Pergamon 0967-0661(95)00063-1 Control Eng. Practice, Vol. 3, No. 6, pp. 805-812, 1995 Copyright © 1995 Elsevier Science Ltd Printed in Great Britain. All rights reserved 0967-0661/95 $9.50 + 0.00 INTELLIGENT SENSOR: OBJECT APPROACH D. Luttenbacher, S. Roth, M. Robert and C. Humbert Centre de Recherche en Automatique de Nancy, CNRS URA D821, Universit~ Henri Poincar~ Nancy 1, ESSTIN, 2 Rue Jean Lamour, 54500 Vandoeuvre, France (Received March 1994; in final form December 1994) Abstract: By way of introduction, the first section of this paper is about the need for models to represent the intelligent sensor (IS) concept. In the second section, the benefits brought by the use of Object Approach are discussed. The third section gives a brief description of the chosen method, the OMT methodology. In section four, an application example is proposed to illustrate an approach for modelling intelligent sensor measurement activity. Finally, as a conclusion, the requirements are shown for reaching the final objective of this work, the design of a CAD tool to provide more assistance for IS design. Keywords: Intelligent sensor, computer-aided design, object approach, Object Modelling Techniques (OMT) 1. INTRODUCTION Smart or "intelligent" sensors are becoming a reality in process control and industrial production systems. In the eighties, the demands for reliable measurements, expressed by engineers, led them to seek solutions that would no longer allow one to systematically put the blame on the sensor whenever a problem arises (Ciame, 1987). It is obviously the progress made in the related fields of microelectronics and microcomputer engineering, in association with the development of microprocessors, micro controllers or digital signal processors, that underlie the recent developments in the field of intelligent sensors (IS). Once they have been integrated in automation systems, then it is not so easy to connect a classical sensor, because intelligent instruments must be able to collaborate and to co-operate in order to make up a real distributed database, which must contain consistent information. It is therefore necessary to build models for IS to define as precisely as possible the services offered, the kind of information they are able to produce or consume, and their behaviour, in order to achieve interoperability (Robert et al., 1992; 1993a; 1993b). From a constructor or vendor's point of view, an approach to the construction of a piece of equipment where only the designer is involved, expressing how to "technologically" realise the equipment, cannot be satisfactorily applied to the realisation of an IS. This will result in a device which offers a certain number of services to the user, but not necessarily those which are really required. The construction should be based on standards, but as these do not yet actually exist, the design of an IS could be undertaken according to Reference Models. In this paper the proposed Object Approach (OA) is shown to be suitable to formalise the IS concept, and to build evolutionary models. 2. OBJECT APPROACH: LIFE CYCLE The main reasons for choosing the object paradigm for modelling the IS concepts are presented in this section. Figure 1 describes the thought processes involved in modelling. In software engineering, the traditional description of the software life cycle is based on a underlying model, commonly referred to as the "waterfall" model (Boehm, 1976). This model initially attempts to discretise the identifiable activities within the software development process as a linear series of actions, each of which must be completed before the next is begun. Any graphical representation of the object-oriented version of the overall software development life cycle must take into account the implicit high degree of overlap and iteration. Rather than using a revised waterfall model, the "Fountain Model" of Fig. 1 seems to be appropriate (Henderson-Sellers et al., 1990). The life cycle thus grows upward to a 805