Force density improvements from increasing the number of airgap surfaces in synchronous linear actuators

A realistic comparison of several electromagnetic architectures for high force density actuators is presented. Four equivalent architectures are chosen and computed with a two-dimensional finite-element model. For each architecture, size is optimised to maximise the force/volume ratio. This optimisation step is performed with a fixed mechanical airgap. A thermal model is then used to calculate the current density in the coils. Results show that global-coil architecture performance increases more sharply than other architectures; a scaling effect is thereby introduced for global-coil architectures. A global-coil multi-airgap actuator is presented to illustrate the theoretical results.