Control and Actuation Optimization of Hyper-Vacuum Artificial Muscles

Hyperbaric Vacuum Artificial Muscles (Hyper-VAM) differ from other pneumatic artificial muscles by utilizing both positive and negative pressures interchangeably. This is achieved by incorporating a vacuum-based actuator within a hyperbaric chamber, which allows for both large deformations made possible by negative pressure and significant forces generated by high-pressure differentials that exceed those attainable through negative pressure alone. However, for most artificial muscles, the performance of the actuator depends on how fast air can be taken into and out of the chamber as the presence of a single chamber entails relatively simple fluidic strategies. Although the Hyper-VAM contains two chambers, and being able to produce a large range of force, lifting heavy payloads (up to 80 kg), its actuation could be improved by controlling its linear deformation, and actuation speed by making use of the pressure equilibrium between these two chambers as the building block for advanced fluidic strategies. A diaphragm pump, a single pneumatic regulator and a linear sensor can be used to control the position of the actuator. Additionally, through closed-loop pneumatic actuation, the actuator can be driven by exchanging air between the two chambers, allowing it to operate using a single pump without requiring air exchange with the environment. It is shown that it is possible to operate the Hyper-VAM in sub- and hyper-atmospheric conditions during closed-loop actuation and to use the atmosphere as a natural pump starting from a sub- or hyper-atmospheric atmospheric equilibrium. This work introduces the implementation of the control of the actuator in closed-loop pneumatic operation, also the demonstration and comparison of new fluidic hardware strategies for driving a Hyper-VAM making use of the pressure equilibrium between chambers to increase the speed of actuation while using a single portable pneumatic pump.