Design and analysis of an ultrasonic motor with a square frame vibrator
Date Issued
2006
Date
2006
Author(s)
Sun, Te-Pei
DOI
zh-TW
Abstract
This study employs the symmetrical characteristics of a square frame to design motion trajectories of the four projections on the square frame and an ultrasonic motor. Adjusting input voltages allows a slider to move in the x direction or y direction or a rotor to rotate along the z axis. Equivalent vibratory models of the vibrator and slider are generated. The horizontal and vertical vibratory systems are used to simulate the coupling driving mechanism. With the assumed harmonic driving forces acting on the vibrator, the time domain of the driving mechanism system is divided into two periods：the separated period and the impact period. During the separated period, no interference occurs between motions of the vibrator and the slider. The boundary condition changed from the separated period to the impact period depends on the configurations of the vibrator and the slider. During the impact period, impact between the vibrator and the slider can be considered as partially elastic impact. The contact force between the vibrator and the slider is calculated by the material deformation of contact surfaces. The Coulomb law is then used to derive the velocity of the slider. If the contact force is zero, it means that the system is transient from the impact period to the separated period. This friction driving mechanism utilizes the 4-th Runge-Kutta method to simulate effects of the vibratory coupling system. A prototype of the ultrasonic motor is fabricated and tested. When the preload of the vibrator and the slider is 4.0 N, the vertical and horizontal piezoelectric driving forces are 4.5 N and 5.0 N, respectively, and the phase angle difference are 120°, the calculated fastest speed can be obtained to be 90.3 mm/s in the direction. The measured fastest speeds of the contact point between the slider and the vibrator in the x and y directions are 69.8 mm/s and 68.3 mm/s, respectively. The deviations between these two speeds obtained from testing and the calculated result are 22.7% and 24.4%, respectively. The fastest rotational speed of the rotor obtained from testing is 2.16 rad/s. Based on this rotational speed, both speed components at the contact point between the rotor and the vibrator in the x or y direction are 65.7 mm/s. The deviation between the measured and the calculated results is 28.3%. With the preload of 4.0 N, the vertical and horizontal piezoelectric driving forces of 4.5 N and 5.0 N and the phase angular difference of 120°, adjusting the thrust load of 0.82N acting on the slider can yield the highest calculated efficiency of 55.3%. The measured highest efficiencies of the slider moving in the x direction and the y direction are 43.5% and 41.4%, respectively, when applying the thrust loads of 0.63 N and 0.61 N in the x and y directions. The deviations between the two efficiencies based on the measured and calculated data are 21.3% and 25.7%, respectively. When applying the torque load of 0.018 Nm on the rotor (the equivalent thrust load of 0.58 N at the contact point of the rotor and the vibrator in the x direction), the highest measured efficiency of rotor is 37.6%.
Subjects
超音波馬達
振動
壓電致動器
ultrasonic motor
vibration
piezoelectric actuator
Type
thesis
File(s)![Thumbnail Image]()
Loading...
Name
ntu-95-R92522630-1.pdf
Size
23.53 KB
Format
Adobe PDF
Checksum
(MD5):ee7f0f0e4014775e87571e5c6f998773