A Sensorless Controller for a Kind of Linear Variable Gap-Reluctance Resonant Drive

This paper describes a new kind of sensorless electronically controlled horn for automobiles. The main benefits of this new horn over the classical electromechanical counterparts are: a much longer lifetime, a lower level of generated electro-magnetic interference, a better behavior against aging and stress, the avoidance of the adjusting operation during manufacturing and its multifunction capabilities. To fulfil all these targets we have substituted the electromechanical breaker of previous designs by a solid state switch controlled by a low-cost microprocessor on board the horn. In order to detect the resonance condition of the horn we use a novel technique based on the analysis of the current across the coil, avoiding the need for any sound-level, position or motion sensor. At present there are commercial products based upon the prototypes built according to this design.