Modelling the inflation of an elastic membrane with a load

One way to achieve large deformations and elongation in soft material robots involves the creation of structures made of a number of inflatable elastic membranes. Physical interactions between the inflated membranes or with their environment can lead to shape changes resulting in forces being exerted to the environment. In this paper, we present an analytical model to describe the inflation of a circular elastic membrane, which is constrained by a load, based on finite deformation theory. Our model will allow to understand the deformation, volume change and the height of the membrane. Our model can predict the height-pressure trend of the deformed membrane shape. Experimental validation includes the investigation of the membrane inflation under load, open-loop force control involving an inflated membrane, and the inflation of a stack of three actuators. The height-pressure model results lay within the experimental data and predict the nonlinear trend well. The model can be used for open-loop force control within a ±15% error. Also, we present the results for a manipulator made of a series of inflated membranes under load conditions.