AS&SPO: A Digital Signal Phase Adjustment Method for High-Precision Spool Displacement Measurement in Electro-Hydraulic Control Valves

Electro-hydraulic control valve (EHCV) with integrated controller commonly utilizes Linear Variable Displacement Transformer (LVDT) to measure spool displacement and achieve closed-loop control. However, the switching power drive circuit controlled by Pulse Width Modulation (PWM) within the controller introduces ripple interference to the electrical signal. Additionally, as an inductive component, the LVDT exhibits hysteresis in its inductive signal, making the design of a high-precision conditioning circuit complicated and limiting the precision of spool displacement measurement. Based on the LVDT signal-conditioning hardware architecture, this study enables efficient and precise signal phase adjustments, achieving adaptive sampling (AS) to mitigate ripple interference. Noise-suppressing high-precision demodulation is further achieved through sampling position optimization (SPO), forming a novel digital conditioning method for spool displacement measurement in EHCVs. The experimental results of signal demodulation indicate that the proposed high-precision digital conditioning method effectively reduces the noise level of the standard spool displacement signal (SSDS). The SSDS’s mean precision is improved to 0.21%, and its mean maximum error is limited to 0.12%. The dynamic and static experimental results of the EHCV further validate that the high-precision digital conditioning method significantly enhances the valve performance.