Research On Multi-span Shaft Dynamics And Vibration Reduction Via Smart Spring Support

Multi-span shaft is widely used in helicopters,generators and other equipments,it has an important impact on the performance of the whole machine.Due to its high rotating speed and flexible structural design,the bending vibration of multi-span shaft becomes particularly prominent.Smart Spring is a new semi-active vibration control method,which can effectively restrain the bending vibration of multi-span shaft.In this paper,the dynamic modeling of multi-span shaft and the bending vibration reduction using Smart Spring support are studied.The main works are as follows.1)According to the modal shape and the critical speed of multi-span shaft,the modal dynamic model of multi-span shaft was established based on the finite element method,the Prohl transfer matrix method and the Riccati transfer matrix method.Through the example of helicopter tail shaft,the calculation results of each method were compared,and the Riccati transfer matrix method was chosen to analysis the influencing factors of the multi-span shaft mode.2)According to the unbalance dynamic response of multi-span shaft,the transient dynamic model of multi-span shaft was established based on the Lagrange method and the motion equations were obtained.A polynomial fitting method for the mode shape function of multi-span shaft was proposed.The fitting functions of mode shapes and their higher-order derivatives were substituted into the motion equations.The dynamic responses of multi-span shaft under different support parameters were solved respectively,and the influence of support damping on unbalance dynamic response of multi-span shaft with elastic supports was analyzed.3)According to the vibration reduction of multi-span shaft via Smart Spring support,the transient dynamic model of that was established.The dynamic responses of multi-span shaft with Smart Spring support under different control forces were calculated,and the vibration reduction effects under the critical speed and operating speed were analyzed.The influences of Smart Spring support parameters on its damping performance were analyzed,and those parameters were optimized using genetic algorithm.The peak vibration reduction rate of the optimized Smart Spring support reaches 81.7%.4)According to the verification test for vibration reduction effect of Smart Spring support,the multi-span shaft test platform was built,and the structural parameters of the Smart Spring support were analyzed.The test of the shaft accelerating over its critical speed was carried out,and the bending vibration responses of the shaft under different control voltages of the Smart Spring support were measured.The peak vibration reduction rate at the maximum control voltage reaches 45.2%.