Adjustable Compliant Robotic Joint for Stiffness and Motion Range
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Solution Overview
Problem
Existing mechanical systems face challenges in transmitting forces and moments with low compliance over a large range of motion while maintaining low overall weight and adjustable stiffness.
Innovation Solution
The development of lightweight rotational joints with independently adjustable compliance, achieved by arranging compliance elements around a rotational joint and adjusting their position to change joint compliance, which also modifies the induced displacement and moment arm length.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If compliance elements are positioned to achieve low compliance (high stiffness), then force and moment transmission is improved, but the range of motion is reduced
Solution Approach 1:
The patent implements dynamically adjustable compliance by allowing the compliance elements to be repositioned along the rotational joint axis. This enables the system to transition between high-stiffness configurations (for force transmission) and low-stiffness configurations (for range of motion), resolving the contradiction through temporal separation of conflicting requirements.
Solution Approach 2:
The patent changes the geometric parameter of compliance element position to simultaneously control both stiffness and range of motion. By adjusting the axial position of compliance elements relative to the rotational joint, the system modifies the moment arm length and induced displacement, thereby achieving independent control over both contradictory parameters.
2Length of moving object
If compliance elements are positioned to achieve high compliance (low stiffness), then range of motion is improved, but force and moment transmission is reduced
Solution Approach 1:
The system uses dynamic repositioning of compliance elements to switch between high-compliance and low-compliance states. When range of motion is prioritized, compliance elements are positioned to maximize displacement; when force transmission is prioritized, they are repositioned to maximize stiffness, allowing the system to adapt to different operational requirements.
Solution Approach 2:
The patent utilizes parameter changes in the position of compliance elements to independently control compliance and range of motion. By varying the axial position, the system adjusts both the induced displacement and moment arm length, enabling optimization of either parameter depending on operational needs.
3Strength
If traditional mechanical structures are used to transmit forces and moments, then structural integrity is maintained, but weight increases
Solution Approach 1:
The patent employs flexible compliance elements that provide structural integrity through elastic deformation rather than rigid support. These compliant mechanisms use thin, flexible structures that maintain strength while significantly reducing weight compared to traditional rigid mechanical joints, as the flexibility itself provides the load-bearing capability.
Solution Approach 2:
The patent replaces traditional rigid mechanical transmission structures with compliant mechanisms that use elastic deformation to transmit forces and moments. This substitution eliminates the need for heavy rigid components and complex mechanical assemblies, achieving weight reduction while maintaining structural integrity through the compliance elements' elastic properties.
4Device complexity
If compliance elements are fixed in position, then structural simplicity is maintained, but adjustability of stiffness is lost
Solution Approach 1:
The patent introduces dynamic adjustability by enabling the compliance elements to be repositioned along the rotational joint axis. This simple dynamic mechanism allows the system to adapt stiffness for different tasks or operating conditions, providing versatility without requiring complex active control systems or multiple compliance elements.
Solution Approach 2:
The patent achieves adjustable stiffness through parameter changes in the position of compliance elements. By simply varying the axial position parameter, the system can tune both compliance and moment arm length, providing adaptability with minimal structural complexity. The adjustment mechanism relies on straightforward geometric reconfiguration rather than complex control systems.
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 allows for a compact mechanical structure with adjustable stiffness, enabling efficient transmission of forces and moments across a wide range of motion while minimizing weight and parasitic moments.
Implementation Method 1
a compliant joint includes a first member, a second member, and a compliance element. The compliance element is arranged to engage the first member and the second member... the compliance element is positioned such that the compliant joint transmits a force from the rotational joint through the compliance element
Data Source
AI summary
Mechanisms to realize lightweight rotational joints having independently adjustable compliance in one or more degrees of freedom are presented herein. In addition, robotic systems incorporating one or more compliant rotational joints as described herein are also presented. In some embodiments, a robotic structure includes a member having adjustable rotational compliance. One or more compliance elements are arranged around a rotational joint. The position of the one or more compliance elements relative to the rotational joint is adjusted to change the overall joint compliance. In some embodiments, the change of position of the one or more compliance elements relative to the rotational joint changes both the induced displacement of the compliance element for a given angular displacement of the rotational joint and the length of the moment arm from the rotational joint to the compliance element.