Fluidic Artificial Muscle Actuator for Bidirectional High-Force Stroke

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Solution Overview

Problem

Existing fluidic artificial muscles are limited to unidirectional motion, requiring complex control systems and larger dimensions, and lack the ability to provide high stroke and force simultaneously.

Innovation Solution

A fluidic artificial muscle actuator combining contractile and extensile segments within a single system, allowing simultaneous pressure control in both segments for bidirectional motion, with a simplified fluid supply system.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If contractile fluidic artificial muscles are used to generate bidirectional motion, then motion in two opposite directions is achieved, but the positioning control becomes difficult and requires separate control of gauge pressures in both muscles

Engineering Contradiction:
Improvebidirectional motion capabilityVSAvoidcontrol system complexity
Core Design Contradiction:
Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent combines a contractile fluidic artificial muscle and an extensile fluidic artificial muscle into a single integrated actuator system. Both muscles are coupled to the same effector, allowing them to work together rather than in separate antagonistic pairs. This merging reduces the number of independent control systems needed while maintaining bidirectional motion capability.

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The effector in the patent serves multiple functions: it is coupled to both the contractile and extensile muscles, and it transmits force in both directions. This multi-functional design allows a single component to handle bidirectional actuation, simplifying the overall control architecture compared to using separate antagonistic muscle pairs.

Inventive Principle:
Principle #6Universality (Multi-functionality)

2Length of moving object

If extensile fluidic artificial muscles are used instead of contractile ones, then larger stroke is produced, but the force generated is much lower

Engineering Contradiction:
Improvestroke lengthVSAvoidactuation force
Core Design Contradiction:
Length of moving objectVSForce

Solution Approach 1:

The patent merges the advantages of both contractile and extensile muscles by integrating them into a single actuator. The contractile muscle provides high force generation through radial expansion, while the extensile muscle provides larger stroke through axial extension. Together, they deliver both high force and large stroke simultaneously, overcoming the limitations of using either type alone.

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The actuator uses a composite structure combining two different types of fluidic muscles with distinct mechanical properties. The contractile muscle segment and extensile muscle segment work in conjunction, creating a composite actuator that leverages the strengths of both configurations to achieve superior overall performance.

Inventive Principle:
Principle #40Composite materials

3Volume of moving object

If radial expansion of the muscle is limited, then the muscle size is reduced for miniaturization, but the force transmission capability is reduced

Engineering Contradiction:
Improveactuator sizeVSAvoidforce transmission
Core Design Contradiction:
Volume of moving objectVSForce

Solution Approach 1:

The patent segments the actuator into distinct contractile and extensile muscle portions, each optimized for different functions. The contractile segment handles force generation through controlled radial expansion, while the extensile segment handles stroke generation. This segmentation allows the radial expansion to be limited in the contractile portion for miniaturization while maintaining force capability, as the overall actuator length can be extended in the axial direction rather than radially.

Inventive Principle:
Principle #1Segmentation

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 higher force transmission and larger stroke with reduced complexity and size, facilitating miniaturization and improved control, suitable for applications like endoscopes and robotic devices.

Implementation Method 1

the first inflatable segment is configured to contract in the first longitudinal direction with increase in fluid pressure in the first inflatable segment and the second inflatable segment is configured to extend in the second longitudinal direction with increase in fluid pressure in the second inflatable segment

Methodology Applied
Scientific EffectPressure increase: Pressure Increase

Implementation Method 2

An inflatable bladder defining a first inflatable segment and a second inflatable segment

Methodology Applied
Scientific EffectElastic deformation: Elasticity

Data Source

PatentEP4408622B1Contractile and extensile fluidic artificial muscle actuator
Publication Date: 2025.08.13 KATHOLIEKE UNIV LEUVEN KU LEUVEN RES & DEV
  • EP4408622B1 patent drawingFigure 1~2
  • EP4408622B1 patent drawingFigure 3A~4B
  • EP4408622B1 patent drawingFigure 5~6

AI summary

A fluidic artificial muscle actuator comprises at least one inflatable bladder defining a first inflatable segment (11) coupled to a first member (14) and to a second member (134) arranged at opposite ends of the first inflatable segment, and a second inflatable segment (12) coupled to a third member (135) and to a fourth member (15) arranged at opposite ends of the second inflatable segment, and an effector coupled to the first inflatable segment and to the second inflatable segment for providing an actuator output. The first inflatable segment is configured to contract in a longitudinal direction (101) with increase in fluid pressure in the first inflatable segment and the second inflatable segment is configured to extend in the longitudinal direction with increase in fluid pressure in the second inflatable segment.