US Patent 11539279 Gap-closing actuator having a double-wound driving coil

A haptic engine includes a gap-closing actuator having a double-wound driving coil in which the two windings can be activated with two driving sources, respectively. Or, the two windings double-wound driving coil can be activated with a single driving source when the two windings are connected with each other either in series or in parallel. By using the double-wound driving coil in the gap-closing actuator as described, an instant inductance of either of the two windings can be determined without having to measure in real time a resistance of the corresponding winding.