Design Optimisation and Prototyping of an Outer Rotor Variable Reluctance Resolver for Position Detection in Electric Aircraft

Abstract

Outer rotor motor configurations are increasingly used in electric aircraft due to their high torque capacity and suitability for vertical take-off and landing applications. Accurate rotor position detection is critical for closed-loop control in these applications making a robust outer rotor position sensor essential. Among available sensors, outer rotor variable reluctance resolvers (OR-VRR) with nonoverlapping windings are promising due to their reliability and winding simplicity. In this paper, an OR-VRR is customised specifically for aircraft use, with its stator optimised to enhance resolver accuracy. A magnetic equivalent circuit (MEC) model is developed for the proposed OR-VRR, and mathematical equations are used to optimise the stator teeth. Optimisation is conducted using particle swarm optimisation (PSO), genetic algorithm (GA), ant colony optimisation (ACO), and differential evolution (DE), yielding six stator configurations. Each algorithm offers distinct search mechanisms, and utilising a diverse set of optimisation strategies, the global minimum is more reliable. To refine these designs, the finite element analysis (FEA) is used to simulate and evaluate boundary effects, leading to the selection of an optimal configuration. The chosen OR-VRR design is then prototyped and mounted on the shaft of an outer rotor brushless motor. Experimental results closely match simulations, validating both the optimisation approach and the effectiveness of the prototyped resolver for precise rotor position detection in electric aircraft.