Power absorption assessment of flight control actuation systems via object-oriented modelling

As a result of the constant trend to technology innovation and integration of functions, modern airborne systems and equipments are characterised by high complexity and multi-physicality. A relevant case is that of the flight control actuators, whose technology solutions recently had a rapid evolution, moving from the traditional servo-hydraulic, to electro-hydrostatic, towards electro-mechanical architectures. The study, the design and the performance characterisation of such systems, as well as the assessment of novel solutions in the early phases of the project, can therefore be problematic (or, at least, time-consuming) if the designer/analyst does not have technical expertise in all the engineering domains. In this context, the object-oriented modelling provides a convenient design approach, since system prototyping and simulation can be carried out easily, rapidly and efficiently. In the work, the object-oriented modelling provided by the Modelica-Dymola environment is used to perform a comparison between different technologies for aircraft actuation systems in terms of power absorption characteristics. Starting from the same set of basic design requirements (working stroke stall force, maximum no-load velocity, settling time of the actuator position response, etc.), three actuators characterised by different technology solutions (servo-hydraulic, electro-hydrostatic and electro-mechanical) have been defined, and the related “objectmodels” have been developed and characterised in terms of dynamic performances. In parallel, the model of a basic flight control system with two ailerons, two elevators and one rudder has been created, including the aerodynamic hinge moment simulation and the simulation of elasticity of the actuator structural links. The actuator models have been then used to obtain three types of actuation systems: a traditional servo-hydraulic one, a “moreelectric” plant with all electro-hydrostatic actuators, and an “all-electric” system. Each system has been finally tested with the same command time history by reproducing a sample flight manoeuvre, and the total power absorption has been analysed. Simulation confirms the superiority of the all-electric solution for energy savings, but it also highlights the necessity of completing the study taking into account the thermal aspects.