Patent number 8606554 is assigned to
The following quote was obtained by the news editors from the background information supplied by the inventors: "The invention relates generally to process control. More specifically, the invention relates to a Heat Flow Model (HFM) methodology for HVAC system fault detection and diagnosis. Embodiments use the modularity of graphs to achieve a direct automated mapping of HVAC structures and components into HFM graphs, and use node behavior model and software libraries to translate the HFM graphs into systems that can be integrated in HVAC control systems.
"Modern Heating, Ventilation and Air Conditioning (HVAC) control systems are often too complex to have proper means for effective Fault Detection and Diagnosis (FDD) and correction. With many existing FDD approaches, the engineering efforts to apply and adapt them to various HVAC systems are great.
"FDD for HVAC has become an important topic with many contributions from academics and industry. However, one problem still remains when the research results are put into practice, since nearly all buildings are different there is a huge variety of HVAC systems. If the FDD system does not match a particular HVAC system, not enough faults are detected. And if it is customized for a specific system, the development effort and cost may be too high in relation to the possible gain.
"The use of expert systems to diagnose faults in HVAC components and systems have been tried and include rule-based methods, fuzzy model based strategies, and Artificial Neural Network (ANN) based classifiers.
"Usually a set of failure rules based on temperature or pressure inequalities is derived to detect faults. In most of the studies, either the rules have been derived manually for each specific HVAC system or the ANN has to be trained offline which may not necessarily cover all of the faults due to the limited training data.
"These processes are time consuming and labor intensive. As the recent advancement in building modeling technology has already impacted the building design and construction engineering process significantly, it is believed that developing an FDD system based on building information models will both enhance building fault diagnosis capability and reduce the engineering process of generating fault rules.
"Multilevel Flow Models (MFM) have been applied to power plants and similar systems. The flow models are graphs representing mass, energy and information flows. Once the graphs are established, rules based on mass and energy conservation laws are extracted and analyzed by an inference engine to realize the FDD in real-time.
"The MFM flow models are graphs representing mass, energy and information flows where mass and energy conservation laws apply and can be used for fault detection and diagnosis. However, to use MFM, the flows have to be measured, which are often not available for an HVAC system.
"What is desired is a system and method that provides FDD to reduce this effort."
In addition to the background information obtained for this patent, VerticalNews journalists also obtained the inventors' summary information for this patent: "The inventors have discovered that it would be desirable to have systems and methods that provide a Heat Flow Model (HFM) methodology. Embodiments automatically translate formal HVAC system descriptions from a
"Embodiments create a hierarchical HFM graph model which can be used for automatic HVAC FDD generation from appropriate BIMs such as Industrial Foundation Class (IFC). HFM has a one-to-one correspondence with the component structure of existing or planned HVAC systems. HFM nodes such as coils, ducts or fans model the dynamic physical behavior (temperature, flow, humidity and pressure) of air and water flows of these components as precise as can be derived from the BIMs. Each node can calculate its upstream and downstream physical behavior parameter values of connected HVAC components with the dynamic output data from the HVAC control system using instrument sensor and control values. The results are propagated through the HFM graph as parameter ranges.
"Embodiments apply failure rules in each HFM node. If calculated estimate and received value ranges do not match, a fault is presumed and its severity is propagated up in the component hierarchy for diagnosis. The diagnosis is performed by a central engine by mapping the rule violations from HFM nodes to the failures of the HVAC system, the mapping relationship is represented by an Associative Network. The HFM based FDD is composed of an engineering tool and runtime system.
"Embodiments create an HFM graph based model for building HVAC system FDD. Embodiments automatically extract the necessary structural and quantitative data about the target system from BIM descriptions, e.g. IFC. Rules for detecting faults that are related to nodes of the graph are defined based on first principles.
"One aspect of the invention provides a Heat Flow Model (HFM) node used in a Heating, Ventilation and Air Conditioning (HVAC) fault detection graph. Aspects according to the HFM node include a FwdIn edge configured to receive parameter ranges from a downstream direction, a FwdOut edge configured to output parameter ranges in the downstream direction, a RevIn edge configured to receive parameter ranges from an upstream direction, a RevOut edge configured to output parameter ranges in the upstream direction, and node specific configuration data that defines the functionality of the node.
"Another aspect of the HFM node is one or more RulesOut edges configured to output a failure rule decision where the node specific data further comprises a failure rule corresponding to each RulesOut edge where, for the downstream direction, a failure rule compares an estimated parameter range with a FwdIn edge parameter range and for the upstream direction, a failure rule compares an estimated parameter range with a RevIn edge parameter range, and if the estimated parameter range is not within the received parameter ranges, a failure is output.
"Another aspect of the HFM node is the node specific configuration data further comprises FwdIn edge parameter range tolerances and RevIn edge parameter range tolerances.
"Another aspect of the HFM node is for the downstream direction, an estimated parameter range is a product of a RevIn edge parameter range and a RevIn edge parameter range tolerance, and for the upstream direction, an estimated parameter range is a product of a FwdIn edge parameter range and a FwdIn edge parameter range tolerance.
"Another aspect of the HFM node is one or more DataIn edges, each configured to receive a dynamic HVAC control system variable, and the node specific configuration data further comprises DataIn edge dynamic HVAC control system variable parameter tolerance values.
"Another aspect of the HFM node is for the downstream and upstream directions, an estimated parameter range is a product of a DataIn edge dynamic HVAC control system variable and its dynamic HVAC control system variable parameter tolerance value.
"Another aspect of the invention is a method of using a Heat Flow Model (HFM) graph for detecting HVAC system faults for a building. Aspects according to the method include translating formal HVAC system descriptions from a
"Another aspect of the method is where each node in the HFM graph estimates upstream and downstream physical behavior values that correspond to their building HVAC components with dynamic output instrument sensor and control data from the building HVAC control system and propagates the upstream and downstream physical behavior values through the HFM graph as parameter ranges.
"Another aspect of the invention is a building Heating, Ventilation and Air Conditioning (HVAC) fault detection system. Aspects according to the method include an interface configured to access a
"Another aspect of the system is an FDD engine configured to instantiate the HFM graph as a runtime system for the building HVAC control system, and an interface configured to access the building HVAC control system, where the FDD engine executes the HFM graph with HVAC control system process and control variable data and applies rules for detecting HVAC system faults.
"The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims."
URL and more information on this patent, see: Zimmermann, Gerhard; Lu, Yan; Lo, George. Heat Flow Model for
Keywords for this news article include: Engineering, Legal Issues,
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