Mixed-domain traveling-wave motor model with lossy (complex) material properties

A piezoelectric traveling-wave motor model has been developed with parameters entirely related to physical properties. The approach is well-rooted in the formulation suggested earlier by Hagood and McFarland, but several model improvements have been integrated in an effort to realize an accurate model suited for automated design optimization. Additional model considerations include a flexible rotor model and a hysteretic stick-slip friction contact model which replace the previous assumptions of a rigid rotor and pure slip. The most notable contribution has been the use of lossy (complex) material properties to account for inherent material losses, supplanting the use of non-physical damping coefficients. The model is partly formulated in the frequency domain, and by representing the modal states and forces as Fourier series expansions and retaining higher harmonic terms, it has been generalized to account for non-ideal traveling-wave excitation. Needing to simulate the hysteretic contact model in the time domain, a mixed-domain solution procedure has been implemented to maintain some of the computational efficiency of frequency domain analysis. A preliminary validation study has demonstrated excellent correlation between simulation results and experimental data for a commercial motor.