A Complete Model of a Two Degree of Freedom Platform Actuated by Three Pneumatic Muscles Elaborated for Control Synthesis

Pneumatic muscles have a high potential in industrial use, as they provide safety, high power over volume ratio, low price and wide range of pulling effort. Nevertheless, their control is quite hard to achieve due to the non linearity and hysteresis phenomena, plus the uncertainties in their behavior. This paper presents the modeling of a two degree of freedom platform actuated by three pneumatic muscles for control purposes. Three servovalves are used to supply airflow inside the muscles. The innovative concept is the modeling of each component including the static and dynamic muscle behavior. The model of the servovalve consists of a look-up table gathering the three variables: airflow, pressure and voltage applied to the servovalve. In addition, a thermodynamic and a mechanical study of the system complete the model. The result is a complete model design having as input the voltage applied to the three servovalves, and as outputs, the two angles of rotation. Simulated and experimental results permit to validate the complete model for high variation in static and dynamic conditions. These results will be helpful for nonlinear control synthesis.