Elastic Force Transmission System for Exoskeleton Energy Efficiency
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Solution Overview
Problem
Powered exoskeletons face energy efficiency issues due to traditional robotics approaches that require high power for joint movements, leading to poor efficiency and stiff-legged gait, which is not comparable to the efficient locomotion mechanisms found in nature like horses.
Innovation Solution
An apparatus with an elastic force transmission system that stores energy during a portion of the movement and releases it during another, using an elongated force transmission component that spans multiple joints, connected to a framework with rotatable members to optimize energy use and reduce muscle forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If traditional robotic approaches with stiff servomotors are used at each joint, then movement control is achieved, but energy efficiency deteriorates and gait becomes stiff-legged
Solution Approach 1:
The patent replaces traditional stiff servomotors with a compliant mechanical system consisting of series elastic actuators. Each actuator includes a motor connected through a spring element to the load, substituting the direct rigid mechanical connection with a compliant one that stores and releases energy elastically, thereby improving energy efficiency while maintaining movement control
Solution Approach 2:
The patent changes the mechanical impedance parameters of the actuation system by introducing series elasticity. This modifies the stiffness and damping characteristics of the actuators, allowing them to be more compliant and energy-efficient while still providing adequate control authority for human-like gait
2Force
If powered exoskeletons use traditional robotic approaches, then joint movement is achieved, but power consumption increases significantly
Solution Approach 1:
The patent utilizes the periodic nature of walking gait to charge and discharge the series elastic energy storage elements. During phases when the muscle would naturally be lengthening under load (absorbing energy), the spring is charged; during phases when the muscle would naturally be shortening (generating energy), the spring discharges, thereby reducing the net power that must be supplied by the motor
3Use of energy by moving object
If muscles are made almost completely tendinous with long series elastic components, then energy efficiency improves through passive elastic mechanisms, but force generation capability may be reduced
Solution Approach 1:
The series elastic element is pre-stretched or pre-loaded to store elastic energy before the muscle contraction phase. This preliminary action allows the elastic element to contribute force during the power stroke, augmenting the muscle's force-generating capability while the muscle itself operates in a more energy-efficient lengthening or isometric mode
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 apparatus reduces muscle forces and metabolic energy required for walking by approximately 46% and minimizes joint moments, allowing for more efficient locomotion and potential use in individuals with muscle function deficits.
Implementation Method 1
The elongated force transmission component may be resiliently extendable to store energy. The elongated force transmission component may be resiliently contractible to release the stored energy.
Data Source
AI summary
An apparatus for assisting in body movement includes a framework which is connectable with a human body and an elastic force transmission system connected with the framework. The elastic force transmission system stores energy during a first portion of movement of the human body and releases the stored energy during a second portion of the movement of the human body. The elastic force transmission system includes an elongated force transmission component which is resiliently extendable under the influence of force transmitted through the framework. Although the apparatus can be used in association with any desired portion of the human body, it may be particularly advantageous to use the apparatus in association with one or both legs of the human body.