Passive Railway Car Secondary Suspension - Force, Power, Deflections, Roll and Comfort
Requirements on forces that need to be delivered by an active secondary railway
suspension system are investigated, as well as the active system’s estimated power
consumption. This is done by calculating the corresponding properties for a specific
train with passive suspension system: the [. . . ] train from Bombardier.
Quasi-static worst case conditions are studied in order to obtain the quasi-static
forces required by each actuator. The obtained quasi-static suspension forces are
used to assess requirements on the actuators in three different, possible, active
systems. All active systems assume four actuators for each railway car. What
differs is which passive components that are replaced with active.
For the first scenario, the active suspension replaces the anti-roll bar and the
secondary vertical damper. Then the results show that each actuator must be able
to deliver quasi-static forces of roughly 32 kN.
For the second scenario, the pneumatic pump system for the air-springs, which
adapts the air pressure to compensate for payload variations, is removed. Instead
the active suspension will be used to keep the carbody at the same vertical position
regardless of the amount of payload. This requires a quasi-static force from each
actuator of about 13 kN, for the worst case.
The third scenario combines the first two cases. The resulting quasi-static
forces that the actuators might need to deliver is the sum of the quasi-static forces
from the two different systems mentioned above, 46 kN.
To get an indication of the peak force each actuator needs to deliver, and an
estimate of the power it needs to deliver, dynamic simulations are carried out on
the passive train during several running conditions. For each running condition, the
peak (i.e. maximum) force, the mean power, and the peak (i.e. maximum) power
are calculated over the simulation time. Then, the largest of each of those three
quantities are selected among all running conditions. The results are, that over
the running conditions the largest peak force is 42 kN, the largest mean power is
0.64 kW, and the largest peak power is 4.6 kW, assuming the first scenario above.
Additional to the required forces and powers, also deflections and roll in the
passive secondary suspension, as well as passenger comfort, are calculated for the
different running conditions. These results form requirements, and measures for
comparison, for future active suspension system.