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1.2 CAD-type tools: modern trends

The increasing use of computers in engineering activities has originated the apparition of numerous packages or frameworks especially conceived to facilitate engineering developments. Some reasons for extensive application of computers in engineering decision and design problems are quite obvious; computer aided tools make the work of engineers both easier and faster. This means that increasingly more complex engineering problems become solvable in reasonable short time, while the effort devoted to solve these problems remains limited mostly to some conceptual work. Some other reasons include the necessity of improving the of quality of engineering solutions, including robustness, reliability and safety and lowering down the cost of manpower spent on developing particular solutions. Moreover, the systems developed with use of computer software can easily be simulated, analysed and reused.

Because of these reasons, the acronym CA (Compute Aided) has been used as a prefix for designing software packages developed to assist engineering tasks. Some principal areas of interest in applying computers for assisting engineers include domains as:

CAD - Computer Aided Design.
CADS - Computer Aided Decision Support, also known as DSS - Decision Support System.
CAE - Computer Aided Engineering.
CACE - Computer Aided Control Engineering.
CAM - Computer Aided Manufacturing.
CASE - Computer Aided Software Engineering.
CACSD - Computer Aided Control Systems Design,

The application of computers becomes more important in everyday engineering activity. Particularly, control engineering community has been actively pursuing avenues for supporting multi-disciplinary design activities for several years. Consequently, the research activity in this field has been increased to support design, implementation and maintenance of control projects. CACSD packages have been developed following these lines. They incorporate representation, analysis and design facilities. Therefore, these packages are dotted of friendly user interfaces, representation capabilities and a wide number of numerical algorithms (modelling and simulation capabilities) to facilitate control systems design, test and validation.

Nowadays, control engineers activities in the industry are not only reduced to control systems design but their activity must also take into account all process behaviour, especially when dealing with complex systems (non-linear, coupled, time dependent, etc.). In such cases, control and process engineers must work together to ensure global quality, safety and reliability in both, product, and process behaviour. This is process supervising. From the control engineers point of view supervisory task consists in closing a high level control loop. Supervisory systems will be designed to observe the process (process measures, visual observations, indices and so on), to decide about its behaviour according to a template (predefined normal operating conditions) and to perform or suggest specific actions (control reconfiguring, set point change, etc.) when necessary. The complexity in designing supervisory systems makes necessary the use of all available information about instantaneous process behaviour. Process measures given by sensors, estimations obtained from models (numerical or qualitative) and expert knowledge obtained from operators and process engineers, must be merged to perform supervisory strategies in the best way. Thus, Expert Supervision is used in this text to design such supervisory strategies that take benefit of expert knowledge about process behaviour.

Following this line, control engineers working in the domain of supervisory systems are also needed for specific software packages to assist their activities. This thesis puts forward several particular solutions in this relatively new area, i.e. Computer Aided Supervisory Systems Design- CASSD.