Acoustic field-mediated robotic manipulation
main / research / acoustic manipulation
The degree of freedom (DOF) in robotic manipulation systems is traditionally closely linked to the number of actuators employed. For instance, moving multiple objects on a surface typically requires at least twice as many actuators as there are objects to achieve independent control. While certain techniques can reduce the number of necessary actuators, this relationship generally holds.
In our research, we have challenged this conventional wisdom by demonstrating that a single actuator can achieve largely independent manipulation of multiple objects. Interestingly, this method can even be driven by musical notes, allowing the organization of a swarm of up to 100 objects into recognizable patterns. Our work has led to the discovery of new motion mechanisms, as well as the development of novel modeling and control strategies, showing that stochastic acoustic fields can be harnessed as programmable media for robotic manipulation.
We have discovered a new motion mechanism on the Chladni plate, expanding the known motion modes on a vibrating plate. The first mode, discovered by E. Chladni about two centuries ago, demonstrates that heavy particles move towards the nodes of vibration. The second mode, also discovered by E. Chladni and later explained by M. Faraday, shows that light particles move towards the antinodes. We have identified a third motion mode, where heavy particles move towards antinodes of vibration on a submerged vibrating plate, forming so-called inverse Chladni patterns.
We have also demystified the long-standing belief in the randomness of particle motion on a vibrating plate before they settle on nodal lines, a misconception present since Ernst Chladni's original experiments in the 1780s. Building on this new understanding, we invented a multi-particle single-actuator acoustic manipulation method. Unlike many acoustic manipulation techniques that rely on potential-trapping, our technology leverages the out-of-nodal-line motion.
Our method enables independent trajectory following, swarm manipulation, and sorting of multiple miniature objects across a diverse range of materials, including electronic components, water droplets on solid carriers, plant seeds, candy balls, and metal parts. To achieve this, we employed both model-based and model-free methods to control the motion. Additionally, we developed a programmable shaping method using a nature-inspired algorithm that can iteratively assemble up to a hundred particles into complex, user-specified shapes on a vibrating plate.
Beyond acoustic manipulation, this work suggests a broader principle for field-mediated robotics: when object motion in a globally actuated physical field is repeatable enough to be statistically modelled, sufficiently fast feedback can convert the field into a high-degree-of-freedom robotic manipulation system. This idea may extend to optical, electrostatic, magnetic, acoustic, fluidic, and air-mediated manipulation systems, and it has directly inspired our later work on airflow field-mediated robotics.
Selected publications:
- Zhou, Q., Sariola, V., Latifi, K., Liimatainen, V., “Controlling the motion of multiple objects on a Chladni plate”, Nature Communications, 7, 12764, 2016.
- Latifi, K., Wijaya, H, and Zhou, Q., “Motion of heavy particles on a submerged Chladni plate”, Physical Review Letters, 122(18), p.184301, 2019.
- Kopitca A., Latifi K., Zhou, Q., “Programmable assembly of particles on a Chladni plate”, Science Advances, 7(39). doi: 10.1126/sciadv.abi7716, 2021.
- Wijaya, H., Latifi, K., and Zhou, Q., “Two-Dimensional Manipulation in Mid-Air Using a Single Transducer Acoustic Levitator”, Micromachines, vol. 10, no. 4, p. 257, Apr. 2019.
- Latifi, K., Kopitca, A., and Zhou, Q., “Model-free control for dynamic-field acoustic manipulation using reinforcement learning”, IEEE Access 8, 20597-20606, 2020.