Modelling and dynamic analysis of underactuated capsule systems with friction-induced hysteresis

This paper studies modelling and dynamic analysis of underactuated capsule systems exhibiting friction-induced hysteresis. The motion mechanism is novel in utilizing internal centripetal torques generated by a vibration micro-motor mounted on the platform. Up to now, most investigations in frictional interactions towards capsule systems were confined into static or quasi-dynamic circumstance, where it is difficult to facilitate online use and control. It is the first time the dynamic frictional characteristics (non-reversible drooping and hysteresis) are studied towards these systems. An analytical study is primarily conducted to reveal the non-reversible characteristic for the static friction, the pre-sliding regime as well as the pure sliding regime, and the frictional limit boundaries are identified. Subsequently, the studies are mainly focused on dynamic analysis, including friction-driven vibrational responses and qualitative changes induced by control parameter (mass ratio) in capsule dynamics. It is found that the models predict periodic responses for the parameters considered and the average capsule velocity can be controlled through proper tuning of the control parameter around identified control points. The results demonstrate good captions of experimentally observed frictional characteristics, quenching of friction-induced vibrations and satisfaction of energy requirements.