Tendon-Sheath Drive with Guide Rod to Reduce Backlash
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Solution Overview
Problem
The tendon-sheath driving method for robots faces issues with backlash and tendon loosening due to friction and bending, which reduces precision and accuracy in actuation, especially when the slave tendon is not fully inserted in the sheath.
Innovation Solution
A tendon-sheath driving apparatus is designed with a flexible sheath, a rigid rod, and a rigid pipe, where the rod is guided by the pipe, and an actuator moves the rod relative to the pipe, minimizing buckling and maintaining tendon alignment through holders and an elastic unit, ensuring smooth movement and precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the slave tendon is not fully inserted in the sheath, then the actuation range is increased, but friction and bending occur causing backlash and reduced precision
Solution Approach 1:
A guide rod is introduced as an intermediary component between the tendon and the external environment. The guide rod extends beyond the sheath while the tendon remains fully inserted, allowing the rod to bear the mechanical load and guide the tendon's movement, thereby preventing bending and friction at the exit point while maintaining full actuation range
Solution Approach 2:
The system is divided into functional segments: the sheath containing the tendon, the guide rod extending beyond the sheath, and the actuator. This segmentation allows the tendon to remain protected and fully inserted within the sheath while the guide rod handles the external guidance and positioning functions, separating the functions of force transmission and positional guidance
2Ease of operation
If the slave tendon is exposed to the outside, then the control flexibility is improved, but the tendon becomes loosened and bent increasing friction
Solution Approach 1:
The guide rod serves as a mediator that provides structural support and guidance. It extends beyond the sheath to provide control flexibility and positioning, while the tendon remains fully inserted in the sheath, supported by the guide rod, preventing loosening and bending. The guide rod absorbs the mechanical stresses that would otherwise affect the tendon
Solution Approach 2:
The guide rod provides beforehand cushioning by being in direct contact with the tendon and the external environment. It absorbs mechanical shocks, friction, and bending stresses before they can affect the tendon, protecting the tendon's integrity and stability while allowing flexible control
Data Source
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AI summary
Disclosed is a tendon-sheath driving apparatus. A tendon-sheath driving apparatus according to an embodiment of the disclosure includes: a sheath having a predetermined length, being flexible and having a hollow shape; a tendon placed inside a hollow of the sheath; a rod coupled to an outer surface of a first side of the tendon, and having higher rigidity than the sheath; and a pipe coupled to an outer surface of a first side of the sheath, and having higher rigidity than the sheath, wherein the tendon is moved through the sheath and the pipe as the rod is moved being guided by the pipe while a portion of the rod is placed inside the pipe.