Seto K., Nishikiori M.

In recent years, factories and warehouses around in the world have tended towards automation to reduce the cost of employees and to cut down production time. Thus, the existence of a transportation system that carries goods, instead of them being carried by employees, is indispensable for factory and warehouse automation. Motion and vibration controls of flexible transport systems for moving equipments and loads from one place to another are considered. In order to reduce settling time, higher speeds and higher positioning accuracy are in increasingly demanded of transportation system. As well, in recent years strong demands for energy savings have also been made. To meet these demands, transport systems are constructed with a light structure, and relatively become flexible. As a result, the transport system suffers a decline in its natural frequency because of its flexibility. Then, increasing acceleration under the operation invites vibration, mainly reducing positioning accuracy. The influence of the vibration occurred in positioning is not negligible on the lose time in settling. In order to reduce the settling time, we have studied basically to control motion and many-modes of vibration for the flexible transportation system. In this study, a structural filtering technique was used to suppress spillover invited by neglected higher modes. In addition, it has been demonstrated that the robust control under changing the position of the load was obtained using LQ control. However, these studies were done by the use of laser sensors with a limitation on measuring range. The next problem is how to measure multi-modes of vibration of the flexible tower structure instead of the laser sensor. Since transportation system moves long distance, no limit in the measuring range of the sensor is required for vibration detection. For the purpose, piezoelectric films pasted on flexible structures are used as the point sensor of vibration detection. To control the first two modes, two DOF lumped mass model is constructed using the reduced-order physical modeling method. Furthermore, a mounting technique of the piezoelectric film to detect the same dynamic behavior with the laser sensor is shown. It is reported that the scaled transportation system is well controlled on the motion and the first two modes of vibration without spillover using two piezoelectric film sensors.