Abstract
One of the main trends in vehicle production today is the developing and correcting the vehicle´s own convenience, in safety operating. One segment is the suspension, since it can ensure the necessary conditions for other safety systems like ABS, ESP, steering system, etc. Simultaneously the suspension has to hold the body of the vehicle in comfort; solving that problem is still difficult. Nowadays passive suspension systems can not fulfill these conflicting requirements anymore, it is becoming more urgent to introduce active and semi-active suspensions in practical use. The direct contact with other safety systems makes the suspension a justified part of the X-by-wire system. This way we can include more functionality in the suspension, since we can access additional information for being used as input data for the active suspension system. A permanent magnet synchronous tubular (TLSM) machine -used as a motor- is capable of acting as an active element in the suspension (axle displacement, vehicle tilting). When used as a generator, there is no energy consumption of the machine itself, it is also capable of acting as a semi-active element. Proper electronic control allows continuously variable acting force between Fmin(~0N) and Fmax, which is covered by switching the stator windings between short-circuit and open-circuit. When used in generator mode, such a configuration produces electrical energy that may be dissipated or recuperated for the vehicle power network. By storing this energy via charging batteries, the tubular generator behaves as an actuator in the same time. The acting force of such a motor depends mostly on geometry and saturation value of the material that is used for constructing the stator. In this paper a geometry optimizing method is introduced. Input parameters of the calculations are the diameter and length of the shock absorber, and magnetic properties of the used materials. A prototype model was manufactured and being measured in a test-rig. Measurements are used for validation of the calculation model. The model includes: magnetic field, induced current, acting magnetic force calculation by moving the piston inside the stator of the machine. Magnetic field is calculated by using finite element modeling. Calculations were implemented in MATLAB and Maple programming environments. Optimization has shown that several kN´s of reacting force can be reached for a shockabsorber having dimensions similar to a conventional design, at a piston speed of 0.5 m/s. Optimal geometry is affected by some other, such as economical or weight-reduction aspects.
Keywords:Suspension, modeling, shock absorber, synchronous tubular motor, permanent magnet