Fabrication, Modeling, and Design of Position and Pressure Control System of a Soft Pneumatic Linear Actuator

The field of Soft Robotics proposes the use of flexible and compliant materials in the fabrication of soft actuators that can interact with humans in a safer way than conventional robots. While soft pneumatic actuators operate with positive pressure inflating their chambers and creating movement, vacuum actuators operate with negative pressure collapsing their chambers to generate movement. The latter have the benefit that they do not burst due to excessive pressure during contraction and since they shrink in size when activated, they can fit into tight spaces and are therefore more compact, aside from possibly being able to expand with positive pressure. This work presents a soft pneumatic linear actuator designed as a bellow-shaped structure made of silicone rubber that operates with negative pressure to contract and with positive pressure to extend. A Finite Element Method dynamic analysis was performed, using the SIMULIA Abaqus software, to predict the actuator's behavior. From the definition of the geometry, molds composed of modular pieces were designed and 3D printed to fabricate the actuator prototype. A test platform was designed to perform tests to characterize the actuator and then implement a position and pressure cascade control system, designed with a fuzzy pressure controller in the inner loop and a PI position controller in the outer loop, to regulate both the contraction and the extension of the actuator.