Pushing the limits of ultrahigh-speed electrical machines.

Acoustic levitation forces can be used to manipulate small objects and liquids without mechanical contact or contamination. This work presents analytical models based on which concepts for the controlled insertion of objects into the acoustic field are developed. This is essential for the use of acoustic levitators as contactless robotic grippers. Three prototypes of such grippers are implemented and used to experimentally verify the lifting of objects into an acoustic pressure field. Lifting of high-density objects (ρ > 7 g/cm3) from acoustically transparent surfaces is demonstrated using a double-sided acoustic gripper that generates standing acoustic waves with dynamically adjustable acoustic power. A combination of multiple acoustic traps is used to lift lower density objects (ρ≤0.25g/cm3) from acoustically reflective surfaces using a single-sided arrangement. Furthermore, a method that uses standing acoustic waves and thin reflectors to lift medium-density objects (ρ≤1g/cm3) from acoustically reflective surfaces is presented. The provided results open up new possibilities for using acoustic levitation in robotic grippers, which has the potential to be applied in a variety of industrial use cases.

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Symmetric multiphase dc-dc converters are widely used in power electronics, as they enable the processing of high power through splitting the overall load-current into multiple phases. Distributing the processed power symmetrically between the phases and performing ripple minimization through interleaving is well understood. However, in recent applications such as maximum power point (MPP) tracking for solar photovoltaic (PV), converters are forced to operate under asymmetric conditions, due to differences in the sources or loads of each converter. This work presents a control technique, based on harmonic elimination, that allows for ripple minimization under asymmetric conditions. The mathematical derivations are outlined and simulations are used to evaluate the performance of the proposed technique. Measurements taken from an experimental prototype, consisting of three dc-dc buck converters, demonstrate significant improvements in ripple reduction over conventional interleaving techniques. When the multi-phase converter is operated at the optimum asymmetric phase-shift found through the techniques presented here, a more than 3x reduction in net current ripple is observed under realistic operating conditions. Additionally, the undesirable first harmonic ripple component is reduced by 14.8 dB with the proposed technique.