Abstract
When a driving voltage opposite to the piezoelectric polarity is applied on the flextensional stator, it will generate the normal force, of which the operating voltage range of piezoelectric actuators will decrease. This paper presents a novel stator design for producing the normal force in which the driving voltage has the same piezoelectric polarity, which is based on the structure of two multilayer piezoelectric actuators clamped in a star-shaped shell. To obtain the two close resonance frequencies of flexural and translation modes, a genetic algorithm combined with the finite element analysis is employed to find the optimal dimensions for the geometry of the stator. The importance of each design parameter is evaluated through a proposed sensitivity analysis method. A prototype resulting from the optimal design was fabricated and the experimental results are given to show that the stator can generate, in practice, the required coupling resonance mode between 35.15 kHz and 36.49 kHz.
Highlights
Ultrasonic motors (USMs) have been developed for various applications in the precision positioning control such as camera lens focusing devices
Brussel et al developed a flextensional USM which has stepping mode and resonance mode [7]; Ho proposed the dynamic model of the flextensional USM [8]; Bouchilloux and Uchino designed a flextensional stator using the genetic algorithm [9]
Compared to the previous simulated result, the simulation of the flexural mode and translation mode yielded 2.4% and 5.6% error, respectively, which highly agree with the predicted performances of the star-shaped flextensional stator
Summary
Ultrasonic motors (USMs) have been developed for various applications in the precision positioning control such as camera lens focusing devices. Similar to the electric motor, a USM mainly consists of a stator and a rotor, where the stator should be designed to generate vibrations by piezoelectric actuators such that the electric energy can be effectively converted into the mechanical power. The stator with two multilayer piezoelectric actuators (MPAs) clamped in an external shell was developed to overcome the tensile stress limit and to amplify the vibration [6]. Such a stator works with simultaneously exciting flexural and translation vibration modes. Since the design of the flextensional stator appears with multivariables, the importance of each designed variable is evaluated through the sensitivity analysis proposed in this paper
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