What is it about?
Bending fluidic actuators are being widely used in soft robotics due to their robustness, simple fabrication (no special equipment needed), large displacement (over 270° bending). They are constituted by an elastomeric chamber actuated by compressed air; fibre-reinforcements drive the chamber expansion into bending. The anisotropic behaviour of the structure together with the large deformations and hyperelastic material behaviour lead to a highly nonlinear response of the actuator. For the first time we developed a fully 3D mathematical model able to capture such nonlinear response. Previous models where over-simplified and ended-up in a linear behaviour, which does not represent those actuators.
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Why is it important?
Our model can be used by engineers to design soft robots using bending fluidic actuators. It computes with great accuracy the angle of bending related to the applied pressure, for any possible geometry and material, since it is fully parametric and no fitting procedure has been involved. Our method consists in an eulerian approach to nonlinear elasticity with the kinematics defined a-priori exploiting the symmetries of the system. It produced an analytical model with an efficient mathematical implementation. Since it is analytical, it can be run with any computational software (e.g., Matlab, Mathematica, C++, Fortran). No FEM is involved and It is also extremely fast.
Perspectives
Nonlinear responses are typical of soft structures. Our model, capturing the relationship between the response curves and the design parameters, allows the tuning of the behaviour of the actuator. Therefore, it is possible to compute not only the bending generated but to design how such bending varies with the applied pressure. The resulting "design of the response curve" is a keystone in the emergent framework of mechanical intelligence aimed by soft robotics. The modelling method proved to be effective to describe soft robotics actuators. Building on it, models of different soft robotics components and systems can be obtained.
Dr Vito Cacucciolo
École polytechnique fédérale de Lausanne (EPFL)
Read the Original
This page is a summary of: Modelling the nonlinear response of fibre-reinforced bending fluidic actuators, Smart Materials and Structures, September 2016, Institute of Physics Publishing,
DOI: 10.1088/0964-1726/25/10/105020.
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