Suspension- and Tilt Module
Active Secondary Suspension
Satisfactory ride comfort on board requires a good decoupling from the excitations induced in the chassis. This can be achieved by a secondary suspension with the lowest possible damping rate. Thus all dampers of the secondary suspension are dispensed with in the module concept presented. The suspension/tilt module combines a low-frequency passive suspension of the body with an active base displacement of the suspensing airspring (secondary suspension). With this active base displacement the vibration of the coach-body is damped and, what is more, the body can be tilted in curves.
Active Suspension/Tilt Technology
The body frame is flexibly connected with the tilting frames by six hydraulic cylinders. The tilting frames are suspended on a total of four airsprings. The principle of active suspension works as follows: the body motions are measured and the cylinders are controlled in such a way that unwanted motions are counteracted. The active suspension increases comfort as compared to conventional spring-damper suspensions. Thus especially strong vibrations, e.g. at track switches, can be absorbed almost completely. Furthermore, the cylinders can be used for tilting the body during cornering by up to 8░, thus increasing ride comfort even more. We can also conceive of an alignment of the cabin floor with the platform edge. To date, a displacement of ▒50 mm is possible, both laterally and vertically.
Unsurpassed Ride Comfort
The information required for the base displacement is provided by appropriate sensors and processed by a multi-variable control. This active suspension technology enables a nearly complete decoupling of the body, especially in the upper frequency range, i.e., the disturbances induced by unevennesses in the rail (lateral and vertical) are hardly transmitted to the body, if at all. The result is an as yet unsurpassed ride comfort both in vertical and horizontal direction.
Testbed for the Suspension/Tilt Technology
In order to show the potential for improvement, we simulated runs along an uneven rail both with a conventional chassis (with damper) and an active suspension (without damper) and then compared the respective coach-body accelerations. With the active suspension, ride comfort could be increased by about 80 %. A feedforward of the cornering acceleration enables tilting by means of the same actuator system and without additional expense.