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.
We report a single transducer acoustic levitator capable of manipulating objects in two-dimensions. The levitator consists of a centrally actuated vibrating plate and a flat reflector. We show that the levitation position of the object depends not only on the vibration frequency, but also on the tilting angle between the plate and the reflector. Additionally, new levitation positions can be created by actuating the plate with a composite signal of two frequencies using frequency switching. Based on recorded levitation positions, such single transducer acoustic levitator can manipulate a cluster of levitated microspheres in predefined trajectories, with mean position error of 155 ± 84 µm.
The 27 th May 2006 Yogyakarta earthquake caused more than 5500 casualties and hundreds of thousands of non-engineered buildings collapsed. It is necessary to investigate the seismic intensity, ground acceleration and building damage index. Direct site investigations to collect the severity distribution of objects, humans and environments have been done. The result of the investigation shows that in general isoseismic lines are in-line with Opak fault, the proposed attenuation relationship for seismic intensity and horizontal ground accelerations are matching well with previous research results and the distribution of the building damage index has a similar pattern with isoseismic lines.
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