Abstract
When the pressure of control signal increases gradually across the switching level of a device, the device switches with varying switching delay. The combination of restrictor and solid capacitor gives ±5% to ±7% in accuracy. To improve the accuracy of a pneumatic delay, it is necessary that the control signal rises rapidly when crossing the switching level of the pneumatic or fluidic device.
To realize the rapid rise, a new delay element using a thin film was developed. A film bag is installed in a chamber with bleed holes. Initially the volume must be reduced to zero. When the signal is turned on, the flow starts to expand the film, but the pressure does not rise until the film is inflated fully in the chamber.
The histograms of the new delay element have shapes similar to those of Gaussian distribution, and the ratio of ±2σn to the mean delay may be regarded as an index of accuracy. The effects of the restrictor, the pressure supply and the type of devices are investigated, and the delay element with the film type capacitor can realize ±0.4% to ±0.7% accuracy.
