ISSN:0883-9514    

DOI:10.1080/08839519508945464

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Understanding the design of a device requires both knowledge of the general physical principles that determine its behavior and knowledge of its intended functions. However, the majority of work in model-based reasoning has focused on using either one of these types of knowledge alone. In order to use both types of knowledge in understanding a device design, one must represent the functional knowledge in such a way that it has a clear interpretation in terms of observed behavior. We propose a new formalism, causal functional representation language (CFRL),for representing device functions with well-defined semantics in terms of behavior. CFRL allows the specification of conditions that a behavior must satisfy, such as occurrence of temporal sequences of events and causal relations among them and the components. We have used CFRL as the basis for afunctional verification program, which determines whether a behavior achieves an intended function.

ISSN:0883-9514    

DOI:10.1080/08839519508945465

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Knowledge of how a device works is important for many tasks. Yet, systems that attempt to base their reasoning on the use of a functional model fail to capture such knowledge or only capture it implicitly. Instead they rely solely on the knowledge of the purpose of the system and provide causal explanations of how this purpose is achieved. This type of model only represents knowledge of what the system is for, not how the system works. However, engineers also rely on knowledge of how a device works to complete tasks successfully. One such task is failure mode effects analysis (FMEA). FMEA involves investigation and assessment of the effects of all possible failure modes on a system. This process is both tedious and time consuming, and it requires detailed expert knowledge of the system under consideration, including information about the structure of the system and its purpose or function. This means that any attempt to automate the whole of the FMEA process must involve both the structural and functional levels. This paper reviews the FMEA process and considers the requirements of an automated FMEA system. It outlines a prototype FMEA system and presents a functional modeling system that relies on the results produced by an underlying structural simulator.

ISSN:0883-9514    

DOI:10.1080/08839519508945466

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Function metrics make early design evaluation possible. A simple definition of function as a pair of behavior expressions that map the utilized part of a component behavior to an intended part of a device behavior enables formal definition of several useful metrics for engineered devices such as sharing, overload, modularity, and criticality. These function metrics can be used to evaluate properties of a given configuration of components in a device as well as to compare alternative configurations of devices for the same design intents. A program called Teleometrics has been implemented that models function representations of devices as graphs and generates function metrics. Four patented accelerometers used for automotive crash sensing are modeled, evaluated, and compared using Teleometrics.

ISSN:0883-9514    

DOI:10.1080/08839519508945467

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

We propose function for candidate discrimination, i.e., suspect ordering during model-based diagnosis. Function offers advantages over structure and fault probabilities currently being used for candidate discrimination. It is readily available from device design, unlike fault probabilities, which are hard to obtain. Function-based discrimination is not dependent on the topology of the device, unlike structure-based discrimination. We propose classes as a scheme for representation of function. As part of classes, we define a set of function primitives and provide a framework for identifying the functions of components and subsystems of a device. The representation scheme is domain independent. We propose a function-based technique for candidate discrimination called the default order technique, and outline a diagnosis algorithm that applies the technique to the class model of a device. Function-based diagnosis is in addition to and as a supplement for model-based diagnosis based on behavior and structure. We demonstrate by qualitative analysis that function-based discrimination is at least as effective as fault probabilities for candidate discrimination of simple devices. In complex devices, function facilitates explanation generation based on causality, which is a desirable feature of diagnosis systems. Our discrimination technique provides a functional basis for partitioning components in the practicable version of the minimum entropy technique proposed by deKleer.

ISSN:0883-9514    

DOI:10.1080/08839519508945468

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

An application of functional reasoning to the repair of communication software is described. This type of repair, called a “work-around,” eliminates a failure, either permanently or temporarily, by reconfiguring the system. The reconfiguration replaces a faulty procedure with a functionally equivalent, working one. In contrast to classical fault-tolerance techniques, functional reasoning is employed to identify implicit functional redundancy. The motivation is the current and future reliability requirements of data and telecommunication networks and their components. The proposed functional model of communication procedures is based on information distributions and is formalized in modal logic. This functional model is appropriate for modeling safety properties of communication systems. The function of the alternating bit protocol (ABP) is described as an example. This example is used to outline the computation of work-arounds, where the functional equivalence is achieved by the correct parameterization of the replacement.

ISSN:0883-9514    

DOI:10.1080/08839519508945469

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Functional models have been extensively investigated in the context of several problemsolving tasks such as device diagnosis and design. In this paper, we view problem solvers themselves as devices, and use structure-behavior-function models to represent how they work. The model representing the functioning of a problem solver explicitly specifies how the knowledge and reasoning of the problem solver result in the achievement of its goals. Then, we employ these models for performance-driven reflective learning. We view performance-driven learning as the task of redesigning the knowledge and reasoning of the problem solver to improve its performance. We use the model of the problem solver to monitor its reasoning. Assign blame when it fails, and appropriately redesign its knowledge and reasoning. This paper focuses on the model-based redesign of a path planner's task structure. It illustrates the modelbased reflection using examples from an operational system called the Autognostic system.

ISSN:0883-9514    

DOI:10.1080/08839519508945470

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor