Investigation of the Temperature Influence on Electrohydraulic Valve Control and Presentation of a Novel Compensation Approach for Independent Metering Valve Systems

Abstract

Abstract In the design of valve control algorithms, the impact of the oil temperature on flow characteristic is often neglected. Generally, the flow mapping for the measured valve flow is considered to depend on only two factors, namely the displacement of the valve core and the pressure drop across control edges. The flow mapping and inverted flow mapping derived from this are implemented in the controller. However, previous investigation have shown that depending on the actual flow state within the valve, temperature variations can cause significant changes in flow rate, which in turn cause errors and increase control effort. Especially in mobile applications, systems are exposed to a wide range of external and internal temperature changes; hence, the impact and possibilities of temperature compensation are the focus of this work. In order to demonstrate and quantify the impact of temperature variations on the valve flow characteristic, two common mobile valves, specifically spool and cartridge type, are measured. Control algorithms using flow mapping and inverse flow mapping for flow and pressure control of an independent metering valve system are implemented and analyzed regarding temperature sensitivity. Secondly, four-dimensional models are proposed to describe the flow rate as a function of temperature, pressure drop, and spool displacement. These flow models are parametrized based on a computational efficient interpolation method considering the fluid flow state inside the valve. After that, the flow descriptions created can be used to refine the previous control strategy. Compared to the control strategy without temperature compensation, the new control strategy not only maintains good dynamic characteristics, but also has more accurate flow rate respectively velocity control.