Exoskeleton Leg Spring Mechanism for Low Power

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Solution Overview

Problem

Ambulatory exoskeletons face high power consumption and safety risks due to the leg actuator taking up all load, which affects autonomy and can be dangerous in power supply failures.

Innovation Solution

Incorporating a spring element with a pretensioning mechanism and a cable system that allows varying the distance between the ends of the leg segment, reducing power consumption by using the spring to absorb vertical forces without power, and a geared motor to adjust the cable length for walking, ensuring no force is applied to the user's foot during swing phases.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If the leg actuator takes up all the load itself, then the exoskeleton can support unknown loads, but the power consumption increases significantly

Engineering Contradiction:

Improveability to support unknown loadsVSAvoidpower consumption

Core Design Contradiction:

Adaptability or versatilityVSUse of energy by moving object

Solution Approach 1:

The load support function is segmented between the spring element (which handles static vertical forces) and the actuator (which handles dynamic control and distance variation). This segmentation allows the spring to absorb the majority of the load passively without power consumption, while the actuator only consumes power when actively adjusting the leg segment distance.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The system uses periodic action by only activating the actuator when distance adjustment is needed, rather than continuously consuming power to maintain load support. The spring element continuously supports the load passively, while the actuator intervenes periodically to adjust the pretensioning and distance between pelvis and foot segments.

Inventive Principle:

Principle #19Periodic action

2Reliability

If the actuator maintains constant force to support the load, then the load can be supported safely, but power is consumed even in static phases

Engineering Contradiction:

Improvesafe load supportVSAvoidpower consumption in static phase

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The spring element acts as a counterweight mechanism that passively supports the vertical load through its elastic properties. The spring is pretensioned to provide the necessary support force without requiring active power consumption from the actuator during static phases, thereby eliminating energy loss while maintaining reliable load support.

Inventive Principle:

Principle #8Anti-weight (Counterweight)

Solution Approach 2:

The spring element provides self-service by automatically supporting the load through its inherent elastic properties without requiring external power input. The system uses the user's own movement and gravity to maintain spring tension, eliminating the need for continuous actuator engagement and associated power consumption.

Inventive Principle:

Principle #25Self-service

3Reliability

If the spring element applies force during swing phases, then the load is continuously supported, but the user's foot is subjected to unwanted force

Engineering Contradiction:

Improvecontinuous load supportVSAvoidforce on user's foot during swing

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The system dynamically adjusts the distance between the pelvis and foot segments using the actuator during swing phases. By varying this distance, the actuator controls the spring element's engagement, ensuring that the spring only supports the load when needed (during stance phases) and does not apply unwanted force to the user's foot during swing phases when the leg is moving forward.

Inventive Principle:

Principle #15Dynamics

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

This configuration reduces power consumption significantly, especially in static phases, and increases safety by allowing the exoskeleton to support unknown loads without parameterization, ensuring minimal power usage and safe operation even in power failures.

Implementation Method 1

the leg segment comprises a spring element for exerting a force that opposes a movement of the ends of the leg segment toward each other

Methodology Applied

Scientific EffectSpring: Spring

Implementation Method 2

The means for varying the distance also comprise a device for pretensioning the spring element

Methodology Applied

Scientific EffectTension: Tension

Data Source

PatentUS11872180B2Lower limb of an exoskeleton with low power consumption

Publication Date: 2024.01.16 COMMISSARIAT A LENERGIE ATOMIQUE ET AUX ENERGIES ALTERNATIVES

AI summary

A lower limb (1) of an ambulatory exoskeleton comprising at least a pelvis segment (10). a leg segment (20) and a foot segment (30), the leg segment (20) being hinged at the First end (21) of same to the pelvis segment (10) and at the second end (24) of same to the foot segment (30). the leg segment (20) comprising a spring element (25) and means (40. 44) for varying the distance (d) separating the ends (21. 24) of the leg segment (20), the means (40. 44) for varying the distance (d) separating the ends (21. 24) of the leg segment (20) being carried by the pelvis segment (10).