DEVELOPMENT OF A NEW OPERATIONAL AMPLIFIER FOR USE IN PNEUMATIC SYSTEM DESIGN

A pneumatic operational-amplifier (op-amp) for use in low pressure applications is developed. The pneumatic op-amp development begins by characterizing the pneumatic control system elements with general models. A new flapper-nozzle valve model which is valid over a broad range is developed during this modeling of elements, as building blocks, of the control system. A flexible pneumatic control system modeling technique, which is constructed from the building block models, is then applied to a case study system. The capability of the modeling technique is demonstrated by comparing the model performance with that of the case study hardware. The results of this modeling study are used to develop the capability to systematically apply the pneumatic op-amp to pneumatic systems in two phases. In the first phase, a specific pneumatic controller is studied, taking into account the fact that both the load driven by the controller and the circuitry upstream of the controller may vary. Sensitivity studies of this case study controller model were performed. Results of these studies were used with the model to develop a systematic procedure for choosing controller parameters to minimize a selected performance index. This procedure is used to redesign the controller to become the pneumatic analog of the electronic op-amp. The second phase of the development of the capability to apply the pneumatic op-amp to pneumatic systems involves studying the effects of adding passive elements to the pneumatic op-amp to provide a wide variety of performance characteristics. The flexibility is made possible by using various model and hardware comparisons of various pneumatic op-amp configurations which provide amplification and filtering. These pneumatic op-amp circuits are based on commonly used electronic op-amp circuits. The modeling of these pneumatic circuits and studies of the performance of the pneumatic hardware indicate that the pneumatic op-amp is analogous to the electronic op-amp and that the modeling technique can be used to accurately predict performance. The advantage of this analogy is that the well-known circuitry for electronic op-amps can be applied to the design of pneumatic systems. The final result of the study, then, is a procedure for systematically choosing passive elements to use with a new tool, the pneumatic op-amp, to get desired performance characteristics in low pressure pneumatic systems