Three-dimensional vibration measurement based on magnetic levitation effect

A magnetic levitation ball system model was designed. The magnetic force that magnetic levitation ball bears was measured under fixed current and changing displacement. The dynamic equation of magnetic levitation ball movement is deduced. The shell of magnetic levitation ball system model joins up with the vibrating object under test rigidly in the test experiment. A photo-electric sensor is used to measure the relative displacement between the shell of the system model and the magnetic levitation ball, and three-dimensional vibration signals are obtained. Standard vibrator test verifies that the maximum absolute error is ± 0.3 Hz and relative error is between ± 1.5% and ± 0.25% for frequency below 120 Hz, the maximum absolute error is ± 1 Hz and relative error is between ± 0.83% and ± 0.02% for frequency between 120 Hz~5 kHz. Because magnetic levitation ball suspends in the air and the system does not have any pasted sensor, the effects from other directions do not exist. The system has excellent frequency feature and the features at different directions are the same. The system sensitivity is high. This method has better characteristics than traditional vibration measurement methods.