Analysis And Optimization Of Dynamic Characteristic Of High-speed Built-in Motorized Hydrostatic Spindle System

Motorized spindle with a wide speed range, small moment of inertia, fastresponse and easy to achieve precise control, etc., while the new form of thehydrostatic bearing spindle structure and built-in spindle systems combined, but alsohas a large carrying capacity and small vibration, long life and other advantages, isbecoming a new hotspot spindle fields. High-speed hydrostatic spindle systems areoften run over critical speed, the analysis and optimization of dynamic characteristicsis very important for this kind of high-speed rotating shaft with integrated structure.Firstly, considered the structural characteristics of motorized hydrostatic spindlesystem, the kinematics model of the system was established and the radial load offront and rear bearing under two conditions of no-load and full-load were calculatedand as a basis of calculation of the stiffness and damping coefficient of the hydrostaticbearing. The dynamic model of the hydrostatic bearing was established and then thestiffness and the damper of the bearing were calculated. Based on the finite elementtheory, a simulation model was established The simulation method is applicable to themotorized hydrostatic spindle system with complex structure and computationallyefficient. By comparison with typical examples, the simulation method provedeffective.Then, the complex modes of the high-speed built-in motorized hydrostaticspindle system were analyzed using the proposed simulation method, and the complexeigenvalues and mode shapes were available. On this basis, the spindle systemstability is analyzed and evaluated based on the stability criterion for system stability.The campbell diagram of the system was mapped out and the critical speed of themotorized spindle system was calculated by the calculation of damped naturalfrequency under different spindle speeds. Then, the forced vibration response causedby each system unbalance was calculated. also, the system dynamic stiffness wascalculated.Finally, an multi-objective optimization method for danamic characteristic of themotorized spindle was suggested based on genetic algorithm. The objective was tomaximize the stability evaluation index and the dynamic stiffness of the system andthe axial size parameters of the spindle system were selected as the design variables.The effective micro genetic algorithm was adopted. Eventually, higher stability and higher danamic stiffness was achieved. In the mean time, the modification of theparameters of complex structure was averted. Projects calculation results showed theeffectiveness of the optimization method.