Active Electromagnetic Suspension System for Improved Vehicle Dynamics Bart L.J. Gysen, Johannes J.H. Paulides, Jeroen L.G. Janssen, and Elena A. Lomonova Eindhoven University of Technology, The Netherlands. Email: B.L.J.Gysen@tue.nl
Abstract—This paper offers motivations for an active suspension system which provides for both additional stability and maneuverability by performing active roll and pitch control during cornering and braking as well as eliminating road irregularities, hence increasing both vehicle and passenger safety and drive comfort. Various technologies are compared to the proposed electromagnetic suspension system which uses a tubular permanent magnet (PM) actuator together with a passive spring. Based upon on-road measurements and results from the literature, several specifications for the design of an electromagnetic suspension system are derived. The measured on-road movement of the passive suspension system is reproduced by electromagnetic actuation on a quarter car setup proving the dynamic capabilities of an electromagnetic suspension system. Keywords—Active Suspension; Permanent Magnet; Tubular Actuator Figure 1. (a) Conventional passive suspension system, (b) electromagnetic suspension system
I. INTRODUCTION Advanced electro-mechanical and electronic systems are increasingly installed to influence the dynamic performance of the vehicle, for example antilock braking systems (ABS), electronic break force distribution (EBD), electronic stability program (ESP), etc. These systems are installed to improve vehicle handling and passenger safety, since this becomes an ever increasing demand for the automotive industry especially when cars tend to become smaller (SMART), incorporate a higher center of gravity (SUV) and reduced footprint. For instance, the transportation research board , reported that 51 % of the serious car accidents are caused by rollover. Another trend in the automotive industry is the ‘more electric car’, for example the Toyota Prius. These hybrid vehicles combine the efficiency of an electric motor together with an internal combustion engine. Due to the global increase in oil prices and the importance of environmental sustainability, the ‘full electric car’ is also gaining attention. Recently, a Dutch energy company, Essent , launched a commercial electric car together with Electric Car Europe. These cars have a totally different weight distribution since the combustion engine is replaced by an electric motor together with a battery pack of around 400 kg. As such, the optimal electrical drivetrain efficiency is reached when completely incorporated in the wheel [3, 4]. However, as a result, the unsprung mass of the vehicle increases which is a disadvantage regarding passenger comfort and handling. These trends clearly show the need of active suspension to be incorporated into vehicles. These systems allow for
greater suspension articulation when driving under lowyaw circumstances (driving relatively straight) to absorb road irregularities and have a much more rigid response when the car is driven through turns which improves vehicle dynamics. In order to facilitate the ideal suspension with regard to comfort, handling and safety, various commercial technologies are used to improve or replace the conventional passive suspension system shown in Fig. 1(a). This paper discusses an active electromagnetic suspension system incorporating a brushless tubular permanent magnet actuator in parallel with a mechanical spring , as illustrated in Fig. 1(b). This topology has been chosen since the tubular structure exhibits a high efficiency and excellent servo characteristics. Furthermore, the mechanical spring supports the sprung mass; hence no continuous power is needed. The main advantage of this system is that it simultaneously allows for both the elimination of the road disturbances and...