Acoustic Levitation apparatus (Robotics Practicals)

The following data contain the information and files, which are required to recreate and build the experimental setup that is described in the Laboratory manual. Further details can be found in the associated publication “A graduate laboratory experiment to study the dynamics of an acoustically levitated particle” (DOI: 10.1088/1361-6404/acf0a4). Laboratory manual - Introduction Standing wave acoustic levitation is achieved by generating forces that counteract gravity to trap objects steadily in mid-air. The forces that counteract gravity are called acoustic radiation forces. They emerge due to acoustic radiation pressure, which is the pressure impinging objects in acoustic fields. Due to nonlinear phenomena, the time-averaged components do not cancel out, and apply constant forces that counteract gravity. This result is not trivial, since acoustic waves are harmonic (i.e., sinusoidal), and the time average of a sinusoid is zero, which leads to zero acoustic radiation forces. However, in the following experimental setup, the acoustic pressure and frequencies are high enough, such that the acoustic wave is no longer harmonic, and as a result, particles can be trapped in mid-air. Acoustic levitators are being used as robotic end-effectors to handle delicate objects while avoiding contamination. Acoustic levitators have an inherent limitation when it comes to the speed of manipulation. The levitators create axisymmetric acoustic traps, where, they generate strong trapping force in the direction counteracting the gravity (z), whereas the force is considerably lower in the radial direction (r). As a result, when the robotic arm translates in any direction other than z, it can only do it relatively slowly without dropping the trapped object. To overcome this limitation, an angular (θ) degree of freedom was introduced, such that the levitator is tilted while translating (u). In this laboratory session, graduate students are asked to characterize such a system, and develop an open-loop control strategy based on numerical simulations. The system consists of two acoustic ultrasonic transducers to generate the acoustic traps, two stepper motors to control the translation and rotation of the levitator, a camera for tracking the object and the levitator, a signal generator to excite the ultrasonic transducers, a microcontroller, and a workstation. {"references": ["Amit Dolev et al 2023 Eur. J. Phys. 44 065801 (DOI: 10.1088/1361-6404/acf0a4)"]}