Design of a Fuselage-Mounted Main Landing Gear of a Medium-Size Civil Transport Aircraft

The subject of the present paper is the design of an innovative fuselage mounted main landing gear, developed for a PrandtlPlane architecture civil transport aircraft with a capacity of about 300 passengers. The paper presents the conceptual design and a preliminary sizing of landing gear structural components and actuation systems, in order to get an estimation of weight and of the required stowage. The adopted design methodology makes use of dynamic modelling and multibody simulation from the very first design stages, with the aim of providing efficient and flexible tools for a preliminary evaluation of performances, as well as enabling to easily update and adapt the design to further modifications. To develop the activity, the multibody dynamics of the landing gear (modelled using Simpack software) has been integrated via co-simulation with dynamic models developed in the Matlab/Simulink environment

Experimental validation of theoretical and numerical models of a DDV linear force motor

The performances of a Direct Drive Valve (DDV) mainly depend on the characteristics of its Linear Force Motor (LFM) and the availability of accurate models of the LFM plays an important role in the whole actuation system design. The present work deals with the modelling and the experimental characterisation of a LFM. By means of a specifically designed test equipment, the force provided by the LFM of an off-the-shelf DDV is measured as a function of the coil current and of the spool position. The experimental data are compared with the results of two models: a theoretical one, based on the magnetic circuit theory, and a numerical one, based on the FEM analysis of the electromagnetic components of the system. The numerical model provided good results over a wide range of test conditions and it allowed to evaluate correction factors for the theoretical model, related to the presence of secondary paths in the magnetic fluxes and to the distortion of the magnetic flux lines

Experimental implementation of a motion-compensated force control in a hydraulic workbench for flight actuators

The paper deals with the design and the experimental implementation of the force control in a hydraulic workbench for flight actuators, to be used for hardware-in-the-loop simulations of modern Fly-By-Wire Flight Control Systems. A basic problem affecting the plant performances is that the force response is sensitive to the flight actuator movements. Simulation results show that a suitable solution can be obtained including a compensation feedback based on the flight actuator acceleration, but sensor nonlinearities can induce relevant disturbances during experiments. In the paper, the model-inverting controller and the acceleration feedback are combined with a Kalman filter for compensating the accelerometer bias, and the performance of the closed-loop force-controlled plant is characterised by performing successive sessions of experiments, up to the simulation of the flight actuator dynamics during a typical flight manoeuvre

AW149 de-risk actuator DDV test results (LLI control)

Il presente lavoro documenta le attività effettuate per caratterizzare sperimentalmente la risposta dinamica della servovalvola DDV dell’attuatore prototipo (De-Risk Actuator) utilizzato per le analisi preliminari e gli studi di fattibilità del sistema dei comandi di volo primari del nuovo elicottero AW149

ACT-TILT project (Work Package 1.2.1) - Hinge moments estimation - Summary of results

This paper summarises the results obtained by the staff of the University of Pisa and TELEAVIO Srl concerning a preliminary estimation of the hinge moments on the aerodynamic control surfaces of the tilt rotor (operating in the "Fixed Wing" mode), carried out in order to allow the pre-design of the actuators of the flight control system. The estimation was accomplished by means of two different methods (provided by ESDU and Hoerner ), whose results are then compared. The basic hypotheses are that the aerodynamic surfaces work in the linear range of incidence and control deflection. Nevertheless, an estimation of the hinge moments in the post-linear range of control deflection is also given

Experimental assessment of temperature effects on the performances of a direct-drive servovalve for primary flight actuators

The paper deals with the experimental study of the temperature sensitivity of the performances of fly-by-wire hydraulic actuators. The activity is carried out by performing an extensive test campaign on the direct-drive electrical motor of a modern fly-by-wire actuator in environmental control conditions. The direct-drive technology, essentially based on the use of rare-earth magnet electrical motors for controlling the valve spool position, demonstrated to be a strategic area for the enhancement of the performance and the reliability of modern fly-by-wire flight control systems. Despite of several advantages in terms of system architecture optimisation, fluid contamination resistance, and control design flexibility, the use of direct-drive servovalves arises design criticalities that were negligible with the traditional flapper-nozzle solution, such as the chip shear force requirement, the sensitivity to electrical failures, as well as the temperature sensitivity of electrical motor performances (caused by the variation of motor air gaps for thermal dilatation, and by the variation of permanent magnet properties). A dedicated experimental set-up is arranged, by integrating a thermal chamber with a real-time actuator control system developed in the Matlab-SimulinkxPC Target environment. Both the static and the dynamic performances of the direct-drive motor are concerned, evaluating the basic equipment characteristics such as threshold, motor gain, open-loop and closed-loop frequency responses. The tests are performed at five temperatures: extreme hot (71°C), extreme cold (-54°C), ambient, and two intermediate cold conditions (-20°C and -40°C). Experimental results are reported and discussed, providing a physical interpretation of the temperature sensitivity phenomena. The conclusions are finally substantiated by means of a detailed model of the direct-drive motor dynamics previously developed and experimentally validated by the authors with reference to the ambient temperature. The model is adapted for taking into account the temperature effects, and a satisfactory matching between simulation and experiments is obtained

AW149 De-risk actuator/FCC models integration and actuator loop control enhancement

Il presente lavoro documenta le attività relative all’integrazione del modello del FCC con quello dell’attuatore prototipo (De-Risk Actuator) e quelle relative allo sviluppo di logiche di controllo alternative a quelle inizialmente impiegate per l’attuatore. A seguito di una rimodulazione del programma di ricerca (necessaria per far fronte a necessità di aggiornamenti delle versione del software FCC, nonché a problematiche di disponibilità del De-Risk Actuator), l’attività relativa al task 1.2.1 è stata ridotta rispetto a quanto inizialmente previsto. Il documento descrive dunque una parte limitata degli studi sperimentali, i quali verranno ripresi ed adeguatamente estesi con riferimento al AW149 Actuator in altri task di lavoro. In accordo fra le parti, il documento viene redatto in lingua inglese

Diagnosis of power switch faults in three-phase permanent magnet synchronous motors via current-signature technique

The paper deals with the development of a model-based current-signature algorithm for the detection and isolation of power switch faults in three-phase Permanent Magnet Synchronous Motors (PMSMs). The algorithm, by elaborating the motor currents feedbacks, reconstructs the current phasor trajectories in the Clarke plane through elliptical fittings, up to detecting and isolating the fault depending on the characteristics of the signature deviation from the nominal one. As a rough approximation, as typically proposed in the literature, the fault of one out of six power switches implies that, at constant speed operation, the phasor trajectory deviates from the nominal circular path up to a semi-circular “D-shape” signature, the inclination of which depends on the failed converter leg. However, this evolution can significantly deviate in practical cases, due to the dynamics related to the transition of motor phase connections from failed to active switches. The study demonstrates that an online ellipse fitting of the current signature can be effective for diagnosis, through correlating the ellipse centre to the location of the failed switch. The performances of the proposed monitoring technique are here assessed via the nonlinear simulation of a PMSM employed for the propulsion of a lightweight fixed-wing Unmanned Aerial Vehicle (UAV), by quantifying the fault latencies and the related transients