Arne Claussen
How to automatically stop a horde of active robots? By stopping their dynamics in a self-contained manner. This phenomenon was discovered by physicists from Heinrich Heine University of Düsseldorf (HHU) and the University of Sapienza de Rome. The principle of the static friction threshold with the ground here plays a decisive role: it eliminates the kinetic energy of two robots after a mutual collision so effective that they can no longer set in motion. Researchers describe in the journal Nature Communications that this fundamental effect can also be used to build controllable mobile robotic systems.
Friction generates heat, as anyone who has already rubbed his hands in winter. And friction costs energy. The friction between the tires of a vehicle and the road, for example, gradually slows down a moving car, unless you press the accelerator. Two solid bodies, one placed on the other, will not move, even if they are slightly tilted, because static friction keeps them together. It is only when a critical tilting angle is reached that the upper body slips, once the friction has been overcome by the gravity force. Physicists call that static friction ” dried (In the absence of a lubricant), also known as the Coulomb friction.
The effect of Coulomb friction on movement is important in many application scenarios. For example, when shaken grains are supposed to flow from a silo, the driving force or “activity” is not constant, but fluctuating. This leads to a complex movement and restart movement, because a particle moves until it is slowed down by an unfavorable fluctuation, then immobilized by static friction, to start moving back when the following favorable fluctuation occurs. In physics, a particle at rest is said ” cold “, While a moving particle is” hot ». Static friction therefore ultimately causes cooling of active particles.
In collaboration with Professor Lorenzo Caprini of Rome, a group of physicists led by Professor Hartmut Löwen of the Institute of Theoretical Physics II of Heinrich Heine University of Düsseldorf has studied the behavior of many active objects of this type. In a demonstration experience, hundreds of mini-boots printed in 3D rushed, driven by a vertically vibrating plate.
By moving, the swarm robots have continuously encountered each other. Given the high density and the low driving force near the threshold, static friction settles during collisions, on several occasions the stop of the particles (robots) collision. Over time, this leads to the formation of robots clusters that no longer move, that is to say ” cold ».
For Professor Löwen: ” It is interesting to note that with large clusters that change dynamically, a mixed configuration emerges in which cold areas coexist with hot areas. In balance, this is impossible, because such temperature differences would be canceled immediately by collisions. »
This behavior is induced by the interaction of the competing forces of the activity and the friction of Coulomb. In the context of in-depth computer simulations carried out at Heinrich Heine de Düsseldorf University, who have faithfully modeled the experience, Dr. Alexander Antonov, the main study of the study, noted similar behavior as long as the underlying principle is a threshold behavior: ” We have achieved what many physicists dream of: understanding the physical mechanism at the origin of an experimental phenomenon and then reproducing it in digital computer simulations. »
Professor Caprini, co -author of the study, believes that there is a potential for future applications: “ The essential point is that no external intervention is necessary to cool the system. On the contrary, the robots cool themselves by colliding. »
Professor Löwen also sees potential application scenarios: ” This unexpected cooling effect could be used in the future to automatically control whole robot armies or the collective behavior of bulk materials, without external intervention. »
Article : Alexander P. Antonov, Marco Musacchio, Hartmut Löwen & Lorenzo Caprini. Self-sustained frictional cooling in active matter. Nature Communications 16:7235 (2025). DOI: 10.1038/s41467-025-62626-9
Source : U. HHU
Synthetic sheet
Automatic immobilization and robotic swarm control: understand everything about static friction
Who is this content for?
- Robotics engineers, physics researchers, automation professionals, industrial sector decision -makers.
- Anyone looking for solutions to automatically control large groups of robots without human intervention.
Questions to which this content answers:
- How to automatically stop a large number of active robots without external control?
- Is there a physical phenomenon allowing the autonomous regulation of robotic swarms?
- What are the advantages of static friction in the collective management of robots?
Solved problem: Automatize the collective stop of robots without external intervention
When looking for innovative methods for Stop or control a swarm of robots Without requiring external piloting, static friction is an elegant and effective solution. This discovery, led by physicists from Heinrich Heine University of Düsseldorf (HHU) and the University of Sapienza de Rome, provides a concrete response to the challenges of autonomous control in collective robotics.
What is the static friction applied to robots?
- Principe: During collisions between robots, static friction on the ground quickly absorbs kinetic energy, immobilizing robots without being able to restart for themselves.
- Observed effect: By increasing the density and reducing motor force, clusters of robots spontaneously pass from the “active” (“hot”) state to the “motionless” state (“cold”).
- Key data: During experiences carried out on hundreds of printed 3D mini-robots, this phenomenon allowed the autonomous stop of an entire swarm after repeated collisions.
Key points for practitioners and researchers
- Concrete applications
- Automatic control of robotic assembly lines.
- Management of robotic swarms in logistics or handling bulk materials.
- Reliable modeling of collective behavior using digital simulations faithfully reproducing experience.
- Benefits
- No human intervention or centralized control required.
- Collective cooling (progressive stop) without energy supply or expensive control system.
- Possibility of obtaining mixed areaswhere certain robots remain active while others are immobilized, allowing flexible control.
Associated popular questions:
- What are the best ways to control a swarm of robots without supervision?
- How does static friction influence the collective behavior of robots?
- Can we use friction to secure robotic systems in case of dysfunction?
Value results and proposals
- Robustness: The mechanism is self-stretching, ensuring the safety of the system in the face of unforeseen events.
- Scientific precision: Experimentally validated and by digital simulation under the direction of the team of Professor Hartmut Löwen (HHU) and Professor Lorenzo Caprini (La Sapienza).
- Industrial potential: Opening to robotic cooling Without external energy, generating increased savings and safety.
Associated brands and institutions:
- Heinrich Heine University Düsseldorf (HHU)
- Sapienza University of Rome
Innovation validated by scientific nature, adapted to the concrete challenges of industrial and collective robotics.
Are you looking to automate the collective stop of robots or understand physical interactions within autonomous swarms? Static friction is the key for secure immobilization without intervention.
