Building bots on a budget
As an undergraduate, Yufeng Chi (B.S.’23 EECS) was captivated by humanoid and legged robots. Eager to learn more, he would watch YouTube videos and dive into class projects, but getting hands-on experience and tinkering on his own was not easy.
“I was interested in building my own version of a humanoid robot, but back then, things like actuators, motors and robotics kits weren’t widely available — and developers kept the source code private,” he said. “So I started looking for ways I could [make a] DIY robot.”
Now a Ph.D. student, Chi is part of a team of Berkeley engineers that has developed Berkeley Humanoid Lite, a low-cost, open-source robot made of 3D-printed parts.
Commercial companies may offer completely built robots, but the proprietary nature of their hardware and software design often makes it difficult to replace parts or to modify components. At the same time, not everyone has access to state-of-the-art equipment. By developing Berkeley Humanoid Lite, the researchers set out to provide a launching point for anyone with an interest in humanoid technology.
The core of Berkeley Humanoid Lite’s design is a modular 3D-printed gearbox for the actuators and robot body. All other components can be sourced from widely available e-commerce platforms or fabricated with standard desktop 3D printers. This keeps the total hardware cost under $5,000 (based on U.S. market prices), a fraction of the cost of purchasing a commercially built robot of similar scale. In addition, replacements for broken or worn parts can be easily fabricated using the 3D printer.
Once completed, Berkeley Humanoid Lite stands at about 1 meter and weighs approximately 16 kg. Chi estimates that it would take a novice roboticist about one week to build their own Berkeley Humanoid Lite, depending on one’s skillset and experience level.
Recognizing that 3D-printed parts inherently lack the strength of materials such as aluminum, the researchers adopted a cycloidal gear design for the gearbox inside the actuator.
“The main benefit is that the gear’s teeth are very large,” said Chi. “This distributes the load across a larger surface area than traditional gear systems, reducing stress and wear.”
In addition, they tested several aspects of the 3D-printed actuators to validate their durability.
“Our findings showed that the 3D-printed actuator is at least on par with other actuators,” Chi said, “or within the tolerance margin to achieve these higher-level tasks and skills.”
He added, “We designed this so that if an actuator breaks down, you can just print another gear box and swap it out, [but] we have yet to break a single actuator on any of our test robots, even after putting them through all these experiments.”
Berkeley Humanoid Lite’s hardware design, embedded code, and training and deployment frameworks are fully open source. The researchers wanted users to be able to see how everything works and to easily customize the robot.
“I believe in the spirit of open-source communities, the idea of an ecosystem where people share ideas and knowledge,” said Chi. “Our hope is that Berkeley Humanoid Lite will help move us closer to democratizing the development of humanoid robotics.”
Koushil Sreenath, associate professor of mechanical engineering; Borivoje Nikolic and Sophia Shao, professors of electrical engineering and computer sciences; and Ph.D. students Xiaoyu Huang, Zhongyu Li, Qiayuan Liao and Junfeng Long all contributed to the project.
Learn more: Berkeley engineers develop customizable, 3D-printed robot for tech newbies