Mode Decoupled Cutting Force Monitoring by Applying Multi Encoder Based Disturbance Observer

High-precision and wideband sensorless cutting force monitoring is one of the important technologies for tool condition monitoring. Particularly in milling, not only the fundamental frequency component of cutting force, but also harmonics need to be monitored, because they could result in the development of chatter. In this study, a process monitoring technique was proposed by the estimation of cutting force components in rigid body mode and vibration mode coordinate systems independently, which was based on multi-encoder based disturbance observer. From milling test results, cutting force including higher harmonics components yielded accurate estimation in the vibration mode without exciting the components that are closer to the resonance frequency.