Variable Stiffness Spring With Self-Locking Pivot Modulation
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Solution Overview
Problem
Existing variable stiffness springs require precisely timed forces to change stiffness efficiently, limiting their practical application in human-adaptive systems where low energy cost modulation is necessary, especially during oscillatory motions.
Innovation Solution
Incorporating a series spring connected to a self-locking pivot point mechanism and a linkage system, allowing users to change stiffness with small and imprecisely timed forces by leveraging the mechanical advantage of a spiral torsion spring, enabling power amplification or de-amplification without the need for precise timing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If precisely timed forces are applied to change stiffness efficiently, then stiffness modulation efficiency is improved, but ease of operation deteriorates due to timing requirements
Solution Approach 1:
The spring system automatically adjusts stiffness based on its deflection state without requiring external timing control. The series spring configuration enables the system to self-regulate stiffness modulation, eliminating the need for precisely timed external forces while maintaining energy efficiency.
Solution Approach 2:
The patent changes the physical parameters of the spring system by introducing a series spring configuration that alters the stiffness characteristics. This parameter change enables continuous stiffness modulation throughout the oscillation cycle without requiring precise timing, as the system naturally transitions between different stiffness states based on deflection.
2Adaptability or versatility
If variable stiffness mechanism is added to spring system, then adaptability is improved, but device complexity increases
Solution Approach 1:
The patent merges the variable stiffness function directly into the spring system by configuring springs in series rather than adding a separate variable stiffness mechanism. This integration achieves stiffness adaptability while minimizing additional complexity by utilizing the inherent properties of the spring arrangement.
Solution Approach 2:
The series spring configuration serves multiple functions simultaneously: it provides the primary elastic restoring force, enables variable stiffness characteristics, and allows continuous modulation throughout the oscillation cycle. This multi-functionality achieves adaptability without requiring separate dedicated mechanisms for each function.
3Force
If series spring mechanism is used for stiffness modulation, then force requirement is reduced, but device complexity increases
Solution Approach 1:
The series spring acts as an intermediary element that mediates between the user-applied force and the main spring system. This intermediary spring amplifies the effect of small forces applied by the user, enabling stiffness modulation with minimal input force while the spring system itself manages the complexity of the modulation mechanism.
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 users to adjust stiffness over a large range during continuous oscillations with small forces, reducing the metabolic cost of tasks like walking and running, and allowing for intuitive control similar to bicycle gear shifting, while maintaining assistive joint torque.
Implementation Method 1
the variable stiffness spring includes a spiral torsion spring
Implementation Method 2
a force applied to the second end of the series spring changes a stiffness of the variable stiffness spring based at least in part on a position of the pivot point
Implementation Method 3
self-locking pivot point mechanism
Implementation Method 4
leveraging the mechanical advantage of a spiral torsion spring
Data Source
AI summary
Various examples of systems, methods, and applications of variable stiffness springs are described. In one example, a variable stiffness joint apparatus can include a torsional spring; a variable stiffness mechanism comprising a self-locking mechanism and a linkage system, the self-locking mechanism comprising an auxiliary spring; and an actuator in communication with the auxiliary spring of the self-locking mechanism. When the actuator changes position, a force is applied to the auxiliary spring by the actuator and a stiffness is adjusted at an energy cost that is independent of the stiffness of the spring and the energy stored by the spring. In another example, a self-adjusting variable stiffness mechanism can include a compression spring. The energy stored by compressing the compression spring and the mechanism can self-adjust a stiffness to enable energy accumulation using a same maximal compression force which is not dependent on the energy accumulated in the spring.