Modeling and Fault Diagnosis of an Electrohydraulic Actuator System with a Multidisciplinary Approach Using Bond Graph

Abstract

An important aspect of mechatronic systems is that the synergy realized by a clever combination of a mechanical system and its embedded control system leads to superior solutions and performances that could not be obtained by solutions in one domain. Models of mechatronic systems are often large and complicated, with many parameters, making the physical interpretation of the model outputs, even by domain experts, difficult. This is particularly true when unnecessary features are included in the model. In mechatronics, where a controlled system is designed as a whole, it is advantageous that model structure and parameters are directly related to physical structure in order to have a direct connection between design or modeling decisions and physical parameters. The bond graph methodology is a convenient and useful complimentary tool for obtaining both the behavioral and the diagnostic models. Moreover, the method presents the unique feature of being able to model systems in different energy domains using the same approach with a single model, thus it becomes ideal for modeling and simulation of mechatronics and control systems. Because of the multi-domain energies involved in the actuators, the bond graph methodology as a multidisciplinary and unified modeling language proves a convenient tool for the given purpose. The advantage of the bond graph modeling compared to other methods is the good visibility of power transfers between all elements, and even between several subsystems in which we can measure efficiency of the system. The proposed model guarantees the reversibility of power flows, at the opposite of other approach for example transfer function. By the bond graph method, it is easy to see the impact of changing one parameter in the complete model of the actuator system. The model structure can also be modified, taking care of the causality. Respecting the causality, computing convergence troubles due to causality conflicts are avoided. The analysis of causal paths highlights variable links. This is an advantage of bond graph method, in order to have a view of energetic dependences and resonances in the model. In this chapter, firstly, the pump-displacement-controlled actuator system with applications in aerospace industries is modeled using the bond graph methodology. Secondly, an 5