I think its time for a new DIY Drones contest which I would like to propose.
The T3 is fun, but it doesn't have any real point other than the winner gets some bragging rights.
At the end of the day, speed is not the goal for most of us so a competition that measuers speed yields no useful information that helps us move forward as a group.
The contest I would like to proprose is an ongoing endurance contest, instead of running over a timeframe, it is continuous and reviewed weekly so that the leaderboard shows who currently has the greatest endurance on each given platform. (Lets stick to commercially available models not custom built ones).
As part of the contest you would submit information such as prop size, battery capacity, cell count, model, weight and payload details etc.
The benefit of this is that we would be able to tabulate the results and publish a document showing the endurance relationship to weight and battery capacity for every type of model that is commonly flown.
That would save us all a LOT of messing around and would be a golden resource for newcomers, even the FPV community could benefit from the data we can extract from an Autopilot.
For each model eg Skywalker, Bixler, Skyfun etc we would be able to publish recommended motors, prop and battery for maximum endurance.
This would also be an excellent resource for people who are trying to choose the right platform.
For example, if you know you need to lift 500 grams of payload then you can find out which model is going to be able to do that with the longest endurance. It would even give you the battery, motor and prop choice in order to achieve your goal.
This information is basic stuff that almost all of us struggle with and can end up costing a lot of money through trial and error trying to figure out. My thinking is that the hardware and software are open source, yet our own individual knowlege is not collated very well, you have to read through thousands of conflicting forum posts to try and put it together yourself. If we all worked together and shared the information we learn daily, then it will make it easier for all of us and we would have some scientific measures behind a lot of the 'opinions' that go into current recommendations. Just as important as the sucessful combinations are the failed ones as these can act as "don't do this" examples for newcomers. These aren't captured anywhere at the moment.
You can also use the data to benchmark changes you make to your own platform, if we have a standardised way of measuring endurance, then instead of just saying "I got 35 minutes" in a post, you can actually measure your real relative performance to other setups, then measure the increase or decrease in performance when a change is made to one of the variables.
The other benefit of this is that it will also push manufacturers to consider efficiency more as they try and get their products into the leaderboard, especially on the airframe front.
I am happy to co-ordinate it and get it off the ground if there is support from the leaders here at DIY Drones.
I can build something to collate and deseminate the data and perhaps later on down the track we could webify it so it is fairly automated.
The key thing where I might need some help is measuring the endurance from a log file in a way that is fair and ideally automated.
I forsee the goal would be something like...
- Launch
- Fly at the slowest speed possible without stalling in Auto mode
- Loiter over a target with 100m radius until your battery cuts out
- Land
Details to be accurately recorded in order to have a valid entry:
| Model Type: | eg Skywalker, Skyfun, Bixler etc |
| Model Modifications: | eg removed landing gear |
| All Up Weight: | preferably metric |
| Cell Count: | 2S, 3S, 2P4S etc |
| Battery Capacity: | in mAh |
| Battery Manufacturer / Model: | |
| Battery weight: | |
| Motor Brand: | |
| Motor Model: | |
| ESC: | |
| Prop Spec: | |
| Payload Description: | GoPro etc |
| Payload Weight: | |
| Approx average speed during flight: | |
| Attach log file: |
For each model we will record the out of box dry weight as a comparison.
There would be no restriction in terms of the numbers of entries per person, the more times you enter, even with poor results, the more valuable the data would become. I would encourage people to enter with every combination of battery they can for their model type.
So what do you all think?
Comments
Good point about capacity. Can we hope most of the participants will have means to measure the actual energy spent? That would completely remove the battery from the equation. APM does actually have sensors for that.
I can't see why I can't measure impact of endurance of a different battery. Since it can be measured, let's suppose I know capacity, discharge curve and weight of all my batteries. If enough people have flown the same frame with different total weights, and on different cruise speeds, and they have specified how much energy they spent and for how long, then I know precisely how every of my batteries affects endurance on different payloads, because it can be calculated from the above data.
That's my main point: if we can reliably measure main frame's aerodynamic characteristics, we can predict endurance for different gear, since everything else can be measured by other means.
For example, I want to assemble an UAV with the best endurance, I have several options for airframe, engine, prop, and battery. Obviously I want to buy only the required equipment and therefore unable to perform any test flights to measure actual endurance directly.
In theory, to compare two different prop-motor-battery-frame setups, I only need to know following things:
- Each propeller's thrust vs. speed vs. power consumption curves.
- Each motor's efficiency vs. rpm.
- Each frame's energy consumption vs. flying weight vs. CG.
- each battery weight and capacity. And possibly discharge curve for different loads, but I don't think they differ too much.
All of that can be calculated from sufficient number of short constant speed level flight experiments measuring the following for different setups:
- airspeed
- total weight (which is equal to lift in our conditions)
- energy consumption
- rpm (not sure about this one, actually)
That would effectively be an approximation of existing setups to my own, based on some relatively safe assumptions and commonly accepted aerodynamics theories.
I'm sure the same approach is valid for copters as well, though their results will probably be affected by weather much greatly than for a plane.
All other data like battery/servos/rx/esc models should be collected as well, just in case there will be some use in it somewhen.
Does that make sense?
