No abstract

In the simulation of a typical ultrasonic traveling wave motor, usually at least four topics have to be considered: modeling the stator, the piezoceramic ring bonded to the stator, the rotor and the contact problem between stator and rotor. Although from experimental observations it is well known that rotor flexibility strongly affects the motor behavior, this has so far not been taken into account in modeling these motors. The aim of this paper is to point out the importance of rotor flexibility in an electromechanical model of an ultrasonic traveling wave motor. A motor of the plate type with one piezoceramic ring is modeled. The simulation is based on the approach suggested by Hagood, where we however incorporate rotor flexibility. The geometrical and material parameters for the model are taken from data of an industrial prototype motor. The coefficient of friction between the contact layer of the rotor and the stator is obtained from the stall torque, and the damping of the disk spring is adjusted to measured torque-speed characteristics of the motor. The steady state dynamical behavior of the model is simulated in the frequency domain. Such an analysis can be carried out much faster than the numerical integration of the equations of motion in the time domain, as originally done by Hagood. It turns out that the measured torque-speed characteristic can not be fitted if rotor flexibility is ignored, while good results are obtained if the flexibility of the rotor is included in the model.

No abstract

In this paper the contact mechanism between stator and rotor will be considered in detail, which plays a key role in ultrasonic motors. A planar contact model for the stator-rotor interaction in traveling-wave type ultrasonic motors is derived, including rotor flexibility and differenciating between stick and slip regions in the contact zones. The model analysis shows that depending on the motor’s operating conditions, complicated contact behavior may occur with several stick-slip subzones in each contact zone. The typical nonlinear resonance observed in ultrasonic motors can be explained with the present analysis. Both the stiffness of the contact layer and of the rotor may drastically influence the speed-torque characteristics. The results will contribute to a better understanding of the contact mechanics in ultrasonic motors.

Das Verformungsverhalten von Holz‐Verbundträgern kann im linear‐elastischen Bereich durch die Lösung der Differentialgleichung oder mittels Näherungsverfahren (Differenzenmethode, Gamma‐Verfahren) berechnet werden. Das ? ‐Verfahren eignet sich vorwiegend für Belastungen mit parabel‐ oder sinusförmigem Momentenbild. Es werden FE‐Modelle erstellt und die Lösungen der analytischen Verfahren mit den Ergebnissen des linearen FE‐Modells verglichen. Im zweiten Schritt wird das FE‐Modell durch aus Versuchen bzw. FE‐Analysen bekannte nichtlineare Dübelkennlinien und durch geeignete Materialmodelle erweitert, um Aussagen zum nichtlinearen Last‐Verformungsverhalten und zur Traglast der Verbundkonstruktion machen zu können. Zur Verifizierung werden die Ergebnisse vorab getätigter Versuche im FE‐Modell abgebildet und die Lösung mit den Versuchsergebnissen verglichen.