Ph. D. Project
Characterization of the health status of waste products for the management of the waste regeneration process
2020/10/05 - 2024/08/31
In recent years, companies have sought to comply with the requirements of sustainable development by contributing to a circular economy. The objectives of the circular economy are to produce goods and services while strongly limiting the consumption and waste of raw materials and non-renewable energy sources and to close the life cycle of products, waste, materials and energy for reuse. In this context, the industrial ecology strategy[1] assumes that sustainability is due to the cyclicality of ecosystems.
The context associated with industry 4.0 is a context where customer demand is characterized by a strong need for product customization within a very short time frame: we talk about mass customization. In addition, the useful life of products tends to decrease, particularly through fashion effects. Combined with this observation, the scarcity of resources and the increase in waste make the need for eco-responsible production systems more and more important. Thus, to enhance the value of the huge deposits of products (consumer or industrial) at the end of their life, it is important to offer more efficient solutions than just material recovery. Other value chains for end-of-life or obsolete products can be envisaged through the industrialisation of the regeneration process, as can be seen in the mobile telephony or automotive sectors, for example, induced by the 2015 Energy Transition Act.
Regeneration[2] can be defined as a set of actions, natural or technical, to restore the regenerated product to a state considered acceptable (functional and operational)[3][4]. We carried out initial work as part of L. Diez's thesis, which formalized the regeneration activities[5].

In order for regeneration to be most effective, it is necessary to create an ecosystem between the three stakeholders: suppliers of waste_products, regenerators and consumers of regenerated products. This ecosystem can operate in two modes: pushed flows or flows from waste products. In the first case of push flow, waste_products can arrive at any time at the regenerators, who must then regenerate them to meet the needs formulated by their customers. Although this mode is the most widely used, there are two major difficulties: (i) difficulties in being provided in a constant time, quality and quantity, (ii) difficulties in selling stocks of undemanded nutrients at any given time. To meet these difficulties, it is possible to switch to pull flow where regenerators receive customer needs and they will seek suppliers or even impose requirements on the waste products to be recovered.

Thesis problem and scientific questions :
In this thesis, we aim to help regenerators/producers to define the regeneration process and more specifically the possible regeneration alternatives to be put in place according to the state of health of the waste_products. To do this, several questions arise:
- What are the criteria that specify a health status of a waste_product for regeneration?
o What useful information should be retrieved on the different life phases of the product to be regenerated?
o How to establish the health status of the product from the health status of the subassemblies or components? and conversely, how to project the health status of the subassemblies or components from the health status of the waste product and the steps in the regeneration process?
- How to determine the different regeneration alternatives according to the health status of the waste_products?
o What are the different possible actions in regenerators?
o What are the criteria for evaluating a regeneration action?
o What are the different possible alternatives for regenerating a waste product?
o How to evaluate the impact of an alternative on production / regeneration flows? How to economically evaluate regeneration alternatives?

In order to answer the questions identified, the work carried out in this thesis will focus on the following points:
- Identify and quantify/qualify the health status of waste products: The definition of a regeneration solution will use the health status of waste products as an input. This involves defining the components of the health status of waste products composed of different sub-assemblies and components, each with its own health status. The work of the SdF-PHM2 project on the state of health of means of production will be exploited and adapted to the problem.
- Identify and quantify/qualify the properties of regeneration actions: Regeneration consists of several actions: several diagnoses at different levels, decomposition of the waste products and recomposition into regenerated products. For each step, it is necessary to specify each of them and to specify the criteria that will allow the different alternatives to be compared.
- Model the transformations undergone by the waste product during regeneration to propose an approach for evaluating regeneration alternatives. In order to choose a regeneration solution, it is necessary to model the impact of the decomposition choice on the recomposition choice[6]. This modeling should present (i) the hypotheses on the health status of the subsets (probability of what is expected to be found at the n-1 level), (ii) the interactions between the models. The tools envisaged stochastic automatons, formal verification
This thesis is part of the current reflection of the PROGRESS 4.0 platform that we wish to set up at the AIPL. This platform will be used as a case study.
Circular economic, industrial regeneration, health status, modelling, evaluation, diagnosis
Modeling and Control of Industrial Systems