Investigation into low power active electromagnetic damping for automotive applications
Fow, A. J. (2015). Investigation into low power active electromagnetic damping for automotive applications (Thesis, Doctor of Philosophy (PhD)). University of Waikato, Hamilton, New Zealand. Retrieved from https://hdl.handle.net/10289/9237
Permanent Research Commons link: https://hdl.handle.net/10289/9237
Automobile suspension systems carry out two important functions; road handling and passenger comfort. Hydraulic passive dampers are the most common system employed on vehicles, yet it is well known that passive suspension systems are less effective on lightweight vehicles. Modern damper technologies such as semi-active and active dampers, offer potential benefits when used in these vehicles. An active electromagnetic (e.m.) damper could offer these same benefits with lower power consumption and with less mechanical complexity than existing active suspension systems. This research investigates the effectiveness of e.m. passive and active damping on the performance of lightweight electric vehicles and develops a novel, fully integrated model of the e.m. damper in both passive and active modes. The proposed e.m. damper consisted of one or more cylindrical permanent magnets that travelled axially through one or more cylindrical solenoids. A magnet/solenoid damper system was modelled for both the passive and active modes. The magnets were modelled as a current carrying solenoid and from Maxwell's Laws the magnetic field was determined. For the passive damper, the magnetic field was used with Faraday's Law to determine the forces generated. In the case of the active damper the magnetic field and the current in the damper solenoid were used to calculate the magnetic force. Both a passive and active e.m. damper were modelled for a small, one degree of freedom experimental system. The active e.m. damper was modelled as a pure Skyhook damper. There was a good correlation between the modelled and experimental data for the magnet, the passive and the active Skyhook dampers. The passive damper model was scaled up as a two degree of freedom system using realistic values for a road legal lightweight electric vehicle and demonstrated that sufficient passive damping could be achieved for automotive uses, but at the price of excessive mass. For the scaled up active damper model, sufficient force could be achieved with a mass similar to a commercial hydraulic damper. The power consumption was less than 5 % of an equivalent active hydraulic suspension system. This demonstrated that the passive damper was currently impractical for lightweight electric vehicles, but the active electromagnetic damper was of sufficiently low weight and power consumption: had enough authority and offered sufficient passenger comfort benefits to include in future lightweight electric vehicle designs.
University of Waikato
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