PER4MANCE

The project considers the case of the final assembly lines in aeronautical industry. Such lines are paced i.e. each aircraft must visit all workstations and change its position in a synchronized way between all workstations. Due to technical, economic and financial constraints, usually such lines are characterized by a relatively small number of workstations (<10) and a relatively large number of tasks assigned to each workstation (between 200 and 3500 tasks). Because of this large number of tasks per workstation, the workstation schedule is sensible to frequent uncertain events: delays in the supply of necessary parts, absence of a qualified operator, quality problems, etc. As a consequence, the workstation schedule is constantly challenged and should be frequently corrected in order to respect the takt time constraint. However, the corresponding planning is a hard combinatorial optimization problem. In practice, the optimization of the initial planning may take several working days. As a result, corrective actions are often carried out without global vision and their quality strongly depends on the experience of the manager. In order to improve the current situation, project "PER4MANCE" aims to develop a novel systemic approach based on the idea to combine robustness, flexibility and resilience in the optimization models. Taking into account the available data, the uncertain events can be classified as frequent, less frequent but relatively probable and rare. The systemic approach will be based on different solution methods dedicated to manage the risks associated with these three categories. For the frequent risks, we propose to explore robust optimization models in order to guarantee the stability of the initial planning and minimize the impacts of the uncertain events. For the less frequent risks, flexible planning models will be studied based on intelligent storage of alternative solutions pre-calculated in advance for possible uncertain events. To deal with rare uncertain events, fast and efficient methods for re-planning will be developed in order to bring the system back to a stable state as quickly as possible. In order to improve the working conditions for the operators of assembly lines, the project will also consider the problem of the physical load evaluation for assembly tasks in aeronautic context. Since the existing methods are not adapted for dynamic and flexible work reassignment, a new evaluation method will be developed on the basis of energetical consumption. The obtained information about the tasks strain will be used at all levels of task planning for a more equitable work assignment and for prevention of musculoskeletal disorders. The expected positive impact of this novel systemic approach includes: improvement of the quality of the resource planning and the efficiency of the resource utilization, reduction of the delivery delays and improvement of social conditions for operators and managers by reducing working stress. From the scientific point of view, the contribution will focus on the development of new mathematical models and optimization methods in order to address efficiently hard problems of combinatorial optimization under high uncertainty conditions.