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Automatic detection test of current sensor faults for induction motor drives at standstill
Get PDFThis paper proposes an automatic detection test of gain faults in current sensors. An offline test is applied when the machine is not operating. The designed test operates at standstill without being necessary to disconnect the machine from the application. Current sensors are part of a commercial induction motor drive composed by a bilevel inverter, an induction motor and an electronic control unit. Therefore, in the selection of the approach, memory usage, computational cost and real-time implementation have been carefully considered. The algorithm, based on the model of the motor, uses the parameter aLs of the machine as a fault indicator. In order to estimate that parameter, firstly, precalculated width voltage pulses are injected into the motor using the inverter. Secondly the generated current slope is measured. Finally the estimation is compared to its nominal value. Once the theoretical basis is explained, the execution sequence of the test and the simulation results are presented. In addition, some enhancements are proposed to improve the resolution and accuracy of the approach, because the real conditions of the test do not follow exactly some of the theoretical assumptions
A new evaluation model of conceptual ideas for products and services based on user experience
Get PDFMore and more companies are integrating the experience design into their development process. This new approach allows to develop new products and services, based on user's emotions and motivations. In order to advance in this new approach of design, this paper presents a new evaluation model for the design of experiences in the conceptual phase. The toolkit consists of a set of three assessment tools (Eyeface, Sheldon test and a questionnaire) that meet the requirements defined in the analysis phase of design experience process.
By applying the toolkit in a experience design project, it is validated that the toolkit suits perfectly into the experience design process and allows to get a better understanding of the users assessment in a very early stage
Influence of tool wear on residual stresses when turning Inconel 718
Get PDFThis paper analyzes the effect of tool wear on residual stresses when turning. Inconel 718 discs were machined for prolonged periods at several cutting speeds, feed-rates and depth of cut. Tests were interrupted to measure and relate tool wear with the subsequent residual stress measurements. The discussion of experimental results is supported by orthogonal cutting simulations. It was found a critical tool wear where tensile surface residual stresses were maximum, decreasing for lower and higher values of tool wear. Nevertheless, it was observed that the compressive residual stress layer increased with increasing tool wear
A useful analytical formula to avoid thermal damage in the adaptive control of dry surface grinding
No full textAn adaptive control is proposed for dry surface grinding to extend the use of the wheel without needing to be dressed, preserving at the same time the surface integrity of the workpiece. The implementation of this adaptive control needs to use predictive models of thermal damage, as in the case of Malkin's model, which calculates the allowable grinding power before the workpiece gets burnt for any working condition. In this latter case, the adaptive control of the cutting depth condition requires solving a quartic equation. Since the analytical procedures for solving quartics given in the literature are quite cumbersome to implement in the numeric control of the grinding machine, we propose a closed analytic formula in order to compute directly the unique positive solution. Moreover, we can enhance Malkin's model in order to consider an arbitrary heat flux profile entering into the workpiece and the kinematical correction to the geometrical contact length, in such a way that we can still using the latter solution to the quartic equation
Sensitivity analysis on an AC600 aluminum skin component
Get PDFNew materials are been introduced on the car body in order to reduce weight and fulfil the international CO2 emission regulations. Among them, the application of aluminum alloys is increasing for skin panels. Even if these alloys are beneficial for the car design, the manufacturing of these components become more complex. In this regard, numerical simulations have become a necessary tool for die designers. There are multiple factors affecting the accuracy of these simulations e.g. hardening, anisotropy, lubrication, elastic behavior. Numerous studies have been conducted in the last years on high strength steels component stamping and on developing new anisotropic models for aluminum cup drawings. However, the impact of the correct modelling on the latest aluminums for the manufacturing of skin panels has been not yet analyzed. In this work, first, the new AC600 aluminum alloy of JLR-Novelis is characterized for anisotropy, kinematic hardening, friction coefficient, elastic behavior. Next, a sensitivity analysis is conducted on the simulation of a U channel(with drawbeads). Then, the numerical an experimental results are correlated in terms of springback and failure. Finally, some conclusions are drawn
Closing the Brand Gap through innovation and design
