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Audi TT Coupe With Delphi SemiActive Suspension
(Photo: Audi)Providing the ride in drive for the Audi TT coupe is Delphi Corp.'s MagneRide Semi-active Suspension - a suspension technology that uses magneto-rheological fluid to provide continuously variable real-time suspension damping control. MagneRide responds in real time to road and driving conditions based on input from sensors that monitor vehicle body and wheel motion, says Delphi.  When in a magnetic field, small iron particles in the suspension fluid align themselves in the direction of the magnetic flux. The electromagnetic coil is integrated into the damper piston in such a way that when it is energized, the magnetic flux runs exactly transversely to the admission ports in the damper piston. If the piston moves, the aligned iron particles create flow resistance in the flowing suspension fluid. This principle enables the system to adapt continuously the damping characteristic to match road conditions, as well as driver gear-shifting in a few milliseconds, adds Delphi.

The greater the energy applied and the stronger the magnetic field, the greater the resistance and damping power. The energy is controlled in relation to driving dynamics and impulses from the road. This means for every road situation optimal damping power is available. This damping power produces - according to OEM desire - a more comfortable feel or sportier vehicle handling. 

In the Audi TT, the magneto-rheological dampers can manage a vehicle's ride for either a "comfort" or a "sport" mode. For a comfortable ride, the total path of the springs is fully used because of the lower level of damping force in basic mode. 

The greater damping of the sports mode results in tighter, sportier handling along with better control in the threshold, says Delphi. It also optimally suppresses the rolling tendency of the car's body in corners. 

Because no mechanical parts must be moved, the system responds spontaneously. The damping force is only dependent on the power applied to the magneto-rheological fluid and can be adjusted up to 1,000 times a second. With the variable control of the power, the damping force can also be set infinitely. This means the magneto-rheological dampers respond almost in real time with great sensitivity to impulses from the road, according to Delphi. The control system loop ensures the greatest possible road-to-wheel contact in the case of uneven road surfaces with the least impulses to the car body. 

Delphi's magneto-rheological monotube damper requires roughly the same space requirements as conventional dampers or struts. If required, the company supplies the complete semiactive system with dampers and struts including the sensors and the control unit. On average, each damper requires just 5 watts of electrical capacity (25 watts at a maximum). 

"MagneRide will assist drivers in truly enjoying driving at the speeds, while also offering refined ride quality on city streets and secondary roads," says Daniel Warrell, Delphi Chassis Systems.

(Source: Delphi)