Abstract:

In this paper, modeling and parameter identification of an aircraft rudder system with an electromechanical actuator (EMA) is discussed to validate its mathematical model through frequency response function (FRF) test. Firstly, a five order transfer function (TF) model of the rudder system is established by synthesizing its two-degree-of-freedom (DOF) dynamic equations and a servo PID controller, in which the rudder axis is modeled as a damped spring and the Coulomb friction is also included. Then, in view of the characteristics of the TF model, an improved parameter identification method based on the rational fraction orthogonal polynomials with a parameter constraint is presented. Finally, the TF parameters are identified by applying the presented method to the FRF test data. It is indicated by the identification results that, 1) the two-DOF model figures the rudder system better than the generally used one-DOF one, and 2) excellent agreement is achieved between the identified mathematical model and the FRF measurement data, which demonstrates the efficacy of the proposed TF parameter identification method for the position tracking systems.

Key words: Air rudder, Electromechanical actuator (EMA), System modeling, Parameter identification