Workflow modelling for human–robot collaborative assembly operations

With the advent of Industry 4.0, industries are requested to provide customisation of the products, with a high number of tailored features, which a pure robotic assembly line cannot provide. This suggests using a collaborative and flexible scenario together with the need for workflow modelling architectures. These can handle the communication and interaction among the actors of the workcell to improve the collaboration, making it more fluent, reliable, and able to correct workers’ oversights. Within this scenario, the main contribution of this paper is the introduction of a general library of atomic Predicates that can be combined with a first-order logic allowing to model general industrial assembly processes in human–robot collaboration. Such logics and Predicates allow to model and supervise the workflow, remaining hidden to the operator through an interface that intervenes only when errors have to be notified. The methodology has been validated on a complex collaborative assembly use case, requiring different tools and characterized by components of several sizes and shapes. Predicates have been mainly exploited to recognize human activities, allowing modelling and supervising the workflow.