Containers monitoring through the Physical Internet: a spatial 3D model based on wireless sensor networks

The Physical Internet concept was developed to address the current unsustainability problem of logistic systems. The key elements are the encapsulation and the handling of world-standard smart green modular containers (pi-containers) throughout an open global logistic infrastructure. Logistic processes such as partial loading/unloading or splitting/merging of pi-containers play an important role for a successful Physical Internet. However, the large variety of transformation processes can introduce desynchronisation between the physical and informational flows, i.e. the real composition of a composite pi-container (a set of stacked pi-containers) can differ of the information stored in the supply chain management system. To overcome this problem, this paper proposes a system to generate and maintain automatically a virtual three-dimensional layout reflecting the spatial distribution of pi-containers. The proposed approach uses smart pi-containers equipped with wireless sensor nodes. The relative position of pi-containers can be determined by the neighbourhood relationships between the sensor nodes. From this information, a constraint set is formulated in a Constraint Satisfaction Problem where each solution is a potential loading pattern. The methodology is developed and computational experiments are proposed, as a proof-of-concept. The results show that our proposed method yields quick and satisfactory results.