Design of a bi-segmented soft actuator with hardware encoded quasi-static inflation sequence

A soft actuator composed of two fluidic bending segments is designed and manufactured having a mechanically programmed sequence of inflation. The sequence is determined by analyzing the equilibrium states between the connected segments at each step of the inflation. To do this, segments are described using their inner pressure vs. volume expansion relationship. Since it may be difficult to formulate this expression analytically for complex soft inflatable structures, an approach based on nonlinear FEM simulations is here introduced: by modelling the inner cavity of an actuator as filled with incompressible fluid and generating a fluid flux during the simulation, the pressure-volume curve is easily obtained, even if highly nonlinear. The resulting nonlinearities are instrumental in generating inflation sequencing of multiple segmented actuators, which is an example of hardware-based intelligence. Exploiting these behaviours will greatly enhance the possibilities and performances of soft robots.