Concentric Series Elastic Actuator for High Power Density
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Solution Overview
Problem
Conventional series elastic actuators (SEAs) face challenges with bulkiness, assembly complexity, and maintenance issues due to their design, which affects their compactness and power density, making them less suitable for dense and high-degree-of-freedom robotic applications.
Innovation Solution
The design repositions spring support mechanisms within the inner circumference of the springs and integrates a single spring deflection sensor on the mechanical ground, reducing the actuator's volume, improving assembly ease, and eliminating maintenance concerns, while maintaining high power density and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If spring support mechanisms are positioned outside the springs, then the actuator provides stable spring support, but the actuator volume increases and power density decreases
Solution Approach 1:
The spring support mechanisms are repositioned inside the inner circumference of the springs, nesting the support structures within the spring assembly itself. This eliminates the need for separate external support housings and reduces the overall actuator volume while maintaining stable spring support functionality.
Solution Approach 2:
The design transitions from a radial arrangement where support mechanisms are outside the springs to an axial arrangement where supports are integrated within the spring inner circumference. This dimensional reorganization allows compact packaging without compromising support stability.
2Measurement precision
If multiple spring deflection sensors are used, then the force sensing accuracy is improved, but the device complexity and assembly difficulty increase
Solution Approach 1:
Multiple spring deflection sensors are merged into a single integrated sensing point on the mechanical ground. This consolidation maintains the ability to accurately measure force while significantly reducing the number of discrete sensor components, simplifying both the device architecture and assembly procedures.
Solution Approach 2:
The single spring deflection sensor location serves multiple sensing functions, effectively replacing what would otherwise require multiple separate sensors. This multi-functional approach reduces complexity while preserving measurement precision through strategic sensor placement.
3Force
If conventional SEA design is used, then the actuator provides adequate force output, but the weight and volume reduce the power-to-weight ratio
Solution Approach 1:
The actuator components are nested concentrically, with the ball screw positioned at the center, springs arranged around it, and support mechanisms integrated within the spring inner circumference. This nested arrangement maximizes component density and minimizes overall actuator volume and weight while preserving force output capability.
Solution Approach 2:
The design utilizes concentric radial arrangement in the transverse dimension and axial stacking in the longitudinal dimension, creating a three-dimensional compact layout that reduces both volume and weight while maintaining the mechanical advantage and force generation of conventional SEA designs.
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 revised SEA design achieves a 1.5× increase in power density compared to prior art and a 4× increase over other SEA designs, offering a compact, lightweight, and efficient actuator suitable for high-performance applications like legged robotics and human orthotics with improved shock absorption and feedback control.
Implementation Method 1
a pair of springs, which are arranged concentrically around a central shaft of the housing for transmitting force to a mechanical ground of the actuator
Implementation Method 2
The spring deflection sensor may be coupled within a recess formed within the mechanical ground of the SEA and may be configured to sense the force transmitted from the springs to the mechanical ground of the SEA
Data Source
AI summary
Embodiments of a series elastic actuator (SEA) disclosed herein include an elastic component coupled in series with a motor, wherein the elastic component comprises a pair of springs arranged concentrically around a central shaft of the housing for transmitting force to a mechanical ground of the SEA, and one or more spring support mechanisms arranged within an inner circumference of the springs. Some embodiments of the SEA may also include a spring deflection sensor, which is coupled within a recess formed within the mechanical ground of the SEA and configured to sense the force transmitted to the mechanical ground of the SEA.