Rats and mice can scurry through dark and tight spaces with ease. In caves, underground burrows, buildings or sewers. Their superpower for this are their whiskers. Now tiny autonomous drones could soon navigate through darkness, dust and smoke using artificial whiskers inspired by these animals. Their small size limits the use of large or heavy sensors for navigation. That's why researchers at Delft University of Technology (The Netherlands) have developed a lightweight whisker-based tactile sensor that enables drones to navigate and explore their surroundings through gentle touch.
Navigating complex environments is a fundamental skill for autonomous robots. However, drones weighing less than 100 grams face severe constraints in terms of sensing, computing power and energy. Conventional sensors like cameras, LiDAR, or rangefinders are often too heavy and become unreliable in low-visibility environments such as smoke-filled buildings, or caves. To address this, Dr. Salua Hamaza and her team developed a lightweight and low-latency tactile perception framework that enables vision-independent navigation. The study has been published in Nature Communications.
Inspired by rodent whiskers
Mounted at the front of a tiny drone, a pair of artificial whiskers inspired by rodent vibrissae provides continuous feedback about the environment during contact. Unlike previous contact-based systems, which often rely on larger drones equipped with robotic arms or mechanical bumpers, this approach enables active, real-time tactile sensing onboard a tiny flying robot, using touch as its primary sensing modality.
"Here, we aim to equip drones with rich tactile sensing—not for manipulation in the air, but for a novel concept of tactile navigation: using touch to explore and fly through the unknown. But this comes with a challenge: for tactile sensing to work on drones, it needs to be lightweight, low-latency, and low-power. Inspired by nature, we found the answer in whiskers." —Salua Hamaza, Associate Professor Aerial Physical Interaction & Embodied Intelligence in Aerial robots at Delft University of Technology.
Each whisker is equipped with three miniature pressure sensors at its base allowing the drone to detect contact in three dimensions. As the whisker bends after making contact with a surface, pressure changes are used to estimate the contact's depth and location in space. This gives the drone detailed information about nearby surfaces and enables behaviors such as obstacle avoidance, surface following and tactile mapping.
Filtering out the noise
A major challenge was separating genuine touch signals from disturbances caused by the drone itself. Airflow generated by the propellers can introduce noise, drift and other distortions. To address this, the team developed a lightweight real-time processing pipeline that corrects for these effects and converts whisker signals into millimetre-precision depth estimates. Using advanced onboard software, the system separates meaningful touch information from the turbulence generated by the drone's own propellers and extracts reliable tactile information during flight only using 34 kilobytes of memory.
"We wanted to show that touch does not have to come at the cost of size or computational power. Our entire tactile perception pipeline runs onboard using just 34 kilobytes of memory, allowing a tiny drone to sense and respond to its environment in real time."
— Chaoxiang Ye, Delft University of Technology.
Running entirely onboard a microcontroller, this pipeline enables real-time sensing, decision-making and autonomous flight without external computing or positioning systems.
Navigating through touch alone
In experiments, the drone was able to follow both rigid and soft surface contours in complete darkness and explore enclosed spaces through wall-following behaviour. By continuously gathering information through its whiskers, it could also build tactile maps of unfamiliar environments and find the exit without relying on cameras or other vision-based sensors.
The work brings aerial robotics a step closer to the capabilities of rats, which use their whiskers to navigate dark and cluttered environments. By combining lightweight hardware with sophisticated onboard processing, the researchers demonstrate that touch can serve as a robust sensing modality even for the smallest, autonomous flying robots.
