Delayed Reference Control for Hotwire Cutting of Expandable Polystyrene Foam

This paper presents the ideation and implementation of a 2-axes robotic system for hotwire cutting of polystyrene plates. In particular, since the quality of the cutting process is strongly affected by, among others, the interaction force between the hotwire and the workpiece, an accurate force control is required. The force control module, which is referred to as delayed reference control (DRC) belongs to the category of nontime based controllers. According to the DRC theory, the desired input reference $xd$ is a function of time and a variable, which plays the role of a time delay: $xd(t−T)$⁠. The time delay $T$ is properly calculated on-line according to the measured force signal in such a way to improve the cutting process quality during the interaction phase. DRC theory and its practical implementation on a 2-axes robot are presented as well as an accurate description of the cutting process. In fact, experimental results validate theoretical predictions.