Active and semi-active suspensions smooth 300 km/h ride

INTRO: Compressed air controlled by accelerometers restrain sway and yaw of the rear car of JR West's Series 500; controlled dampers perform a similar function to improve the ride of first class cars and those carrying pantographs

BYLINE: Hisashi Norinao

Rolling Stock DeptJR West

ON MARCH 22, Japan joined the exclusive club of nations operating trains at 300 km/h. JR West welcomed passengers aboard the first Series 500 trainsets, which now transport 1324 passengers over the 553·7 km between Shin-Osaka and Hakata in 2h 17min, including three intermediate stops.

Series 500 is the most advanced shinkansen train in service and has a design speed of 320 km/h. The prototype was ordered in November 1994 at the conclusion of technical trials with JR West's WIN350 test train, which began running in June 1992.

Among the innovations which feature in Series 500 (RG 3.96 p135), many are designed to meet environmental criteria such as lineside noise which is the principal barrier to higher speeds in Japan. For commercial operation at 300 km/h, it was also necessary to maintain satisfactory lateral ride quality, especially in first class, in the rear car, and those carrying pantographs where sway must be restricted.

Initially, passive suspension parameters as in the bogie to body spring/damper system were optimised to ensure good ride comfort:

Â?First, the air spring stiffness was changed from linear to non-linear, so that stiffness at small lateral displacements became softer. This improved ride quality outside tunnels.

Â?Secondly, inter-car yaw dampers as used in the French TGV were tried. However, there were some difficulties initially in applying these to Series 500 because it is not an articulated train like TGV.

Even when passive suspension was optimised in these ways, there remained a possibility of reduced ride quality at the higher speeds, especially in tunnels which account for half the total length on the Sanyo Shinkansen. Aerodynamic flows in tunnels exert very large forces on the car body, especially when passing a train going the opposite way.

To deal with this situation, Series 500 incorporates both active and semi-active suspensions with their associated control systems. The primary objective in both cases is to limit sway and yaw of the car body on its bogies.

While the active suspension is fitted to both end driving cars, it is only operative on the rear car for each direction of travel. Semi-active suspension has been adopted on the three first class (8, 9, 10) and two pantograph-equipped (5, 13) coaches.

Active suspension

We tested on WIN350 a number of active suspensions. These achieved both tilt and lateral control, using either pneumatic or hydraulic actuators. The system selected for Series 500 uses a pneumatic actuator powered from the train's main reservoir brake pipe. To boost capacity close to where it is needed, additional air reservoirs for the active suspension are formed within the box-section bogie side-frames.

At each bogie, one actuator consisting of a piston in a double-ended cylinder is fixed tranversely (parallel to the lateral dampers) between the centre pivot under the car body and bogie frame (Fig 1). The actuator has two sensors to measure air pressure on both sides of the piston. Within the actuator, two flow-rate valves regulate the pressure difference across the piston by admitting or exhausting air at a controlled flow.

The maximum force which this actuator can produce is less than 7 kN, which is rather weak compared to other active suspension systems with hydraulic actuators. Ordinary lateral dampers are also used in case of actuator failure; if this happens, air pressure in both parts of the actuator cylinder is released by the valves, and the suspension reverts to passive operation.

Four accelerometers on each car body, located as in Fig 1, measure lateral and vertical movement. The H° controller processes the data from these accelerometers to produce lateral, yaw and roll accelerations.

The H° controller attempts to keep these accelerations below target values which are known as a 'weighting function'. There are other functions for lateral and yaw displacement, and for actuator forces.

We tested mainly two types of weighting function with WIN350. The first was designed to reduce yaw accelerations of relatively low frequency which typically occur in the open air. The second reduced yaw acceleration at the higher frequencies mainly caused by aerodynamic forces encountered in tunnels.

In Series 500, the weighting function aimed at low (open air) frequencies was used for the first trial, and produced satisfactory ride comfort.

Semi-active suspension

The semi-active suspension system installed on cars 5, 8, 9, 10 and 13 of the Series 500 comprises lateral dampers with a variable damping coefficient. It does not require an external energy source such as a hydraulic pump or air compressor.. The two passive dampers found on the bogies of other cars are replaced by semi-active dampers, and two lateral accelerometers are fitted on the car body above each bogie.

