Variable Stiffness Output Link via Rotating Elastic Member
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Solution Overview
Problem
Conventional methods for controlling the stiffness of robot joints are complex, costly, and inefficient, particularly in achieving stable and variable stiffness for rotational and translational movements, due to the need for force/torque sensors and additional devices that increase volume and complicate control algorithms.
Innovation Solution
A stiffness control apparatus that uses an elongated hole and shaft mechanism with elastic members to adjust the stiffness of an output link by rotating a member with a circular, elliptical, or polygonal cross-section, allowing for continuous or stepwise stiffness control in rotational or translational movements, thereby optimizing stiffness adjustment without the need for complex sensors or additional devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If force/torque sensor is installed to adjust stiffness of robot joint, then stiffness control capability is improved, but manufacturing cost increases and control algorithm becomes complicated
Solution Approach 1:
The patent extracts and eliminates the force/torque sensor from the system, replacing it with a passive elastic member mechanism. The stiffness control is achieved through the mechanical structure itself (elastic member deformation) rather than through active sensing and control algorithms, thereby removing the source of complexity while maintaining stiffness control capability
Solution Approach 2:
The elastic member automatically provides stiffness control based on the joint's position and load conditions without requiring external sensing or complex control algorithms. The mechanism self-regulates stiffness through its elastic properties, making the system self-sufficient and eliminating the need for additional control complexity
2Reliability
If additional stiffness adjusting device is inserted into joint, then stiffness control capability is improved, but joint volume increases
Solution Approach 1:
The patent merges the stiffness control function with the existing joint structure by integrating the elastic member directly into the joint mechanism. This combination eliminates the need for separate additional devices, achieving stiffness control while maintaining compact joint dimensions
Solution Approach 2:
The elastic member serves multiple functions simultaneously: it provides stiffness control, acts as a mechanical element within the joint structure, and enables both rotational and translational stiffness adjustment. This multi-functionality reduces the need for dedicated separate components, thereby minimizing volume increase
3Adaptability or versatility
If structure simulating human muscles is adopted to achieve nonlinear stiffness characteristic, then torque with nonlinear characteristic is obtained, but control becomes complicated when position changes
Solution Approach 1:
The patent achieves nonlinear stiffness characteristics by changing the physical parameters of the elastic member (such as its elastic coefficient and geometric configuration) rather than through complex control algorithms. The nonlinear behavior emerges naturally from the elastic member's physical properties, providing adaptability without increasing control complexity
Solution Approach 2:
The elastic member dynamically adapts its stiffness characteristics based on the joint's position and load conditions through its inherent elastic deformation. This dynamic adaptation occurs passively through mechanical means rather than requiring active control, maintaining simplicity while achieving the desired nonlinear characteristics
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
Enables rapid and easy adjustment of stiffness, stabilizing the operation of moving mechanisms by effectively controlling stiffness in both rotational and translational motions, applicable to both actuators and robots, reducing manufacturing costs and complexity.
Implementation Method 1
at least one stiffness control unit includes an elastic member between a first end of the elongated hole in a longitudinal direction thereof and the shaft
Data Source
Figure 1a~1b
Figure 2a~2b
Figure 3a~3b
AI summary
A stiffness control apparatus includes an output link and at least one stiffness control unit configured to control stiffness of the output link. The at least one stiffness control unit includes a rotating member rotatably arranged on outer side or inner side of the output link and configured to restrict the output link and a shaft for rotating the rotating member. The stiffness control apparatus is configured to control the stiffness of the output link in rotational or translational movement based on a rotation angle of the rotating member.