Dynamic Modeling and Validation of a Lorentz, Self-Bearing Motor Test Rig

Abstract

A new type of self-bearing motor that uses Lorentz-type forces to generate both bearing force and motoring torque has been developed. The motor stator is of slotless construction with four three-phase windings. The motor rotor is constructed of 16 surface mounted permanent magnets (PM’s). The main advantage of the design is that it eliminates the tradeoff between motoring torque and bearing force with PM thickness as found in previous designs. This paper presents the dynamic model for the self-bearing motor and illustrates how the model is integrated into the overall system model of the motor test rig. The dynamic model is validated against experimentally measured transfer functions with good agreement between the two.

Nonlinear Bearing Force and Torque Model for a Toothless Self-Bearing Servomotor

“…Finally, cross terms result from the Maxwell integrals (6) and yield the following terms, once again discounting terms with quadratic position dependence: (13) Similar to the Lorentz force expressions, the cross force terms are linear in , and hence interfere most directly with the fundamental Lorentz operating principle. These terms are significant to the model and were not accounted for in earlier 1-D modeling [19]- [21]. The total bearing forces , and torque is the sum of terms (9)-(13) (14)…”

“…The corresponding continuous distribution is given by where the air gap flux due to windings is displaced with respect to the current distribution, and we have defined constants and . A related winding flux analysis is provided in earlier modeling efforts in [21].…”

“…This will be the focus of attention in this paper. We acknowledge significant TSBS modeling efforts that already exist based on one-dimensional (1-D) [19]- [21] and two-dimensional (2-D) [22], [23] flux models. The 1-D work offers good physical insight while the 2-D work shows elegance and improved accuracy.…”