Build log
Several robots in one home: how they avoid each other.
One flying robot in a home has to avoid walls, furniture and people. Two or three have to avoid each other too, in narrow hallways, through the same door, on the way to the same dock.
In short. Robots that share a room need to know where the others are, a rule for who gives way, and a plan for when messages arrive late or not at all. A widely used method, reciprocal collision avoidance, has each robot take half the work of avoiding the other. Alkyon’s design adds a keep-right rule and margins that grow when information is old. In our simulation, several robots swapped places in one room without touching, even with delayed and lost messages. It is a concept, tested in simulation so far.
Why it is hard
- Everyone moves at once. By the time one robot has reacted to another, the other has moved too.
- Messages are late or lost. Radio links in a home drop packets, especially through walls.
- Homes are narrow. Hallways and doors leave little room to step aside.
- Politeness can freeze. Two robots that both give way to each other can end up waiting forever, like two people in a corridor stepping the same way.
The ideas that make it work
- Share what you know. Each robot tells the others where it is and where it is heading, and they share one map of the home.
- Split the work. In reciprocal collision avoidance, described by Jur van den Berg, Stephen Guy, Ming Lin and Dinesh Manocha, each robot picks a velocity that avoids a collision over the next few seconds, assuming the other robot takes the other half of the evasive move. Neither has to do it all, and neither has to wait for the other to decide.
- Agree on a traffic rule. A keep-right rule means two robots meeting head-on both turn the same way, which breaks the stand-off.
- Trust old information less. The older a robot’s last news about the others, the wider the berth it keeps; if news stops, it slows and stops.
- Take turns. When one runs low, it lands, its dock swaps the battery, and another is ready: a dock that swaps the battery.
- People come first. Every robot keeps its distance from people, and a stop from your ring applies to all of them: a ring as the remote.
What we have tested, and what not
In our simulation, several robots swapped places in one room, crossing in the middle, with delayed and lost messages between them: none touched another, and none got stuck. That is a simulation. Real radios, real drafts and real rooms come next, on a test stand and then in flight, and we will publish what we find. How a single robot finds its way: how indoor drones navigate.
Source, read 4 November 2026: van den Berg, Guy, Lin and Manocha, reciprocal n-body collision avoidance, Robotics Research, Springer Tracts in Advanced Robotics, 2011. Alkyon is a concept in development, for Europe only.
Questions
How do several drones avoid each other?
Usually by sharing positions and planned movements, and choosing velocities that keep them apart a few seconds ahead. In the widely used reciprocal method, each robot takes half the responsibility for getting out of the way.
What happens if robots lose contact with each other?
A careful design keeps wider margins when information is old, and slows or stops when messages stop coming. In our simulation, Alkyon robots kept apart even with delayed and lost messages; real tests come later.