An application for constraint suspension: Fault diagnosis in an air conditioning unit

[摘要] Building energy management systems (BEMS) not only perform real-time control functions but also provide enormous amounts of data which can be analysed for purposes of energy management and fault detection and diagnosis. Unfortunately there are few tools available to perform these tasks leaving the onus on skilled engineering staff to analyse the data manually. This has prevented the realization of the full potential of BEMS technology. This thesis examines whether the technique, known as constraint suspension, could provide an appropriate tool for fault detection and diagnosis. The aim of this study is specifically to examine the suitability of the technique of constraint suspension within the context of the particular example of an air conditioning unit installed at a medium sized factory for the production of aerospace components.1 The thesis contains 5 chapters. Chapter 1 provides a brief introduction. This is followed, in Chapter 2, by a detailed account of research to date into fault detection systems applied to BEMS. It is found that these systems require complex programming and are not readily transferred from one building to another. Chapter 3 introduces the concept of constraint suspension and argues that this could provide a general tool, based on simplified, static models, that could be readily transferred to any air conditioning plant with suitably located sensors. The chapter goes on to describe the application of constraint suspension to a particular case of an air conditioning unit installed at a medium sized factory. Chapter 4 presents some results and assesses the effectiveness of the application in diagnosing faults in the air conditioning unit, control system and control strategy. Chapter 5 concludes the study with an analysis of the (ii) air conditioning plant in a light engineering factory have been considered. The following faults have been identified and verified: o the output of the sensor measuring the chilled water temperature out of the mixing valve, o the BEMS driver output for the fresh air and recirculating air dampers, o the control strategy for dehumidification. The findings demonstrate that the system proposed, based upon constraint suspension technology, is capable of detecting and diagnosing sensor and driver faults. The rule based system of assessing the control strategy can indicate faults in the strategy. The viability of the application of constraint suspension to the detection and diagnosis of fault conditions in an air conditioning unit using simple static models has been demonstrated. The rather arbitrary nature of locating sensors in air conditioning plant has been identified. The importance of providing a complete specification for the BEMS including exact locations and numbers of sensors to facilitate fault detection and diagnosis procedures has been highlighted.

[发布机构] University:University of Glasgow

[关键词] Mechanical engineering, Architectural engineering