This works presents the theoretical analysis and experimental observations of the bidirectional motion of a millimeter-scale bristle robot (milli-bristlebot) with an on-board piezoelectric actuator. First, the theory of the motion, based on the dry-friction model, is developed and the frequency regions of the forward and backward motion, along with the resonant frequencies of the system are predicted. Secondly, milli-bristlebots with two different bristle tilt angles are fabricated, and their bidirectional motions are experimentally investigated. The dependency of the robot speed on the actuation frequency is studied, which reveals two distinct frequency regions for the forward and backward motion that matches well with our theoretical predictions. Furthermore, the dependencies of the resonance frequency and robot speed on the bristle tilt angle are experimentally studied and tied to the theoretical model. This work marks the first demonstration of bidirectional motion at the millimeter scales, achieved for bristlebots with a single on-board actuator.

这项工作提出了带有车载压电致动器的毫米级刷毛机器人（milli-bristlebot）的双向运动的理论分析和实验观察。首先，基于干摩擦模型，建立了运动理论，并预测了向前和向后运动的频率区域以及系统的共振频率。其次，制造了具有两个不同刷毛倾斜角的微型刷毛机器人，并通过实验研究了它们的双向运动。研究了机器人速度对驱动频率的依赖性，揭示了向前和向后运动的两个不同的频率区域，与我们的理论预测相吻合。此外，实验研究了共振频率和机器人速度对刷毛倾斜角的依赖性，并将其与理论模型联系起来。这项工作标志着具有单个车载执行器的刚毛机器人首次实现了毫米级的双向运动演示。