Continuous maintenance and the future – Foundations and technological challenges

High value and long life products require continuous maintenance throughout their life cycle to achieve required performance with optimum through-life cost. This paper presents foundations and technologies required to offer the maintenance service. Component and system level degradation science, assessment and modelling along with life cycle ‘big data’ analytics are the two most important knowledge and skill base required for the continuous maintenance. Advanced computing and visualisation technologies will improve efficiency of the maintenance and reduce through-life cost of the product. Future of continuous maintenance within the Industry 4.0 context also identifies the role of IoT, standards and cyber security

Development of a Non-Invasive On-Chip Interconnect Health Sensing Method Based on Bit Error Rates

Electronic products and systems are widely used in industrial network systems, control devices, and data acquisition devices across many industry sectors. Failures of such electronic systems might lead to unexpected downtime, loss of productivity, additional work for repairs, and delay in product and service development. Thus, developing an appropriate sensing technique is necessary, because it is the first step in system fault diagnosis and prognosis. Many sensing techniques often require external and additional sensing devices, which might disturb system operation and consequently increase operating costs. In this study, we present an on-chip health sensing method for non-destructive and non-invasive interconnect degradation detection. Bit error rate (BER), which represents data integrity during digital signal transmission, was selected to sense interconnect health without connecting external sensing devices. To verify the health sensing performance, corrosion tests were conducted with in situ monitoring of the BER and direct current (DC) resistance. The eye size, extracted from the BER measurement, showed the highest separation between the intact and failed interconnect, as well as a gradual transition, compared with abrupt changes in the DC resistance, during interconnect degradation. These experimental results demonstrate the potential of the proposed sensing method for on-chip interconnect health monitoring applications without disturbing system operation

Output Power and Gain Monitoring in RF CMOS Class A Power Amplifiers by Thermal Imaging

© 2019 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes,creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.The viability of using off-chip single-shot imaging techniques for local thermal testing in integrated Radio Frequency (RF) power amplifiers (PA’s) is analyzed. With this approach, the frequency response of the output power and power gain of a Class A RF PA is measured, also deriving information about the intrinsic operation of its transistors. To carry out this case study, the PA is heterodynally driven, and its electrical behavior is down converted into a lower frequency thermal field acquirable with an InfraRed Lock-In Thermography (IR-LIT) system. After discussing the theory, the feasibility of the proposed approach is demonstrated and assessed with thermal sensors monolithically integrated in the PA. As crucial advantages to RF-testing, this local approach is noninvasive and demands less complex instrumentation than the mainstream commercially available solutions.Peer ReviewedPostprint (author's final draft

Real-time monitoring of photovoltaic panels

Capstone Project submitted to the Department of Engineering, Ashesi University in partial fulfillment of the requirements for the award of Bachelor of Science degree in Electrical and Electronic Engineering, May 2022With the increase in population comes the increase in demand for electricity. Day in and day out, the non-renewable sources of energy are getting depleted; thus, many countries and continents are switching to renewable energy sources. Solar energy has proven to be pollution-free and the most accessible form of renewable energy. Photovoltaic Panels (PV) Panels are the devices used to harness solar power, and they have a life span of 25 years. However, several faults can occur in the PV panel and drastically reduce the efficiency and lifespan of the Solar Panel. In this research project, a real-time monitoring system is developed to observe the emergence of any faults and put a plan of action to preserve efficiency. The system would provide both a visual and thermographic assessment of the Photovoltaic Panel. This is achieved using Internet of Things.Ashesi Universit

Towards a More Flexible, Sustainable, Efficient and Reliable Induction Cooking: A Power Semiconductor Device Perspective

Esta tesis tiene como objetivo fundamental la mejora de la flexibilidad, sostenibilidad, eficiencia y fiabilidad de las cocinas de inducción por medio de la utilización de dispositivos semiconductores de potencia: Dentro de este marco, existe una funcionalidad que presenta un amplio rango de mejora. Se trata de la función de multiplexación de potencia, la cual pretende resolverse de una manera más eficaz por medio de la sustitución de los comúnmente utilizados relés electromecánicos por dispositivos de estado sólido. De entre todas las posibles implementaciones, se ha identificado entre las más prometedoras a aquellas basadas en dispositivos de alta movilidad de electrones (HEMT) de Nitruro de Galio (GaN) y de aquellas basadas en Carburo de Silicio (SiC), pues presentan unas características muy superiores a los relés a los que se pretende sustituir. Por el contrario, otras soluciones que inicialmente parecían ser muy prometedoras, como los MOSFETs de Súper-Unión, han presentado una serie de comportamientos anómalos, que han sido estudiados minuciosamente por medio de simulaciones físicas a nivel de chip. Además, se analiza en distintas condiciones la capacidad en cortocircuito de dispositivos convencionalmente empleados en cocinas de inducción, como son los IGBTs, tratándose de encontrar el equilibrio entre un comportamiento robusto al tiempo que se mantienen bajas las pérdidas de potencia. Por otra parte, también se estudia la robustez y fiabilidad de varios GaN HEMT de 600- 650 V tanto de forma experimental como por medio de simulaciones físicas. Finalmente se aborda el cálculo de las pérdidas de potencia en convertidores de potencia resonantes empleando técnicas de termografía infrarroja. Por medio de esta técnica no solo es posible medir de forma precisa las diferentes contribuciones de las pérdidas, sino que también es posible apreciar cómo se distribuye la corriente a nivel de chip cuando, por ejemplo, el componente opera en modo de conmutación dura. Como resultado, se obtiene información relevante relacionada con modos de fallo. Además, también ha sido aprovechar las caracterizaciones realizadas para obtener un modelo térmico de simulación.This thesis is focused on addressing a more flexible, sustainable, efficient and reliable induction cooking approach from a power semiconductor device perspective. In this framework, this PhD Thesis has identified the following activities to cover such demands: In view of the growing interest for an effective power multiplexing in Induction Heating (IH) applications, improved and efficient Solid State Relays (SSRs) as an alternative to the electromechanical relays (EMRs) are deeply investigated. In this context, emerging Gallium Nitride (GaN) High‐Electron‐Mobility Transistors (GaN HEMTs) and Silicon Carbide (SiC) based devices are identified as potential candidates for the mentioned application, featuring several improved characteristics over EMRs. On the contrary, other solutions, which seemed to be very promising, resulted to suffer from anomalous behaviors; i.e. SJ MOSFETs are thoroughly analysed by electro‐thermal physical simulations at the device level. Additionally, the Short Circuit (SC) capability of power semiconductor devices employed or with potential to be used in IH appliances is also analysed. On the one hand, conventional IGBTs SC behavior is evaluated under different test conditions so that to obtain the trade‐off between ruggedness and low power losses. Moreover, ruggedness and reliability of several normally‐off 600‐650 V GaN HEMTs are deeply investigated by experimentation and physics‐based simulation. Finally, power losses calculation at die‐level is performed for resonant power converters by means of using Infrared Thermography (IRT). This method assists to determine, at the die‐level, the power losses and current distribution in IGBTs used in resonant soft‐switching power converters when functioning within or outside the Zero Voltage Switching (ZVS) condition. As a result, relevant information is obtained related to decreasing the power losses during commutation in the final application, and a thermal model is extracted for simulation purposes.<br /

