Real time machine tool chatter identification and control system

Chatter in machining processes is one of the most important factors limiting production rates. In order to suppress machine tool chatter during orthogonal cutting processes, a real time active chatter controller is designed and implemented that is able to adapt to the continuously changing machining parameters. An electro-hydraulic servo system is used to control the movement of the cutting tool. The cutting force, workpiece acceleration, and tool displacement are measured in real time. The transfer function of the workpiece is estimated by using the cutting force and the acceleration of the workpiece. All the digital signal acquisition and processing tasks are performed by a digital signal processor (MicroStar DAP3200a/415). The digital controller is designed such that the servo/actuator dynamics is adjusted to match the workpiece dynamics to suppress chatter. To make the controller adaptive to the changing dynamics of the workpiece, a recursive least square technique is used to identify the workpiece dynamics in real time. The estimated workpiece dynamics parameters are then used in the digital controller to calculate a new servo output, thus controlling the tool movement. Simulations show that chatter can be suppressed successfully by using this method. Experiments agree well with simulations.