They don’t even have to figure it out, just buy it in like a lot of the other clever tech they package. Question might be why they haven’t- would be a good seeking point and it’s all in software.
Flying with a disabled prop or motor (P4P)
- Thread starter Kristina Fowler
- Start date
The reason they haven't done it is: LOTS OF DOLLARS WHEN A PHANTOM CRASHES......FOR DJI...LOL
Stability and control of a quadrocopter despite the complete loss of one, two, or three propellers
http://www.mwm.im/ResearchFiles/Pap...eTheCompleteLossOfOneTwoOrThreePropellers.pdf
He demos it in his TED Talk.
http://www.mwm.im/ResearchFiles/Pap...eTheCompleteLossOfOneTwoOrThreePropellers.pdf
He demos it in his TED Talk.
No, not within the warranty period anyway- hardware failure would be a repair at DJI’s cost.
This is false. It's a balance issue. Tri-rotors are designed to be balanced with 3 rotors. A square shaped 4 rotor is not.
- Joined
- Jun 14, 2016
- Messages
- 1,744
- Reaction score
- 791
- Age
- 65
Any given rotor would have to be able to almost instantaneously switch rotational direction as needed to keep the quad level along the axis missing the prop or motor. Another option would be counter-rotating props (i.e., two props per motor). Either way, the quad would be able to keep itself fairly level with one prop/motor not functioning. Would require new firmware and a newly designed controller board.
That's an fascinating analysis. For the aircraft that they tested the 3-prop steady solution approached a vehicle spin rate of around 300 rpm (5 rotations per second). That's about twice as fast as a Phantom spins when it loses a prop, but obviously the Phantom FC is not actually programmed with a 3-prop solution. Whether that could be implemented with no change in hardware is an interesting question.
N017RW
Premium Pilot
The demos I've seen show experimental quads with lots of computing power going into rapid yaw rotation due to torque imbalance. They don't have cameras or gimbals attached indicating extreme balance is an important criterion. A Phantom landing in those conditions would seemingly suffer damage as well.
For those saying how easy this is to do please provide some links or other materials. I believe it requires more sophisticated sensors and higher computing power to deal with the rapid state of change.
For those saying how easy this is to do please provide some links or other materials. I believe it requires more sophisticated sensors and higher computing power to deal with the rapid state of change.
N017RW
Premium Pilot
Agreed. At least one solution exists. Could be hardware costs and possible patent issues or IP licensing making it too expensive for this tier of drone. Also may require a higher level of weight/balance making it impractical for this form factor.
I agree on the damage issue - landing while spinning at 300 rpm is going to go badly. As for the computing power and sensors, that's a tougher question. The modern solid state strapdown sensor packages are good to those kinds of rotational rates without any problem, and we know that the DJI aircraft can recover from free-fall after a motor restart which suggests that they have the computing power to deal with relatively high rotation rates.
That was my first though, the solution may be limited by hardware/computing power however the developer claims the algorithm can be implemented with any quadcooter- New algorithm makes quadrocopters safer
There is no need to switch rotational direction, varying propulsion output and rotation of the AC is all that is required.
N017RW
Premium Pilot
Has free-fall recovery been demonstrated as an absolute, or has it happened on occasion?
Is it the same as uncontrolled yaw in which altitude stabilization would require more power thus seemingly increasing yaw rate?
I'm erring on the side of- there's much more going on here and it's not easy.
Is it the same as uncontrolled yaw in which altitude stabilization would require more power thus seemingly increasing yaw rate?
I'm erring on the side of- there's much more going on here and it's not easy.
Back since the old NAZA units, when it's been tested it seems to have worked, and I've not seen tests from a reasonable height that did not work. That does not consitute proof that it will always work, of course, but it does suggest that the FC has enough computing power to get out of the tumbling spin.
The FC clock speed is apparently 4.5 MHz, processing the rate gyro and accelerometer data at 200 Hz and modulating the motors at 50 Hz, which should be plenty to follow ~ 5 Hz rotations.
Yes, it would take a new FC to accommodate reversing a motor, something that other acrobatic 3D drones have today to fly upside down. They're pretty amazing to see fly. The DJI firmware and sensors would have to have enough speed and sample rate to execute a quasi soft landing on 3 of 4 drone props, if something happened to one prop or motor. I'm sure this is doable, just a matter to time and direction. Eventually DJI will want to brag they can do it, in case of emergencies. I'm sure this is on their "to do" list at some point, just a matter of time.
But remember, the more you crash, the more DJI sells. I'm not sure that a 3 prop contingency mode will happen very soon, but there will be something that will trigger this new feature someday.
When a quad loses one rotor, the opposite one cannot be used for lift without flipping the whole thing over, so you have a bicopter with half the lift available. Engaging the third rotor generates a yaw imbalance making the aircraft rotate. At best you are going to have a controlled crash of a spinning aircraft. A delicate gimbal will likely not survive. It has been demonstrated, in the laboratory that it is possible to land a lightweight quad with a rotor loss. With a heavier quad carrying a camera, you are going to fall in the lake.
With a hexcopter, one rotor loss means you now have a quadcopter with two thirds of the lift available. Having 4 rotors, you can still control yaw.
With a hexcopter, one rotor loss means you now have a quadcopter with two thirds of the lift available. Having 4 rotors, you can still control yaw.
I don't get why people don't understand this. Could you *theoretically* balance on two rotors and use the third by itself to control the other axis? Sure. But in reality, with a center of gravity that's so far from ideal for 3 rotor use and no way to control yaw, a Phantom or any square shaped quad is never flying without all four rotors operational.
i might be you haven’t caught up with what is being discussed here. We aren’t suggesting a quad that has lost a prop/motor might, through implementation of a software solution, continue to maintain normal flight characteristics. It is possible for it to maintain a hover and return to land in a controlled manner however.
