Designing the pneumatic actuators

The first step in this project was to design the pneumatic actuators. The idea was to design actuators that extend when compressed air is injected inside them, contrary to the operation of the McKibben actuators that contract when pressurized. Actuators made of silicone that do not require a braided sleeve in order to constrain the deformation were desired. This choice led to a design of our actuators with a “folded” shape, similar to an accordion.

pic_actuator.png

When pressure is applied inside the cavity of the actuator, the walls of the actuator unfold and produce an elongation of the actuator.

Since the time required to build the actuators is considerable, we first simulated it to confirm the expected behavior. This simulation is based on the Finite Element model of the actuator and was performed using the SOFA Framework (https://www.sofa-framework.org). Once the simulation provides satisfying results, we proceed with the fabrication of the actuators.

Having the simulation of the deformable parts of the prototype is of great help because it gives a good idea how  these parts will behave before their fabrication. By analyzing the simulation, we know if the design needs modifications without having to test the real part in the lab. Also, a suitable way to pilot this model is by using using this model in open loop with the real prototype.