Patent US 3,967,515

A method and apparatus for controlling vibrational chatter in a machine tool operation wherein a workpiece and a tool are mounted in a manner to permit controlled and forced engagement of the tool and workpiece to remove material from said workpiece. A first transducer is spatially disposed from the tool-workpiece interface and generates an electrical signal representative of the applied cutting forces on the workpiece. This force signal is applied to a workpiece movement synthesis circuit for continuous calculation of the workpiece displacement in response to cutting forces and in accordance with continuously updated static and dynamic characteristics of the machine structure and the workpiece. Simultaneously, another transducer on the machine structure continuously provides a tool acceleration signal for use in deriving an electrical signal representing the actual displacement of the tool. The synthesis circuit output signal representing the calculated workpiece displacement is electronically compared with the signal representing the actual tool displacement, with vibrational chatter occurring whenever the two signals are not equal and offsetting. When the two signals are not equal, the differential therebetween is used to generate an error signal for controlling a compensatory force actuator mounted on the machine structure. The compensatory actuator provides forces of controlled magnitude and frequency to the machine structure to offset and eliminate the vibrational chatter.