Conversation

I haven't had much time to invest in big hardware projects lately, but this guy is seriously inviting me to reconsider my time budget.

I built a #drone from scratch a while ago, running on a RPi + PWM controller, and Platypush to manage the communication bus.

It has lifted from the floor by 2 meters at most in all of its career. In the process of learning how to make it fly, it destroyed ~10 plastic propellers and damaged two pieces of furniture in my house.

That's because building a real-time control loop that keeps a device as aerodynamic as a brick hovering in the air is not easy. Even if you get all the physics right, the slightest unbalance in the propeller's thrust, or the slightest tenth-of-second-magnitude delay in the control loop line, will make the difference between a nice flying machine and an uncontrollable brick with killer blades ready to smash on the ground.

But what if it hadn't to be like that? What if you build a drone that is both aerodynamic and disturbance-tolerant by design?

This guy definitely got this right. He built a drone with three propellers placed at 120 degrees from each other. The drone's shape is aerodynamic, the weight is carefully balanced, and even if 2/3 propellers are off the drone can still hover - it will spin a lot, but its y rotation axis won't change.

If the drone's mechanics and aerodynamics are carefully designed, and the drone tends to inertially retain its hovering state, then we can easily relax some other constraints. We don't need complex real-time control loop logic on dedicated (often expensive) flight controllers, a tenth-of-a-second delay won't make the drone crash, and even a Python script on a RPi can handle that.

And we can actually save A LOT on battery consumption, since a lot of the energy from the battery actually goes in keeping a brick hovering instead of actually moving it. That translates either in smaller battery requirements, or much longer flight times.

It looks like I'll have a nice outdoor project to work on this spring.

https://hackaday.com/2022/11/09/clever-control-loop-makes-this-spinning-drone-fault-tolerant/