Title: The Step Feed of a Pneumatic Cylinder with Very Small Displacement by Using Serial Solenoid Valves
Abstract: Recently, the solenoid valves are often used to positioning the air cylinder to the desired position. The positioning accuracy of cylinder is effected by the accuracy of total flow volume through the valve. But the solenoid valve is switching element essentially then it can not control the air to very small flow rate in comparison with such as proportional valves. It is very important to improve the performance when the small flow volume is needed for the high accuracy positioning, so the method by using serial solenoid valves is proposed in this paper. That is composed by double serial stages of solenoid valves and chambers inter the valves. When the valves open without overlap, the air through the valves is pooled in the chamber once. If the chamber volume is set small, the flow volume can be limited to small naturally.The step feed of air cylinder with very small displacement is executed by limiting the charging and discharging air in this manner. One of the serial valves is used to the charging side and the other is used to discharging side of cylinder. As the results of step feed, the stepping displacement is effected not only supply pressure and chamber volume also the initial pressure in the cylinder, and the stepping displacement can be very small when the initial pressure is set to supply pressure. The positioning against the desired position is carried out by constructing the feed back loop using micro-processor unit. The cylinder moves to near the desired position quickly by opening the all valves at the same time. Then moves slightly with step feed toward the desired position. The total accuracy of experimental positioning is better than that of conventional valve method and it is enable to execute the positioning within 0.004mm from the desired position. But the settling time takes fairly long and it must be improved to practical use.