Method for reducing waveform distortion by increasing damping strength for electromagnetic vibrators

Voice coil motors are frequently used as force drivers in electromagnetic vibrators. As a constant current is applied, the generated driving force is not constant but varies with displacement due to the inhomogeneous magnetic field within the stroke range. When a sinusoidal current is applied to the voice coil motors, the above effect can lead to a severe waveform distortion on the output acceleration. In order to find an effective method to reduce it, a general nonlinear dynamic model has been established and analyzed with a focus on the effect of the damping strength of the vibrator on the waveform distortion. The numerical calculations show that the waveform distortion can be efficiently reduced by increasing the damping strength under various working conditions. Based on these results, an eddy current damper (ECD) was designed with a maximized damping coefficient and applied to our home-made vibrator. Once the ECD is incorporated, the waveform distortion of the output acceleration is significantly reduced, which validates our modeling.