Hierarchical supervisory optimal control design approach for industrial sustainable systems
Creators: name: MANZOCCHI, Diego
Publisher: name: Universit� degli studi di Bergamo
Year: 2015

description: The production landscape is changing. Traditionally, the energy costs represented a small part of the production expenses, meaning that the design of production facilities usually neglected investments in efficient energy usage in favour of more important factors, such as the maximization of production throughput; the energy consumption of factories has been in fact always high, but the cost of energy has increased dramatically in the last decades, pushing the industrial representatives to search for higher level of efficiency. This scenario, however, is changing rapidly. According to the International Energy Agency, manufacturing is responsible for approximately 37% of global primary energy consumption being the largest energy consumer and CO2 producer. Improvement of energy/resource efficiency is the key to reduce environmental impact and is mentioned as driver to reach European 20/20/20 goals. In order to obtain an efficient work and material flow, and achieve such challenging results, an overall optimization of the whole concept of Factory has to be pursued, introducing a new holistic vision of the production environment, with comprehensive interventions acting both at methodological and technological level. During the last decades, pushed by eco-oriented policies and standards, the European manufacturing industries has seen a clear path of introduction of new technologies within the production environment (or on its boundaries) conceived to reduce energy consumption, recycle wastes or filter emissions. However, in the majority of those cases, ?production is still the king? and these systems are regarded mainly as a support function whose objective is to provide additional services to the production unit. Within this situation, in spite of the fact that the activity level of these add-in systems is dependent on the production management of the main process, the energy, waste and emissions considerations are rarely included during design phase or in the planning, scheduling and control procedures. Recently, new technologies have done important steps regarding energy efficiency in terms of mechanisms, actuators and sensors. Complementary to this improvements at component level, considerable savings, with minor efforts for a factory, can also be obtained by introducing new adaptive control architectures, as supervisory optimizers of the pre-existing controllers, able to predict the evolution of the system and consequently modify its current behaviour in order to achieve the same production results but with less energy consumed (remark: energy is considered as the main performance criterion to be optimized, but the techniques are clearly independent from that effectively selected). The main techniques studied and successfully applied in real-case scenarios to perform the adaptive control of a process are usually grouped under the Model Predictive Control (MPC) family, but their implementation in complex, non-linear industrial environments is still limited, and requires the development of ad-hoc engineered solutions. Different implementation of MPC can be found in a wide variety of industrial application areas, including chemicals, food processing, automotive and aerospace with better results than classical control approaches such as a cascade control. Especially, in Iron&amp;Steel industry, can be find application of MPC techniques in the Continuous Emission Monitoring Systems (CEMS or PEMS) (i.e. Pavilion8 by Rockwell-Automation) but almost nothing, for instance, in the Energy Management System (EMS), and in the control of furnaces and related equipment, that represent the most energy intensive elements with respect to the rest of the plant.