More economical mobile respirator thanks to better modelling

Respiratory systems had, until recently, been bulky devices based on large respirators that were only found in hospitals. In the past few years the first portable ‘lung-support systems’ came on the market. These contain very small but ultrafast spinning respirators that give patients more mobility and independence. Low battery consumption is, of course, a highly desirable feature to enable the respiratory system to run for an extended period. But there had not been any easy solution to designing the ultrafast mini-electrical motors for these respirators. Sultan Jumayev, a PhD researcher at Eindhoven University of Technology, therefore came up with models and a design procedure that can predict quickly and accurately the behavior of such electric motors. The first prototype that he developed was already up to ten percent more energy-efficient than its predecessor. Jumayev receives his doctorate on 1 June.

The electric motors contain a stator with a slotless winding and rotor with permanent magnet. The interaction of the fields created by the winding and permanent magnet create torque to drive the respirator. Traditionally, the windings consist of several individual coils but for small motors with a high rotational speed, it is beneficial to have a single continuous coil around it. These windings are then subject to less torque ripple since there is no fluctuation in the magnetic field and this, moreover, leads to less noise. An additional benefit is that production can be automated and, as a consequence, cheaper. Such a motor is called a ‘high-speed slotless permanent magnet machine’.

Various three-dimensional designs are possible for winding the single continuous coil around the rod, each causing a different electromagnetic behavior in the motor. Sultan Jumayev developed models that accurately predict what this behavior will be, for example power consumption, and how this behavior is influenced by different methods of power electronics control. Moreover, Jumayev’s models are quite a bit faster than the current 3D finite-element models. With the winding process being a key aspect of the price of an electric motor, he had to take account of the production costs, and some winding designs are easier and cheaper to realize than others.

What makes the task more complex is that the small electric motors often do not spin with constancy but are very dynamic in their use. The prototype developed by Jumayev on the basis of his models is a good example of this. One moment the rotational speed is 80000 to help a patient breathe in, and the next moment is low to allow the patient to breathe out. On top of that, different kinds of patients must also be able to use the respirator, from the older patient to premature babies. He managed to make a prototype that covers this entire spectrum and uses less power than the motor already produced by the manufacturer where he did his research.

Jumayev expects the manufacturer, the Dutch company Demcon, to use the results of his PhD study to design faster and better ‘high-speed slotless permanent magnet machines’, for instance for respiratory systems.

The doctorate award for the Turkmen researcher is a double award. Not only is he the recipient of a PhD from Eindhoven but also from Lappeenranta University of Technology in Finland. Jumayev did his PhD study in the Electromechanics and Power Electronics group of professor Elena Lomonova. His thesis is entitled ‘High speed slotless permanent magnet machines: modeling and design frameworks’.

Sultan Jumayev is the 5000th PhD student of TU/e to be awarded his doctorate. The first was in 1959.