Improved PNM Control of Oil Hydraulic Cylinder

Abstract

Quick response solenoid valves acting as simple on-off hydraulic control devices are inexpensive and easy to operate. There are several hydraulic cylinder control methods using the quick response solenoid valves, which control the flow rate by varying the number of opened valves. Based on these methods, multiple valves open and close simultaneously so that the flow rate and the corresponding cylinder motion become stepwise. This might cause noise and/or vibration on the hydraulic system or the machinery moved by the cylinder. We have developed a new hydraulic cylinder control method to cope with this problem. Based on the method, in addition to the number of the opened valves, the period of the open time of each valve is appropriately controlled, while shifting the timing of the opening action. This improves the continuity of the cylinder motion in a wide range of flow rate. This paper presents the specification of the method and the result of application to the servo control of heavy machinery.