Active Structural Control of Vertical Turning Lathe Vibrations

An active control system has been developed to suppress tool vibration on a Vertical Turning Lathe (VTL). This system reduced surface roughness by two-thirds and raised by 23% the metal removal rate achievable before the onset of chatter. The system mechanical and sensor portions are contained completely within the VTL ram envelope. The electronic components are in a separate enclosure which also provides a simple user interface. Accelerometers embedded in the VTL ram sense the ram motion in two directions. Signal conditioning and integration electronics pass the ram velocity to the digital controller which computes the forces needed to reduce the tool tip motion error. Control signals are input to highly-efficient switched-capacitor amplifiers which drive high-force electrostrictive actuators to deliver the required forces in two directions. The controller also executes the system identification programs and tracks the ram length to compensate for resonance changes.