To determine the functional and radiographic outcome of low Weber C ankle fractures and to evaluate the contribution of the syndesmotic screw in their outcome.
Prospective evaluation of a consecutive ...series.
Level I trauma center.
Forty-five patients divided into two groups matched for age, sex, and severity of injury. Twenty-six patients were treated with open reduction, internal fixation, and a supplemental syndesmotic screw, and nineteen patients were treated without a syndesmotic screw. Minimum time to follow-up was three years.
A subjective, objective, and radiographic ankle scoring system was used. Logistical regression analysis was performed to determine whether the presence or absence of a syndesmotic screw was a predictor of a poor outcome. The likelihood ratio test was used to evaluate the significance of each variable in both univariate and multivariate analyses.
There was no statistically significant difference between either group, either using subjective outcome criteria (p = 0.86) or in ankle range of motion (p = 0.94). Logistical regression analysis indicated that fracture dislocation could be used as a predictor of a poor outcome for either group. Inadequate reduction and advancing age were also found to be significant predictors of a poorer outcome regardless of the use of a syndesmotic screw (p = 0.003, p = 0.004).
Judicious fixation of Weber C type injuries within five centimeters of the ankle joint, with or without a syndesmotic screw, gives similar results. Obligatory fixation of these fractures with syndesmotic screws appears to have no benefit and creates the need for an additional procedure.
Abstract
Electro-Mechanical Actuators (EMAs) deployment as aircraft flight control actuators is an imperative step towards more electric concepts, which propose an increased electrification in ...aircraft subsystems at the expense of the hydraulic system. Despite the strong benefits linked to EMAs adoption, their deployment is slowed down due to the lack of statistical data and analyses concerning their often-critical failure modes. Prognostics and Health Management (PHM) techniques can support their adoption in safety critical domains. A very promising approach involves the development of model-driven prognostics methodologies based on metaheuristic bio-inspired algorithms. Evolutionary (Differential Evolution (DE)) and swarm intelligence (particle swarm (PSO), grey wolf (GWO)) methods are approached for PMSM based EMAs. Furthermore, two models were developed: a reference, high fidelity model and a monitoring, low fidelity counterpart. Several failure modes have implemented: dry friction, backlash, short circuit, eccentricity and proportional gain. The results show that these algorithms could be employed in pre-flight checks or during the flight at specific time intervals. Therefore, EMA actual state can be assessed and PHM strategies can provide technicians with the right information to monitor the system and to plan and act accordingly (e.g. estimating components Remaining Useful Life (RUL)), thus enhancing the system availability, reliability and safety.
Abstract The contemporary design of flight control systems demands the utilization of intricate models for the in-depth analysis of individual components or subsystems. Conversely, there is a ...parallel need for more foundational and synthetic models that offer sufficient accuracy, specifically tailored for preliminary design, monitoring, or diagnostic purposes. This paper centers on electro-hydraulic servomechanisms designed for aeronautical applications, emphasizing their contemporary significance. These systems play a crucial role, particularly in primary flight commands characterized by precise position servo control. The great variety of configurations and applications, their complexity and the criticality that characterizes this servomechanisms, deemed appropriate to devote particular attention to their modeling and the development of numerical simulation systems models that are versatile and reliable (flexible and easily applicable to different real systems but capable of providing realistic simulations). In particular, in this work are presented two innovative Coulomb friction models which are applied through MATLAB/Simulink block diagram structure to the model of the electrohydraulic servomechanism. The two friction models are foreseen to overcome the problematic of standard models for the friction, giving more realistic results, increasing the accuracy of the simulations.
In recent years aeronautical systems are becoming increasingly complex, as they are often required to perform various functions. New intelligent systems are required capable of self-monitoring their ...operation parameters, able to estimate their health status, and possibly perform diagnostic or prognostic functions. For these purposes, these systems frequently need to acquire several different signal types; although it is sometimes possible to implement virtual sensor techniques, it is usually necessary to implement dedicated sensing hardware. On the other hand, the installation of the required sensors can, however, significantly increase the complexity, the weight, the costs and the failure rate of the entire system. To overcome these drawbacks, new types of optical sensors, minimally invasive for measuring the system parameters and having a high spatial resolution and a minimum added complexity are now available. Fiber Bragg Gratings (FBGs) sensors are suitable for measuring various technical parameters in static and dynamic mode and meet all these requirements. In aerospace, they can replace several traditional sensors, both in structural monitoring and in other system applications, including mechatronic systems diagnostics and prognostics. This work reports the results of our experimental research aimed at evaluating and validating different FBG installation solutions such as deformation, bending, vibration, and temperature sensors. These were compared with numerical simulations results and measurements performed with traditional strain gauges and accelerometers.
The development and detail design of complex electrohydraulic actuators for aircraft flight controls require the use of accurate, high fidelity fluid-dynamic simulations in order to predict the ...behaviour of the system within its whole operating envelope. However, those simulations are usually computationally expensive, and simplified models are useful for the preliminary design phases and real-time health monitoring. Within this context, this work presents a review of low fidelity models for the fluid-dynamic behaviour of an electrohydraulic servovalve. Those are intended to run in real time as digital twins of the physical system, in order to enable the execution of diagnostic and prognostic algorithms. The accuracy of the simulations is assessed by comparing their results against a detailed, physics-based high fidelity model, which computes the response of the equipment accounting for the pressure-flow characteristics across all the internal passageways of the valve.
