Humanoid Shoulder Joint With Variable-Length Links for Compact Power
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Solution Overview
Problem
Conventional humanoid robots struggle to achieve a compact joint design with sufficient power output, especially when requiring two rotational degrees of freedom, which limits their ability to perform motions like torsion and mimic human-like movements.
Innovation Solution
The design incorporates a shoulder joint with two rotational degrees of freedom, utilizing a chest-side main link attaching unit and an upper arm main link attaching unit, along with variable length links and actuators, to allow for compact and powerful motion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a motor and gear are disposed in a joint with two rotational degrees of freedom, then the joint can be driven with sufficient power, but the joint becomes large and cannot be made compact
Solution Approach 1:
The joint is divided into multiple independent drive units, each responsible for one rotational degree of freedom. Each drive unit contains a motor and gear disposed along a rotation axis, and multiple such units are arranged around a central axis to collectively provide two rotational degrees of freedom. This segmentation allows each unit to be compact while the aggregate provides sufficient power.
Solution Approach 2:
The joint structure transitions from a single-axis arrangement to a multi-axis three-dimensional configuration. Multiple drive units are arranged radially around a central axis, utilizing spatial distribution in three dimensions rather than linear arrangement. This dimensional change enables compact packaging of multiple motors and gears while maintaining sufficient power output.
2Volume of moving object
If the joint structure is made compact, then the robot can achieve human-like proportions, but the distance between the fulcrum and action point becomes short, reducing power output
Solution Approach 1:
The joint is segmented into multiple drive units arranged radially, with each unit contributing to the total power output. This allows the joint to maintain a compact overall size while distributing multiple power sources around the circumference, effectively increasing total power without increasing the joint's radial footprint.
Solution Approach 2:
Multiple drive units are merged into a single integrated joint structure, where several motors and gears work together around a central axis. This merging of multiple power sources in a compact radial arrangement enables the joint to achieve both compact dimensions and sufficient power output simultaneously.
3Device complexity
If a parallel link mechanism with fixed length links is used, then the structure is simplified, but the mechanism cannot rotate around the fixed length link, restricting motion capability
Solution Approach 1:
The fixed length link is replaced with a variable length link that can dynamically adjust its length. This variable length link is driven by an actuator that changes its length to enable rotation around the link, while maintaining structural simplicity. The dynamic adjustment of link length provides rotational freedom without significantly increasing mechanism complexity.
Data Source
AI summary
A robot includes: a chest; a pair of right and left upper limbs; and a pair of right and left shoulders connecting the right and left upper arms rotatably to the chest with two rotational degrees of freedom, respectively. The shoulder includes: a shoulder joint connecting the upper arm rotatably; a chest-side main link attaching unit provided; an upper arm main link attaching unit provided in the upper arm; an upper arm drive main actuator including an upper arm drive main link having a variable length and a power source for generating force changing the length of the upper arm drive main link; a chest-side auxiliary link attaching unit provided in the chest; an upper-arm-drive-main-link-side auxiliary link attaching unit provided in the upper arm drive main link; and an upper arm drive auxiliary actuator including an upper arm drive auxiliary link having a variable length and a power source for generating force changing the length of the upper arm drive auxiliary link.