Research On Single Rod MR Damper And Wind Vibration Control On Stayed Cables

As the main force component of the long-span cable-stayed bridge,the cable-stayed cable is characterized by large flexibility,low quality and small damping.It can easily cause great vibration under external excitation,resulting in great security risk.MR dampers have the advantages of fast response,good controllability,wide adjustable range,low energy consumption and strong adaptability,which make them ideal vibration control technique for cable-stayed cable.One form of them,single-rod MR damper is more popular because of its large movement of piston,good sealing,requires short space for installation and so on,and it is much more considerable by scientific researchers.So far,domestic and foreign scholars have made many theoretical and experimental researches on(single-rod)MR damper and its vibration control of cable-stayed cable,they achieved some goals,but there are still some problems to be solved,such as the volumetric compensation of single-rod MR damper,the development and performance test of the MR damper,describing reverse control current of the MR damper mechanical model,the semi-active control algorithm of stay cable with the MR damper,etc.Starting from the single-rod MR damper,this paper used the CB22 MR fluid,which is developed by the research group.A single-rod MR damper,whose volume compensation is isolated,is designed and manufacture.The mechanical properties of damper are tested,and the parameters of damper are identified.Then the semi-active control algorithm based on optimal equivalent model for stay cable is proposed in this thesis,and the semi-active control effect of stay cable with MR damper was analyzed under the wind vibration.The main contents of this paper and the relevant conclusions are as follows:(1)One volume compensation device,whose volume compensation was isolated,is redesigned,and improved.It could effectively solve the problem that MR fluid in the working chamber would infiltrate to the volume compensation chamber or the air in the volume compensation chamber would flow into the working chamber.And the validity is verified by the results of single-rod MR damper's mechanical performance test.(2)Based on the idea of unified optimized design,a single-rod MR damper,and the damping force is about 1.5KN,designed and fabricated.The type of MR fluid used in the damper is developed by the research group.(3)The effects of current,excitation frequency and displacement amplitude on damping force are analyzed.Based on the results of the performance test,the modified Sigmoid model of damper is identified.Compared with experimental results,the identified parameters of model show high accuracy.In order to track the real-time control force required in the semi-active vibration control,the control current of the parametric model is reversed by an iterative method on the basis of the control point's measured response,so that the actual output force of the MR damper would approximate the required control force.Finally,the validity and adaptability of the iterative method are verified by the random signals.(4)The semi-active control algorithm based on optimal equivalent model for stay cable is proposed in this thesis.Considering the direction of MR damper's damping force,the algorithm optimizes the weight coefficient of LQR active control,and is combined with an equivalent model for tracking LQR control.Under the wind vibration,the semi-active control effect of stay cable with MR damper is numerically simulated,and the results show that the semi-active control effect is significant and better than the optimal passive control.