Robot Tube Joint Design for Stiff Lightweight Rehabilitation
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Solution Overview
Problem
Existing robot structures, particularly in rehabilitation devices, face challenges in achieving reliable and cost-effective operation while maintaining structural stiffness and lightweight design.
Innovation Solution
A robot structure comprising links and joints, where at least one link includes a first tube piece with a first jacket outer wall and a second tube piece with a second jacket outer wall, arranged at an angle and connected via first and second connection elements, which provide a stiff and lightweight corner connection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If traditional connection methods are used to join tube pieces, then structural stiffness can be maintained, but the device becomes more complex and less cost-effective
Solution Approach 1:
The connection element integrates multiple functions into a single component: it provides structural joining between tube pieces, maintains precise angular positioning, and ensures rigid connection without requiring separate positioning fixtures or multiple fastening components. This merging reduces overall device complexity while maintaining stiffness.
Solution Approach 2:
The connection element is designed as a universal component that can be used at multiple joints throughout the robot structure, standardizing the connection approach across different links and reducing the variety of parts needed, thereby simplifying manufacturing and assembly while maintaining structural integrity.
2Strength
If more material is used to increase structural stiffness, then reliability improves, but the device becomes heavier and more expensive
Solution Approach 1:
The tube pieces and connection elements are designed with optimized local thickness and geometry: the tube walls have sufficient thickness at critical stress points while being thinner in non-critical areas. The connection element features localized reinforcement zones exactly where loads are transmitted, providing maximum stiffness with minimum material.
Solution Approach 2:
The structure combines different materials strategically: aluminum tube pieces provide lightweight structural support, while the plastic connection elements provide rigid joining with integrated positioning features. This composite approach achieves high stiffness-to-weight ratio by using each material where it is most effective.
3Manufacturing precision
If complex connection elements are used to achieve precise angular positioning, then positioning accuracy improves, but manufacturing cost and device complexity increase
Solution Approach 1:
The connection element is pre-formed with integrated positioning features (protrusions and recesses) that automatically establish the correct angular relationship between tube pieces during assembly. This preliminary preparation of positioning features eliminates the need for complex adjustment mechanisms or post-assembly calibration, achieving high precision through simple snap-fit engagement.
Solution Approach 2:
The connection element's geometry is designed so that the tube pieces self-align and self-position at the correct angle through the shape-complementary protrusions and recesses. The structure performs its own positioning function without requiring external alignment tools or complex fixture systems, reducing manufacturing complexity while maintaining precision.
Data Source
AI summary
A robot structure and a rehabilitation device have multiple elements and joints connecting the elements. At least one of the elements includes a first tubular piece with a first outer lateral surface wall, and a second tubular piece with a second outer lateral surface wall. The second tubular piece is arranged such that the length thereof is at an angle to the length of the first tubular piece so that the second tubular piece is inserted into two opposing tubular sections of the first tubular piece, and the second tubular piece passes through the first outer lateral surface wall of the first tubular piece at opposite sides. The second tubular piece is rigidly connected to the first tubular piece by a first connection element and a second connection element.