Vibration control of active suspension actuated with pneumatic servo.

The primary purpose of this study is to develop an actively controlled suspension for automobiles or railway cars. To improve the riding quality, since pretty low frequency vibrations have to be attenuated, the very low natural frequency of a suspension is required. This has been usually accomplished by using an air spring. When an actuator is mounted to control this suspension, it is preferable for the actuator to have as low stiffness as an air spring. A pneumatic actuator is most suitable for such applications.In this study, an active suspension is constructed using a pneumatic servo comprising a pneumatic cylinder and electro-pneumatic proportional pressure control valves. Some control schemes are examined to find the effective control method to improve the vibration control performance. As a result of comparing some types of feedback control, it was proven that the relative displacement feedback control with a negative feedback gain is most effective to attenuate the vibration, and in which the control performance is most insensitive to the operating delay of the pneumatic servo system. Further, an optimal regulator is applied to this suspension, and a modeling procedure of the suspension and a suitable performance index necessary to design the control system are clarified. Through this study, it is indicated that a pneumatic servo can be available to an active suspension, and of which performance may be additionally improved by compensating for the operating delay of the control valves.