Abstract
Optical fibers have revolutionized several technological sectors in recent decades, above all that of communication, and have also found many applications in the medical, lighting ...engineering, and infrastructural fields. In the aerospace field, many studies investigated the adoption of fiber optics considering the planned transition from fly-by-wire to fly-by-light flight controls. A significant feature of optical fiber is its ability to be used not only as a transmission medium but also as a basis for fiber-embedded sensors; one of the most prominent types is based on Bragg gratings (FBGs). FBGs can replace several traditional sensors, providing measures of temperature, vibrations, and mechanical deformation. Optical sensors provide many advantages over traditional, electrical-based sensors, including EMI insensitivity, ease of multiplexing on a single line, resilience to harsh environments, very compact sizes and global weight saving. Furthermore, punctual knowledge of the temperature field is essential to perform the thermal compensation of the optical sensors used for strain measurements. In this work, the authors analyzed the performance of thermal sensors based on FBGs to verify their stability, accuracy, and sensitivity to operating conditions. Two different methods of FBGs surface application have been considered (gluing with pre-tensioning vs. non-tensioned bonding). The results were then compared to those acquired using typical temperature sensors to determine the relationship between the observed temperature and the Bragg wavelength variation (i.e. the proportionality coefficient Kt). The effects on the proportionality coefficient Kt, arising from fiber pre-tensioning and thermal expansion of the structural support, were then evaluated by comparing the results obtained with the two bonding approaches.
Abstract The research described was conducted by a student team dedicated to finding sustainable and long-endurance systems and outlines an innovative solar panel UAV aircraft solution. Our prototype ...demonstrated the feasibility of the concept, while the second aircraft, currently in the design phase, aims to improve performance further and allow for extended self-powered flight time. The sustainable approach of our project addresses the growing need to reduce the environmental impact of transportation technologies. The main objective of this study is to address the requirements of the Specific Category - Civil Drones regulation, promulgated by EASA, regarding the risk associated with the impact of the aircraft on the ground in case of an in-flight failure. To address this issue, we conducted an in-depth analysis of possible failure scenarios and their consequences on the safety of the aircraft and people on the ground. Furthermore, the team developed models for risk assessment to evaluate the risk associated with solar panel UAV operation. To mitigate the risk of impact, we considered using a parachute, the effectiveness of which was analysed using a dynamic model implemented in Simulink. The analysis allowed us to evaluate the semi-controlled descent of the aircraft with the parachute attached, providing valuable information to optimize the safety system further. In conclusion, our study significantly contributes to ensuring the safety of our model in flight and on the ground through ground-impact risk management while promoting the development of sustainable and innovative solutions in the aviation field.
In recent years, aerospace systems have undergone a huge technical-scientific impulse, evolving new high-performance intelligent solutions able to perform diagnostic and prognostic functions ...autonomously. In this scenario, an important role is certainly played by the new types of sensors combining high performance (in terms of sensibility, accuracy, and reliability) with a marked resilience to external disturbances (e.g. EM noise or electrostatic discharges) and other environmental factors. Fiber Bragg Gratings (FBGs)sensors, suitable for measuring various engineering parameters in both static and dynamic modes, meet all these requirements; in aerospace, they could replace several traditional sensors, not only in structural monitoring but also in a much wider range of system applications including the diagnostic and prognostic of mechatronic devices. In this paper, the authors propose the first results of their investigation about the use of optical sensors for Electromechanical (EMA) and Electrohydrostatic Actuators (EHA). FBGs allow determination of aerodynamic hinge loads and minimally invasive measurements of local temperatures: the firsts are needed for in-flight model-based prognostics, whereas the detection of local heating allows to early infer an incipient partial short circuit of EM motor, a progressive power electronics failure or abnormal friction dissipation e.g. at bearing level. In order to assess the capabilities of optical sensors, evaluating different installation techniques and defining suitable configurations for the aforementioned mechatronic systems, a dedicated test bench has been developed and used for calibrating FBGs, analyzing their behaviour in different conditions of strain and temperature and conceiving a proper thermo-mechanical compensation strategy.
Future generation actuation systems will be characterized by ever-increasing complexity. In this context, it will be necessary to adopt advanced health monitoring strategies to guarantee a high level ...of operational safety and system reliability. Prognostics and Health Management (PHM) is thus emerging as an enabling discipline for the design and operation of future advanced, complex systems. Smart systems with embedded self-monitoring capabilities are nowadays required in order to provide early faults identification and to perform innovative diagnostic and prognostic functions. In aerospace applications, the use of smart sensors could replace various types of traditional sensing elements, commonly used in structural monitoring with the additional capability of performing some prognostics or diagnostics tasks. This work proposes the first results of an experimental campaign aimed at evaluating and validating various packaging solutions for vibration amplification and detection using optical sensors (Fiber Bragg Gratings, FBGs), since characteristics frequencies can be good prognostics indicators of particular failure modes of a system. Several test samples were created by using 3D printed PLA and compared using a variety of bench tests. Results were compared in order to identify the strengths and weaknesses of the various proposed configurations, and were validated by comparing them with numerical simulations and experimental measurements performed with traditional sensors such as strain gages and accelerometers.
PDF
