Performance evaluation of a Ball Screw mechanism through a multibody dynamic model

Ball screws are mechanism to convert the rotational into linear motion and viceversa and are widespread in a variety of different sectors. A detailed high-fidelity dynamic mathematical model of such component is paramount in several fields and, in particular, in the definition of a PHM system for flight control EMAs in order to increase their reliability. In fact they can be used as a virtual test bench on which inject artificial defects and study their effect on specific indicators. This paper presents a MBD model of a single-nut ball screw with internal recirculation able of describing the full dynamic of each internal component allowing a more in-depth understanding of the system behavior and poses the basis for PHM-oriented analyses on different degradations

Design and Preliminary Performance Assessment of a PHM System for Electromechanical Flight Control Actuators

The evolution toward “more electric” aircraft has seen a decisive push in the last decade due to growing environmental concerns and the development of new market segments (flying taxis). Such a push has involved both the propulsion components and the aircraft systems, with the latter seeing a progressive trend in replacing traditional solutions based on hydraulic power with electrical or electromechanical devices. Flight Control Systems (FCSs) are one of the aircraft systems affected the most since the adoption of Electromechanical Actuators (EMAs) would provide several advantages over traditional electrohydraulic or mechanical solutions, but their application is still limited due to their sensitivity to certain single points of failure that can lead to mechanical jams. The development of an effective and reliable Prognostics and Health Management (PHM) system for EMAs could help in mitigating the risk of a sudden critical failure by properly recognizing and tracking the ongoing fault and anticipating its evolution, thus boosting the acceptance of EMAs as the primary flight-control actuators in commercial aircraft. The paper is focused on the results of the preliminary activities performed within the CleanSky 2/Astib research program, dedicated to the definition of the iron bird of a new regional-transport aircraft able to provide some prognostic capabilities and act as a technological demonstrator for new PHM strategies for EMAs employed in-flight control systems. The paper is organized as follows. At first, a proper introduction to the research program is provided, along with a brief description of the employed approach. Hence the simulation models adopted for the study are presented and used to build synthetic databases to inform the definition of the PHM algorithm. The prognostic framework is then presented, and a preliminary assessment of its expected performance is discussed

On the effects of strain wave gear kinematic errors on the behaviour of an electro-mechanical flight control actuator for eVTOL aircrafts

In recent years, the increasingly growing overcrowding of urban environments and the resulting road traffic congestion have pushed toward the search for alternative mobility solutions, among which there are novel Urban Air Mobility (UAM) technologies. The UAM, together with the development of electric actuation systems, would allow decongesting the streets by exploiting the sky using electric Vertical Take-Off and Landing (eVTOL) aircrafts. Urban air mobility vehicles are primarily based on fully electrical flight control systems with rotary output. Since such technology is relatively new and unproven, Prognostic and Health Management (PHM) algorithms, able to continuously monitor the health status of such systems, are of particular interest. The diffusion of these systems strongly depends on the general confidence of possible customers. The present paper proposes a preliminary study on the effects of the kinematic error of a Strain Wave Gear (SWG), the most used reducer for this kind of applications, on the behaviour of an Electro-Mechanical Actuator (EMA) used as a flight control actuator for an eVTOL aircraft. The simulation results show how the unavoidable kinematic error affects the EMA performances and how its presence can be detected and quantified in strain wave gears

CO19 168. Impacto de la hipertensión pulmonar en la evolución de los ancianos sometidos a sustitución valvular aórtica

ObjetivoEstudiar la influencia de la hipertensión pulmonar (HTP) en la evolución de los ancianos sometidos a sustitución valvular aórtica (SVA).Material y métodosDesde octubre de 1999 hasta noviembre de 2009, 517 ancianos (rango 70-87 años) fueron sometidos a SVA. Trescientos cincuenta y cinco (68,7%) enfermos (grupo I) tenían hipertensión pulmonar (ligera 157; moderada 149; grave 49) frente a 162 (31,3%) (grupo II) con presiones pulmonares normales. El seguimiento medio fue de 4,3 años.ResultadosLa edad media fue de 76,4±3,9 años. La fibrilación auricular (29,5 vs 5,6%; p=0,001) y la insuficiencia mitral moderada preoperatorias (13,7 vs 5,1%; p=0,003) fueron más frecuentes en el grupo I. La mortalidad hospitalaria fue 4,3%, siendo significativamente superior en los pacientes con HTP (I: 5,7% vs II: 0,8%; p=0,027). Los pacientes con HTP moderada (7,3%) o grave (13,9%) tuvieron una mortalidad significativamente superior a la de los pacientes con HTP ligera (1,7%) (p=0,016). La supervivencia actuarial a los 5 años, de los pacientes dados de alta, aunque superior en los pacientes sin HTP (I: 80,9% vs II: 90,6%; p=0,162), no alcanzó significación. La HTP moderada-grave se asoció de manera independiente a la mortalidad hospitalaria (odds ratio [OR]: 2,07; p=0,015), pero no a una menor supervivencia en el seguimiento.ConclusionesLa HTP moderada-grave es un factor de riesgo independiente de mortalidad hospitalaria en los ancianos sometidos a SVA. Su influencia en la supervivencia a medio plazo es menos clara