Analysis of building maintenance requests using a text mining approach: building services evaluation

End users’ maintenance requests gathered from computerized maintenance management systems (CMMS) configure a rich source of information to evaluate the occupants’ satisfaction and the building systems. Nevertheless, the non-standardized data gathered from CMMS makes it difficult to carry out analytics. This paper presents a text mining approach to extract information from end users’ maintenance requests and an analysis of 6,830 maintenance requests derived from 46 buildings including offices, academic buildings and laboratories over two and a half years. The research results reveal that the most common maintenance requests during building operation and maintenance are related to problems in electrical and HVAC fixtures. Although the year of construction is not related to the occupants’ maintenance requests, the type of building use and building property do influence them. The implementation of control and preventive strategies based on these results may increase facility managers’ productivity and building systems’ performance.Peer ReviewedPostprint (author's final draft

Path towards an attainable quality : the effect of tooling design on the product competency and process efficiency

People gradually started to rely on electronic devices such as computers, smartphones, and so on as their lives became increasingly dependent on them. These products are made up ofseveral Integrated Circuits (IC) which are connected among themselves with copper traces and undergo numerous processes before becoming a finished product. Due to its importance, it is vital to produce printed circuit board assemblies that are high in quality and low in the probability of malfunctioning. Therefore, certain issues need to be carefully resolved to ensure the reliability of the products. In addition, several problems have been identified during this study. A large yield drop and high rejects have been observed at specific stations where operators perform mechanical assembly of printed circuit boards. In addition, the lack of a clear understanding of the process of the operators has led to defects at the station. Aside from that, operators manually assemble the mechanical part using poorly designed tooling that is not designed for printed circuit board assembly. Since it is highly error-prone due to human error, this technique is known to have a high rejection rate. As a result of high rejects and unfit tooling used, the cycle time of producing the product has been increasing abruptly. To produce defect-free products, this study will explore a technical method to explore defect occurrences and classify their root causes by using existing quality tools, such as defect cycle analysis and fault tree analysis (FTA). Additionally, this study examines the possibilities of designing tooling using more structured guidelines such as "Verein Deutscher !ngenieure 2221" (VDT 2221), which makes the process simpler and allows for the evaluation of each task taken in designing and its significant impact. Eventually, the processing time of the products is brought down to optimal, which maximizes productivity and increases customer satisfaction. The data for this study were collected through various channels such as system data, observations, semi-structured interviews among the operators, discussion and brainstorming, and finally real-time experiments and trials. In sum, this study helped eliminate all defects related to mechanical assembly, which resulted in a reduction of overall defects by 81.3%, a reduction of scrap by 57% (total saving ofUSD 5920), and a reduction of the cycle time by 28.57% (saving of USD 419 in two quarters). Based on these results, it is crucial to identify the correct method of defect detection, the point ofoccurrence, and the root cause ofthe defect. Through this study, a well-organized generic method of designing tooling has been developed as well. Nonetheless, this study hopes to offer a few techniques that are being practiced to increase quality with a lesser time used

Improved micro-contact resistance model that considers material deformation, electron transport and thin film characteristics

This paper reports on an improved analytic model forpredicting micro-contact resistance needed for designing microelectro-mechanical systems (MEMS) switches. The originalmodel had two primary considerations: 1) contact materialdeformation (i.e. elastic, plastic, or elastic-plastic) and 2) effectivecontact area radius. The model also assumed that individual aspotswere close together and that their interactions weredependent on each other which led to using the single effective aspotcontact area model. This single effective area model wasused to determine specific electron transport regions (i.e. ballistic,quasi-ballistic, or diffusive) by comparing the effective radius andthe mean free path of an electron. Using this model required thatmicro-switch contact materials be deposited, during devicefabrication, with processes ensuring low surface roughness values(i.e. sputtered films). Sputtered thin film electric contacts,however, do not behave like bulk materials and the effects of thinfilm contacts and spreading resistance must be considered. Theimproved micro-contact resistance model accounts for the twoprimary considerations above, as well as, using thin film,sputtered, electric contact