Drilling of bone: a robust automatic method for the detection of drill bit break-through

The aim of this investigation is to devise a robust detection method for drill bit breakthrough when drilling into long bones using an automated drilling system that is associated with mechatronic assisted surgery. This investigation looks into the effects of system compliance and inherent drilling force fluctuation on the profiles of drilling force, drilling force difference between successive samples and drill bit rotational speed. It is shown that these effects have significant influences on the bone drilling related profiles and thus on the detection of drill bit break-through. A robust method, based on a Kalman filter, has been proposed. Using a modified Kalman filter, it is possible to convert the profiles of drilling force difference between successive samples and/or the drill bit rotational speed into easily recognizable and more consistent profiles, allowing a robust and repeatable detection of drill bit break-through.