Variable Stiffness Series Elastic Actuator With Rotating Contactor
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Solution Overview
Problem
Conventional robots using high stiffness actuators face issues with contact instability, noise, low power density, and limited adaptability in unstructured environments, where variable stiffness actuators are needed for compliance and accurate force control.
Innovation Solution
A variable stiffness actuator design featuring a flexure plate with a cantilevered beam and a contactor system that adjusts stiffness by rotating about a revolute joint, allowing for real-time selection of stiffness through varying the angle of engagement between the contactor and the cantilevered beam, enabling high stiffness in free space and low stiffness in constrained directions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If high stiffness actuators are used for absolute positioning accuracy, then positioning precision is improved, but contact instability and noise increase
Solution Approach 1:
The actuator implements variable stiffness through a movable contactor that can rotate about a revolute joint, dynamically adjusting the engagement angle with the cantilevered beam. This allows the system to transition between high stiffness (for positioning accuracy) and low stiffness (for contact stability) states as needed, rather than being fixed at a single stiffness value.
Solution Approach 2:
The invention changes the stiffness parameter of the actuator by varying the contactor engagement angle. When the contactor engages the cantilevered beam at different angles, the effective stiffness of the mechanical connection changes, enabling the system to optimize between positioning precision and contact stability based on operational requirements.
2Manufacturing precision
If high stiffness actuators are used for positioning precision, then positioning accuracy is improved, but power density decreases
Solution Approach 1:
The variable stiffness mechanism allows the actuator to use high stiffness only when positioning precision is required, and switch to low stiffness when power efficiency is more important. This dynamic adjustment optimizes the power-to-performance ratio by avoiding continuous high stiffness operation.
3Manufacturing precision
If high stiffness actuators are used for positioning accuracy, then positioning precision is improved, but adaptability in unstructured environments deteriorates
Solution Approach 1:
The actuator can dynamically adjust its stiffness characteristic to match the environmental requirements. In structured environments with precise positioning needs, it operates at high stiffness. In unstructured environments requiring compliance and force control, it switches to low stiffness, thereby achieving both positioning accuracy and environmental adaptability.
Solution Approach 2:
By changing the stiffness parameter through contactor angle adjustment, the actuator adapts to different operational contexts and environmental conditions, providing high positioning accuracy when needed and compliance when interacting with unknown or dynamic environments.
4Adaptability or versatility
If variable stiffness is implemented through contactor rotation, then stiffness range is improved, but device complexity increases
Solution Approach 1:
The actuator is divided into distinct functional components: the flexure plate with cantilevered beam, the revolute joint, and the rotatable contactor. This segmentation allows each component to perform a specific function and simplifies the overall design by avoiding complex mechanisms, achieving variable stiffness through the simple rotation of the contactor about a fixed axis.
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 perform precise and reliable manipulation tasks in unstructured environments with a selectable range of stiffness, from near-zero to high, enhancing shock tolerance, accuracy, and energy efficiency, exceeding the capabilities of current series elastic actuators.
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
Data Source
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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.