Get PDFExisting brands already have certain products and services that generate a particular experience in the mindof custome.However, distortions exist between what the brands what to communicate and what the customer perceive referred to as the Brand Gap.This paper presents a tool to identify innovation and design opportunities through the Brand Gap.The tool aims to help companies narrowing the gap between brand values and customer experience through innovation and design. The study explores different levels for opportunity identification (short, medium andlong term) and it suggests thatto take an experience perspective, brandscanstart identifying opportunities based on the Brand Gap
Machine Learning Techniques for the Detection of Shockable Rhythms in Automated External Defibrillators
Get PDFEarly recognition of ventricular fibrillation (VF) and electrical therapy are key for the survivalof out-of-hospital cardiac arrest (OHCA) patients treated with automated external defibrilla-tors (AED). AED algorithms for VF-detection are customarily assessed using Holter record-ings from public electrocardiogram (ECG) databases, which may be different from the ECGseen during OHCA events. This study evaluates VF-detection using data from both OHCApatients and public Holter recordings. ECG-segments of 4-s and 8-s duration were ana-lyzed. For each segment 30 features were computed and fed to state of the art machinelearning (ML) algorithms. ML-algorithms with built-in feature selection capabilities wereused to determine the optimal feature subsets for both databases. Patient-wise bootstraptechniques were used to evaluate algorithm performance in terms of sensitivity (Se), speci-ficity (Sp) and balanced error rate (BER). Performance was significantly better for publicdata with a mean Se of 96.6%, Sp of 98.8% and BER 2.2% compared to a mean Se of94.7%, Sp of 96.5% and BER 4.4% for OHCA data. OHCA data required two times morefeatures than the data from public databases for an accurate detection (6 vs 3). No signifi-cant differences in performance were found for different segment lengths, the BER differ-ences were below 0.5-points in all cases. Our results show that VF-detection is morechallenging for OHCA data than for data from public databases, and that accurate VF-detection is possible with segments as short as 4-s
Surface Integrity Analysis when Machining Inconel 718 with Conventional and Cryogenic Cooling
Get PDFCryogenic machining together with minimum quantity lubrication (MQL), is claimed to be a promising alternative to flood cooling in industrial applications since it avoids the use of large amounts of cutting fluids and it improves the functional performance of machined components through its superior surface integrity characteristics. In this paper, the suitability of replacing conventional cutting fluids by liquid nitrogen cooling + MQL for finishing operations in industry will be discussed.
Turning operations have been carried out on Inconel 718, in finishing conditions similar to those utilized in industry for the machining of nickel-based superalloys. With both cooling/lubricating approaches, the coolant has been applied to the rake face of the tool. Tool wear and surface integrity in terms of surface roughness, microstructural damage and microhardness profile have been analysed. The results show that conventional cooling is the best option from both the machinability and the surface integrity point of view
An all-in-one numerical methodology for fretting wear and fatigue life assessment
Get PDFMany mechanical components such as, bearing housings, flexible couplings and spines or orthopedic devices are simultaneously subjected to a fretting wear and fatigue damage. For this reason, the combined study on a single model of wear, crack initiation and propagation is of great interest. This paper presents an all-in-one 2D cylinder on flat numerical model for life assessment on coupled fretting wear and fatigue phenomena. In the literature, two stages are usually distinguished: crack nucleation and its subsequent growth. The method combines the Archard wear model, a critical-plane implementation of the Smith-Watson- Topper (SWT) multiaxial fatigue criterion coupled with the Miner-Palmgren accumulation damage rule for crack initiation prediction. Then, the Linear Elastic Fracture Mechanics (LEFM) via eXtended Finite Element Method (X-FEM) embedded into the commercial finite element code Abaqus FEA has been employed to determine the crack propagation stage. Therefore, the sum of the two stages gives a total life prediction. Finally, the numerical model was validated with experimental data reported in the literature and a good agreement was obtained
Social Networks, Big Data and Transport Planning
Get PDFThe characteristics of people who are related or tied to each individual affects her activity-travel behavior. That influence is especially associated to social and recreational activities, which are increasingly important. Collecting high quality data from those social networks is very difficult using traditional travel surveys, because respondents are asked about their general social life, which is most demanding to remember that specific facts.
On the other hand, currently there are different potential sources of transport data, which is characterized by the huge amount of information available, the velocity with it is obtained and the variety of format in which is presented. This sort of information is commonly known as Big Data. To use this data on Transport Planning application is a challenge, which require employing complex data mining techniques.
In this paper, we identify potential sources of social network related big data that can be used in Transport Planning, discussing their advantages and limitations. Then, a review of current applications in Transport Planning is presented. Finally, some future prospects of using social network related big data that are included in the MINERVA project are highlighted