Precision Motion Control using Nonlinear Contact Force Model in a Surgical Device.

Otitis media with effusion (OME) is a common middle ear disease in children. The Ventilation Tube Applicator is an ear surgical device to treat OME by inserting a grommet into tympanic membrane (TM). This grommet insertion process requires very delicate control to minimise trauma to the TM and to ensure that the grommet is successfully inserted. This paper introduces a precision motion controller using Hunt-Crossley contact force model to provide a good prediction of the force on the TM during the insertion process. This predicted force was used to reject the disturbance in the motion control scheme and resulted in tremendous improvement in precision and accuracy. The maximum absolute tracking error of the motion controller was reduced by up to 29%, and the root mean square error was reduced by up to 43%. This novel use of a nonlinear contact force model has been proven to work well and can be considered for other robotic surgeries that involves contact and requires placement accuracy.