Observer-based Fault Detection and Diagnosis for Mechanical Transmission Systems with Sensorless Variable Speed Drives

Observer based approaches are commonly embedded in sensorless variable speed drives for the purpose of speed control. It estimates system variables to produce errors or residual signals in conjunction with corresponding measurements. The residual signals then are relied to tune control parameters to maintain operational performance even if there are considerable disturbances such as noises and component faults. Obviously, this control strategy outcomes robust control performances. However, it may produce adverse consequences to the system when faults progress to high severity. To prevent the occurrences of such consequences, this research proposes the utilisation of residual signals as detection features to raise alerts for incipient faults. Based on a gear transmission system with a sensorless variable speed drive (VSD), observers for speed, flux and torque are developed for examining their residuals under two mechanical faults: tooth breakage with different degrees of severities and shortage of lubricant at different levels are investigated. It shows that power residual signals can be based on to indicate different faults, showing that the observer based approaches are effective for monitoring VSD based mechanical systems. Moreover, it also shows that these two types fault can be separated based on the dynamic components in the voltage signals

Detection and Diagnosis of Motor Stator Faults using Electric Signals from Variable Speed Drives

Motor current signature analysis has been investigated widely for diagnosing faults of induction motors. However, most of these studies are based on open loop drives. This paper examines the performance of diagnosing motor stator faults under both open and closed loop operation modes. It examines the effectiveness of conventional diagnosis features in both motor current and voltage signals using spectrum analysis. Evaluation results show that the stator fault causes an increase in the sideband amplitude of motor current signature only when the motor is under the open loop control. However, the increase in sidebands can be observed in both the current and voltage signals under the sensorless control mode, showing that it is more promising in diagnosing the stator faults under the sensorless control operation

The Detection of Shaft Misalignments using Motor Current Signals from a Sensorless Variable Speed Drive

Shaft misalignments are common problems in rotating machines which cause additional dynamic and static loads, and vibrations in the system, leading to early damages and energy loss. It has been shown previously that it is possible to use motor current signature analysis to detect and diagnose this fault in motor drives. However, with a variable speed drive (VSD) system, it becomes dif-ficult to detect faults as the drive compensates for the small changes from fault ef-fects and increased noise in the measured data. In this paper, motor current signa-tures including dynamic and static data have been investigated for misalignment diagnosis in a VSD system. The study has made a systemic comparison of differ-ent control parameters between two common operation modes: open loop and sen-sorless control. Results show that fault detection features on the motor current from the sensorless mode can be the same as those of the open loop mode, however, the detection and diagnosis is significantly more difficult. In contrast, because of the additional frictional load, features from static data show results of early detection and diagnosis of different degrees of misalignment is as good as that from conventional vibration methods

Promoting Goal Setting: An Experimental Study of Positive Psychology in an EFL Context

The present quasi-experimental study addresses the impact of a Character Strength Based Positive Psychology Intervention (CSBPPI) on Goal Setting (GS) of TEFL university students in Iran. In so doing, the study utilized an experimental design with 18 participants in the control group and 18 participants in the experimental group which totalled 7 male and 29 female students. The pretest showed that the participants of the two groups were homogenous with regard to their proficiency level as well as their goal setting. Data was collected over five months using Erickson et al. (2015) goal setting questionnaire before and after an MA course. The results of the post-test revealed that PP has a positive and significant impact on learners’ goal setting. The findings from this research suggest positive paths from positive psychology to understanding, managing and successfully setting the goals

Investigating the Effect of Water Contamination on Gearbox Lubrication based on Motor Control Data from a Sensorless Drive

Water is one of the most significant destructive contaminations to lubricants which in turn lead to more power consumption and early damage to rotating machines. This study explores the effect of water contents in gearbox lube oil on the responses of electrical supply parameters. A two stage gearbox based mechanical transmission system driven by a sensorless variable speed drive (VSD) is utilised to investigate experimentally any measurable changes in these signals that can be correlated with water contamination levels. Results show that the supply parameters obtained from both external measurements and the VSD control data can be correlated to the contamination levels of oil with water and hence can be based on for an instant diagnosis of water contamination. Particularly, the voltage and hence the power responses are more sensitive to the water contents than that of current because the VSD regulates more the voltage to adapt the small load changes due to the water induced lubrication degradation. Simultaneously, vibration also shows changes which agree with that of power supply parameters

Modélisation du processus de pilotage d'un atelier en temps réel à l'aide de la simulation en ligne couplée à l'exécution

