A Hybrid Sensorless Observer for the Robust Global Asymptotic Flux Reconstruction of Permanent Magnet Synchronous Machines

We propose a hybrid sensorless observer for permanent magnet synchronous machines with global asymptotic stability guarantees. Exploiting the constraint of the rotor flux on a circle of unknown radius, we design an integrator system with periodic jumps triggered by a clock to generate a linear regression containing the flux estimation error. Then, a normalized projected gradient descent identifier provides the observer estimates. For the closed-loop system, it is shown that there exists a robustly globally asymptotically stable compact attractor, which, additionally, ensures zero estimation error if appropriate Persistency of Excitation (PE) conditions are satisfied. In this respect, sufficient conditions ensuring PE are provided for the angular speed and the clock period

Design of a test rig for railway Axle-boxes

Abstract Railway axle-boxes are one of the more critical components of the railway vehicle. The axle-box is the housing of the bearings, which support the axle-load of the vehicle, and the confinement of the lubricant required to maintain the performances of the bearings. Therefore, the axle-box is involved both in problems related to vehicle safety, and in problems related to maintenance, becoming an important part of the life cycle cost of the vehicle. To improve safety and reliability of the axle-box, in recent years, diagnostic systems are adopted to detect malfunctions, damage or degradation of the performances of the bearings. This is made both using onboard or wayside monitoring systems, which can be based on vibration or thermal analysis. The effectiveness of these systems rely in the accuracy of the algorithms, that are used to predict the condition status of the bearings. Therefore, it is necessary to be able to validate and tune the algorithms, by means of experimental tests. The tests can be performed on the track, but this implies high variability, costs and the impossibility to experience critical conditions (due to the related risks). The aim of this work is to design an experimental test rig, able to perform tests on railway axle-boxes and to reproduce the real conditions (axle-load, velocity). Several design layout are considered, each one evidencing some benefits and some limitations. The use of the test rig allows to reproduce different failures of the bearings in a safe environment. The repeatability of the tests and the controlled environmental conditions, allow a better setup of the monitoring system being developed

a mixed numerical approach to evaluate the dynamic behavior of long trains

Abstract The evaluation of the longitudinal forces exchanged between the wagons composing a long train is very complex due to the large number of d.o.fs to be considered and due to the non linearities introduced by the coupling elements. The most common approach to simulate long trains is the use of simplified wagon models realized considering only the longitudinal d.o.f. In this way the number of d.o.fs used for the full vehicle model is equal or a little greater than the number of the connected cars. The efficiency of this approach, in calculating the in train forces during traction and braking operations, has been demonstrated by several authors in the literature. In particular the long train simulators have been developed with the aim to evaluate the longitudinal forces during the braking operations in order to optimize the braking strategy and the mass distribution along the train. This method is efficient to optimize the train configuration in order to minimize the in train forces, but it does not allow to evaluate the vehicle safety indexes (such as derailment, wheel unload and lateral force) because the wheel-rail contact forces are completely neglected. This work shows a novel approach where the long train numerical model, realized using the Simpack multibody code, is developed considering both simplified wagon models, with few d.o.fs and no contact module, and detailed wagon models, which include several d.o.fs and the algorithm for the contact forces evaluation. In particular this mixed technique allows to evaluate both the longitudinal train dynamic and the behavior of some of the wagons when the train is running on curve. The position of the detailed wagon models along the train combination can be selected by the user in order to evaluate the influence of a particular wagon position on the vehicle safety

Monitoring of railway freight vehicles using onboard systems

Rail freight transport plays a key role in reducing polluting emissions, so major efforts are underway to strengthen the sector. However, this requires an improvement in the performance of the vehicles, and their more efficient use, with an increase of the axle-load and the speed. In relation to these aspects it is important to strengthen the safety of railway transport, by improving the maintenance system and at the same time reducing the vehicle's impact on the line, which can be achieved both by improving the technical characteristics of the vehicles and by reducing the geometric irregularities of the track. The possibility of extending circulation on High Speed lines also to freight vehicles is nowadays of great interest. The improvement of the maintenance level can be achieved by adopting procedures based on the actual condition of the vehicle ("on condition") instead of on the basis of cyclical programming (time or mileage). This requires knowledge of the actual condition of the vehicle and its components, which can be achieved by installing onboard monitoring devices capable of analyzing the behavior of the vehicle in real time. The work illustrates the experimental tests carried out using an innovative monitoring system, installed on board two different types of freight vehicles used for intermodal transport. The tests were performed on different lines: on the historic Gotthard line, and on the new Gotthard high-speed line, including the base tunnel. In this way, it was possible to demonstrate the application of the monitoring system to a rail freight vehicle. Furthermore, the results obtained in terms of accelerations measured on two different types of lines were compared, detecting the different impact of the vehicle on good quality lines compared to lines with significant defects

The use of carboxymethylcellulose for the tartaric stabilization of white wines, in comparison with other oenological additives

The aim of this study was to test the effectiveness of two types of carboxymethylcellulose (CMC), at different doses, for the prevention of tartaric precipitations in two white wines (Pinot Blanc and Chardonnay), in comparison with metatartaric acid and a commercial arabic gum. After the addition of the additives to the wines, the mini-contact test was carried out and the saturation temperature was determined by Ridomi’s method. The determination of the saturation temperature was then repeated on the same trials kept at -4 °C for 10 days. Both kinds of CMC caused a significant decrease in tartaric precipitations induced by the addition of potassium bitartrate (KHT) (mini-contact test), by limiting the growth of the added KHT crystals. Their effectiveness increased with the dose, following a hyperbolic trend. The stabilizing effect of the two kinds of CMC, particularly CMC2 (more viscous), was similar to the one of metatartaric acid. Their use must be considered complementary to the cold treatment (chillproofing).

Study of wheel-rail adhesion during braking maneuvers

The present work aims to better understand the phenomenon of adhesion under degraded conditions during railway braking maneuvers with the aim of optimizing the anti-slip algorithms in order to reduce damage to the profiles of wheels and rails and to minimize the braking distance. The proposed approach is based on the analysis of experimental data acquired during braking tests carried out on track, considering different types of vehicles and different types of contaminants, able to reproduce the typical degraded adhesion conditions occurring during normal operation. The work describes a numerical model that allows to evaluate the dynamics of the vehicle during the braking operation and to correlate the pressures to the brake cylinder, which are related to the braking forces, and the angular velocities measured on the axles of the vehicle, with the adhesion coefficient

Use of polyaspartates for the tartaric stabilisation of white and red wines and side effects on wine characteristics

Aim: The stabilising efficacy against tartaric precipitations of polyaspartates-based products (PAs), in particular potassium polyaspartate (KPA), was tested with six different wines (three white and three red). Some side effects on wine characteristics (white wine colour stability, wine turbidity and filterability) were also studied. Results and conclusions: All PAs showed good stabilising efficacy against tartaric precipitations according to the cold test. With the same test, the PAs were stable in wine for 1 year of storage, which was the total duration of the study. The dose of 100 mg/L was sufficient to stabilise the tested wines. No differences in filterability were observed in comparison with MTA (metatartaric acid). The hypothesised protective effect against colour browning in white wines was not observed. Significance and impact of the study: The international wine trade requires stable wines. This paper provides information to support wineries in managing the use of KPA, as little information is available to date in the literature on this stabilising additive