Dry Friction Discontinuous Computational Algorithms

The design of high position accuracy servo mechanisms (such as an aircraft primary command EHA), involves the deep knowledge of their behaviour, markedly affected by the Coulomb friction. The proper evaluation of the friction forces and torques is usually necessary when an accurate simulation of the servomechanisms dynamic behaviour is requested in order to perform a suitable design of the system itself. To the purpose, the authors consider a servomechanism consisting of a hydraulic motor element (translational or rotary) coupled with an electro-hydraulic servovalve as a controller; the dynamic behaviour of these elements may be strongly dependent on the dry friction forces or torques acting on the moving parts, particularly of the motor element.