FEMM Hub presents paper on robotic placement of magnets at recent Electric Drives Production Conference

Dr Alexei Winter from Grand Challenge 2.3 recently presented his paper ‘Robotic placement of high-strength permanent magnets for a wind turbine generator’ at the 2021 Electric Drives Production Conference, held virtually from 7 to 9 December.

The research was carried out at the University of Sheffield’s Advanced Manufacturing Research Centre (AMRC) in conjunction with Magnomatics and the Offshore Wind Growth Partnership (OWGP).

Magnomatics are developing a compact, high-energy generator for use in offshore wind turbines. The generator is designed around their magnetic gearbox concept, which uses interacting magnetic poles to translate rotational speeds at high torques. 

This concept uses a substantial number of large, high-strength permanent magnet arrays, which must be placed on the steel hub. The process of placement was previously being carried out manually, and was taking two operators close to one hour to place a single magnet array. Quite apart from the significant danger posed by these magnets to the operators, for commercial reasons a new solution was sought to allow these magnets to be placed more quickly.

The FEMM hub researchers at the AMRC developed a process involving an end effector - a device that is attached to the end of a robotic arm, mounted on an industrial robot - to place the magnet. However, the force generated by a magnet array was predicted by modelling to be greater than five kilonewtons, exceeding the payload of all but the largest (and most expensive) robots on the market.

The AMRC end effector was therefore designed to brace itself against the steel hub, thus isolating the robot from the extreme magnetic loading. Testing was carried out and showed that the magnet arrays could be placed reliably in less than one minute (a 98% reduction in process time), consequently transforming the procedure from a slow, dangerous, manual one to something far more commercially attractive.

Measurements taken during the trials confirmed that the forces generated during placement exceeded five kilonewtons. Most significantly, magnet arrays could be placed using a robot that had a load capacity significantly lower than the force generated by the array, thus allowing smallest, more cost-effective robots to carry out the operation.