5 ms·

Computerized stability control systems exist, are quite prevalent, and have a thriving open source community. Check out: https://github.com/betaflight/betaflig

Computerized stability control systems exist, are quite prevalent, and have a thriving open source community. Check out: https://github.com/betaflight/betaflight/wiki https://github.com/betaflight/betaflight/wiki Granted, it's for hobby scale drones, but the same principles apply.

dfox 8y ago
The physics involved in multi-rotor drones (or even counter rotating dual rotor toy-level RC helicopters) is significantly different from single rotor+stabilizer helicopters in that there is at least in theory point where the thing is dynamically stable.
- bri3d 8y ago
  For what it's worth many toy RC helis exist with collective pitch tail rotor setups and full feedback stabilization - it started with tailrotor yaw hold automation and now they can stabilize in all axes. Check out something like Blade mCPx
  - gjhan 8y ago
    The dynamics, which are not just the rigid body dynamics plus the aerodynamics of the vehicle but also include many structural modes of the rotorhead and blades, are not scale invariant. An RC helicopter is proportionally stiffer in certain degrees of freedom by an order of magnitude (in rotor angular velocity and thrust:weight ratio e.g.), and so can ignore dynamical factors that dominate the control and structural sizing for manned helicopters.
    - halbritt 8y ago
      Do you think a PID control would would fail to be able to accommodate those dynamic factors?
- namibj 8y ago
  I thought quadrocopters were so unstable that flying one without a PD controller, or better a full PID, would lead to a crash within seconds. A Helicopter, possibly only of the counterrotating coaxial variant, should not be affected by this instability, I think.
  - halbritt 8y ago
    That's correct. The controllers use full PID loops for each axis.
- halbritt 8y ago
  The physics involved in multi-rotor drones and fixed wing aircraft are quite different. However, there is control software that works on either. https://github.com/iNavFlight/inav/wiki https://github.com/iNavFlight/inav/wiki The underlying differences in how they fly aren't that relevant. You have a six-axis IMU, various controls that influence how the craft behaves in those axes and various PID loops that influence the controls. I don't really understand the downvotes. Obviously, having a type certificated auto-pilot for a commercial helicopter is a world apart from the flight control system for a hobby-scale drone, but the gap between them has nothing to do with the technology and everything to do with the process of type certification. My point is that it's pretty impressive what these software projects are able to achieve with sub $100 MCUs. Some of them now have 32khz control loops with 32khz IMU sampling. Anyone that's ever peeked under the hood of a commercial auto-pilot would be amazed by that.

dfox 8y ago

The physics involved in multi-rotor drones (or even counter rotating dual rotor toy-level RC helicopters) is significantly different from single rotor+stabilizer helicopters in that there is at least in theory point where the thing is dynamically stable.

bri3d 8y ago
For what it's worth many toy RC helis exist with collective pitch tail rotor setups and full feedback stabilization - it started with tailrotor yaw hold automation and now they can stabilize in all axes. Check out something like Blade mCPx
- gjhan 8y ago
  The dynamics, which are not just the rigid body dynamics plus the aerodynamics of the vehicle but also include many structural modes of the rotorhead and blades, are not scale invariant. An RC helicopter is proportionally stiffer in certain degrees of freedom by an order of magnitude (in rotor angular velocity and thrust:weight ratio e.g.), and so can ignore dynamical factors that dominate the control and structural sizing for manned helicopters.
  - halbritt 8y ago
    Do you think a PID control would would fail to be able to accommodate those dynamic factors?
namibj 8y ago
I thought quadrocopters were so unstable that flying one without a PD controller, or better a full PID, would lead to a crash within seconds. A Helicopter, possibly only of the counterrotating coaxial variant, should not be affected by this instability, I think.
- halbritt 8y ago
  That's correct. The controllers use full PID loops for each axis.
halbritt 8y ago
The physics involved in multi-rotor drones and fixed wing aircraft are quite different. However, there is control software that works on either. https://github.com/iNavFlight/inav/wiki https://github.com/iNavFlight/inav/wiki The underlying differences in how they fly aren't that relevant. You have a six-axis IMU, various controls that influence how the craft behaves in those axes and various PID loops that influence the controls. I don't really understand the downvotes. Obviously, having a type certificated auto-pilot for a commercial helicopter is a world apart from the flight control system for a hobby-scale drone, but the gap between them has nothing to do with the technology and everything to do with the process of type certification. My point is that it's pretty impressive what these software projects are able to achieve with sub $100 MCUs. Some of them now have 32khz control loops with 32khz IMU sampling. Anyone that's ever peeked under the hood of a commercial auto-pilot would be amazed by that.