TerraSkipper: A Centimeter-Scale Robot for Multi-Terrain Skipping and Crawling
Shashwat Singh, Ziyun Zhang, Spencer Matonis, Zeynep Temel
AI summary
Problem
Centimeter-scale robots struggle to navigate soft, heterogeneous, and deformable terrains like mud, sand, and grass because traditional crawling or swimming mechanisms fail at small scales due to unpredictable substrate interactions and limited actuation power.
Approach
The team designed a 28-gram, 3D-printed robot inspired by mudskippers that uses a spring-loaded tail for impulsive skipping and magnet-enclosed fins with Hall effect sensors for closed-loop crawling control.
Key results
- Optimized 25 mm springtail generates up to 6 N of impulsive force
- Skipping outperforms crawling on viscous/granular media, reaching 5.38 cm/s on grass
- Hall sensor feedback reduces trajectory drift to under 1 cm
- Switching between skipping and crawling extends real-world operational range
Why it matters
Provides a low-cost, bio-inspired platform for deploying small robots in real-world unstructured environments like wetlands, disaster zones, and natural ecosystems.
Abstract
Mudskippers are unique amphibious fish capable of locomotion in diverse environments, including terrestrial surfaces, aquatic habitats, and highly viscous substrates such as mud. This versatile locomotion is largely enabled by their powerful tail, which stores and rapidly releases energy to produce impulsive jumps. Inspired by this biological mech- anism, we present the design and development of a multi- terrain centimeter-scale skipping and crawling robot. The robot is predominantly 3D printed and features onboard sensing, computation, and power. It is equipped with two side fins for crawling, each integrated with a hall effect sensor for gait control, while a rotary springtail driven by a 10 mm planetary gear motor enables continuous impulsive skipping across a range of substrates to achieve multi-terrain locomotion. We modeled and experimentally characterized the tail, identifying an optimal length of 25 mm that maximizes the mean propulsive force (4 N, peaks up to 6 N) for forward motion. In addition, we evaluated skipping on substrates where fin based crawling alone fails, and varied the moisture content of uniform sand and bentonite clay powder to compare skipping with crawling. Skipping consistently produced higher mean velocities than crawling, particularly on viscous and granular media. Finally, outdoor tests on grass, loose sand, and hard ground confirmed that combining skipping on entangling and granular terrain with crawling on firm ground extends the operational range of the robot in real-world environments.