Zippy: The smallest power-autonomous bipedal robot

2025-05-08

AI Summary

Confronted with the challenge of achieving stable dynamic gaits in millimeter-scale bipedal robots under stringent constraints of size, power consumption, and actuator precision, this work proposes a minimalist design paradigm grounded in quasi-passive dynamic walking principles. We present Zippy—the smallest fully autonomous, self-contained bipedal robot to date—standing 3.6 cm tall. It employs a single motor with open-loop pulsed actuation, sensorless arc-shaped feet, and a micro-integrated power system, eliminating conventional feedback control and complex joint mechanisms. To our knowledge, Zippy is the first millimeter-scale biped to demonstrate quasi-passive dynamic locomotion and full autonomy, achieving forward walking at 25 cm/s (10 leg lengths/s—the highest among peers), stable steering, jumping, and stair climbing. This work experimentally validates the feasibility of dynamic bipedal locomotion in miniaturized systems operating under low-dimensional control and high energy efficiency.

Technology Category

• Intelligent Robots: Motion and Path Planning
• Humans and AI: Human-Aware Planning and Behavior Prediction
• Natural Language Processing: Safety and Robustness

Application Category

• Responsible Web: Machine-in-the-loop, human agency and autonomy
• Security and Privacy: Large-scale security measurements
• Systems and Infrastructure for Web, Mobile and WoT: Energy management for devices in mobile Web and WoT environments

Abstract

Miniaturizing legged robot platforms is challenging due to hardware limitations that constrain the number, power density, and precision of actuators at that size. By leveraging design principles of quasi-passive walking robots at any scale, stable locomotion and steering can be achieved with simple mechanisms and open-loop control. Here, we present the design and control of"Zippy", the smallest self-contained bipedal walking robot at only 3.6 cm tall. Zippy has rounded feet, a single motor without feedback control, and is capable of turning, skipping, and ascending steps. At its fastest pace, the robot achieves a forward walking speed of 25 cm/s, which is 10 leg lengths per second, the fastest biped robot of any size by that metric. This work explores the design and performance of the robot and compares it to similar dynamic walking robots at larger scales.

Problem

• Miniaturizing legged robots with hardware constraints
• Achieving stable locomotion using simple mechanisms
• Designing smallest self-contained bipedal walking robot

Innovation

• Quasi-passive walking design principles
• Single motor without feedback control
• Rounded feet for stable locomotion