1,721,037 research outputs found
Performance Evaluation of a Prognostic Framework for Electro-Hydraulic Actuators for Stability Control Augmentation Systems with Different Sensors Suites
Full text linkStability Control Augmentation Systems (SCAS) are widely adopted to enhance the flight stability of rotary-wing aircraft operating in difficult aerodynamic conditions, such as low altitude missions, stationary flight nearby vertical walls or in presence of heavy gusts. Such systems are based upon small electro-hydraulic servosystems controlled in position through a dedicated servovalve. The SCAS operates with limited authority over the main control linkage translating the pilot input in the movement of the main flight control actuator. Being critical for the operability of the helicopter, the definition of a Prognostics and Health Management (PHM) framework for the SCAS systems would provide significant advantages, such as better risk mitigation, improved availability, and a reduction in the occurrences of unpredicted failures which still represent one of the most known downsides of helicopters due to their very severe operational environment. Since SCAS actuators are usually equipped with a low number of sensors, it is at the present time unclear whether a fully realized PHM system can be prepared without resorting to the introduction of additional sensors. This paper deals with this subject evaluating the performances of a fault diagnosis tool operating considering different sensors suite (traditional and with additional sensors), and different PHM strategies, using in-flight data or their combination with dedicated pre-flight checks to cover the most common failure modes. The analysis is then completed with an evaluation of the prognostic capabilities of the proposed strategies, highlighting benefits and limitations of the proposed solutions
Kinematic Analysis and Centrodes Between Rotating Tool with Reciprocating Motion and Workpiece
No full textA general algorithm for the kinematic analysis and the determination of both fixed and moving centrodes of the relative motion between rotating tool and workpiece, is proposed to analyze the effects of the working parameters on the quality of the machining process. The reciprocating motion of the rotating tool can be generated by both offset slider-crank mechanism with the driving crank and offset slider-rocker mechanism with the driving coupler. The proposed algorithm has been implemented in Matlab and validated by means of significant examples
Design and Preliminary Performance Assessment of a PHM System for Electromechanical Flight Control Actuators
Full text linkThe 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
Sensitivity Analysis for the Effect of Misalignments on Performance Parameters of Harmonic Reducers
No full textThe rise of Urban Air Mobility (UAM) heralds a new era in transportation, offering efficient and sustainable aerial solutions tailored for urban settings. Crucial to this evolution are compact electromechanical actuators (EMA), facilitating precise control of electric Vertical Take-Off and Landing (eVTOL) aircrafts components with agility and responsiveness. Compared to traditional hydraulic or pneumatic systems, EMA offer heightened efficiency, faster response times, and reduced maintenance needs, ideal for the UAM. At the core of rotary compact EMA lies the harmonic reducer, ensuring high reduction ratios with minimal backlash and robust torque transmission. Its role in maintaining precision and minimizing losses is vital for system efficiency and reliability. Reliability is paramount in UAM, necessitating redundancy measures and the adoption of Prognostics and Health Management (PHM) strategies. PHM integrates data-driven algorithms to predict component health, enabling proactive maintenance and mitigating failures. This paper delves into the impact of misalignment on harmonic reducer performance, aiming to enhance the reliability and efficiency of EMA systems in UAM. By analyzing reducer dynamics, it aims to contribute to the advancement of UAM technologies, fostering safer and more dependable urban air mobility systems
Performance evaluation of a Ball Screw mechanism through a multibody dynamic model
Full text linkBall 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
A Novel Hydraulic Solution to Simulate Inertial Forces on a Landing Gear Qualification Test Rig
No full textThe proposed test rig consists of a multi-functional intelligent test facility with the objective to perform all the tests and analyses required to assess the maturity of an electro-mechanical landing gear and demonstrate the feasibility of Prognostics and Health Management (PHM) functionalities for the electrical brake system. One of the most critical elements in the design of such iron-bird is the definition of the system replicating the aircraft inertia, which presence is necessary to properly assess the behavior of both the brake and its anti-skid logic during landing. The most common solution foresees to bring the landing gear leg in contact against a rotating cylinder, or runway simulator, which moment of inertia is equivalent to the aircraft mass. Although it is possible to reduce the system encumbrance through the introduction of a geared reducer, such architecture is usually extremely heavy and requires significant space in the test facilities. This architecture is also difficult to adapt to different aircrafts, since it would require the addition or replacement of these heavy flywheels, which is both difficult and dangerous. This paper deals with the definition of a possible alternative, based on a hydraulic solution, where two variable-displacement hydraulic motors, connected to a light rotating cylinder, are used to replicate most of the aircraft inertial forces during braking. The paper opens with the preliminary sizing of such system, presents the high-fidelity simulation environment used to assess its expected performances and compare the behavior of the hydraulic solution with that of the traditional configuration, finally presenting both the benefits and the disadvantages of the proposed architecture
ADAMS MULTIBODY SIMULATION OF JAMMING IN THE RECIRCULATION CHANNEL OF A SINGLE-NUT BALL SCREW
No full textBall screw jamming is a significant concern as it can have a detrimental impact on the performance and reliability of ball screw systems, potentially leading to a complete loss of mechanical power transmission. However, no studies in the literature have conducted dynamic analyses to investigate the effect of such fault on the performance of this mechanism. This article reports on the findings of a simulation analysis using a detailed multibody dynamic model developed in the MSC ADAMS environment to exploit its capabilities of describing contacts between arbitrary shaped bodies and accounting for the complete dynamics of each subcomponent. The analysis focused on a single-nut not preloaded ball screw with three axisymmetric sphere internal recirculating circuits and compliant constraints. The results of an extensive validation process of the mathematical model against literature data in nominal conditions are firstly presented to enhance the reliability of the results. Then, the outcomes of the simulation campaign are presented, investigating the impact of different numbers of recirculation channel jammings on the overall mechanical efficiency and the internal behavior of the spheres, for different lubrication conditions. The findings of this study provide valuable insights into the behavior of ball screw systems under jamming conditions and can lay the foundations for in-depth analyses and the development of a prognostic framework for such devices
A SIMULATION SURVEY ON THE EFFECTS OF PROGRESSING FAULTS WITHIN THE SCAS OF A FLIGHT CONTROL ACTUATOR FOR HELICOPTERS
No full textStability Control Augmentation Systems (SCAS) are widely adopted to enhance the flight stability of rotary-wing aircraft operating in difficult aerodynamic conditions, such as low altitude missions, stationary flight nearby vertical walls or in presence of heavy gusts. Such systems are based upon small electro-hydraulic servosystems controlled in position through a dedicated servovalve. The SCAS operates with limited authority over the main control linkage translating the pilot input in the movement of the main flight control actuator. Being critical for the operability of the helicopter, the definition of a Prognostics and Health Management (PHM) framework for the SCAS systems would provide significant advantages, such as better risk mitigation, improved availability, and a reduction in the occurrences of unpredicted failures which still represent one of the most known downsides of helicopters. This paper provides the results of a preliminary analysis on the effects of the inception and progression of several degradation types within a simulated SCAS system. Signals usually available within such devices are hence combined with measurements provided by additional sensors to check the feasibility of a PHM system with and without dedicated sensors. The resulting features selection process shows that although the dedicated measurements are required to design a complete PHM system, it appears nonetheless possible to obtain valuable information on the health status of the SCAS system without resorting to additional sensors
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