Power absorption optimisation in electromechanical primary flight actuators via control laws design

This paper deals with the design of optimal control laws for an electromechanical actuator used for primary flight controls. The reference actuator, essentially composed of a brushless DC motor coupled with a low-pitch ball-screw, is controlled is by two nested loops, on motor current and output position respectively. A basic structure of the actuator regulators is preliminarily defined by using a detailed model of the actuator, and then verified through experiments. Starting from this basic design, an optimisation of the regulators is performed by applying the LQR technique. Once linearized the detailed model of the actuator, different versions of optimal control laws are obtained by varying the structure of the optimisation cost function. The actuator responses with “tracking-oriented” optimisations (more focused on the tracking error minimisation) and “power-oriented” optimisations (more driven towards the current absorption reduction) are finally compared, highlighting and discussing advantages and drawbacks of the two approaches