Modelling of continuous dragline formation in a mobile robot

A dragline-forming technology has been previously proposed to enable locomotion through an open-space where no solid surfaces present. The technology is intended for situations where payload requirements are unanticipated. In those situations, variability in dragline's diameter can minimize the use of material hence increase self-sufficiency of the robot. In a previous study, a robot was designed, prototyped and proven to be able to descend through an open-space by forming a thermoplastic dragline with a diameter range of 1.1-4.5 mm. However, the speed of locomotion was rather low due to the lack of an adequate control method for thermoplastic dragline formation. In this paper, models of mass flow and thermodynamics along dragline formation pathway are presented. The models are validated in a newly prototyped robot which forms a dragline continuously. Experiment results show that, when compared to the previous prototype and control method which consists of repeated sequences of discrete events, the speed of descending locomotion is significantly increased and reaches 12.0 cm/min.