Harmonic drives are profusely used in aerospace mainly because of their compactness and large reduction ratio. However, their use in cryogenic environments is still a challenge. Lubrication and fatigue are non-trivial issues under these conditions. The objective of the Magnetic-Superconductor Cryogenic Non-contact Harmonic Drive (MAGDRIVE) project, funded by the EU Space FP7, is to design, build, and test a new concept of MAGDRIVE. Non-contact interactions among magnets, soft magnetic materials, and superconductors are efficiently used to provide a high reduction ratio gear that smoothly and naturally operates at cryogenic environments. The limiting elements of conventional harmonic drives (teeth, flexspline, and ball bearings) are substituted by contactless mechanical components (magnetic gear and superconducting magnetic bearings). The absence of contact between moving parts prevents wear, lubricants are no longer required, and the operational lifetime is greatly increased. This is the first mechanical reducer in mechanical engineering history without any contact between moving parts. In this paper, the test results of a −1:20 inverse reduction ratio MAGDRIVE prototype are reported. In these tests, successful operation at 40 K and 10⁻³ Pa was demonstrated for more than 1.5 million input cycles. A maximum torque of 3 N·m and an efficiency of 80% were demonstrated. The maximum tested input speed was 3000 rpm, six times the previous existing record for harmonic drives at cryogenic temperatures.

In this paper, a noncontact linear positioner based on superconducting magnetic levitation for high-precision positioning has been tested under cryogenic conditions (~20 K and ~10 ^-6Pa). The prototype is able to achieve submicrometric positioning resolution of 230 ± 30 nm RMS along a stroke of ±9 mm length with a current resolution of 15 μA, and a peak current requirement lower than ±500 mA. In addition, it was demonstrated that an open-loop control strategy could be used for positioning the moving part with the accuracy of the order of 1 μm. On the other hand, deviations of the slider position were found to be ±650 μrad for the pitch, lower than 100 μrad for the yaw, ±2000 μrad for the roll, and ±4 μm for the lateral run, all of them related to a full stroke motion. These results reveal a good performance of the device and demonstrate the potential of a new tool for applications, where high-precision positioning is required within a long range in cryogenic environments like far-infrared interferometry.

When an electrically conductive material is exposed to time-varying magnetic fields, eddy currents are generated inside the conductor which oppose the change in the magnetic field. When eddy currents circulate through the conductor they are dissipated in form of heat due to the resistivity of the material. For low frequency vibrations, eddy current damping force is proportional to the vibration speed. Therefore, damping of vibrations at low frequencies or displacement amplitudes becomes increasingly difficult using this technology. Typical damping densities of eddy current dampers range between 0.1 for most devices and 2 MN s m ⁻⁴ for best-in-class prototypes. Those values are relatively low compared with, for examples, hydraulic dampers that can reach up to 4 MN s m ⁻⁴ . This low density limits potential applications of the technology. In addition, certain applications like vibration isolation of aircraft engines may require the damper to operate at high temperatures. However, most of current damping solutions are rarely effective at temperature higher than 100 °C because they frequently use NdFe magnets. In this paper, a passive eddy current damper with enhanced performance for use in high temperatures is presented. The Z-Damper takes advantage from impedance matching inside a magnetic linear gear to amplify the input vibration motion, maximizing the effectiveness of an integrated eddy current damper. SmCo magnets and high temperature components are used in the Z-Damper, potentially enabling operation in a wide temperature range. A theoretical model describing the dynamic behavior of the Z-Damper is presented and a set of experiments were conducted to evaluate its performance. A prototype of the Z-Damper has been designed, manufactured and experimentally demonstrated in a temperature range from 25 °C to 200 °C under low frequency (up to 60 Hz) harmonic excitations. A maximum equivalent viscous damping coefficient of 35 Ns mm ⁻¹ , measured at 200 °C, has been achieved. A damping density of 8.4 MN s m ⁻⁴ is calculated.

Although forces between magnets and superconductors have been profusely studied in many previous papers, little attention has been paid to calculations or measurements of the torque exerted. In this paper, we focus on the equilibrium orientation of a magnet when it is levitating over a superconductor and present measurements for different positions and configurations. We compare these measurements with values predicted by our proposed local model. Agreement between predicted values and experimental values demonstrates that the model is useful for calculating torques in addition to forces. The angle of equilibrium varies along the path over the superconducting cylinder. Therefore, shape and size determine the angle of equilibrium of the magnet.