Design and implementation of high precision servo channel loading card for fatigue testing of aircraft wings

A servo channel loading card (SCLC) with high precision data acquisition and output is developed for static and fatigue testing of aircraft wings. A high-performance processor field programmable gate array (FPGA) is at the core to control the excitation source (ES) output circuit to provide excitation for the force and displacement sensor. To improve the precision of the ES output circuit, a 3DA-based ES auto-calibration circuit is designed. Simulation results show that the 3DA improves the precision of the automatic calibration of the ES circuit. The sensor signals are collected through high precision analog channels, and the signals are automatically zero calibrated and numerical control gain processed. Ultimately, a voltage or current signal is generated through the drive circuit to control the electro-hydraulic servo loading system to complete a high precision force loading test on the aircraft wings. The experimental results show that the board designed has high reliability in both acquisition and output. The ES output achieved a precision of 0.1375 mV/V, the precision of signal acquisition achieves a precision of -0.175 mV/V, and the servo drive output achieves a precision of -0.06 mV/V, meeting the expected design precision of 1 mV/V.