Variable Stiffness Series Elastic Actuator With Angle-Tuned Compliance
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Solution Overview
Problem
Current robots using high stiffness actuators face issues with contact instability, noise, and low power density in unstructured environments, while existing variable stiffness actuators lack the range of stiffness required for precise motion control and compliance with dynamic environments.
Innovation Solution
A variable stiffness actuator design featuring a flexure plate with cantilevered beams and rotatable contactors that adjust stiffness by changing the angle of engagement, allowing for real-time selection of stiffness ratios up to theoretically infinite, enabling robots to perform precise and compliant tasks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high stiffness actuators are used, then positioning accuracy is improved, but contact stability deteriorates and noise increases
Solution Approach 1:
The actuator employs a series elastic element with variable stiffness that can be dynamically adjusted based on task requirements. The stiffness is changed by modifying the engagement angle of controllable elements with the elastic element, allowing the system to transition between high stiffness for positioning accuracy and low stiffness for compliant interaction, thereby resolving the contradiction between positioning accuracy and contact stability
Solution Approach 2:
The actuator changes the physical parameter of stiffness by altering the engagement angle of the controllable elements with the series elastic element. By varying this angle, the effective stiffness of the actuator can be continuously adjusted, enabling high positioning accuracy when needed while maintaining contact stability through compliant behavior when required
2Measurement precision
If high stiffness actuators are used, then positioning accuracy is improved, but power density deteriorates
Solution Approach 1:
The actuator uses dynamic stiffness adjustment through variable engagement angles of controllable elements. When high power density is needed, the stiffness is reduced by decreasing the engagement angle, allowing more efficient energy transfer. When positioning accuracy is prioritized, stiffness is increased by increasing the engagement angle, demonstrating adaptive optimization of power density based on task requirements
3Adaptability or versatility
If variable stiffness actuators are used, then compliance with environment is improved, but range of stiffness deteriorates
Solution Approach 1:
The actuator segments the stiffness control function by using multiple controllable elements that can independently engage with different portions of the series elastic element. Each controllable element can be adjusted to a specific engagement angle, creating discrete stiffness levels that collectively provide a wide continuous range of stiffness values, thus improving compliance while managing complexity through modular segmentation
Solution Approach 2:
The actuator introduces an angular dimension for stiffness control by varying the engagement angle of controllable elements with the elastic element. This angular degree of freedom provides an additional control parameter that expands the achievable stiffness range without proportionally increasing mechanical complexity, enabling broad adaptability through geometric configuration rather than numerous components
4Reliability
If variable stiffness actuators are used, then shock tolerance is improved, but friction increases
Solution Approach 1:
The actuator dynamically changes the stiffness parameter by adjusting the engagement angle of controllable elements. During shock events, the stiffness is reduced by decreasing the engagement angle, allowing the series elastic element to absorb冲击 energy while minimizing frictional losses. During normal operation, stiffness is optimized by increasing the engagement angle, balancing shock tolerance and friction reduction through parameter adaptation
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 robots to achieve high accuracy positioning in free space and compliance with unstructured environments, providing a wide range of stiffness options for effective interaction and minimizing damage to the robot and environment.
Implementation Method 1
A first contactor engages the first cantilevered beam at a variable angle about the rotation axis to adjust a stiffness of a mechanical connection between the flexure plate and the housing
Data Source
AI summary
A variable stiffness actuator comprises a flexure plate which comprises a first cantilevered beam that extends inwards from an outer periphery of the flexure plate. A housing and the flexure plate rotatable about a common joint axis. A first contactor is pivotably secured at a revolute joint to the housing. The first contactor rotates about the revolute joint at a first rotation axis. The first rotation axis offset on the housing from the joint axis. The first contactor engages the first cantilevered beam at a variable angle about the rotation axis to adjust a stiffness of a mechanical connection between the flexure plate and the housing.