HyperG - A New Hydro Pneumatic Catapult Type Sled 2003-01-0496
Sled testing is one of the most important test methods for the evaluation of vehicles interior with respect to crash safety. This method allows one to simulate real crash conditions without destroying the vehicle structure.
In addition to conventional sleds which are accelerated smoothly using a bungee cord or other device and then impact a deformation element, catapult sled types act in a reverse mode. The sled is thus accelerated for approximately 100 ms to the impact speed and then smoothly decelerated.
To ensure good correlation with the full scale crash test an accurate modelling of the vehicles crash pulse must be guaranteed
Catapult type sleds guarantee, that the sled will not move before the pulse starts. Therefore well defined initial conditions especially regarding dummy positioning can be guaranteed.
While conventional catapult type sleds mainly work on hydraulic or pneumatic modulation of the pulse. Hyper-G combines a simple pneumatic spring with a hydraulic brake directly acting on the ram. While the pneumatic air spring provides a rather constant force, the pulse is modeled by varying the brake force.
As only little hydraulic flows are required to control the brake, standard valves with very fast response and small through flows can be used. In this way it was possible to use a closed loop system which automatically compensates for dynamic masses.
This paper shows the principle functionality, safety aspects, handling and performance of this new system.