Vibration Feedback Control for Robotic Bone Milling

Abstract

Bone milling is commonly performed in many surgical interventions, but it often suffers from unpredictable deflection of the bone and potential damage to critical anatomical structures. In this study, a method is proposed to control the depth of cut based on the milling vibration monitored in real time. An accelerometer is mounted on the surgical power tool to record its vibration. In order to extract characteristic information from the acceleration signal, a quality factor is defined to select the optimal harmonic in the signal. A mapping is then established between the amplitude of the optimal harmonic and the depth of cut measured by a displacement sensor. During automatic milling in a single type of material, the depth of cut is estimated by inputting the current harmonic amplitude into the mapping, and the robot's position is adjusted based on the deviation between the desired and the estimated depth of cut. When the cutting area is located between the cancellous bone and the cortical bone, the depth of cut is calculated based on the mapping for the cancellous bone, the mapping for the cortical bone, and the percentage of these two tissues. Thus, automatic milling is also available in this area. Validation of the proposed method via automatic milling experiments shows effectiveness and stableness of the control algorithm, and the safety and efficiency are ensured.