Laser-cut patterned tubes: improved flexural rigidity and stability in concentric-tube robots

The problem

A challenge with concentric-tube robots (CTRs) is the tradeoff between specific performance and design stability. A larger range of motion and dexterity entails a decrease in stability, which limits the capabilities of the robot in practice. Modifying the structural properties of the tubes to increase stability also comes with other tradeoffs, such as reduced strength. Elastic stability of the tubes is compromised when their curvature overlaps, causing the tubes to "snap" to a different configuration with high velocity, potentially causing patient injury.

The solution

Researchers at the University of Tennessee and Louisiana State University have invented a concentric-tube steerable device which has the improved structural modification of laser cut patterning on the tubes. The nested tubes can then have different flexural rigidity properties. The tubes having asymmetric stiffness properties improves the CTR's arm stability while minimally sacrificing strength. This modification also gives the tubes a wider range of motion, eliminating the unstable region that causes snapping.

Benefits

• Maintains CTR movement range and bending angle without significant reduction in stiffness
• Improves CTR stability while preserving strength
• Reduces likelihood of injury to the patient
• Prevents "snapping"

Patent status

Granted: US 11,964,387 B2.