Design of bearings for rotor systems based on stability.

摘要

Selection of hydrodynamic bearing and magnetic bearing controller parameters for incorporation into rotor systems is usually performed employing analysis tools. A method that emphasizes on the synthesis, or design approach, with a view to improving stability characteristics of the dynamic system is presented. A user-specified set of practical design criteria, including ensurance of stability, satisfying specified logarithmic decrements, maintaining an operating speed separation margin, and restricting the bearing parameters within specified bounds, are translated into objective functions for minimization and inequality constraints. These specifications define an acceptable region in the design and parameter spaces, and the goal is to translate the system closed-loop eigenvalues into this region through proper choice of bearing parameters. This is accomplished by a sequential multi-phase algorithm, with each phase involving the solution of a non-linear constrained minimization problem. The method of feasible directions is employed to seek acceptable bearing designs.; The method is demonstrated for multiple rotor systems, and is shown to be equally effective for both hydrodynamic bearing and magnetic bearing controller designs. The effects of increasing aerodynamic instability mechanisms, and increasing rotor operating speed on the solution set are presented. The beneficial effects of bearing anisotropy and cross-coupled coefficients (or, transfer functions in the case of magnetic controllers) are demonstrated.