2. Mechanical Engineering
  3. Research Data (No.1799)

Semi-active Suspension for Railway Vehicle

Construction of semi-active suspension.

Fig.1 Construction of semi-active suspension.

Hydraulic circuit of changeable damper (proportional relief valve type).

Fig.2 Hydraulic circuit of changeable damper (proportional relief valve type).

Damping force of proportional relief valve type damper.

Fig.3 Damping force of proportional relief valve type damper.

1. Abstract

A semi-active suspension system for railway vehicles has been developed. High-speed operation causes a large lateral vibration to railway vehicles. Mainly, it is caused by transmission from bogie vibration running on the truck, and aero-dynamical forces which work on carbody directly. Traditional passive suspensions are not enough to reduce the both vibrations because each vibration has a different pass of transmission.

To improve riding comfort of high-speed trains, a lateral semi-active suspension system, which reduces the both vibrations, has been developed. The performance and security of the system were confirmed in running tests. As the result, this system was installed to the Shinkansen train since 1996, as the first vibration control system of commercial trains. In this system, the damping forces are switched through selecting a combination of working orifices by high cycle solenoid valves.

As the second generation of the semi-active suspension, a low-cost and upgrading performance system, which uses a proportional relief valve, has been developed. This system is used in various types of trains, such as older series of Shinkansen trains before 1996, or new high speed trains.

2. Technology

Fig.1 shows the construction of the semi-active suspension. The damping forces of lateral dampers, which are installed between the truck and the carbody, are controlled according to absolute velocity of the carbody. This control method is called sky-hook control.

The damping force of semi-active suspension depends on the direction of piston velocity of the damper. Therefore, semi-active suspension can not generate complete proportioning damping force against the absolute velocity of carbody. As the second best, the system makes the damping force to the minimum, when the piston velocity direction disagrees with the direction of damping force calculated by the sky-hook control. This is called "Karnopp's switching low".

The hydraulic circuit of changeable damper (proportional relief valve type) is shown in Fig.2. This damper has two solenoid valves, which select the direction of damping force. These valves make possible to realize the Karnopp's switching low without finding truck velocity. There are two ways to change the damping force amplitude. The first way, the damper, which is shown in Fig.2, changes the damping force by changing drive current of proportional relief valve as shown in Fig.3. In another way, the damper changes its damping coefficient by switching combination of orifices by more than one of solenoid valves instead of the proportional relief valve. This type of damper is used in the early versions of semi-active suspensions.

When the system is down, the both type dampers behave as a traditional passive damper. Thus, the train safety is kept.

3. Conclusions

The system developed has been used in practical use since 1996, and has contributed to upgrading the riding comfort in about 1100 cars of trains. The cars equipped with semi-active suspension are increasing. It is thought that this system has been accepted as an effective way to improve the riding comfort of high speed trains.

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