Passive Railway Car Secondary Suspension - Force, Power, Deflections, Roll and Comfort

Report, 2005

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.