The Need:

Magnetic gears exploit modulation of rotor magnetic field harmonics to perform gearing operations with only bearing contact between the parts of non-zero relative velocity. A magnetic outer rotor, magnetic inner rotor, and flux modulator operate in concert to either decrease or increase the speed of a shaft while increasing or decreasing the torque of the shaft. The absence of contact between these three moving parts offers distinct advantages over conventional gearing systems, including protection against overload damage, a limited need for lubrication, reduced noise and vibration, and the ability to be directly incorporated into motors and generators. Implementation of magnetic gearing systems may help drive innovation in the field of space travel where traditional lubrication requirements make application in zero gravity difficult. Their limited maintenance requirements indicate that these systems also have potential uses in machines that operate in remote locations such as offshore drilling rigs and large wind turbines. Current magnetic gear configurations, however, generate end-effect losses that contribute to 65%-85% of overall magnetic efficiency losses. There is, therefore, a need for a magnetic gearing system that increases the overall magnetic efficiency and torque transmission by mitigating end-effect losses.

The Technology:

To address this need, researchers in The Ohio State University’s Smart Materials and Structures Lab, led by Dr. Marcelo Dapino, have created a magnetic gearing system which utilizes Halbach array cladding magnets to improve magnetic efficiency. Halbach array cladding magnets are permanent magnetic materials that have a magnetization vector with a non-zero axial component. The permanent magnets of the Halbach array cladding magnets are arranged to focus magnetic flux towards one side of the array. By focusing the magnetic flux axially in this manner, end-effect losses can be significantly reduced such that a greater proportion of flux is preserved and available for torque contribution. Indeed, simulations with a magnetic gear system configured with axial-end Halbach array cladding magnets showed a 10% increase in specific torque output for a machine design of similar size or weight.

Commercial Applications:

• Distributed electric propulsion for manned and unmanned small aircraft. These aircraft are often limited by noise requirements and magnetic gearing could be a useful solution to this problem for novel applications like city air taxis.
• Smaller scale use in automotive vehicles such as gearing for electric seat adjustment.

• Gearing for spacecraft where traditional lubrication requirements make application in zero gravity difficult.
• Gearing for "hard to reach" places which could greatly benefit from reduced maintenance requirements.

Benefits/Advantages:

• A 10% increase in specific torque output compared to conventional gearing systems of similar size or weight
• Significantly reduced end-effects loss in magnetic efficiency
• Reduces the output power needed to generate lift
• Improves efficiency of the drone's power supply
• Torque requirements can be met with less mass, which improves design flexibility and system efficiency
• Torque requirements can be met with a lower volume of magnetically active material which reduces cost of the magnetic gear design

Research Interest:

The Ohio State University laboratory that developed this novel magnetic gear design has expertise in the modeling of magnetic gearing systems for both general and aerospace applications. They specialize in 2D and 3D finite element modeling (FEM), analytical modeling, and representative experiment design for model validation. The lab is focused on design optimization to improve torque and efficiency performance, innovative methods for reduced computation time of magnetic gear models, and experimental design and fabrication of a cladding magnet gear. The lab is open for collaboration on further products and investigational routes.