Abstract
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.
Highlights
Electromagnetic vibration platforms have been widely used in testing the dynamic performance of inertial sensors,1–4 such as measuring the frequency-dependent transfer functions and cross coupling effects of accelerometers. These platforms are usually constructed as forced oscillators, and voice coil motors are frequently utilized as force drivers for convenience
One of the most important is the variation in electromagnetic force within the stroke range though the current fed in the voice coil motors is kept constant
Comparative tests showed that the waveform distortion can be significantly reduced when the vibrator’s damping strength increases with eddy current damper (ECD). These findings provide an additional technological choice for solving the problem of waveform distortion, which is generally valid for the nonlinear electromagnetic vibrator and requires neither parameter adjustment nor detailed modeling analysis
Summary
Electromagnetic vibration platforms have been widely used in testing the dynamic performance of inertial sensors, such as measuring the frequency-dependent transfer functions and cross coupling effects of accelerometers. Li and Shang clarified various nonlinear mechanisms, including the inhomogeneous magnetic field, the imperfect suspension system, the mechanical damping, and the power amplifier for low-frequency electromagnetic horizontal vibration platforms He et al. presented a novel closed-double-magnetic circuit to achieve high and uniform magnetic flux density in the air gap of a long-stroke horizontal electromagnetic vibration exciter. Comparative tests showed that the waveform distortion can be significantly reduced when the vibrator’s damping strength increases with ECD These findings provide an additional technological choice for solving the problem of waveform distortion, which is generally valid for the nonlinear electromagnetic vibrator and requires neither parameter adjustment nor detailed modeling analysis
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