Ball Joint Differential Linkage for 2-DoF Robot Limb Motion
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Solution Overview
Problem
Existing joint designs for robot limbs offer limited degrees of freedom, restricting the versatility and range of motion in humanoid and industrial robots.
Innovation Solution
A 2-DoF joint mechanism utilizing rigid linkages that allow the output link to revolve around a first axis and rotate around a second axis orthogonal to the first, with input elements connected by driving rods, enabling independent rotation and simultaneous articulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If traditional joint designs (actuators, bevel gear differentials, cable differentials) are used, then the structure is relatively simple, but the degrees of freedom are limited
Solution Approach 1:
The joint mechanism is segmented into multiple independent components: a first linkage element, a second linkage element, and a third linkage element, each capable of independent rotation around the first axis. This segmentation allows each element to contribute to different degrees of freedom, enabling the output link to achieve both revolution around the first axis and rotation around the second orthogonal axis through the coordinated motion of segmented components.
Solution Approach 2:
The mechanism transitions from one-dimensional rotation to two-dimensional motion by introducing a second axis of rotation that is orthogonal to the first axis. The output link is configured to rotate around the second axis while the intermediate link rotates around the first axis, adding dimensional complexity to the motion capability and enabling sophisticated articulated movement beyond simple single-axis rotation.
2Ease of operation
If connecting rods run directly from actuator output to distal link, then the mechanism is simple, but the range of motion is restricted
Solution Approach 1:
An intermediate link is introduced as a mediator between the input elements and the output link. This intermediate link rotates around the first axis and provides a platform for the output link to be mounted, enabling the output link to achieve rotation around the second orthogonal axis. The intermediary component facilitates complex motion paths and expands the range of motion without requiring direct connection between actuators and distal links.
Solution Approach 2:
The linkage structure is designed to be dynamically adaptable, with the output link capable of changing its orientation and position through coordinated rotation of multiple elements around different axes. The mechanism transitions from static, fixed-position linkages to dynamic, multi-axis articulated linkages that can adapt their configuration to achieve various degrees of freedom and motion ranges.
Data Source
AI summary
Rigid linkages are used implement a 2-DoF joint. The output link of the joint can revolve around a first axis and can rotate around a second axis that is orthogonal to and offset from the first axis. The output link is mounted on an intermediate link, which rotates around the first axis. The output link is connected by driving rods to a pair of input elements, which also rotate around the first axis. When the input elements rotate in the same direction around the first axis, the intermediate link and the output link revolve around the first axis in that same direction. When the input elements rotate in different directions or by different amounts around the first axis, the output link rotates around the second axis and also may revolve around the first axis.