Levitation Bearing Characteristics of Linear Transportation System Based on Coupling of Acoustic Field and Flow Field

The ultrasonic system interacts with the transported object side to generate a traveling wave acoustic field, driving the object to move. 【Method】The acoustic structure coupling physical field was established using acoustic theory and solved using finite element method. Based on the flow conservation equation, N-S equation, and Darcy's law, the pressure control equation for the flow field region of porous bearings is derived and solved using finite difference method.

Explored the relationship between levitation height and load capacity, and studied the effects of acoustic field gap thickness and traveling wave intensity on the magnitude of traveling wave thrust. An experimental platform for linear transportation system was built for verification. 【Results】The experimental measurement shows that the resonant frequency of the ultrasonic system vibrating plate is 20 kHz, and the vibration mode is bending vibration.

The theoretical calculation result is 20.252 kHz. The new coupled transportation system can achieve the transported object with a unit area load capacity of 1.85 kN/m2. Under a gas supply pressure of 0.3 MPa, the object with a levitation height of 35.7 μm can be suspended, and the calculated levitation height is 38.8 μm. The error is 7.5%.

The max traveling wave thrust generated when the excitation amplitude is 4 μm is 5.6 mN. 【Conclusion】Under the same gas supply pressure, the load capacity decreases sharply with the increase of levitation height. At the same time, with the increase of permeability of porous materials, the load capacity is enhanced. As the thickness of porous materials decreases, their load capacity becomes stronger.

The thrust exhibits periodic changes over time, with the average thrust varying with the excitation amplitude and acoustic gap thickness. The average thrust is negatively correlated with the acoustic gap thickness, and as the acoustic gap thickness increases, the average thrust weakens. The average thrust is positively correlated with the excitation amplitude, and with the excitation amplitude increases, the value of the average thrust also increases.