@Alexy. Yes you can measure 'A' flight time, but how do you consistently ensure that everyone is ending their flights with the same amount of battery capacity left.
yes, weight is easy, and yes extremely good point, we should include CG as that can drastically affect endurance.
It is true you can measure battery characteristics on the ground, but you can't easily measure the impact to endurance of a different battery. For example, if you have a 1000mAh battery that weights 50grams and gives you an endurance of 10min. If you double the battery to 2000mAh with a weight of 100grams, what does that do to the flight time. I suspect different airframes will respond differently to adding more weight and will have a different relationship as far as endurance goes. Having this data would save a lot of trial and error.
In terms of displaying the data, there are a few key things to show which can all be calculated fairly easily.
Well, I don't really see any problem in the first key thing.
There are not too many things to measure:
- flight time (any watch, 1 minute precision is ok)
- weight (most of us know how much our gear weights)
- CG
All other relevant specs are usually known for commercial planes and don't change, batteries are all factory-made, and can be tested better on the ground, same for motors.
People that decided to repeat the experiment would have to decide which deviations from the original report gear are critical, how to interpret the results, and which deviations should be introduced to acquire the most important knowledge.
For example there is no point in testing different battery sizes on the same frame since all key battery characteristics can be measured much better and faster on the ground without any flying.
As an opposite example, smart researcher would try more different cruise speeds and flying weights - that would help to allow to collect some important aerodynamic data like max eff. speed for different wing loadings.
Another example would be trying different props on different cruise speeds, to solve that damned prop selection problem once and for good.
This all actually makes second two things a little more complicated, because they should offer some useful analytical tools and they may actually be not so easy to design. From my experience things like that are never easy, when you need at least some usability in their interface and features.
PS: if only everybody had an AOA sensor! this project would then be the perfect substitute for a wind tunnel (-:
Distance flown is not of great use to most UAV applications.
For instance you could build a lightweight foamie with a screamer on it that could cover an enormous distance at 200kph and then have a flat battery after 10 minutes. For most UAV applications, Time in the air is much more valuable than speed over ground or speed in the air.
A model with a long endurance can stay over a single point for a long period of time or cover a great deal of distance. However a model that goes extremely fast can only cover a great deal of distance.
This is why I think time in the air is far more important to measure than distance covered which could distort the results if we included it (unless it performed the test ata fixed speed which is harder to implement as most airframes have an optimum speed for efficiency that is different and might penalise an aiframe designed to fly exceedingly slow for a long period of time).
Just to be clear, I think this is less about the competition aspect and more about the information sharing aspect. The competition just becomes a prompter to get people involved and sharing, the actual data is the valuable part that would move us forward as a community.
I agree about including copters, I see no reason why it couldn't cover both.
I'm still on the fence about custom built airframes, unless they are revolutionary, they don't offer the community any advantage because they are harder for the community to replicate. Unless the plans are published and available and there is more than one person flying the airframe, then a custom airframe is a dead end development path and the data from it offers no value to the community.
Of course, if someone builds a custom airframe that has revolutionary endurance for our needs, then open sourced the design specs, or had it contract manufactured so that it was available, then that offers immesurable value.
I personally see that people with custom airframes would use the data from what is proposed to benchmark their custom airframe against a known quantity (commercial aiframes), if they can get it to a point where their airframe is better, then its worth looking at making their airframe available publicly?
Including 500 different custom aiframes where there is only one example of each in the world would cloud the data and make it difficult to compare. The real value comes from multiple people submitting data on the same airframes, eg, if two people with identical setups except for battery capacity submit data, then you can measure the relative gain of adding more battery weight in terms of impact on net endurance.
If 5 people submit data on their custom airframes and they all have different batteries and weights, then its impossible to measure relative performance. However, if the same person submits data on their custom aiframe with 3 different batteries, then they can measure their own relative performance (to the community and of course their own battery choices), but does having this data published (unless it is really good) benefit the community?
Perhaps for these reasons we need to take the contest aspect out of it and just make it a 'benchmarking' resource.
Thekeythings we need are..
The second two are easy.
I don't see anything wrong with one entry being able to participate in more than one flight category. Time flown and distance covered are both good.
How about instead of time aloft, use distance flown? Not simply A-B since some are concerned about LOS, etc. But just an odometer. This would be particularly relevant for airplanes. Copters might be better tested with time aloft.
I think a Custom class is just as important for the mechanic comparisons and upgrades as long as the non airframe parts are the same (e.g drive and control)
Does (custom) carbon-covered and very overloaded commercial foamie count?
The contest should also actually stretch things, just drilling holes in the sky with RTFs is not really all that challenging. To test our EPP and how it reacted to UV I flew one particular airframe for more than 100 hours. During that time I got so used to it that I was quickly able to trim it out to fly circles no auto anything.
Anything must be done within VLOS and below 400' of course.
So perhaps this table should be outside of the T3 realm and I look forward to seeing what data is discovered.
This is a fantastic idea.
I think you should keep it simple. Two divisions - one for planes, one for copters...winner from each group is just the person who keeps it in the air the longest and lands safely. It's up to them what they use, how much danger they expose their airframe to (of course nothing stupid that would endanger hapless 3rd party people or property).
Clearly automatic flight is a must (between the initial take-off and landing) but leave it up to the individual whether they use loiter, circle, way points, etc.
again, great idea!
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