Control of a reluctance actuator using hybrid flux estimation

Abstract

Reluctance actuators boast a high motor constant in small air-gap applications when compared to Lorentz actuators. Inherent non-linearities in the F-I relation limit force predictability. Replacing conventional current control with flux control can greatly improve force predictability. Traditionally, hall sensors or hysteresis modelling are employed for accurate flux estimation. This thesis proposes a calibration strategy and control architecture for hybrid flux estimation. The novel control architecture is implemented on a test set-up at MI-Partners. The flux estimator consists of a high pass filtered sense coil and a low pass filtered current probe for integration drift correction. Through comparison of force estimation errors due to magnetic hysteresis, (analog) integration drift and integration errors the optimal crossover frequency was calculated to be 13 mHz. The hybrid control architecture is capable of force prediction accuracy on par with hall control. Simulated positioning accuracy even shows an improvement of 13%, simulations show an improvement in maximum error from 423  micrometer to 369 micrometer. A positioning accuracy improvement of up to 332% over a similar current controlled system has been demonstrated.