Cutting Depth Compensation Based on Milling Acoustic Signal for Robotic-Assisted Laminectomy

Abstract

To optimize the cutting depth in robotic-assisted laminectomy, we present a real-time method to adjust the preoperatively planned feed rate in the depth direction of the robot cutting trajectory. Not only the linearity between the harmonic amplitude of the milling acoustic signal and the cutting depth is discussed by analyzing the milling dynamic model, but its influencing variables are analyzed. The amplitude of the harmonic components whose frequency are integer multiples of the spindle frequency of the surgical power tool is extracted by FFT (Fast Fourier transform). A digital PD (Proportional-Differential) controller with a dead zone generates the speed compensation amount according to the deviation of the harmonic amplitude from the expected value. In artificial bone sensitivity test experiments, the cutting depth can be estimated with a resolution of 0.15mm within the cutting depth range of 0-1.2mm by the harmonic amplitude signal. Furthermore, the safety of the proposed method under different bone deformations is verified by cutting depth control experiments.