Is there a mathematical solution for preventing fly-aways?
My understanding is that the following is what causes them:
- Accel z goes negative due to ship vibration versus an actual drop in altitude
- The ship corrects by adding power
- The added power causes a larger vibration-induced negative z
- The ship corrects the pseudo altitude drop by adding more power
- A fly away occurs
My understanding of mathematical solutions are:
- A filtered or weighted z only diminishes (does not solve) the effect.
Has anyone tried a "significant z", z / s, where s is the moving average of the variation of z?
- when the IMU isn't vibrating, s is low so the magnitude of z / s is high
... z is significant
... z can be trusted for use in altitude control
- when the IMU is vibrating, s is high so the magnitude of z / s is low
... z / s has less effect
... and will not caused a flyaway
Replies
There is another way of looking at this problem and that is by comparison to "norms". A norm or benchmark is used to establish acceptable levels of performance of a product. An individual experience can change someone's perception of what is normal, so we see different extremes of experience being stated in this thread, sometimes passionately, as the absolute truth.
However, once you start talking about an entire industry, the individual experience becomes a single point in a very big statistical set. And the bigger the industry, the bigger the data set and the more that previously insignificant few percent of outliers start looking like a major problem.
Once drones become a fully fledged industry, not just the new kid on the block, the norms will change significantly. Surprisingly, the biggest push for change comes not from the FAA, but from the insurance companies. The insurance companies have a vested interest in not paying out claims, so they are the single biggest contributor to the standards that we all take for granted in every other established industry, like air travel or motor cars or oil refineries.
We find ourselves at the point of transition from a hobby into a professional industry. The norms will change, and there is an actuary right now calculating the cost of "drone fly-aways" to his insurance company. New standards will be imposed and drone manufacturers will have to prove that their products meet these standards. Human error will not be accepted as an excuse for something going wrong. They will demand that solutions are found or else… no insurance cover! Many companies in the drone sector are already asking for ISO9001 certification from their suppliers. Such fun ;)
LaserDev
A good point on yet how another financial industry service provider interferes with technological development! :-(
Legalized gamblers called insurance companies need to take a back seat IMHO...the focus should be on implementing standards and systems to avoid risks completely, NOT to make money from them.
Classic example is cars. We easily have the technology to adopt a much better rail based system that avoids the necessity for every automation system included in a "Google car", bar your awesome range measuring LIDAR products, and would make personal travel safe, faster and more efficient, and not cost 100,000's of lives a year on our perverted road system which is still based on the horse drawn cart from thousands of years ago. We can do much better IF we can overcome the faulty stimulus for decisions, caused by a corrupted financial system.
In this case a possible remedy is to use sensory information that drones do not currently have, but that currently gives pilots an advantage. That is vision.
Most drones are currently flying around "blind" in that there frame of reference is purely the result of susceptible sensory inputs. None of which have the capacity to determine attitude, position or orientation by visual cues (remember the old IR LED horizon sensor?). We're constantly flying drones IFR...it's silly. I firmly believe that the next step is to incorporate visual data into the FC method, which will result in a comparable, if not overall far superior FC system. Thanks to mobiles the mobile processing power and camera hardware is there, we just need the software.
Who's up for doing visual flight control?
Regards
+1. This is also my intuition that visual camùera input is the only way out via the top.
As long has you have a FC that accepts inputs and runs proper code (like pure gyro mode - without accelerometer trashing a not needed horizon) and as long as you have a pilot that can fly RC you will have no flyaways at all. If RC contact breaks do Barometer autoland (with drift) or shut down motors so no flyaway in that case as well. It can't get any simpler that this. Acc-Z jumbo-mumbo will take you nowhere. If you blame all flyaways on vibration alone you will first have to have a specific onboard sensor that just picks up vibration (maybe a little piezo-plate?) and is not disturbed by accelerations. Just my point of view.
@Crashpilot1000
Although I agree that the pilot can prevent flyaway, however, as the UAV progresses and automous flying becomes a norm, the UAV must have the self-correcting functions in place in case of component failure.. my 0.02.
That's why the industry is pushing to image/video recognition because that can solve the problem. Currently we are in the gap between marketing hype of what future technology could do (projected to this point in time ofcourse for the sales) and what the average FC can do.
I have been playing with kinect/real sense image system for two years, the problems are the payload, distance and computational resource. I also tried the multi-view algorithm. I got it working on MATLAB
But what is the point when a HW failure can STILL cause a crazy fly away... what is the FC SW going to do then ? You are asking of a DYI community what the aviation airliner industry has not accomplished yet. Full autonomous flight with 100 % reliability. We are not going to get there any time soon and not with this thread. I think crashpilot1000 has a very valid point. Pilot skill level is crucial. As well as pilot understanding the risks and safety measures. And every fly away has to be treated as a separate incident and all should be dealt with in case by case basis. No one fix it all here. At this point i personally have been able to achieve an extremely reliable flights with good weather conditions (crucial). What has contributed to my success is vibration control as unwanted vibration (noise) in mechanical form is number 1 enemy. Not even EMC/EMF as that can be more easily managed by physical distance. I am truly amazed what my quad is capable of very reliably. Where do we draw the line to what we ask the developers to do here from an open source project ??
But the modern aviation industry has improved airplanes to do exactly that - autonomous flight with incredible reliability, through a combination of incremental learning from incidents, improved redundancy and diversity of hardware, but also largely through software improvements. Most modern planes are fly by wire and the software is designed to specifically cope with hardware failures and unexpected scenarios through redundancy, voting systems etc. If you look back through most of the recent crashes they were due to pilot error - quite often by overriding the autopilot which was coping at the time.
Pilot skill will never be as good as FC software that has been incrementally improved by hundreds of skilled developers and engineers over a long period of time to cope with avoidable problems. We're at a comparatively early stage with drones and yet as you say they still perform amazingly well.
if we can adapt the FC to specifically cope with loss of motors, props, sensors, surely that's a good thing? Its been proved and demonstrated that even a quad can cope with a loss of a motor given specific algorithms to deal with that scenario, but APM can't, and it's a bit hit and miss even with hexes. Granted it won't be easy and will take time, but I don't think the project should just give up and not bother, it would be a fantastic safety improvement, and that's just one example, one scenario.
fnoop,
I fly with a private license in Canada. The airliner industry's pilot procedures are written with all emphasis on human control. The autopilot today is very capable to fly reliably however the pilot takes control in all situations where there is an emergency or adverse weather conditions. This is exactly what we are saying not to do here. And i say NO. When your drone flies away. You have to manually take control and bring it back. Thats IT. My drone has NEVER failed me. And even when i thought it was going to i switched it in stabilize and fly it very very comfortably. I dont really see the point to this thread still.
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