One semi-active damper includes three fast-response electro-pneumatic valves, two operating check valves, and relief valves for high pressure and low pressure (Fig 2). The two dampers on the same bogie are operated in concert. Altogether, six damping characteristics can be selected by using combinations of three orifices which are put into the oil circuit by three fast-response valves.

If all three valves are closed, the damping characteristic becomes P0 which is nearly the same as that of an ordinary passive damper. This makes the system very reliable. If no damping force is required, one of the two unload valves opens.

To measure displacement between the bogie and the car body, there is a magnetic scale on the damper rod. As seen in the control diagram (Fig 3), the stroke is differentiated to produce relative velocity. Very high accuracy of the stroke sensor is needed, and it can detect a shift of 0·01mm.

The semi-active damper is operated by quasi-skyhook damper control. Thanks to this, the lateral acceleration level has been reduced, resulting in better ride quality on the Series 500 at 300 km/h than was achieved before at lower speeds.

Finally, it was shown that the performance of both suspension systems was satisfactory in the ride quality improvement even in tunnel running. Considering the operating speed of 300 km/h and the mass production of the system after this, the semi-active suspension system seems to be sufficient. Thus the active suspension system in both driving cars was changed to semi-active before commercial operation. o

CAPTION: Fig 1. Four accelerometers enable the H° controller to limit sway, roll and yaw motions of the body on its bogies by using the two pneumatic actuators

CAPTION: Fig 2. Three fast-response electro-pneumatic valves enable the response of the semi-active lateral damper to be varied by combining orifices of different sizes

CAPTION: Pneumatic actuator for the active suspension system

CAPTION: Fig 3. Signals from the lateral accelerometer and displacement sensor on the semi-active damper are combined instantaneously to operate the valves controlling its characteristics

CAPTION: Semi-active damper

Des suspensions actives et semi-actives adoucissent le trajet à 300 km/h

Le déplacement latéral et le lacet de la voiture arrière de la Série 500 de JR West - le premier train à entrer en service au Japon à 300 km/h - sont restreints en injectant de l'air comprimé dans les dispositifs de commande reliant la caisse et le bogie, tout en utilisant des accéléromètres pour contrâ€?ler les soupapes. Les voitures de première classe et celles qui sont munies de pantographes, sont dotées d'amortisseurs latéraux semi-actifs (non commandés) pour réduire l'oscillation et améliorer la qualité de roulement. Ces deux systèmes résistent à l'effet des forces aérodynamiques lorsque les trains traversent les nombreux tunnels à grande vitesseAngenehme Fahrt bei 300 km/h durch aktive und halbaktive Aufhängungen

Seitliche Verschiebung und Gierung des hinteren Wagens der JR West Serie 500 - dem ersten Zug, der in Japan mit einer Geschwindigkeit von 300 km/h betrieben werden soll - werden durch Einspritzen von Druckluft in Stellglieder, die Karosserie und Drehgestell verbinden, reduziert, wobei Beschleunigungsmesser zur Ventilsteuerung verwendet werden. Wagen der ersten Klasse und solche, die mit Pantographen versehen sind, verfügen über halbaktive seitliche Dämpfer (ohne Motorantrieb), die Schaukelbewegungen reduzieren und die Fahrqualität verbessern. Beide Systeme halten beim Durchqueren der vielen Tunnels mit hoher Zuggeschwindigkeit der Wirkung aerodynamischer Kräfte standUnas suspensiones activas y semiactivas suavizan el trayecto de 300 km/h

El desplazamiento lateral y el  ngulo de inclinación del eje del coche trasero en la Serie 500 de JR West (el primer tren que ha entrado en servicio en Japón a 300 km/h) ha quedado restringido al inyectar aire comprimido en los activadores que unen el chasis con el bogie usando acelerómetros para controlar las v lvulas. Los coches de primera clase y aquéllos que llevan pantógrafos llevan amortiguadores laterales semiactivos (sin potencia) para reducir y mejorar la calidad del trayecto. Ambos sistemas resisten el efecto de las fuerzas aerodin micas cuando pasan los trenes a alta velocidad por los numerosos túneles japoneses