Sphebot: A New Form of Robotic Locomotion

概要

Sphebot is a sphere-shaped robot that moves autonomously in all directions by lifting its surface panels from inside. Combining the strengths of legged and wheeled robots, it offers high mobility that enables applications such as emergency and exploration

経緯

Typical mobile robots are usually wheeled or legged, but both types sometimes have limitations in terms of mobility. So, we started looking into the possibility of sphere-shaped robots that can roll in any direction. It's common for such robots to rely on internal mass transfer or pendulum mechanisms, but we wondered if we could come up with a more direct and controllable mechanism. Initially, we used a rack-and-pinion system to drive the structure, and then we got the idea to use a screw. This idea was inspired by everyday objects like bottle caps. Can we adopt a screw into the mechanism? This simple idea became the core of our project.

機能

Sphebot is a 3D-printed sphere-shaped robot designed to move in any direction. Its outer shell is divided into 12 parts, each of which can move outward and back in on its own. By pressing against the ground with these parts, Sphebot rolls itself forward — not by shifting its weight, but by actively making contact with the ground. By choosing which panels to extend, Sphebot can go forward, turn, or stop as needed. This makes it able to move on bumpy or uneven surfaces without trouble. The robot has full-color LED lights on its surface. These lights help it know where it is and how it’s tilted, so it can move by itself without needing a person to control it. Because all of its parts are safely placed inside the shell, Sphebot can be used in tough conditions, like disaster zones or on other planets. Its way of moving is different from walking robots or wheeled ones, offering a new answer to mobility in hard environments.

開発過程

Sphebot began with the idea that sphere-shaped robots offer strong impact resistance and omnidirectional mobility. We made two types of prototypes until now. In Ver1, we built a dodecahedral structure where each face had a rack-and-pinion leg driven by a Futaba command servo. A Jetson processed inertial sensors and LED-based visual markers to estimate pose, and a machine learning model was trained to select the optimal leg for movement. While omnidirectional motion was confirmed, Ver1 faced issues such as slippage and wear, insufficient structural stiffness to maintain surface angles, inadequate torque output, and incomplete electrical design, all of which limited its practical use. In Ver2, legs were replaced with 12 circular panels pushed outward by a large central screw. This improved stiffness and torque transfer. Three internal guide arms constrain motion to vertical only. A Jetson now controls 12 Raspberry Pi Zero 2W units over TCP/IP, each operating a Kondo ICS servo, a full-color LED lights and a Full HD camera module. After extensive testing and refinement, Sphebot evolved into a structurally simple, reliable, and ready to operate in the field.

差別化

The structure is completely different from existing conventional robots. Most existing sphere-shaped robots rely on shifting internal weights or rotating masses to roll the outer shell. While these systems are mechanically simple and impact-resistant, they move passively and lack precise control, making it difficult to stop instantly or move in an exact direction. Legged robots, on the other hand, offer strong terrain adaptability but are often complex, heavy, and hard to control. Sphebot integrates the strengths of both: omnidirectional mobility from its sphere-shape and active propulsion from internally pushing its surface panels like legs. This enables it to stop and start movement in any direction at any time. Its unique system enables active propulsion not found in conventional robots. The fully enclosed shell protects internal electronics from dust and radiation, making Sphebot ideal for extreme environments. It represents a new category of mobile robots.

将来の計画

In the future, we envision Sphebot as a robot that can roll freely through complex environments while recognizing its surroundings. Its sphere-shaped body makes it naturally robust—safe to bump into things, great at going downhill, and high energy-efficiency. With smarter control, it will adapt to changing terrain and navigate on its own. One day, Sphebot might become a friendly presence: a machine you can kick like a ball, only to have it roll back and follow you—no remote, no leash, just curiosity. From disaster zones to daily life, it aims to roll wherever it's needed.

他アワードでの受賞歴

The initial version of this project, Sphebot Ver1, was presented as a poster at the 2024 Robotics and Mechatronics Conference (ROBOMECH 2024) organized by the Japan Society of Mechanical Engineers. Although not an award, it received significant attention and positive feedback from attendees and experts.