１．Overview

One way to increase the running speed on curved sections of railways is to use a tilting vehicle that tilts the car body on curves. This has the effect of countering the centrifugal force acting on the passengers as the car body tilts towards the inside of the curve along with the passengers inside. Aiming to further improve the ride comfort of tilting vehicles, the authors developed a next-generation tilt control system based on three key elements: (1) vehicle position detection, (2) car body tilt operation that takes into account the ride comfort on curves, and (3) highly responsive and highly accurate tilt actuator control. Figure 1 shows the system configuration.

Fig.1　System configuration

２．Details of the technology

(1) Vehicle position detection

In this system, the vehicle’s yaw angular velocity is detected by a gyroscope sensor mounted on the vehicle, and at the same time, speed information is received from the vehicle to calculate the “curvature”, which is the inverse of the radius of curvature. First, the system travels along the route to be scheduled for operation without tilt control, acquires curvature data, and registers it on the vehicle as map data. Next, when the vehicle is traveling in the mode of tilt control, it acquires curvature data while traveling, while also referring to the curvature data registered as map data, and searches for the vehicle’s position on the map data where the two most closely match, thereby frequently correcting the vehicle’s position.

(2) Car body tilting operation that takes into account ride comfort on curves

To calculate the appropriate car body tilt angle for each curve, information on the curvature and the cant, which is the difference in height between the rails on the inside and outside of the curve, is required. This system holds the curvature and cant calculated using a gyroscope and speed information as map data, and by referencing the map data based on the detected vehicle position information, it grasps the curvature and cant of the preceding section. Then, taking into account the current traveling speed, it performs optimization calculations based on a ride comfort evaluation index based on ergonomic knowledge to determine the ideal car body tilt angle for the curve that will be traveled immediately after, thereby realizing car body tilting operation that optimizes the index.

(3) High-response, high-precision tilt actuator control

Car body tilt control is performed using a pneumatic actuator installed on each bogie. In addition to the conventional displacement feedback control, velocity and acceleration feedback control and feedforward control are incorporated to achieve both high responsiveness and stability, realizing the ideal car body tilt operation described in (2). In addition, the actuator is equipped with a damper mechanism that generates a damping force using air pressure when the control system is inactive.

３．Performance evaluation through running test

To evaluate the effect of ride comfort improvement, a running test was conducted with the entire system temporarily installed on an existing tilting vehicle. Figure 2 shows the variation in the vehicle position as recognized by the system when passing the same point. The mean value of position error was 0.01m, with a maximum value of 2m and a standard deviation of 0.65m, demonstrating sufficient accuracy for controlling the tilt of the car body. Figure 3 also shows the motion sickness dose value (MSDVy), an index that quantifies the effects of motion sickness. On average, a reduction of approximately 23% in MSDVy was observed compared to the conventional control method.

Fig.2　Vehicle position accuracy

Fig.3　Comparison of MSDVy

Fig.4　273 series tilting train-cars and installed tilt actuator

４．Practical application

In April 2024, JR West’s 273 series train (Fig. 4), the first to be equipped with this system, began operation as the new “Yakumo” limited express train. Since the start of operations, the system has been highly praised for its ride comfort. Moving forward, we plan to deploy this system in conjunction with the renewal of existing tilting vehicles.

Akihito Kazato
Railway Technical Research Institute, (2-8-38 Hikari-cho, Kokubunji, Tokyo 185-8540, Japan)

Yasutaka Maki
Railway Technical Research Institute, (2-8-38 Hikari-cho, Kokubunji, Tokyo 185-8540, Japan)

Takeshi Nomoto
West Japan Railway Company, (Shin-Osaka Dai-san NK Building, 4-6-35 Miyahara, Yodogawa-ku, Osaka-shi, Osaka , 532-0003, Japan)

Kazuo Sakemi
West Japan Railway Company, (Shin-Osaka Dai-san NK Building, 4-6-35 Miyahara, Yodogawa-ku, Osaka-shi, Osaka , 532-0003, Japan)

Katsumi Sasaki
Pneumatic Servo Controls LTD., (241-1 Hirakocho Higashi, Owariasahi, Aichi 488-0871, Japan)