A NEW ONLINE SPINDLE SPEED REGULATION STRATEGY FOR CHATTER CONTROL

A new on-line central method to suppress regenerative chatter vibratio n during the machining process by regulating spindle speed is proposed . The dynamic cutting force signal collected from a dynamometer is pas sed through a low pass filter, and then digitized. The fast Fourier tr ansform is carried out to obtain the corresponding power spectrum. The chatter frequency is identified when the intensity at a certain frequ ency other than the spindle speed and tooth passing frequency exceeds a critical value. Based on the identified chatter frequency, a new spi ndle speed is computed by applying the principle of keeping the phase between the present and previous undulations to 90 degrees. The new sp eed command is executed while the cutting proceeds. It is found from s imulation that the chatter vibration can be suppressed by this approac h in the shortest time. This method is also verified by experiments th rough actual cutting of various materials by a computer numerically co ntrolled milling machine. The main feature of this approach is that th e feed of the machine tool does not need to be halted during the chang e of spindle speed. Hence, tool wear can be reduced. Furthermore, no s ystem identification of the machine tool structure is needed, and ther efore it has great potential in actual applications.