DYNAMICS AND CONTROL OF AN ELASTIC GUIDEWAY UNDER A MOVING MASS

摘要

Lightweight structures under moving loads occur in robotics, ground transportation and in space stations. Increasing velocities lead to an excitation of structural vibrations with high amplitudes. This phenomenon may affect the precision of machine tools and robots and the safety of transport operations. An example of such a lightweight structure is a flexible beam under a moving load. In this paper we investigate the possibility of active vibration control of the elastic beam using a king post truss system (KPTS). The system is excited by both a mass moving with constant velocity and a mass performing an accelerated motion. The aims are to minimize the vibrations of the system and the transverse deflections under the moving mass. The system to be analysed and controlled is time variant due to the moving mass. The fast motion of the mass leads to a highly dynamic system with a fast changing system matrix. We use control inputs at fixed positions for control of the system with distributed parameters. The system is modelled by a finite element approach to implement the moving mass in the system description. To reduce the numerical complexity of the system a modal transformation is applied and numerical investigations of the system are performed. We apply two different control strategies to reach the aims. The first one is an optimal discrete time approach which allows to reach both aims. The second one is an adaptive control strategy with a simple model to minimize the deflection under the moving mass. The numerical results are compared with experimental data. In the case of a constant mass velocity the optimal control strategy leads to a reduction of the deflection under the moving mass of more than 98% compared to the uncontrolled system. The reduction of the deflection under the moving mass applying adaptive control results in a smaller reduction of about 96%.