Research On Piezoelectric Disk Torsional Actuator With Spiral Interdigitated Electrodes

Recently, piezoelectric material is one of the most widely used materials in intelligent materials and structures. From beginning, piezoelectric actuator is one of the most popular researching content in this area. After a long term research, the University of Science and Technology of China first fabricated a piezoelectric fiber torsional actuator with spiral electrodes which could be fabricated easily and produced an big torsional angle. Based on the spiral electrodes structure, an idea was proposed to make a piezoelectric disk torsional actuator with spiral interdigitated electrodes. According to the deformation change principle of piezoelectric fiber, the design of torsional actuator based on piezoelectric disk is the first task in the subject. In the paper, a torsional piezoelectric disk actuator with spiral electrodes is proposed. Its working principle is explained with strain transforming principle and the static model is created. Using mathematical analysis method, the expressions of torsional deformation is educed and it points out that such an actuator can produce relatively large torsional strain. The detailed influences of electrode helical angle and torsional displacement are analyzed.In order to obtain more information of the influence of external helical electrodes on actuation performance, the electric field distribution of disk are analyzed with the help of finite element analysis software ANSYS. The discrepancies of electric field between actual state and mathematical model are pointed out and the mathematical expression of torsional deformation is modified. It appears that an electrode helical angle of 45°can get the largest torsional strain.Prototype actuators are manufactured using piezoelectric disk with an outer diameter of 28mm and a thichness of 0.2mm. The static and dynamic characters of prototype actuator are tested utilizing激光多普勒测振仪and laser reflection method, the test results indicate that such an actuator has many outstanding characters. The angle was about 0.0052o when the driving voltage ranged from -500 to +500V. The largest amplitude of the in-plane torsional angle is 0.0184°at the resonant frequency of 225.6 kHz when the energizing voltage was set to 10Vp-p. A lower resonant frequency occurs at 152 kHz and its amplitude is only 0.0021°which is nearly nine times smaller than the largest one. Another resonant frequency occurs at 81.2 kHz where torsional angle is 0.00086°. We have proved that the relationship between the torsional angle and driving voltage has a fine linearity.