Dielectric Elastomer Variable Stiffness Actuator for Robotic Joints
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Solution Overview
Problem
Variable stiffness actuators (VSAs) face challenges with excessive weight, energy consumption, and durability due to complex mechanisms and additional components, limiting their implementation in robots, especially for human-interaction applications where stiffness modulation is required.
Innovation Solution
A dielectric elastomer system (DES) VSA with a mechanically simple variable stiffness mechanism that softens when energized and stiffens when unpowered, allowing independent control of stiffness and equilibrium position, using a compliant membrane or elastomer sheets with electrically controlled stiffness and a ball screw mechanism for actuation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If traditional variable stiffness mechanisms with additional motors and moving parts are used, then stiffness modulation capability is improved, but weight, volume, and device complexity increase
Solution Approach 1:
The patent replaces traditional mechanical stiffness modulation mechanisms (which use additional motors and moving parts) with a dielectric elastomer system that uses electrical fields to control stiffness. The dielectric elastomer's inherent material properties allow it to change stiffness in response to electrical stimulation, eliminating the need for complex mechanical variable stiffness mechanisms while maintaining the desired adaptability.
Solution Approach 2:
The patent changes the physical state parameters of the dielectric elastomer material through electrical field application. By controlling the electrical properties (voltage, frequency) of the dielectric elastomer, the stiffness parameter is dynamically adjusted without mechanical moving parts. This parameter-based control achieves stiffness modulation while reducing device complexity.
2Adaptability or versatility
If traditional variable stiffness mechanisms with additional motors are used, then stiffness modulation capability is improved, but weight and volume increase
Solution Approach 1:
The patent eliminates additional motors and mechanical components by using a dielectric elastomer system. The electrical actuation of the dielectric elastomer provides stiffness modulation without requiring the weight of additional motors, gears, or mechanical linkages, thereby reducing the overall actuator weight while maintaining stiffness modulation capability.
3Adaptability or versatility
If traditional variable stiffness mechanisms with additional components are used, then stiffness modulation capability is improved, but energy consumption increases
Solution Approach 1:
The patent replaces energy-intensive mechanical stiffness modulation systems with a dielectric elastomer system that uses electrical fields. The dielectric elastomer can be activated and deactivated electrically, providing stiffness modulation with lower energy consumption compared to continuous mechanical actuation required by traditional systems with separate stiffness modulation motors.
4Adaptability or versatility
If traditional variable stiffness mechanisms are used, then stiffness modulation capability is improved, but durability decreases
Solution Approach 1:
The patent eliminates mechanical moving parts and additional components that are prone to wear and failure. The dielectric elastomer system uses electrical field control to achieve stiffness modulation, removing mechanical elements that would reduce durability. This results in a more reliable and durable actuator while maintaining the ability to modulate stiffness.
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 DES VSA achieves low-power stiffness modulation with reduced energy consumption, capable of exerting significant forces, and is suitable for larger-scale robotic applications, including robotic prosthetic legs, with improved durability and efficiency in cyclic tasks like legged locomotion.
Implementation Method 1
The VSM includes a dielectric elastomer (DES) that softens when energized and stiffens when unpowered
Data Source
AI summary
A dielectric elastomer system (DES) variable stiffness actuator (VSA) is provided. In an embodiment, the DES VSA includes a variable stiffness module (VSM). The VSM includes a DES that softens when energized and stiffens when unpowered, an outer frame, and an inner frame member. The stiffness of the DES is variable. The outer frame supports the DES and the inner frame member, which is disposed within the DES. The inner frame member is configured to be displaceable with respect to the outer frame. The DES VSA also includes an actuation motor mechanically coupled to the inner frame member that is configured to cause a force to be applied to the inner frame member and the actuation motor is configured to control an equilibrium position of the DES VSA.