Experimental Investigation On Stability Analysis Of Acoustically Levitation And Sound Field Optimization

Near Field Acoustic Levitation (NFAL) is a phenomenon which use a high energy density ultrasonic acting on the surface of an object which has a small areal density and levitating it in a distance less than a wavelength. But Near Field Acoustic Levitation technology is immature. The levitation process is not stable. It limits the technology apply in the practical manufacturing. In this paper, based on experiments, studied the stability of Near Field Acoustic Levitation and the factors that can affect it. Two methods was proposed to improve the stability of the levitation. A modeling method about restoring force was also presented. And makes a quantitative evaluation.Analyzed the squeeze film between the vibration plate and levitated disk. We have built a model of the squeeze film. According to the model, we can get a distribution law of internal sound pressure produced by the film. The model also contains vibration speed of air molecules in two directions and the laminar flow in the film. Theoretical analyzed the restoring force acting on the levitated object by analyze the laminar film and the potential of levitated object obtained from the sound field. We pointed out the maximum eccentric distance for stable levitation. It is a very important theoretical basis.We suggested apply optical method to track the motion of levitated objects. Also, a motion capture device was designed and made. By using voluntarily compile software, the displacement information was extracted and processed. With those data we can make a accurate describe of the levitated objectThe connection of movement state and the location of the levitated object was built in this paper. We calculated the restoring force acting on the levitated object and found the change rules of the restoring force. According to the hysteresis characteristics of the system. We have built theoretical hysteresis models of the restoring force acting of the levitated object. Based on the model the quantitative analysis of levitated stability has done. This model connect theoretical researches and experimental studies of Near Field Acoustic Levitation. Offering a method study the experimental phenomena with theoretical studies, and providing experimental supporters for theoretical study.By qualitative analysis of the relationship between acoustic viscous force, local potential and the distribution of the vibrator, We proposed two optimization methods for sound field by changing the vibration distribution and the surface shape of the vibrator. Based on the two optimization methods, two horn which was design and made. We measured the sound pressure of the optimized sound field. We proved the optimized sound field can produce stronger restoring force by analysis it’s restoring force model.