Estimation of tool position based on vibration sense during robotic bone milling

In order to achieve high safety of the surgery robot, this paper presents a vibration signal acquiring and processing method to estimate the tool position during bone milling process. The dynamic of surgical milling is analyzed theoretically, and then it is proved that the vibration magnitude of the milling device decreases when the burr is close to the bone boundary. During the real milling operation, the vibration signal of the milling device is recorded by an accelerometer. The signal is decomposed into some frequency sub-bands through the wavelet packet transform, and the product of the wavelet energy is calculated to determine whether the cutting tool is located near the boundary between two bones. The proposed method is experimentally verified through the robotic milling operation in in vitro porcine spines, and the experimental results indicates that the product becomes smaller when the distance between the milling location and the bone boundary decreases, so the robot can stop feeding before the burr contacts the boundary, and the proposed method can improve the safety of the surgery robot.