A Multi-Cellular PZT Actuator/Generator with Tunable Stiffness and Resonant Frequencies

具有可调刚度和谐振频率的多单元 PZT 致动器/发生器

• 批准号: 1000727
• 负责人: Haruhiko Asada
• 金额: $ 31.35万
• 依托单位: Massachusetts Institute of Technology
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-09-15 至 2013-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1000727&HistoricalAwards=false
• 关键词: Multi; Cellular; PZT; Actuator; Generator

A skeletal muscle consists of a number of independent muscle fibers, each producing a mechanical output efficiently in a compact body. Collective behaviors of a bundle of muscle fibers exhibit unique features and functionality that today's actuators are unable to produce. Unlike conventional electric motors, for example, muscles are mechanically flexible and adaptable to load conditions. Muscles can vary effective stiffness and output impedance in a wide range. Furthermore, a variety of muscles having a wide range of size, power, and degrees of freedom can be built from the same module, i.e., the muscle fiber. Inspired by this skeletal muscle architecture, this project investigates cellular artificial muscles using actuator materials, in particular, PZT (Lead Zirconate Titanate). Like a muscle fiber, a PZT cellular unit is an independent unit that is designed for optimal efficiency and functionality. Using an effective flexure, each PZT cell can produce large displacement and force comparable to a skeletal muscle fiber. Such an optimal unit is inevitably small to drive a large load. Arranging the PZT cells in series, parallel, and antagonistic configurations, a bundle of PZT units collectively exhibit unique features and functionality that a single bulk PZT actuator cannot produce. These include: A). Variable stiffness: Switching individual cellular units ON or OFF creates a significant change to the aggregate stiffness of the multi-cellular system. B). Tailored force-displacement characteristics: By exploiting the ON-OFF nonlinearity of individual units and superimposing the multitude of the nonlinear functions, we can tailor the aggregate force-displacement curve to task goals and environment conditions. This allows us to physically implement the "work loop" characteristics of animal motion at the actuator level. C). Variable resonant frequencies: The multi-cellular PZT actuator forms a network of mass-spring systems due to the combined effect of a flexure and PZT stack at each unit. This multi d.o.f. system has resonant frequencies at which the output displacement becomes much larger than its static stroke, making cyclic motion, such as flapping and running, very efficient. Furthermore, ON-OFF switching of individual units causes a change to the mass distribution and thereby makes the resonant frequency highly tunable. D). Energy harvesting: The new actuator is completely backdriveable having negligibly small friction. Low friction and tunable resonance capability enables a multi cell array to capture energy at a resonant frequency that is the most effective for the environmentally imposed forcing.

骨骼肌由许多独立的肌肉纤维组成，每种肌肉纤维在紧凑的身体中有效产生机械输出。一堆肌肉纤维的集体行为表现出独特的功能和功能，当今执行器无法产生。例如，与常规的电动机不同，肌肉在机械上是柔韧性的，并且适应负载条件。肌肉可以在广泛的范围内改变有效的刚度和输出阻抗。此外，可以从同一模块（即肌肉纤维）建立各种具有广泛尺寸，功率和自由度的肌肉。受这种骨骼肌肉结构的启发，该项目使用执行材料（尤其是PZT）研究细胞人造肌肉（钛酸铅钛酸盐）。像肌肉纤维一样，PZT细胞单元是一个独立的单元，其设计为最佳效率和功能。使用有效的弯曲，每个PZT细胞都会产生较大的位移并与骨骼肌纤维相当。这样的最佳单元不可避免地很小，可以驱动大负载。一系列PZT单元集体地表现出单个批量PZT执行器无法产生的独特功能和功能，以串联的PZT单元格排列PZT细胞。这些包括：a）。可变刚度：开关或关闭单个蜂窝单元会对多细胞系统的总刚度产生重大变化。 b）。量身定制的力置换特征：通过利用单个单元的on-Off非线性并叠加非线性功能，我们可以根据任务目标和环境条件来定制聚合力 - 置换曲线。这使我们能够在执行器层面物理实施动物运动的“工作环”特征。 c）。可变谐振频率：多细胞PZT执行器由于每个单元的挠曲和PZT堆栈的综合效果而形成了质量弹簧系统网络。这个多d.o.f.系统具有共振频率，即输出位移比其静态中风大得多，从而产生循环运动，例如拍打和运行，非常有效。此外，单个单元的开关开关会导致质量分布的变化，从而使谐振频率高度可调。 D）。能量收集：新的执行器完全可以背后摩擦。低摩擦和可调节的共振能力使多细胞阵列以谐振频率捕获能量，这对于环保强迫最有效。