Snake-Arm Robot Joints With Rolling Contact to Reduce Elastic Instability
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Solution Overview
Problem
Snake-arm robots face limitations in payload capacity and stiffness due to elastic instability and loading limits, particularly in confined spaces like gas turbine engines, which restrict their access and functionality.
Innovation Solution
The design of snake-arm robots with joints featuring convex contact portions in rolling contact, where the line of action of the net force coincides with the reference line between contact points, reducing elastic instability and increasing payload capacity and stiffness, while allowing for miniaturization and enhanced motion range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional snake-arm robot joints are used, then the robot can access confined spaces, but payload capacity and stiffness are limited due to elastic instability
Solution Approach 1:
The patent applies spherical contact surfaces at the joints of the snake-arm robot, replacing conventional point or line contacts with curved spherical interfaces. This curvature distributes contact stresses more evenly across the joint interface, reducing stress concentrations that lead to elastic instability. The spherical geometry allows for more uniform load distribution while maintaining the compact joint design needed for confined space access, thereby increasing payload capacity without sacrificing stability.
2Strength
If conventional snake-arm robot joints are used, then the robot can access confined spaces, but stiffness is reduced due to loading limits
Solution Approach 1:
The spherical contact surfaces increase the effective contact area at each joint, distributing applied loads more uniformly across the interface. This reduces peak stresses and prevents early onset of elastic instability, allowing the robot to maintain higher stiffness levels even when carrying heavier payloads or operating in extended configurations. The curved geometry also improves load bearing capacity compared to conventional joint designs.
3Volume of moving object
If robot size is reduced to access smaller environments, then access capability improves, but payload capacity and stiffness decrease
Solution Approach 1:
The spherical joint contacts enable a more efficient structural design that maximizes strength-to-volume ratio. By distributing stresses uniformly across curved surfaces, the robot can maintain adequate payload capacity and stiffness with smaller overall dimensions. This allows the robot to access confined spaces while retaining sufficient structural integrity to perform maintenance tasks.
Solution Approach 2:
The patent utilizes composite material construction for the robot links and joints, combining materials with different mechanical properties to achieve optimal strength-to-weight ratios. This allows the robot to be miniaturized for confined space access while maintaining the payload capacity and stiffness required for effective operation through strategic material selection and composition.
4Device complexity
If conventional joint designs are used, then the robot structure is simpler, but complexity increases due to multiple specialized tools required for different openings
Solution Approach 1:
The spherical contact joint design creates a universal interface that can accommodate various link configurations and tool attachments. This standardized joint architecture allows the same robot platform to be adapted for different opening sizes and geometries by simply changing the end effector or link configuration, eliminating the need for multiple specialized robot systems and reducing overall device complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration enhances the robot's payload capacity, stiffness, and reduces complexity, enabling access to smaller environments by minimizing elastic instability and improving joint motion.
Implementation Method 1
joints featuring convex contact portions in rolling contact, where the line of action of the net force coincides with the reference line between contact points
Data Source
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AI summary
A snake-arm robot assembly (100) may include a first link (106A) and a second link (108A) with a joint (110) formed therebetween including first and second contact portions (118, 120) in rolling contact with one another to allow the first and second links (106A, 108B) to pivot with respect to one another. The first and second contact portions (118, 120) are configured to contact one another at first and second contact points (144, 146) corresponding to a first orientation and third and fourth contact points (148, 150) corresponding to a second orientation. The joint (110) may be configured such that a line of action of a net force acting on the joint (110) is incident with a first reference line (R1) extending between the first and second contact points (144, 146) with the links (106A, 108A in the first orientation, and the line of action is incident with a second reference line (R2) extending between the third and fourth contact points (148, 150) when the links (106A, 108A) are in the second orientation.