Mathematical Modeling and Performance Evaluation of Electro-Hydraulic Servo Actuators

Tanveer discusses how ADE developed a detailed equation and physical component-based model of a servo valve controlled electro-hydraulic flight control actuator using MATLAB^® and Simulink^®. The model consists of three modular blocks for servo electronics, servo valve, and hydraulic actuator. A servo amplifier–based lead-lag controller is designed to meet frequency and time response requirements. Various modelling levels from a simple linear model to a detailed nonlinear model for the servo valve are considered. The electrohydraulic servo valve components like torque motor, nozzle-flapper, and spool stage are also modelled in detail. Simple flow-based to nonlinear force-based models are considered for hydraulic actuator as well. The effect of each nonlinearity, including dead band, friction, hysteresis, and compressibility, is considered in the detailed model. Novel methods are introduced to handle friction in equation-based models. MATLAB code is developed for data processing and obtaining the frequency response of the nonlinear models. Various simpler lower-order real-time models are derived from these complex models for hardware-in-the-loop simulation (HILS). A force controller-based model of a testing rig is developed for actuator testing. MATLAB and Simulink can be effective tools for arriving at thresholds for flight operational software based on model studies. Features of the presentation include:

• Fly-by-wire flight control systems and actuators
• Equation and physical component-based model
• Modelling hydraulic components
• Model reduction techniques and linearization
• Modelling non–linearities
• Controller design optimization and DOE
• Loading rig simulation and force controller design
• Software logic verification using models