Lead-free programmable multistable piezo-thermal actuators (LEAP)

无铅可编程多稳态压电热执行器 (LEAP)

• 批准号: 438866249
• 负责人: Professor Dr.-Ing. Thomas Hanemann
• 金额: --
• 依托单位: Institut für Angewandte Materialien - Werkstoffkunde (IAM-WK)
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/438866249?language=en
• 关键词: Lead; free; programmable; multistable; piezo

We aim to develop novel multistable and programmable actuators based on the combination of piezoelectric and thermal actuation. Whilst generally creating new performance and functionality compared to present piezo actuators, we address the key challenge of implementing lead-free alternatives to conventional lead-ziconate-titanate (PZT) based ceramics: As lead is highly toxic and can accumulate in the environment (e.g. due to improper recycling and disposal), it is generically banned from electronic products and PZT relies on a temporary ROHS exemption. Lead-free piezo materials, piezo actuation and thermal actuation alone pose the following set of problems and limitations that we aim to overcome:a) The displacement is typically enhanced with lever mechanisms - bending and buckling - but at the cost of reduced force, keeping their product approximately constant. b) Lead free piezo materials have much lower charge coefficients than PZT.c) Thermal actuators have a high power consumption, in particular also when holding a position.d) Buckling actuators typically have only one ground state, not true multistability where a position is held without an applied electric signal.e) In addition to wanted or unwanted deformations, the temperature affects the piezoelectric response and may depolarize the piezo material above the Curie temperature.f) Lead-free piezo materials also have a lower Curie temperature than PZT. One key concept are mechanically multistable designs that use thermal actuation in combination with piezo actuation to switch between the different stable states, allowing us to design higher energy barriers that would not be overcome by piezo actuation alone (d). This keeps the power consumption low (c) and it enables higher forces and larger displacements, (a) and (b). Piezo actuation is then used to provide fine tuning around a stable point, and we aim to develop systems where the fine tuning range around different stable states overlaps, providing continuous displacement. The second key concept is to re-pole the piezo material with different micro-polarization patterns with a combination of in- and out-of-plane polarization of the piezo sheets assisted by heating to the Curie temperature - turning (e) and (f) into virtues. The remnant displacement then defines additional stable states, and the actuators can be re-programmed to have different electromechanical responses. While this will provide additional functionality, it will also increase the overall range of strains of the piezo material. Mechanically, we will use combined bending and buckling and aim to develop pre-tensioned planar spring systems with non-trivial order buckling states and transitions between these states. To avoid separate heating layers we aim to heat with ultrasound using the piezo material. Following the idea of structural simplicity, we will explore self-sensing through the frequency-dependent impedance of the piezo actuators.

我们的目标是开发基于压电和热驱动相结合的新型多稳态可编程执行器。虽然与目前的压电致动器相比，我们总体上创造了新的性能和功能，但我们解决了实施传统PZT(PZT)基陶瓷的无铅替代品的关键挑战：由于铅具有剧毒，并且会在环境中积累(例如，由于不当回收和处置)，一般情况下，它被禁止用于电子产品，而PZT依赖临时ROHS豁免。无铅压电材料、压电驱动和热驱动本身就会带来以下一系列问题和限制，我们将致力于克服这些问题和限制：a)通常通过杠杆机构(弯曲和屈曲)来增加位移，但代价是力降低，从而使其产品保持大致恒定。B)无铅压电材料具有比PZT低得多的电荷系数。c)热致动器具有高功率消耗，尤其是在保持位置时。d)屈曲致动器通常只有一个基态，在没有施加电信号的情况下保持位置时不具有真正的多稳定性。e)除了想要或不想要的变形之外，温度还会影响压电响应，并可能在居里温度以上使压电材料去极化。f)无铅压电材料也具有比PZT更低的居里温度。一个关键的概念是机械多稳态设计，它使用热驱动和压电驱动相结合来在不同的稳定状态之间切换，使我们能够设计出更高的能量屏障，而单靠压电驱动是无法克服的(D)。这保持了低功耗(C)，并且能够实现更大的力和更大的位移，(A)和(B)。然后使用压电驱动来提供围绕稳定点的微调，我们的目标是开发不同稳定状态的微调范围重叠的系统，提供连续的位移。第二个关键概念是通过将压电片的面内极化和面外极化结合到居里温度来重新极化具有不同微极化模式的压电材料-将(E)和(F)转变为优点。然后，残余位移定义了额外的稳定状态，并且执行器可以被重新编程以具有不同的机电响应。虽然这将提供额外的功能，但它也将增加压电材料的整体应变范围。在力学上，我们将使用弯曲和屈曲相结合的方法，目标是开发具有非平凡顺序屈曲状态和这些状态之间的转变的预拉伸平面弹簧系统。为了避免分开的加热层，我们的目标是使用压电材料通过超声波加热。遵循结构简单的思想，我们将通过压电致动器的频率相关阻抗来探索自感知。