Coulomb Friction Model Analysis, Acting on an Aerospace Servocommand

Modern flight control system design necessitates using highly detailed models to analyze individual components or subsystems; on the other hand, more fundamental and synthetic models with adequate accuracy are required for preliminary design, monitoring or diagnostic issues. One of key problems for especially primary flight commands which are depicted as position servo command with high degree of accuracy is the necessity to acknowledge their behavior, under the influence of the dry friction or the friction forces (or their momentum) acting on a generic movable mechanical part of a servo command, or on an entire transmission. In general this forces depends from the relative velocity of the transmission, or from the exchange load between parts of the mechanism. For this reasons it become very important to take into account these forces or their momentums in relation of their behaviour during the construction of the detailed mathematical models. In this work we present some generic considerations of the dry friction and dynamic friction applied on an aerospace servo command, with the related mathematical model run in MATLAB/Simulink, and compared to previously tests done for this servo command.