Multi-particle acoustic manipulation on a Chladni plate

Abstract

Abstract-Controlling the motion of multiple miniature objects independently and simultaneously is a grand challenge in microrobotics. In this paper, we report our recent achievements in acoustic manipulation that can control the motion of multiple objects simultaneously and independently on a centrally actuated vibrating plate. By employing spatially highly nonlinear excitation fields on the plate, we can control the motion of multiple objects with relaxed properties. The paper reports the modelling of the excitation fields, open-loop control based on pre-calculated control sequence, and closed loop control using model predictive control (MPC) and linear programming methods. The experimental results show that with appropriate planning, object motion on vibrating plate is sufficiently predictable to be controlled even in open-loop. The experimental results with closed-loop control show that the methods allow various applications including trajectory following, particle assembling, and droplet merging. Despite the reported method is based on acoustic manipulation on a Chladni plate, the method can be extended to other energy fields as soon as they are spatially highly nonlinear and such nonlinearity can be excited.

Rapid mode-switching for acoustic manipulation

“…We have successfully shown controlled manipulation of sub-mm objects on predefined trajectories on the plate. The method is applicable to other types of particles with different shapes and materials, similar to the ones reported in [3], [15]. The high-speed switching methodology can also be applied to other dynamic-field acoustic methods, such as SAW devices, acoustic levitators, and in-fluid acoustic devices.…”

“…Additionally, we experimentally show that the modeswitching is performed faster than the time constant associated with the particle motion in our device. Here the highspeed controller enables rapid mode-switching with a short delay of approximately 2 milliseconds, almost two orders of magnitude faster than our previous implementation [3], [15].…”

“…We have implemented a closed-loop control scheme to plan and control the motion of a particle on the plate [15]. We use a camera to capture the top-view of the plate, and repeatedly measure the position of the objects on the plate.…”

“…In our previous works [3], [15], the closed-loop controller performed multiple computational processes in series including the image processing, particle detection, control optimization, and signal generation. This resulted in a relatively long computational process of approximately 500 milliseconds, allowing merely pulse-based excitation of the system.…”

“…In this paper, we suggest employing a high-speed controller to minimize the switching time. We apply such idea to a centrally-actuated vibrating plate, commonly referred to as a Chladni plate, which is a classic acoustic manipulation device [3], [15]. In our device, the high-speed controller calculates the best mode to play, and switches the frequency accordingly.…”