Modeling of servopneumatics and applications to helium fluid power systems

While the use of pneumatic power remains as ubiquitous today as it has traditionally been for discrete actuation, only recently has it started reclaiming its rightful place among the suite of industrial motion servocontrol offerings. This change is brought about by advances in modeling, technologies and nonlinear control theory which close a decades-long lapse in the development of compressed gas servoactuators, enabling their advantages over electrics in terms of simplicity, reliability, weight, packaging and cost to be realized.; In further contribution to this field, this dissertation introduces the use of helium gas as an alternative means of enhancing the performance of fluid power systems, concluding by way of theory and experiment that helium provides a three-fold increase in pressure dynamics from its higher volumetric orifice flow rate (low density) and, to a lesser extent, from its higher bulk modulus (high specific heat ratio). This analysis is led and supported by strengthened models for static and dynamic spool servovalve characterization as well as chamber pressure and temperature dynamics, where a justification and experimental verification, previously unreported, of the thermal wall capacitance approach is presented.