Estimating the Size of Incipient Faults in HVAC Equipment

Abstract

It may be necessary to estimate the size of a fault if the fault develops slowly and the associated loss of performance could go unnoticed for a long period of time. This paper describes an observer-based method of estimating the magnitudes of slowly evolving faults in HVAC equipment. The sizes of two types of incipient faults in a cooling coil subsystem are estimated using a fault identification scheme based on a fuzzy relational proportional-integral observer. Because it would take a long time for a fault to develop in a real system, a detailed computer simulation is used to assess the performance of the scheme. The main causes of inaccuracy in the fault estimates are examined and long-term simulation results are presented, which demonstrate that an adaptive version of the scheme can generate satisfactory estimates of the sizes of the faults.

An adaptive fault tolerant PI controller for an information-poor, nonlinear system

“…A schematic diagram of the cooling coil subsystem is shown in Fig. 4 [19]. The chilled water supply, at temperature T cws • C, is pumped through the copper tubes of the cooling coil.…”

“…Computer simulation is used to collect the training data based on a software package known as SIMBAD (Simulator of Building And Devices), developed for the design of HVAC systems. Nine different designs of cooling coil (to cover all operating conditions) have been developed by the control group at Oxford University, where one design (D1) is selected for the study and the parameters and detailed coil data are referred in Table I [19]. Based on the physical theory and the control viewpoint, the Fuzzy Relational Model (FRM) of the cooling coil subsystem (D1) (random selection)has five inputs and one output and the model structure is shown in Fig.…”

An adaptive fault tolerant neuro-fuzzy based proportional-integral controller for a nonlinear system

“…The schematic diagram of the air-conditioning system is illustrated in Figure 1 (Zhou and Dexter, 2009). When the ambient environmental temperature is too high, the cooling subsystem will be functioning which can take away the heat from the room and keep the room temperature at a certain value via circulation.…”