Shakebot: A Low-cost, Open-source Robotic Shake Table for Earthquake Research and Education

TL;DR

Shakebot addresses the need for affordable earthquake simulation tools by delivering a low-cost, open-source shake table built around ROS. The platform achieves up to $11.8 m/s^2$ acceleration and $0.5 m/s$ velocity on a $2 kg$ payload using a closed-loop NEMA 34 stepper with a toothed-belt transmission, complemented by camera- and accelerometer-based perception. The authors detail the hardware design, perception and motion software, calibration methods, and demonstrate PBR overturning experiments with validation against a virtual shake robot, highlighting strong cross-checks between physical and simulated results. This work lowers barriers to earthquake research and education, offering a reusable, ROS-enabled platform suitable for resource-constrained settings.

Abstract

Shake tables serve as a critical tool for simulating earthquake events and testing the response of structures to seismic forces. However, existing shake tables are either expensive or proprietary. This paper presents the design and implementation of a low-cost, open-source shake table named \textit{Shakebot} for earthquake engineering research and education, built using Robot Operating System (ROS) and principles of robotics. The Shakebot adapts affordable and high-accuracy components from 3D printers, particularly a closed-loop stepper motor for actuation and a toothed belt for transmission. The stepper motor enables the bed to reach a maximum horizontal acceleration of 11.8 $m/s^2$ (1.2 $\mathbf{g}$), and velocity of 0.5 $m/s$, with a 2 $kg$ specimen. The Shakebot is equipped with an accelerometer and a high frame-rate camera for bed motion estimation. The low cost and easy use make the Shakebot accessible to a wide range of users, including students, educators, and researchers in resource-constrained settings. The Shakebot, along with its digital twin--a virtual shake robot--has showcased significant potential in advancing ground motion research. Specifically, this study examines the dynamics of precariously balanced rocks. The Shakebot provides an approach to validate the simulation through physical experiments. The ROS-based perception and motion software facilitates the code transition from our virtual shake robot to the physical Shakebot. The reuse of the control programs ensures that the implemented ground motions are consistent for both the simulation and physical experiments, which is critical to validate our simulation experiments.

Figures (8)

• Figure 1: Shakebot CAD model and actual experimental setup. Stepper motor actuates pedestal through toothed belt and pulley transmission. Control box includes power supply, stepper motor driver, Raspberry Pi, emergency push button, and touchscreen. For scale, the control box has a dimension of 390$\times$290$\times$160 $mm$.
• Figure 2: Shakebot from top-down view illustrating double emergency mechanism.
• Figure 3: Velocity fusion workflow. Estimated velocity is regression of velocities from displacement and acceleration.
• Figure 4: Motion system supports two types of ground motions: single-pulse cosine displacement and realistic ground motion from seismogram acceleration recordings. Single-pulse cosine displacement is defined by peak ground velocity (PGV) and peak ground acceleration (PGA).
• Figure 5: Precariously Balanced Rock (PBR) at Double Rock site in coastal Central California. The yaw orientation indicates the relative direction of single-pulse cosine displacement motion.