Self-Sensing Actuation and Control with Shape Memory Alloys

形状记忆合金（sma）已被用于各种驱动、能量吸收和传感应用。这种材料的主要特点是它能够承受大的看似塑性的应变，并随后恢复这些应变，当负载被移除或材料被加热。这种独特的能力源于奥氏体和马氏体之间可逆的热弹性相变。这一关键特性使得sma可以作为非常紧凑的执行器。由于sma既可用于材料增强，又可用于能量吸收，因此在智能结构领域引起了广泛的关注。此外，没有其他材料或装置可以在占用如此小的体积的情况下产生大位移的显著拉伸力。许多sma的第二个有用特征是电阻率随应变变化而变化。当SMA承受应变时电阻率的变化使研究人员能够将其用作粗位置传感器。这种粗糙是由于电阻率与材料状态之间的复杂关系以及它与机械载荷和温度的耦合。鉴于上述材料特性，形状记忆合金可以实现经济、功率密集的自传感驱动（SSA）。然而，SMA驱动和传感的非线性特性、对SMA热机械响应的不完全理解以及缺乏合适的控制模型，导致这种有用材料作为致动器、传感器和SSA的利用不足。在本研究中，重点工作将集中在(1)改善传感和控制环境下sma的表征，(2)改进材料建模，(3)开发基于模型的控制算法，以及(4)在硬件中演示这些算法，以促进sma作为执行器、传感器和SSAs的理解和应用范围。

Cate Brinson, Michael Peshkin, Bruce Wilson Northwestern University Shape memory alloys (SMAs) have been used in a variety of actuation, energy-absorbing, and sensing applications. The key feature of this material is its ability to undergo large seemingly-plastic strains and subsequently recover these strains when a load is removed or the material is heated. This unique ability occurs due to a reversible thermoelastic phase transformation between austenite and martensite. The key feature allows SMAs to serve as very compact actuators. As SMAs can be used for both material-stiffening and energy-absorption, they have generated much interest in the smart structures field. Further, no other material or device can generate significant tensile forces over a large displacement while occupying such a small volume. A second useful feature of many SMAs is a change in resistivity with a change in strain. The change in resistivity as an SMA undergoes strain has enabled investigators to use them as coarse position sensors. The coarseness is due to a complex relationship between resistivity and the material state and its coupling with mechanical load and temperature. Given the material characteristics above, economical, power-dense self-sensing-actuation (SSA) can be achieved with shape memory alloys. However, the nonlinear nature of SMA actuation and sensing, incomplete understanding of SMA thermomechanical response and the lack of suitable models for control result in an under-utilization of this useful material as an actuator, sensor, and SSA. In this research, a focused effort will be targeted at (1) improving the characterization of SMAs for a sensing and control context, (2) refining material modeling, (3) developing model-based control algorithms, and (4) demonstrating these in hardware to advance the understanding and range of applications of SMAs as actuators, sensors, and SSAs.