Analytical modelling of air-gap magnetic field of surface mounted permanent magnet motors for drones

Drones -- small (or not so small) remotely controlled flying devices -- are seeing rapidly increasing use in many fields of application and human activities ranging from recreation, competitive sports, last-mile logistics, espionage, exploration, to media production, and even warfare. The abundance of these devices brings with it the risk of them becoming an audible nuisance due to the high pitched noise produced by their surface-mount (SM) PMSMs. The acoustic noise produced in these motors is the product of multiple factors, but chief among them is the vibration of the motor's external shell, which is the stator for internal rotor type motors and the rotor for external rotor type. This shell vibrates in various oscillation modes as a result of the magnetic forces acting on it, which are an inevitable result of the motor's internal magnetic field and the armature currents that produce them. This motivates research effort into reducing this noise through modulation or control strategies employed by the inverter powering the motor. In order to develop a control model, first the motor itself must be understood. In this thesis, the electromagnetic aspect of surface-mount-PMSMs will be developed, i.e. an analytical model will be established of the air gap magnetic field in SM-PMSMs. First, the armature reaction field for arbitrary winding types will be derived, followed by a detailed derivation of equations typically used to model the rotor magnets in SM-PMSMs. A derivation of the effect of stator slotting on the air gap magnetc field will be provided, and concluded with a combination of the three previously mentioned aspects, and the dimension of time will be incorporated in the model. Accompanying this thesis will be a set of MATLAB code that will be made publicly available for research and instruction in academia.
Electrical Engineering | Electrical Power Engineering