Autopilot systems are capable of reliably following flight plans under normal circumstances, but even the most advanced flight-management systems cannot provide robust response to most anomalous events including in-flight failures. This paper describes an emergency flight-management architecture that can be applied to piloted or autonomous aircraft, with focus on the design and implementation of an adaptive flight planner (AFP) that dynamically adjusts its model to compute feasible flight plans in response to events that degrade aircraft performance. A two-step landing-site selection/trajectory generation process defines safe emergency plans in real time for situations that require landing at an alternate airport. A constraint-based search algorithm selects and prioritizes feasible emergency landing sites, then the AFP synthesizes a segmented trajectory to the best site based on postfailure flight dynamics. The AFP architecture is general for any failure situation; however, operational success is guaranteed only with accurate postfailure performance characterization and a trajectory generation strategy that respects degraded flight envelope boundaries. A real-time segmented trajectory planning algorithm and case study results are presented for total loss of thrust failure scenarios. This emergency is surprisingly common and necessitates an immediate approach and landing without a go-around option.
The more demanding safety and comfort requirements combined with the increasing maximum speed of trains have lead to a growing concern in aspects such as the determination of the modal parameters of railway vehicles. Until now, the modal parameters of a vehicle have been obtained by EMA (Experimental Modal Analysis) based on the application of an impact force on the vehicle frame. However this kind of test is not optimal for railway vehicles because, due to their large dimensions, an impact force is unable to excite all the points of the structure. Also, with this method only the structural modes can be analyzed. Because of these drawbacks, a new modal analysis methodology is proposed, in which the excitation force comes from a specially designed shaker mounted under a point of a test track. In this manner, real excitation conditions can be simulated and it allows to determine not only the structural modes, but also the vibration modes associated with the suspensions. In first place, a description of the test facilities is presented. Afterwards, we present a test carried out in one of the coaches of a high speed train. The instrumentation employed, test methodology and test results are described. Finally, the test results are compared with the results obtained from a modal test in which impact excitation was used. Also the vibration modes obtained in the test are compared with the theoretical ones, which have been calculated with a combination of a FEM (Finite Element Method) and a MBS (Multi-Body Simulation).
All railway vehicles running on a track have to overcome a resistance to motion. The resistance to motion is due to mechanical and electrical losses, as well as to aerodynamic drag. In order to evaluate this resistance, two different experimental methodologies can be used. The first one consists on a conventional method which takes into account the energy stored in rotating masses and the equivalent curving and grade resistance. The application of this method is based on a coasting test procedure done on a straight track without slope. The second methodology consists on the experimental acquisition of electrical signals in the traction power line and strain measurements at the traction links of the bogie-truck, with different speeds. The electrical signals allow obtaining the efficiencies of the equipments in the traction power line. Once the different efficiencies of the equipments in the traction power line are known, the power transmitted to each wheel can be determined and consequently the resistance to motion is calculated. This paper summarizes an experimental procedure based on both methodologies. The designed instrumentation uses voltage and current probes for the recording of electrical signals in the traction line, piezorresistive accelerometers in order to obtain the uncompensated and the longitudinal accelerations of the train, extensometric gauges in full bridge configuration for the acquisition of stresses at the traction links, and a gyroscope for the detection of curves along the track. Several tests have been done by means of the described methods in light rail vehicles. Also, the vehicles have been tested in order to evaluate the influence of the air conditioning and air intakes, the circulation in curves and the cooling of traction equipments in the resistance to motion. Through these experimental methods, a useful tool for the prediction and analysis of the resistance to motion is provided. Additionally, the results obtained by means of these methodologies permit to calculate the influence of different running conditions in the resistance to motion.
Nowadays the application of experimental modal analysis techniques on railway vehicles is gaining importance. A correct identification of modal characteristics allows improving the dynamic behavior design of the vehicle and so reaching higher running speeds and accomplishing better comfort levels. So far, in the railway sector only conventional modal analysis techniques have been used. With these techniques, the modal parameters are determined during a static test by measuring the responses of the system to one or multiple known forces. This paper presents the application of the Operational Modal Analysis (OMA) technique on a railway vehicle. This technique determines the modal parameters employing only the responses of the system to an unknown excitation. In this way, the data to be used can be acquired during on track test which presents three main advantages. The first one is that the nonlinear components of the suspensions are working in their normal operating condition which is difficult to achieve during a static test. The second one is that the wheel spinning effect is taken into account. Finally, the test can be combined with other type of track tests, reducing the period of time before delivery of the vehicle to the client. In the case under study, the OMA technique is applied by means of commercial software to measurements performed on a passengers train. The modal parameters obtained for the carbody and one of the bogies are presented.
This paper presents a theoretical and experimental study done on an electro-diesel locomotive in order to evaluate the dynamic behavior of the vehicle in terms of safety, running performance and wheel-track interaction. The vibration analysis has been made by means of different experimental methodologies. The first one consists on the acquisition of accelerations at points located at the wheelset, the truck frame and the coach, using piezorresistive accelerometers. The registered signals allow to validate the locomotive in terms of safety against derailment and running behavior, according the UIC 518 leaflet. The second method is based on the modal analysis theory and includes the dynamic properties estimation under vibrational excitation. This procedure takes into account the determination of modal parameters such as natural frequencies, modal damping ratios and mode shapes, by means of a control hydraulic actuator. The third methodology consists on the operational modal analysis done with the experimental measurements acquired on track tests, in order to validate the results obtained by modal analysis and evaluate the dynamic behavior under different speed ranges and cant deficiencies. Several tests have been done by means of the described methods in an electro-diesel locomotive composed by a primary suspension with dampers and a secondary suspension with rigid stiffness. In addition, two types of dampers have been evaluated with the purpose of optimizing the damping properties of the vehicle’s primary suspension. Through these experimental methods, a useful tool for the prediction and analysis of the dynamic behavior is provided. Additionally, the results obtained by means of these methodologies permit examining the influence of different running conditions and vehicle properties on the modal parameters.
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