Online Estimation Without Pressure Sensors of the Pressure Drop at Valve Ports in Direct-Acting Electrohydraulic Control Valves

The advent of the industry 4.0 concept has led to the integration of online measurement functions in valves, which provides the system with more status information and enables the realization of intelligent functions. To improve functions, such as condition monitoring and fault diagnosis, in highly reliable hydraulic systems, this article proposes a virtual estimation method of pressure drop at valve ports without additional sensors, which avoid introducing pressure loss and potential failure points. This article presents an online pressure drop estimation method to address this problem by analyzing dynamics in valves. First, flow force is found the most significant term related to pressure drop. Both flow force and unmodelled term are obtained using a disturbance observer to build an accurate pressure-dependent integrated flow force model. Based on this model, the pressure drop is then estimated using a parameter estimation algorithm using the principle of immersion and invariance. The effectiveness of the proposed estimation method is finally validated through experimental setups under different working conditions, concluding with a performance analysis and insightful discussions.