In this paper, we present a novel method for indirect characterization of eddy currents damping and loss coefficients, as well as the equivalent electrical conductivity of metal foams. The proposed method is based in the measurement of the braking torque when the metal foams are exposed to an alternating magnetic field generated by a set of rotating permanent magnets. Measurements are carried out in a low-frequency range (< 50 Hz) and for high amplitude magnetic fields (up to 0.4 T), both typical values observed in electromechanical devices. This method was used for accurate characterization of a set of open-cell aluminum foams with different compositions and porosities. Experimental results, in good agreement with the theoretical models, confirm the viscous damping behavior of aluminum foams in the tested frequency range. The quadratic dependency of the damping coefficient on the magnetic flux density is also confirmed in the measurement range.

A novel concept of a rotary electromagnetic actuator for positioning with ultra-low power consumption is presented. The device is based on harnessing potential magnetic energy stored between permanent magnets facing each other with opposing magnetization polarities. When combined with an active electromagnetic control and passive stabilization system, the rotor of the device can switch between stable equilibrium positions in a fast way with a minimal fraction of the power and energy consumption of a traditional electromagnetic actuator. In this paper, a theoretical model, supported by finite element analysis results, is presented. The actuator has been designed in detail to operate as an optical filter wheel actuator. Calculations demonstrate that the device has the potential to provide a power-consumption saving of up to 86.6% and an energy consumption reduction of up to 58.6% with respect to a traditional filter wheel actuator.

This paper presents a novel rotary electromagnetic actuator designed for high-speed and high-precision positioning with ultra-low power consumption, intended for industrial and scientific applications such as rotary index tables, pick and place robots, or optical systems, among others. The actuator is based on harnessing electromagnetic potential energy and its transformation into kinetic energy to enable accurate and rapid changes between different equilibrium positions of the device. A prototype with an outer diameter of 86 mm and a thickness of 25 mm and a mass of about 0.57 kg has been manufactured and tested. It presents eight equilibrium positions evenly separated to 45 degrees, reachable in just 48 ms with a positioning accuracy of 20 arcmin. Experimental results demonstrate that the device generates a torque of 590 mNm, maximum angular speed and acceleration up to 663 rpm and 14,500 rad/s², respectively, with an input current of ±500 mA and a maximum power consumption of just 6.3 W. This value of power consumption represents a power saving up to 80% when compared to a conventional electromagnetic actuator that reproduces the same motion profile. An energy saving up to 38% is calculated for a change between two adjacent equilibrium positions. This innovative technology provides a new tool for precise positioning in highly dynamic applications with unprecedented energy and power savings.