Abstract:To improve ride comfort in railway vehicles, the suppression of vertical bending vibration and rigid-body-mode vibration in the car body is essential. In this paper, a system is proposed that aims to reduce bending and rigid-body-mode vibration simultaneously by introducing damping control devices in the primary and secondary suspensions. The technique involves a control system of primary vertical dampers and air springs; the former are used to suppress the first bending mode vibration; the latter, to suppress the rigid-body-mode vibration. The results of both simulations and vehicle running tests on the Sanyo-Shinkansen line demonstrate that this system reduced vertical vibrations in the bogies and the car body using the sky-hook control theory. In the running tests in particular, the system reduced the vertical vibration acceleration PSD peak value in the first bending mode to almost 20 per cent and in the rigid body mode to almost 50 per cent compared with the case when the system was not used. As a result, the ride quality level L T (a widely used index of ride comfort in Japan) decreased by at least 3 dB, indicating greater ride comfort.

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We propose an optimization method for a semi-active shock absorber for use in aircraft landing gear, in order to handle variations in the maximum vertical acceleration of an aircraft during landing caused by the variation of the aircraft mass due to the variations in the number of passengers, and the amounts of cargo and fuel. In this optimization, the maximum vertical acceleration of an aircraft is set as an objective function to be minimized. Design variables searched in the first step of this optimization are discrete orifice areas formed by the outer surface of a hollow metering pin and a hole in the semi-active shock absorber. The design variable searched in the second step is a compensating orifice area which is controlled based on the mass variation. Using the optimum target orifice area obtained in the second step, we optimally determine a practical orifice area that is controlled by a stepping motor. The optimizations for a passive shock absorber and for semi-active shock absorbers with target and practical orifice areas indicate that the semi-active shock absorbers can handle aircraft mass variation much better than the optimum passive shock absorber. Furthermore, the robustness of the optimum practical orifice area controlled by a stepping motor is shown via simulation.

Suppression of the vertical bending vibration of carbodies has recently become essential in improving the ride comfort of railway vehicles. In this paper, we propose a method of controlling vibration in the primary suspension of rolling stock to reduce carbody vibration. Systems conceivable for this purpose include a semi-active suspension system with variable axle dampers that can control damping force continuously by command current to the damping force control valve. Based on LQG control theory, we carried out numerical simulations and performed excitation testing with a carbody equivalent to an actual Shinkansen vehicle fitted with variable axle dampers to selectively suppress the first mode bending vibration of the carbody. The results show that this LQG control method reduces the power spectral density (PSD) of acceleration on the floor more effectively than the sky-hook control method, which does not consider the vibration modes of the carbody.

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