4-Bar Variable Stiffness Transmission for Robot Torque-Bandwidth Tradeoffs
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Solution Overview
Problem
Conventional robots face limitations in versatility due to fixed gear ratios and stiffness, leading to issues with energy loss, reduced control bandwidth, and vulnerability to shocks, necessitating a mechanism that combines variable transmission with variable stiffness.
Innovation Solution
A robot with active variable stiffness and transmission mechanism, utilizing a 4-bar linkage system with adjustable input links, motors, and springs to simultaneously control transmission ratio and stiffness, enhancing system bandwidth and shock resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a high gear ratio transmission is used to increase torque capacity, then torque capacity is improved, but control bandwidth is reduced and the system becomes vulnerable to shocks
Solution Approach 1:
The patent implements a variable stiffness mechanism that dynamically adjusts the stiffness of the actuation unit based on operational requirements. By changing the stiffness in real-time, the system can operate with high torque capacity when needed while maintaining control bandwidth and shock resistance through reduced stiffness during dynamic tasks.
Solution Approach 2:
The patent changes the physical parameter of stiffness in the actuation unit by introducing a variable stiffness mechanism. This allows the system to transition between different stiffness states, enabling high torque capacity when high stiffness is configured, and maintaining control bandwidth when low stiffness is configured, thus resolving the contradiction between torque capacity and control bandwidth.
2Reliability
If a low gear ratio transmission is used to improve control bandwidth, then control bandwidth is improved, but torque capacity is reduced
Solution Approach 1:
The variable stiffness mechanism allows the system to dynamically adjust stiffness based on the gear ratio being used. When operating with low gear ratio for high control bandwidth, the system reduces stiffness to compensate for reduced torque capacity, maintaining overall performance. When high gear ratio is used, stiffness is increased to maximize torque capacity.
Solution Approach 2:
The patent changes the stiffness parameter in response to gear ratio changes. By coordinating variable stiffness adjustment with gear ratio selection, the system compensates for torque capacity reductions at low gear ratios while maintaining control bandwidth, and maximizes torque capacity at high gear ratios.
3Force
If variable stiffness mechanism is added to resolve torque-bandwidth contradiction, then torque capacity and control bandwidth are improved, but device complexity increases
Solution Approach 1:
The patent merges the variable stiffness mechanism with the existing actuation unit, integrating multiple functions into a unified structure. By combining the stiffness adjustment capability with the transmission system, the patent reduces overall device complexity compared to having separate independent mechanisms for torque control and stiffness control.
Solution Approach 2:
The variable stiffness mechanism serves multiple functions simultaneously: it adjusts torque capacity, maintains control bandwidth, and provides shock resistance. This multi-functionality reduces the need for separate dedicated mechanisms, thereby limiting the increase in device complexity while achieving multiple performance improvements.
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 mechanism allows for increased stiffness in low transmission ratios for faster response and decreased stiffness in high ratios for shock resistance, improving the robot's operational performance.
Implementation Method 1
a connecting link (330) having one end (330a) reciprocatably screwed to an outer peripheral surface of the input link (310)
Implementation Method 2
a stiffness adjustment unit (600) configured to adjust stiffness depending on the length of the input link (310)
Data Source
AI summary
Disclosed herein is a robot with active variable stiffness and transmission mechanism, which is capable of simultaneously controlling the transmission ratio and stiffness of an actuation unit, thereby increasing the stiffness in a low transmission ratio range to enhance system bandwidth while decreasing the stiffness in a high transmission ratio range to make it resistant to system-applied shocks during operation.