Larsen T, Doll J C, Loizeau F, Hosseini N, Peng A W, Fantner G, Ricci A J, Pruitt B L
Department of Mechanical Engineering, Stanford University, Stanford, California, 94305, USA.
Laboratory for Bio- and Nano-Instrumentation, École Polytechnique Fédérale de Lausanne, Batiment BM 3109 Station 17, 1015 Lausanne, Switzerland.
J Micromech Microeng. 2017;27(4). doi: 10.1088/1361-6439/aa5fd2. Epub 2017 Feb 24.
Electrothermal actuators have many advantages compared to other actuators used in Micro-Electro-Mechanical Systems (MEMS). They are simple to design, easy to fabricate and provide large displacements at low voltages. Low voltages enable less stringent passivation requirements for operation in liquid. Despite these advantages, thermal actuation is typically limited to a few kHz bandwidth when using step inputs due to its intrinsic thermal time constant. However, the use of pre-shaped input signals offers a route for reducing the rise time of these actuators by orders of magnitude. We started with an electrothermally actuated cantilever having an initial 10-90% rise time of 85 μs in air and 234 μs in water for a standard open-loop step input. We experimentally characterized the linearity and frequency response of the cantilever when operated in air and water, allowing us to obtain transfer functions for the two cases. We used these transfer functions, along with functions describing desired reduced rise-time system responses, to numerically simulate the required input signals. Using these pre-shaped input signals, we improved the open-loop 10-90% rise time from 85 μs to 3 μs in air and from 234 μs to 5 μs in water, an improvement by a factor of 28 and 47, respectively. Using this simple control strategy for MEMS electrothermal actuators makes them an attractive alternative to other high speed micromechanical actuators such as piezoelectric stacks or electrostatic comb structures which are more complex to design, fabricate, or operate.
与微机电系统（MEMS）中使用的其他致动器相比，电热致动器具有许多优点。它们设计简单，易于制造，并且在低电压下能提供大位移。低电压使得在液体中运行时对钝化的要求不那么严格。尽管有这些优点，但由于其固有的热时间常数，在使用阶跃输入时，热驱动通常限于几kHz的带宽。然而，使用预整形输入信号提供了一种将这些致动器的上升时间降低几个数量级的途径。我们从一个电热驱动的悬臂梁开始，对于标准的开环阶跃输入，其在空气中的初始10 - 90%上升时间为85μs，在水中为234μs。我们通过实验表征了悬臂梁在空气和水中运行时的线性度和频率响应，从而获得了两种情况下的传递函数。我们使用这些传递函数以及描述所需的降低上升时间系统响应的函数，对所需的输入信号进行数值模拟。使用这些预整形输入信号，我们将开环10 - 90%上升时间在空气中从85μs提高到3μs，在水中从234μs提高到5μs，分别提高了28倍和47倍。对MEMS电热致动器采用这种简单的控制策略，使其成为其他高速微机械致动器（如压电叠堆或静电梳状结构）有吸引力的替代方案，后两者在设计、制造或操作上更为复杂。
