A demonstration of the new suspension system
starts with a striking scene: a standard-
looking, dark blue BMW 530i that hops up and
down like a ‘lowrider’ in hip-hop video clips.
“Of course that isn’t the intention”, explains ir.
Bart Gysen, who is working for his PhD on the
development of the system. “But it certainly
shows what the system can do.” The car’s
wheels can be raised and lowered
independently in a fraction of a second. And
this high speed is one of the most special
features of the system. There are already
active suspension systems, but these are
hydraulic, which means their response is not
fast enough to cancel out the rapid vibrations
caused by irregularities in the road surface.
The new system can do this effectively, which
explains the better ride quality.
Vibration-free ambulances
The system developed by Gysen was tested last
year on a testbed that simulates road-surface
vibrations on just one wheel. That resulted in
an increase of 60 percent in ride quality. “We
expect that this increased comfort can also be
achieved with a real car”, Gysen explains. “And
possibly even more, when all four wheels are
fitted with the system.” The aim is ultimately
to develop more comfortable cars that also
have higher safety. This is because the
roadholding is improved and the car no longer
rolls in bends. For example a car fitted with
this suspension system will be much less likely
to overturn as a result of abrupt steering
maneuvers, such as the slaloming involved in
the notorious ‘elk test’. Gysen also believes the
system will be attractive for use in
ambulances. “An ambulance fitted with this
system will be able to transport patients
quickly and free of disturbing road-surface
vibrations.”
Inherently safe
The system replaces the normal shock absorber
in a car, and itself has approximately the same
size as a shock absorber. It consists of a
passive spring, a powerful electromagnetic
actuator, a control unit and batteries. The
system is designed to be inherently safe. Even
if the electrical power fails, the springing and
shock absorbers will continue to work. The
passive spring in the system provides springing,
and the magnets provide passive, magnetic
shock absorption.
Generating power
According to Gysen the system’s energy
consumption is modest. “If you install this
suspension system on all four wheels, the peak
consumption is 500 watt – half of what an air-
conditioning system uses. Hydraulic suspension
systems use four times as much power. And the
consumption of our system can probably be
reduced still further by optimization. This is
only the first version.” As well as that the
system can even use the vibrations from the
road surface to generate electricity, which is
fed back into the battery.
Coordination
The suspension system is installed on two
wheels of a test car for practical tests and
further development. One of the tasks is to
coordinate the behavior of the active
suspension on the individual wheels. At present
the separate wheel systems still work
independently. SKF, which has financed
Gysen’s doctoral research and has also
patented the technology, is currently
considering whether to market the new
suspension system.