A Method Of Dynamic Balancing Without Trying Weight Based On Parameter Identification Of Rotor-bearing System

Rotating machinery is moving from low speed and low power to high speed and high power.Rotor vibration affects the efficient operation of the mechanical system.Studies have shown that about 70% of rotor vibration failures are caused by rotor imbalance.Therefore,the research on rotor dynamic balance methods is very important.In the existing dynamic balancing methods,most of them need to add trial weights,which will inevitably reduce the balance efficiency and cause damage to the surface structure of the parts to a certain extent.Therefore,more and more scholars have carried out researches on the balance method without trial weights;In addition,the centralized unbalanced mass model is widely used in the identification of rotor unbalance parameters.At this time,the arbitrary distribution of unbalance on the shaft and the influence of bearing characteristic parameters on rotor vibration are not considered;And when the number of balance plates is limited,the effect of traditional balancing methods is not obvious.Therefore,based on the basic assumption that the eccentricity of the rotor is a spatial curve,the distribution unbalance and bearing characteristic parameters are identified through the vibration of the bearing and applied to the modal balance method without trial weight.This article first introduces the relevant knowledge of rotor dynamics,including the calculation of critical speed,modal shape,and unbalanced response,briefly outlines the classification criteria of rotors,and elaborates on the influence coefficient method and modal balancing method without trial weights,which provides theoretical basis for dynamic balance simulation;Secondly,the rotor-bearing system model was established by the finite element sub-structure method,and the relationship matrix between the vibration of the bearing and the mass eccentricity curve coefficient was constructed.By giving the rotor mass eccentricity,the vibration data of the bearing at multiple speeds were obtained;Then,the relationship matrix between the response at the bearing and the eccentric curve coefficient and the bearing characteristic parameters is constructed.Through the vibration data,the identification of the eccentric curve coefficient and the bearing characteristic parameters is realized,the influence of the degree of refinement of the finite element mesh and the number of speeds on the parameter identification is analyzed.The modal shape is calculated based on the identified bearing characteristic parameters under actual operating conditions,and the cubic spline function and Lagrangian interpolation function are used.After curve fitting the discrete mode data,the mode function is obtained.Finally,the counterweight is solved by the mass eccentric curve and the mode function to realize the dynamic balance of the mode without trial weight.Taking the cantilever single-disk rotor-bearing system as an example,the fifth-order polynomial function is used to characterize the rotor mass eccentricity,and the influence of different eccentric curve coefficient combinations on the unbalanced response is analyzed.The vibration at the first double frequency of the rotor is measured at four different speeds.As the unbalance and speed increase,the vibration at the bearing is greater;then the parameter identification is carried out through the above-mentioned vibration data,and then the counterweight is solved,and the counterweight is added to the counterweight plate.The result shows that the rotor vibration after balance is reduced About 50%,the effectiveness of the dynamic balance method is verified.From the balance effect,it can be seen that the better the modal function fitting effect,the higher the dynamic balance accuracy;finally,the balance effect of this method and the single-sided influence coefficient method is compared Analysis shows that the method of modal balance without trial weight is better than the method of influence coefficient.In this paper,the distributed unbalanced mass model is considered.The dynamic balance of the rotor can be achieved only by measuring the vibration at the bearing,without adding a test weight,ensuring that the surface structure of the part is not damaged,improving the balance efficiency,and providing a balancing method for the high-speed running rotor,which reduce the vibration at the bearing,and this method can provide guidance for the monitoring of the rotor vibration state.