insertion operations requiring high back drivability, higher gain is applied. During positioning operations where stability is critical, gain is reduced to prevent oscillations. This contextual parameter adjustment resolves the contradiction between back drivability and stability.
Solution Approach 2:
The control system dynamically adjusts the force control loop gain based on the operational phase and system state. This dynamic adaptation allows the system to achieve high back drivability when needed while maintaining stability during precision operations, resolving the contradiction through real-time parameter optimization.
Data Source
AI summary
A control system for a continuum robot including at least one curvable unit driven by a wire and configured to be curvable, and a driving unit driving the wire includes: a position control unit performing control so that an error between a target displacement of push-pull driving of the wire by the driving unit and a displacement of a wire holding mechanism holding the wire obtained from a continuum robot is compensated; a force control unit performing control so that an error between a target generated force corresponding to a target tension of the wire output from the position control unit and a generated force corresponding to a tension of the wire obtained from the continuum robot is compensated; and wherein a first loop control system including the force control unit and a second loop control system including the position control unit.