Active Vibration Control of Elastic Vehicle Body with Smart Structure

摘要

Railway vehicle is required for further speeding up to compete with other transportations. There are various approaches for the speed-up of the railway vehicle, for example, reducing the air resistance and improving the curving speed, etc. Especially, the vehicle is extensively lightened since this leads to the reduction of the ground vibration, the running cost reduction, and the contribution to noise reduction etc. However, the simplification of car body shell structure and the alternative light material inevitably causes the deterioration of the body rigidity compared with the conventional vehicles, and leads to the increase in vertical bending vibration of the body which was not dominantly found in the old-type steel-structured body. In addition, the deterioration of riding comfort concerns to this issue, because the natural frequency (around 9 Hz) of the above mentioned vertical vibration overlaps with human's uncomfortable sensitive frequency band (around 6 Hz). Up to now, there have been many strategies for the issue of this vibration, i.e. a method to conduct active control for the secondary suspension system between the body and bogie, and a method to attach viscoelastic layers and constraint layers on the outside sheathing of the car body. Nevertheless, this faces problems such as upsizing and weight increase of the device, because the control unit needs power source such as oil pressure supply. For such circumstances, it is necessary to examine a new control technique to suppress the vehicle vibration while keeping the vehicle light as possible. On the other hand, in a field of space structure, a study about smart structural technology that controls internal force of a structure is carried out by building a small actuator and sensor into structured members. A piezo-electric element mainly attracting researchers' attention as a small actuator is a ceramic element who converts electric energy into mechanical energy. This study aims to decrease the vertical bending vibration due to car body lightweighting. Consequently, this paper presents a technique that utilizes a smart structural technology with the piezo-electric actuator, and a control method to suppress bending vibration of the body by actively generating the bending moment at the body. Moreover, the H_∞ control theory is applied for the design of the controller. This control theory has the feature that the controller with robustness against parameter uncertainties, i.e. vehicle mass, can be designed, and the output feedback control method is possible. Typically, this paper employs 1/6 body scale-model experimental setup that aims to mimic the vertical vibration including body bending vibration. On the scale-model, the piezo-electric actuator was embedded into this setup, and the effectiveness of the proposed controller was verified.