Maria Cristina Piccirilli

Determination of an optimum set of testable components in the fault diagnosis of analog linear circuits

A procedure for the determination of an optimum set of testable components in the fault diagnosis of analog linear circuits is presented. The proposed method has its theoretical foundation in the testability concept and in the canonical ambiguity group concept. New considerations relevant to the existence of unique solution in the k-fault diagnosis problem of analog linear circuits are presented, and examples of application of the developed procedure are considered by exploiting a software package based on symbolic analysis techniques.

Finding ambiguity groups in low testability analog circuits

This paper discusses a numerically efficient approach to identify complex ambiguity groups for the purpose of analog fault diagnosis in low-testability circuits. The approach presented uses a numerically efficient QR factorization technique applied to the testability matrix. Various ambiguity groups are identified. This helps to find unique solution of fault diagnosis equations or identifies which groups of components can be uniquely determined. This work extends results reported earlier in literature, where QR factorization was used in low-testability circuits, significantly increasing efficiency to determine ambiguity groups. A Matlab program that implements this method was integrated with a symbolic analysis program that generates test equations. The method is illustrated on two low-testability electronic circuits. Finally, method efficiency is tested on larger electronic circuits with several hundred tested parameters.

On the application of symbolic techniques to the multiple fault location in low testability analog circuits

A new approach for the multiple fault location in linear analog circuits is proposed. It presents the characteristic of using classical numerical procedures together with symbolic analysis techniques, which is particularly useful in the parametric fault diagnosis field. The proposed approach is based on the k-fault hypothesis and is provided with efficient algorithms for fault location also in the case of low testability circuits. The developed algorithms have been used for realizing a software package prototype which implements a fully automated system for the fault location in linear analog circuits of moderate size.

A Method for the Automatic Selection of Test Frequencies in Analog Fault Diagnosis

A new procedure for the selection of test frequencies in the parametric fault diagnosis of analog circuits is presented. It is based on the evaluation of algebraic indices, as the condition number and the norm of the inverse, of a sensitivity matrix of the circuit under test. This matrix is obtained starting from the testability analysis of the circuit. A test index (T.I.) that permits the selection of the set of frequencies that better leads to locating parametric faults in analog circuits is defined. By exploiting symbolic analysis techniques, a program that implements the proposed procedure has been developed. It yields the requested set of frequencies by means of an optimization procedure based on a genetic algorithm that minimizes the T.I. Examples of the application of the proposed procedure are also included.

A singular-value decomposition approach for ambiguity group determination in analog circuits

An efficient approach for ambiguity group determination in low-testability analog linear circuits is presented. It is based on the use of the singular-value decomposition of the testability matrix of the circuit under test, and permits us to determine canonical ambiguity groups also in the case of circuits of relatively large dimensions. The new approach is characterized by a numerical robustness not present in previous approaches, which give only an estimate of both testability and ambiguity groups. A program implementing the proposed method has been developed by exploiting symbolic analysis techniques. Examples of application of the new approach are considered through the use of this program.

A new efficient method for analog circuit testability measurement

Testing an electronic circuit is a vital part of its overall design and fabrication process. This problem is even going to be more critical with technology improvements and with the coexistence on a chip of analog and digital components. In fact the testing of mixed signal microsystems is very difficult compared to digital only devices. They do not lend themselves to earlier and simpler test routines. The entire mixed signal segment is hampered by the lack of design for testability methodologies and tools. In this field the concept of analog circuit testability is of fundamental importance. The aim of this work is to present a new symbolic approach for testability measurement of analog networks. The new method presents noteworthy advantages from a computational point of view with respect to previous techniques. In fact it does not require the computation of the sensitivities of the network functions but it is based only on the study of the network function symbolic coefficients. The new approach allows also the formulation of simple necessary conditions for maximum testability based only on the order of the network functions.<<ETX>>

A new symbolic program package for the interactive design of analog circuits

A new program package which constitutes an environment for the interactive exploration and improvement of analog circuit topologies is presented in this paper. The environment is provided with functionalities which permit the graphical schematic entry of the circuit, the symbolic analysis, the approximation of the symbolic results, the use of an external numerical simulator and the graphical postprocessing of both the symbolic and numerical simulation results. These functionalities allow us to immediately evaluate the influence of both topology and component value changes on the circuit behavior. The result is useful for educational/training purposes and for the interactive synthesis of new high-performance analog circuits.

Automatic test point selection for linear analog network fault diagnosis

A program for the selection of test points in linear analog networks is presented. The program, written in PROLOG, is based on a knowledge base constituted by simple rules derived from experience and heuristic reasoning. It utilizes a program previously developed by the authors which is able to compute network testability, having specified a set of test points. Illustrative examples are given.<<ETX>>

Symbolic Techniques for the Selection of Test Frequencies in Analog Fault Diagnosis

In this work symbolic methods are used for implementing a procedure for the selection of test frequencies in multifrequency parametric fault diagnosis of analog linear circuits. The proposed approach is based on the evaluation of the condition number and the norm of a sensitivity matrix of the circuit under test. This matrix is determined by exploiting the testability and ambiguity group concepts. A Test Error Index (T.E.I.) is obtained which permits to select the set of frequencies which better leads to locate parametric faults in analog linear circuits. A program implementing the proposed procedure has been realized by using symbolic techniques. Examples of application are also included.

A symbolic approach to the fault location in analog circuits

The increased complexity of electronic circuits due to technological improvement has caused the need of always more sophisticated testing and fault diagnosis methodologies. However, while for digital systems these methodologies have now reached full automation, for analog and mixed signal systems there is a lack of efficient and simple methods in this field. The aim of this work is to present a completely new methodology for the parametric fault diagnosis of linear analog circuits. The new method, which is based on the k-fault diagnosis hypothesis and takes into account tolerances and measurement errors, has been fully automated. The automatic fault diagnosis system has been developed by exploiting symbolic techniques, which permit a significant reduction in the computational complexity.