Bimorph

About: Bimorph is a research topic. Over the lifetime, 3339 publications have been published within this topic receiving 51880 citations.

Domain configuration and switching contributions to the enhanced performance of rainbow actuators

Abstract: Stress-biased actuators, such as Rainbow and ThunderTM devices, offer enhanced displacement performance compared to unimorph and bimorph actuators. Quantifying the relative contributions of mechanics (layer thickness ratio) versus stress effects on actuator performance has proven difficult. In this paper, the importance of domain switching and altered domain configuration on actuator performance is considered. X-ray diffraction has been used to characterize the initial domain configuration in the surface region of the actuators, as well as the domain switching characteristics of the devices under moderate electric fields. Samples with different reduced layer thicknesses were fabricated to alter device stress state, and consequently, domain configuration and switching characteristics. Compared to poled polycrystalline ceramics of the same composition, Rainbow actuators display a slightly higher a-domain population in the surface region of the devices. Interestingly, despite the presence of comparatively large lateral tensile stresses in this region of the device, x-ray diffraction indicates these devices also display greater 90 degree(s) (a- to c-domain) switching, which contributes to the large displacement responses that are observed. The contribution of stress to the enhanced performance of Rainbow and ThunderTM devices is, thus, more accurately described as arising from a change in the initial domain configuration together with minimal suppression in the switching response under high lateral tensile stresses, rather than simply a stress-enhancement of domain switching. The effects of stress on the initial domain configuration and switching response were quantified to define the specific role of stress on the electromechanical response of the devices.© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Piezoelectric relay construction

Abstract: A piezoelectric relay construction in which the active element comprises a bimorph sheet having a substantially "U" shaped perforation therethrough to present an armature section having a free end deflectable within the boundaries of the sheet and a frame section for the armature section. A first contact is mounted on the free end of the armature section and a second contact is mounted in opposition to and spaced apart from the first contact on a conductive clip affixed to the frame section. Remanent polarizations are induced in the piezoelectric layers of the bimorph sheet which are in opposition in the armature section and the frame section of the sheet. Suitable terminals on the frame section interconnected with circuit means including the electrode surfaces of the bimorph sheet are provided for the application of operating voltages. Similarly, additional terminals on the frame section and other circuit means including the contacts and conductive clip provide means for connecting the relay in external circuitry to be controlled.

Functionally gradient piezoelectric bimorph-type actuator

Abstract: A new type of piezoelectric actuator has been developed by combining two piezoelectric Functionally Gradient Material (FGM) composite laminates into a bimorph to produce an actuator with large out of plane displacements while having reduced mid-plane stresses. This combination of high displacement with reduced stress keeps the benefit of the bimorph while reducing one of its drawbacks. These properties are varied symmetrically about the mid-plane of the actuator with the entire actuator being poled in one direction through the thickness of the device. These deices are produced by stacking individual layers of piezoelectric fibers in a modified epoxy matrix with varying fiber volume fraction form layer to layer thereby leading to varying material properties through the thickness of the composite. The focus of this work has been to use the finite element method to first predict the material properties for individual piezoelectric fiber based layers using a symmetrical unit cell model, which allowed the inter-layer and intra-layer volume fractions to be varied independently reflecting the rectangular packing of fibers present in the actual devices. And, then to predict the behavior of the actual composite devices using these predicted properties.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Self-sensing control of piezoelectric positioning stage by detecting permittivity

Abstract: Piezoelectric displacement contains hysteresis and creep properties. Therefore, a displacement sensor is indispensable in precise positioning devices; however, the additional space and cost are problems. On the other hand, self-sensing methods that utilize the piezoelectric actuator itself as the displacement sensor have been proposed. With these self-sensing methods, precise positioning becomes possible without an additional displacement sensor. We developed a self-sensing method utilizing the non-hysteresis relationship between the permittivity change and the piezoelectric displacement. Furthermore, a differential current measurement method using two piezoelectric elements with a bimorph actuator could improve the positioning accuracy. In this study, we examine the control of a positioning stage using two multilayered piezoelectric actuators by applying the differential current measurement method for self-sensing control. The results indicate that the differential current measurement method is effective for precise positioning control. The positioning errors due to hysteresis decreased from 0.8 μm to 0.1 μm for a 10 μm displacement range. In addition, permittivity feedback control could compensate for the creep property.