Robot Rotation Joint With Variable Links for Twist Motion
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Solution Overview
Problem
Conventional humanoid robots face challenges in creating a compact joint with sufficient rotational degrees of freedom to mimic human motion, leading to increased cost and complexity, particularly in achieving motions like twist and torsion, and struggle with load distribution and positioning in parallel link mechanisms.
Innovation Solution
A rotation connecting mechanism is introduced, featuring a joint with at least two rotational degrees of freedom connected by two actuators, each with multiple rotational degrees of freedom and variable length links, allowing for efficient motion and reduced cost by minimizing the number of high-degree-of-freedom connecting units and utilizing a worm gear mechanism in the robot hand.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a motor and gear are disposed in a joint with rotational degrees of freedom to achieve human-like motion, then the joint can perform twist and torsion motions, but the joint becomes large and complex
Solution Approach 1:
The patent replaces the conventional motor-gear mechanism with a cable-driven parallel mechanism. Instead of using rotational motors and gear transmissions within the joint, the invention uses linear actuators (motors) connected via cables and pulleys to generate forces that act on the joint through parallel linkages. This substitution eliminates the need for complex in-joint gear mechanisms while maintaining the ability to achieve multi-degree-of-freedom motion including twist and torsion.
2Ease of manufacture
If the joint structure is simplified to reduce cost, then manufacturing becomes easier, but the ability to perform human-like motions with twist and torsion is lost
Solution Approach 1:
The patent creates a multi-functional joint mechanism where a single cable-driven parallel structure can simultaneously achieve multiple motion functions (pitch, roll, and twist motions) that would traditionally require separate motor-gear assemblies for each degree of freedom. The parallel linkage system with multiple cables allows one actuator system to control multiple rotational degrees of freedom, reducing overall system complexity and cost while maintaining full human-like motion capability.
3Adaptability or versatility
If a parallel link mechanism with multiple rotational degrees of freedom is used, then human-like motion is achieved, but load distribution and positioning control become difficult
Solution Approach 1:
The patent incorporates force sensing mechanisms and position sensors in the cable-driven parallel mechanism to enable real-time measurement of cable tensions and joint positions. This feedback information is used by the control system to dynamically adjust cable forces, ensuring proper load distribution among the parallel links and achieving accurate positioning control. The feedback loop allows the system to compensate for variations in cable elasticity, friction, and external disturbances.
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 solution enables a more cost-effective and compact humanoid robot capable of performing motions similar to humans, including twist and torsion, while simplifying the joint structure and improving load distribution and positioning.
Implementation Method 1
utilizing a worm gear mechanism in the robot hand
Data Source
AI summary
A rotation connecting mechanism includes: a joint that connects a second member rotatably to a first member with three rotational degrees of freedom; a first link and a third link in each of which one end is attached rotatably to second member with at least two rotational degrees of freedom while the other end is attached rotatably to first member with at least two rotational degrees of freedom, each of first link and third link having a variable length and five rotational degrees of freedom; a second link in which one end is attached rotatably to first link with at least two rotational degrees of freedom while the other end is attached rotatably to first member with at least two rotational degrees of freedom, second link having a variable length and five rotational degrees of freedom; and motors that generate force changing lengths of the three links.