Ce travail de recherche met en avant l'intérêt qu'offre la simulation en ligne comme outil d'aide à la décision, outil centré sur le pilotage d'atelier vis-à-vis d'événements se produisant en temps réel et pour un horizon à très court terme. Après avoir présenté le contexte général du pilotage des systèmes de production, nous avons étudié les outils existants et utilisés industriellement pour l'exploitation de la production, de même que les outils d'aide au pilotage permettant d'assurer le respect optimal des objectifs fixés. Après un travail préalable sur la simulation hors ligne, nous proposons de coupler un outil de simulation en ligne à un outil d'exécution d'atelier de type MES afin de piloter en temps réel le processus de production. Une démarche de modélisation faisant appel de façon complémentaire à deux approches, analytique et simulatoire, est finalement mise en place. Nous mettons en exergue l'utilisation de la simulation de flux en ligne pour aider au pilotage d'un processus opérationnel. Ainsi nous modélisons le processus de pilotage en temps réel afin de décrire les fonctions requises. Pour cela, nous utilisons différentes stratégies d'utilisation des simulateurs en ligne pour le pilotage, avec un ou deux modèles et avec plusieurs méthodes d'utilisation de ces modèles. La simulation en ligne apporte alors des informations objectives sur les conséquences à court terme d'un événement, ainsi que sur les divers scenarii de correction envisagés. Pour mieux convaincre les industriels de l'intérêt de la simulation en ligne, nous présentons des solutions pratiques aux spécifications et besoins énoncés précédemment en nous appuyant sur une plate-forme expérimentale. ABSTRACT : This research work highlights the interest of online simulation as a decision support tool. This tool is focused on workshop control in relation with real time and short-term events. Online simulation enables to analyze and compare scenarios affecting the production, such as failures or unexpected orders. Moreover online simulation allows a very short term projection in the future in order to quantify the consequences of some unexpected event: we call it projection simulation. Finally, online simulation is helpful to choose the solution that will reduce the impact of a critical event, through the simulation of several scenarios. To conclude, online simulation is one the most interesting decision support tool in workshop piloting. However, there are few industrial applications in manufacturing systems. The first part of this research work introduces the overall context of production system management. The different generic functions of controlling the production, the modes of piloting and the evolutions of workshop are detailed. We also explain piloting typologies according to their reactivity. In the second part, we study the existing software tools used in industry for the operation of production, and support tools that ensure optimal compliance in regard to the objectives. After a preliminary work on the offline simulation, we propose to couple an online simulation tool with a type MES delivery tool in order to control the production process in real time. A modeling approach using two complementary approaches, an analytical one and simulation, is then introduced. The objective of the third part is to emphasize the use of online flow simulation to assist in operating a production process. Thus we model the process in real time to describe the required functions. Therefore we try out different strategies of use of online simulators, through one or two models and several methods of using these models. Online simulation then provides realistic information on the short-term consequences of an event, as well as on the different ways of correcting the scenarios. To convince industry of the relevance of online simulation, the fourth part presents practical solutions to the specifications and requirements previously stated. An experimental platform helped us validate the concept of online simulation as piloting support tool, but also underline the difficulties of development

Fight against administrative corruption within governmental organizations from motto to practice (case study: Ministry of Economic Affairs and Finance)

Administrative corruption in a simple definition is violation of a law for personal benefits by utilization of job position. It is a phenomenon within today’s world as one of the most important obstacles on the way of societies’ progress. The impact of different factors in forming corruption has given it a complicated nature. Administrative corruption is a correlative issue and it is different according to value system of each society. This article is trying to present a solution in order to fight against administrative corruption through classification of staff with the help of explaining the relation of their perception, sensation and commitment towards corruption and corrupted situations. Present study in terms of purpose is developmental-practical, and in terms of execution and based upon research purposes is a survey. The study population is the staff of Ministry of Economic Affairs and Finance in 2015. In order to explain perception, sensation and the behavior of staff, the questionnaire of administrative corruption is designed in three dimensions: perceptive aspect (cognitive) which includes items for assessing the status of awareness and recognition of staff from instances and consequences of administrative corruption; sensation aspect which includes items for assessing the vision and tendencies of staff towards corruption, and behavioral aspect which is formed from items for assessing the behavior of staff in facing with corruptive situations. In order to identify the reasons of corruption two questionnaires of “National identity” and “Organizational culture” have been designed. The result of the research was that the perpetrators of corruption can be divided into three categories. First category is the staff that their perception is positive, it means that they have adequate cognition from manifestations and corruption consequences and their feeling about corruption is negative, it means that they consider it as an ominous phenomenon, but they are guilty of corruption. Second category is the staff that their perception is positive, they don’t see corruption as an ominous phenomenon. Consequently, their feeling toward corruption is positive, and they perpetrate it. The third category is the staff whose perception is negative, their feeling is uncertain, and they perpetrate it. The behavior of these categories will be interpreted in form of related theories. The significant note is that despite the tendency average to practice administrative corruption among governmental staff is lower than assumed average and it indicates that there is a protection of corruption perpetration, but the rank of our country is not favorable the International Organization report. This warning made the researchers to provide new solutions to help resolving this social issue by reviewing current solutions for prevention, and fighting against administrative corruption, regarding the richness of evaluating system in Iran. Keywords: corruption, administrative corruption, corruption perception, sense of corruption, corruption behavior, organizational culture, national identity. JEL Classification: D73, M12, Z1

Knowledge and Practice of Midwives in Golestan Province, North of Iran: An Evidence-based Practice

Introduction: Given the role of evidence-based practice (EBP) in the improvement of patient care including midwifery care, the current study aimed at investigating knowledge and practice of midwives worked in health centers in terms of EBP in Golestan Province, North of Iran. Methods: The current cross sectional study was conducted in Golestan Province, North of Iran in 2014. Of 389 midwives worked in family health centers of Golestan Province, 262 subjects were selected using census sampling method. Data collection tool was a self-report questionnaire consisted of three parts: 1) Demographic characteristics; 2) Participants's knowledge about EBP; 3) Participant's practice of EBP. Data were finally analyzed with SPSS version 16. P-value < 0.05 was considered as the level of significance. Results: The mean score of the study subjects in knowledge and use of EBP were 13.2 ± 6.3 and 2.1 ± 1.2, respectively. In other words, 90% of midwives got the score < 22. Significant relationships were found between knowledge and participants’ age (P = 0.001), marital status (P = 0.008), and level of education (P = 0.039). Also, there was a significant relationship between use of EBP and type of recruitment (P = 0.014), workplace (urban or rural) (P ≥ 0.05), and age (P < 0.05). According to Spearman test, there was a remarkable, linear relationship between knowledge and use of EBP (r = 0.437). Conclusions: Knowledge and use of EBP in daily practice among midwives was poor. Given the role of EBP in the improvement of patient care, it is necessary to improve the level of knowledge and utilize EBP efficiently and effectively among healthcare workers using appropriate plans designed by health policymakers