Soft Pneumatic Actuator Model Based on a Pressure-Dependent Spatial Nonlinear Rod Theory

To describe the mechanical behavior of a soft pneumatic actuator, we present a nonlinear rod theory, which recognizes the chamber pressurization as contribution to the resultant contact forces and couples. Accordingly, the pressure actuation can be considered as part of the rod's constitutive l...

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Bibliographic Details
Published in:IEEE robotics and automation letters 2022-04, Vol.7 (2), p.2471-2478
Main Authors: Eugster, Simon R., Harsch, Jonas, Bartholdt, Max, Herrmann, Marco, Wiese, Mats, Capobianco, Giuseppe
Format: Article
Language:English
Subjects:
Actuation
Actuators
Contact force
Contact pressure
control and learning for soft robots
Deviation
End effectors
flexible robotics
Formability
Kinematics
Mechanical properties
Modeling
Numerical models
Pneumatic actuators
Pneumatic systems
Pneumatics
Predictive models
Pressure chambers
Pressure dependence
Robots
soft sensors and actuators
Static equilibrium
Strain
Stress
Test sets
Training
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Summary:To describe the mechanical behavior of a soft pneumatic actuator, we present a nonlinear rod theory, which recognizes the chamber pressurization as contribution to the resultant contact forces and couples. Accordingly, the pressure actuation can be considered as part of the rod's constitutive laws, which relate the contact interactions with the rod's kinematics and the chamber pressures. The theory allows for nonlinear constitutive laws, which are capable of describing strengthening or softening behavior of largely deformable materials. The theory was applied to a three-chamber actuator to predict its centerline as well as the cross-section orientations in static equilibrium. The resulting governing equations were spatially discretized using beam finite elements. We evaluated four different actuator models that are contained in the presented theory regarding describability and predictability of the end effector position. Existing rod models with linear elastic material laws can describe the tip-displacement with an averaged deviation of 9.1 mm in the training set and 11.4 mm in the test set. With a deviation of 2.8 mm and 4.9 mm in the training and test set, respectively, the most enhanced model, for which the pressure chamber radii increase with increasing pressure, is more than 2 times more accurate.
ISSN:2377-3766
2377-3766
DOI:10.1109/LRA.2022.3144788