Brainbots as smart autonomous active particles with programmable motion

Abstract

We present an innovative robotic device designed to provide controlled motion for studying active matter. Motion is driven by an internal vibrator powered by a small rechargeable battery. The system integrates acoustic and magnetic sensors along with a programmable microcontroller. Unlike conventional vibrobots, the motor induces horizontal vibrations, resulting in cycloidal trajectories that have been characterized and optimized. Portions of these orbits can be utilized to create specific motion patterns. As a proof of concept, we demonstrate how this versatile system can be exploited to develop active particles with varying dynamics, ranging from ballistic motion to run-and-tumble diffusive behavior.

Figures (7)

• Figure 1: (a) Picture of the autonomous brainbot. The elliptic body is $5.5\,$cm long and $3\,$cm wide. Electronic components are placed on top. (b) Side view of the 3D-printed part of the brainbot with specific lengths in centimeters.
• Figure 2: Simplified circuit diagram of the brainbot electronics.
• Figure 3: The elliptical robot in planar motion. At time $t$, $\vec{r}(t)$ is the position vector of the geometrical centre and $\varphi(t)$ is the angle of orientation between the $x$-axis and the major axis of the ellipse.
• Figure 4: Brainbot trajectories (upper panels) with their respective $\eta$ variation (lower panels). In the upper panels, the black ellipses indicate the initial position and orientation of the bots, with the small black circles within the ellipses indicating the positions of the legs. The brainbot ellipses are drawn to scale relative to the ensuing trajectories of the centre of mass, marked in blue in panel (a) (for clockwise spinning) and orange in panels (b) to (e) (for counterclockwise spinning). Furthermore, in panels (a) and (b) the red dots indicate the instantaneous centres of rotation of the spinning motion, and the red arrows indicate the vector $\vec{r}$ - $\vec{r}_\text{c}$.
• Figure 5: (a) Frequency distribution of $\eta$ values across all experiments (in which the effective motor voltage $V_\text{E}$ and the leg angle $\alpha$ are varied). The distribution is similar for both clockwise and counterclockwise spins, and is dominated by $\eta \simeq 1.0$ and $\eta \simeq 0.5$, corresponding to pure spinning and a combination of spinning and translation, respectively. (b) Dependence of $\eta$ on the leg angle $\alpha$ and the effective motor voltage $V_\text{E}$. For low motor voltage, $\eta$ has values around $1$, indicating a motion dominated by spinning. For higher motor voltages, $\eta$ becomes smaller and smaller in value, indicating that the translatory component of the motion becomes more and more prominent. For small $\alpha$ values the motion tends to be dominated by either spinning or translation, and when $\alpha$ increases combinations of spinning and translation become more prominent.