Abstract
Most pneumatic resistors have non-linear flow characteristics, though a linear one is desirable for easy design of pneumatic circuits. A capillary is a linear pneumatic resistor, but its linearity is limited within a small pressure difference.
The flow rate of a non-linear resistor such as an orifice or a nozzle is proportional to the product of the opening area and the square root of the pressure difference. Therefore, if the opening area can be changed proportional to the square root of the pressure difference, the flow rate must become proportional to the pressure difference. The linear pneumatic resistor reported here is based on this principle. The resistor consists of a bendable diaphragm and a fixed partition with a port. The diaphragm, overlapped on the port, forms an opening slit along the fixed partition, when it bends. The negative pressure developed in the slit grows with the overlap, and controls the opening area of the slit to produce the linearity. The resistor with an appropriate overlap shows a good linearity in the wide range of the pressure difference. A guide for desining the linear resistor is shown based on experiments and analysis.
