We present the design, fabrication and experimental testing of SMALLBug, a 30-mg crawling microrobot that is 13 mm in length and can locomote at actuation frequencies of up to 20 Hz. The robot is driven by an electrically-powered 6-mg bending actuator that is composed of a thin shape-memory alloy (SMA) wire and a carbon-fiber piece that acts as a loading leaf-spring. This configuration enables the generation of high-speed thermally-induced phase transformations of the SMA material to produce high-frequency periodic actuation. During development, several actuator prototypes with different mechanical stiffnesses were tested and characterized by measuring their bending motions when excited with pulse-width modulation (PWM) voltages with a variety of frequencies and duty cycles (DCs). In a similar manner, the displacement–force characteristic of the actuator chosen to drive SMALLBug was identified by measuring its bending displacements under a number of different loads ranging from 4.22 to 83.8 mN. The locomotion capabilities of SMALLBug were experimentally tested at three different input actuation frequencies, which were observed to produce three distinct gaits. At the low frequency of 2 Hz, the robot locomotes with a crawling gait similar to that of inchworms; at the moderate frequency of 10 Hz, the robot advances smoothly at an approximately constant speed using a shuffling gait; and at the high frequency of 20 Hz, the robot generates small and fast jumps in a galloping gait, reaching average speeds of up to 17 $\boldsymbol{\text {mm}} \cdot \boldsymbol{\text {s}}^{\boldsymbol{\text {--}}\boldsymbol{\text {1}}}$, equivalent to 1.3 body-lengths per second (BLPS).

中文翻译：

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SMALLBug：由高频柔性 SMA 微执行器驱动的 30 毫克爬行机器人

我们展示了 SMALLBug 的设计、制造和实验测试，SMALLBug 是一种 30 毫克的爬行微型机器人，长 13 毫米，可以在高达 20 Hz 的驱动频率下移动。该机器人由电动 6 毫克弯曲致动器驱动，该致动器由一个薄的形状记忆合金(SMA) 线和用作加载板簧的碳纤维片。这种配置能够产生 SMA 材料的高速热致相变，从而产生高频周期性驱动。在开发过程中，测试了几个具有不同机械刚度的执行器原型，并通过测量它们在激发时的弯曲运动来表征。脉冲宽度调制 (PWM) 电压具有各种频率和 占空比(DC)。以类似的方式，通过测量其在 4.22 至 83.8 mN 范围内的多种不同负载下的弯曲位移，确定了选择用于驱动 SMALLBug 的致动器的位移-力特性。SMALLBug 的运动能力在三种不同的输入驱动频率下进行了实验测试，观察到产生三种不同的步态。在低的 频率为 2 Hz，机器人以 爬行步态类似于尺蠖；在缓和 频率为 10 Hz，机器人使用一个近似恒定的速度平稳地前进 蹒跚的步态; 并在高的 频率为 20 Hz，机器人在一个 奔腾的步态, 平均速度可达 17 $\boldsymbol{\text {mm}} \cdot \boldsymbol{\text {s}}^{\boldsymbol{\text {--}}\boldsymbol{\text {1}}}$，相当于 1.3 每秒体长 (BLPS)。