Abstract: For the mechanical vibration tapping machine, it is hard to measure vibration parameter when spindle has rotary vibration as well as rotary motion and axial movement. The major difficulty is to pick up the vibration signals. The torsion vibration signals with changed amplitude and unchanged frequency are obtained by the sine derivative modulation of the constant amplitude. After the modulation, the torsional vibration signals contain the information of vibration frequency and amplitude. By using the virtual instrument technology, vibration frequency and amplitude can be obtained from the modulated signals. Because the measuring range of the displacement sensor is larger than the range of torsional vibration amplitude, a high accuracy of A/D converter is required. The instrument can realize online real-time calibration. By combining the signal modulation technology with the virtual instrument technology, the vibration parameter measurement problem of the vibration tapping machine is solved. This measurement principle is proved feasible by experiments.

Key words: Amplitude, Measurement, Torsional vibration, Vibration frequency, Vibration tapping machine, Virtual instrument