Mechatronic piezo mechanisms for active vibration control

Inhalt:
The current trend in the market to solve long boring bar related chatter problems are passive dampers integrated in the boring bar, which has derived in patents [1] and commercial products [2]; This solution, however, is not feasible in very slender bars or trepanning operations, due to small space available in the tool. Active damping has been tested and industrialised in different applications, including machine tool structures, but never in internal turning tools. The application of active damping on boring bars has been proposed in several researches [3] but its industrialisation has not been tackled yet due to its technical complexity. To address this issue, specific piezoelectric actuators were developed for diameter 32x10Dmm boring bars. Indeed, such slender tool holders can usually not perform conventional manufacturing without an integrated damping device because of the chatter vibrations. The dynamic of those boring bars was studied using FRF analyses and the piezoelectric actuators were appropriately designed so that they provide maximum force to volume ratio at the system resonant frequencies. One of the main challenges is to properly control the actuators to damp the first vibration modes of the boring bars without exciting higher frequencies. Two active damping concepts were investigated: - Bending force damper based on PPA20M piezoelectric actuators from Cedrat Technologies; - Two axes proof-mass piezoelectric actuator PM35XS based on a different configuration than the preloaded PM150M presented in 2018 [4]; For both designs, appropriated accelerometer sensors were chosen to measure the boring bars dynamics and to close the control loop with on-the-shelf controller UC55 from Cedrat Technologies.