Abstract
The annular jet proximity sensor used in a pneumatic control system sometimes exhibits instability when the distance between the nozzle and an object is in a certain range. The instability is undesirable for designing a stable pneumatic system. In this study, this instability phenomenon is investigated experimentally and theoretically. First, the authors make it clear experimentally that the instability of this sensor is caused by a negative resistance existing in the output characteristics, i.e., the relation between the output pressure and the output flow. Second, the authors point out that self-oscillations occur in a fluidic system composed of a volume, a connecting conduit and the annular jet nozzle with the negative resistance. They propose a mathematical model of these oscillations. This model is analyzed in detail and these results are compared with the experimental results. Their agreements are fairly well.
