Variable Stiffness Power Transmission via Spring Worm Actuation
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Solution Overview
Problem
Existing power transmission devices for robot joints lack the ability to variably control stiffness and viscosity characteristics, leading to inflexibility and potential structural complications when attempting to adapt to different environmental conditions or tasks.
Innovation Solution
A power transmission device with a simple structure comprising a wire member, roller members, a rotary gear, a spring worm, and a cylinder structure, allowing for adjustable stiffness and viscosity control through the rotation of the spring worm and manipulation of the orifice area, enabling elastic and viscous forces to be generated between pulley members.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a highly rigid power transmission structure is used to accurately control joint displacement, then positioning precision is improved, but flexibility and adaptability to external disturbances deteriorate
Solution Approach 1:
The patent applies dynamics by making the stiffness characteristic variable rather than fixed. The stiffness adjustment mechanism allows the power transmission system to dynamically change its rigidity level according to task requirements and external conditions, enabling the system to be rigid when precision is needed and flexible when adaptability is needed, thus resolving the contradiction between positioning precision and flexibility
Solution Approach 2:
The patent changes the physical parameter of stiffness by introducing a stiffness adjustment mechanism that can vary the rigidity of the power transmission system. This parameter change enables the system to adapt to different operational conditions, maintaining high positioning precision when required while providing flexibility under unexpected external disturbances, thereby resolving the contradiction
2Adaptability or versatility
If stiffness and viscosity characteristics are made variable to adapt to different tasks and environments, then adaptability is improved, but device complexity increases
Solution Approach 1:
The patent merges the stiffness adjustment function and viscosity control function into a single integrated power transmission mechanism. By combining these functions in one system rather than using separate mechanisms, the patent achieves variable stiffness and viscosity characteristics for improved adaptability while minimizing the increase in device complexity
Solution Approach 2:
The power transmission mechanism is designed with multi-functionality, where a single mechanism serves both stiffness adjustment and viscosity control purposes. This universal design allows the system to adapt to different tasks and environments through variable characteristics without requiring multiple separate components, thus improving adaptability while controlling device complexity
3Adaptability or versatility
If additional mechanisms are added to enable variable stiffness and viscosity control, then adaptability is improved, but drive efficiency deteriorates
Solution Approach 1:
The patent replaces complex mechanical transmission mechanisms with a more efficient configuration that minimizes energy loss. By using a direct-drive or simplified transmission approach with the stiffness adjustment mechanism, the system achieves variable stiffness and viscosity control while maintaining high drive efficiency and minimizing energy loss between the motor and load
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
The device achieves flexible motion and adaptable power transmission with minimal impact on drive efficiency, allowing for variable stiffness and viscosity characteristics to suit different tasks and environments, enhancing the robot's operational capabilities.
Implementation Method 1
a spring worm engaged with the rotary gear
Implementation Method 2
a roller member, the outer peripheral portion of which is pressed against the wire member such that the wire member is curved between the two pulley members
Data Source
AI summary
A power transmission device has two roller members which are rotatable on their own axes and the outer peripheral portions of which are pressed against a wire member tightly stretched between two pulley members, a rotary gear which is rotatable around a revolution axial center of the roller members integrally with a supporting member which supports the roller members, a spring worm meshed with the rotary gear, and an actuator which controls the rotation amount of the spring worm.