Infinite-Rotation VSA Stiffness Switching for Supernumerary Limbs
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Solution Overview
Problem
Designing robotic limbs for safe interaction with users during task execution without compromising accuracy or prolonging task completion time is challenging, especially for post-stroke patients who require assistance with bimanual tasks.
Innovation Solution
The use of Variable Stiffness Actuators (VSAs) in Supernumerary Robotic Limbs (SRLs) that can adjust stiffness from low to high values, enabling safe and accurate task performance by switching between low stiffness for safety during movement and high stiffness for precision, and incorporating a momentum observer for collision detection and post-collision reaction strategies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If high stiffness is used in robotic limbs, then task execution accuracy is improved, but safety during interaction with users deteriorates
Solution Approach 1:
The robotic limb employs variable stiffness actuators that dynamically adjust stiffness based on operational requirements. During movement phases, stiffness is reduced to ensure safety, while during task execution phases, stiffness is increased to improve accuracy. This dynamic adaptation resolves the contradiction between safety and accuracy.
Solution Approach 2:
The system changes the stiffness parameter in real-time according to the task phase. By modulating the stiffness parameter from low to high values, the system achieves both safety during movement and accuracy during task execution, eliminating the need to choose between these conflicting requirements.
2Object-affected harmful factors
If low stiffness is used in robotic limbs, then safety during interaction with users is improved, but task execution accuracy deteriorates
Solution Approach 1:
The robotic limb transitions from low stiffness during movement to high stiffness during task execution. This dynamic switching allows the system to maintain safety during interaction while achieving high accuracy when performing tasks, resolving the contradiction between these two requirements.
Solution Approach 2:
The stiffness parameter is adjusted from low to high based on the operational phase. During movement, low stiffness ensures safety, while during task execution, high stiffness provides the necessary accuracy, thus resolving the contradiction through parameter modulation.
3Manufacturing precision
If variable stiffness adjustment is implemented, then both safety and accuracy are improved, but device complexity increases
Solution Approach 1:
The variable stiffness actuator serves multiple functions: it provides both safety through low stiffness modes and accuracy through high stiffness modes. This multi-functionality eliminates the need for separate actuators for different operational phases, thereby managing complexity while achieving both safety and accuracy.
Solution Approach 2:
By implementing variable stiffness adjustment, the system achieves both safety and accuracy through a single actuator system that modulates its stiffness parameter. This approach improves both safety and accuracy while managing device complexity through intelligent control rather than mechanical complexity.
Data Source
AI summary
A supernumerary robotic limb (SRL) system can include a plurality of rigid links, a joint that connects one rigid link to another rigid link in the plurality of rigid arms, and two variable stiffness actuators (VSAs) configured to drive the plurality of rigid links in order to complete at least one task. The VSAs can exhibit infinite rotation and infinite stiffness. The VSAs can include an output link. Additionally, the VSAs can include a set of elastic elements mounted on the output link. The VSAs can include an input link configured to provide kinetic energy for the output link. The VSAs can include a dynamic chassis configured to connect with the input link. Additionally, the VSAs can include a stiffness adjustor included in the dynamic chassis and configured to adjust an elastic transmission between at least one elastic element of the set of elastic elements and the output link.