OEMs have put emphasis on different strategies which allow effective improvements in engine downsizing and cylinder deactivation because of the need for fuel economy and emission restriction. The cancellation of a significant vibration increase caused by the engine is a key topic for the automotive industry. The choice of actuators being used must take into account the full performances and overall cost of the solutions. This paper provides a presentation of an electromagnetic actuator to prove it is the most convenient solution.
The authors began by comparing moving magnet and moving coil actuators. Electrodynamic and electromagnetic actuators may share the same magnetic equations, but their magnetic flux paths differ and lead to multiple designs with their own benefits. The author provides cited examples. The first example discusses better dynamics ability due to a low inductance and a low electrical time constant, while the second shows a higher force constant per magnet mass and a better coil thermal dissipation.
MMT developed two different actuators on the basis of realistic specifications based on the automotive field. An electrodynamic one and an electromagnetic one and compared the performances. In both cases, the actuators have been prototyped and have the same dimensions. For given dynamic performances, the moving magnet actuator has an important gain on the overall magnet mass as well as on the magnet grade. Even with an electric time constant that is height times the one of the electrodynamic actuator, the electromagnetic actuator response time is only 40ms above so that the ability to change the frequency of the actuators will remain in the same order of magnitude. The power consumed by the actuators is equivalent in both cases. MMT built a full-size mock-up that was exposed in several automotive events, to demonstrate the full viability of moving magnet actuators for the active vibration application. MMT’s developments are low cost designs with the design simplification of using ferrite magnet.
Automotive vibration cancellation is a rising issue. The authors implementation of an electromagnetic actuator with a moving magnet is the best solution. Since it allows good performances over the frequency range, with the main benefit being the low magnet mass and the potential use of low magnet grades.
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