To build a dji f330 or f450 or just get phantom rtf.

[Kaen]

Sure you can, but the problem is that cheap sonars don't work well enough.

how big is the height of your home.... at most I'd say 6-8m. Cheap sonars will do fine in these scenarios. ;)
Besides, indoors there is much lesser interference... making the readings more accurate and easier to stabilize

[perdification]

how big is the height of your home.... at most I'd say 6-8m. Cheap sonars will do fine in these scenarios. ;)
Besides, indoors there is much lesser interference... making the readings more accurate and easier to stabilize

But I guess the cheap sonar sensors, apart from lesser range. would have poorer resolution as well. That means that it is less accurate when holding. Optical flow sensors for stabilisation would be better i suppose, but cause a ton.

[perdification]

But I guess the cheap sonar sensors, apart from lesser range. would have poorer resolution as well. That means that it is less accurate when holding. Optical flow sensors for stabilisation would be better i suppose, but cause a ton.

My bad, "cause" should be "cost"

[Kaen]

But I guess the cheap sonar sensors, apart from lesser range. would have poorer resolution as well. That means that it is less accurate when holding. Optical flow sensors for stabilisation would be better i suppose, but cause a ton.

Usually Sonar is used as a situational replacement for barometric sensors. By default, It does not do position hold, only altitude hold. I was actually thinking of mounting sonars in a 6 axis setup to give it pseudo position awareness and position hold ability. This will only work indoors and small rooms. But the code is a mess though hehe.... shelving for later...

Based on reading and charting a ton of sonar/baro log dumps from other users... I'm pretty confident that sonar is fairly redundant thus far, even at low altitudes, the baro is damned accurate, giving similar readings as a sonar. So the sonar is relegated only to failsafe object detection... when the baro and sonar readings dont match up.... provide a warning to the FC! ie. Don't auto land when theres something below you! Find alternate landing spot!!

btw if the threadstarter just wants an indoor toy.... go buy an InfraX from Walkera... sonar alt hold and infrared object avoidance... small, light and cheap. sorta ideal for indoors flying.

[perdification]

Usually Sonar is used as a situational replacement for barometric sensors. By default, It does not do position hold, only altitude hold. I was actually thinking of mounting sonars in a 6 axis setup to give it pseudo position awareness and position hold ability. This will only work indoors and small rooms. But the code is a mess though hehe.... shelving for later...

Based on reading and charting a ton of sonar/baro log dumps from other users... I'm pretty confident that sonar is fairly redundant thus far, even at low altitudes, the baro is damned accurate, giving similar readings as a sonar. So the sonar is relegated only to failsafe object detection... when the baro and sonar readings dont match up.... provide a warning to the FC! ie. Don't auto land when theres something below you! Find alternate landing spot!!

btw if the threadstarter just wants an indoor toy.... go buy an InfraX from Walkera... sonar alt hold and infrared object avoidance... small, light and cheap. sorta ideal for indoors flying.

Yup, I do know that. By "holding" I meant alti hold, not position hold. Position hold requires GPS. Lol hey that sounds interesting... you'll need six sonar sensors in six different directions, more if you want a better position hold. But the problem is that if you're in the room, and you move about, the quad might think that it is moving relative to the room and start compensating wrongly as well.

I guess when auto landing, sonar plays an important part when at very low altitudes, say 10cm off the ground. For a very gentle and controlled descent, I believe the barometer just doesn't have enough spatial resolution when compared to sonar... Sonar is extremely accurate and is immune to disturbances, compared to minute changes in air pressure for the baro, which can be affected by prop wash/wind as well, however minimal the effects might be. Thus, it might not be totally redundant.

[Kaen]

Yup, I do know that. By "holding" I meant alti hold, not position hold. Position hold requires GPS. Lol hey that sounds interesting... you'll need six sonar sensors in six different directions, more if you want a better position hold. But the problem is that if you're in the room, and you move about, the quad might think that it is moving relative to the room and start compensating wrongly as well.

I guess when auto landing, sonar plays an important part when at very low altitudes, say 10cm off the ground. For a very gentle and controlled descent, I believe the barometer just doesn't have enough spatial resolution when compared to sonar... Sonar is extremely accurate and is immune to disturbances, compared to minute changes in air pressure for the baro, which can be affected by prop wash/wind as well, however minimal the effects might be. Thus, it might not be totally redundant.

You might be over-rating sonar by a bit much... it's based on reflected sound... which means way more interference from wind/prop wash and vibrations!
Btw sonar will most likely not even work at 10cm off the ground. I think the minimum range for sonar to work is about 20cm+... to be specific you need to check the model of sonar you are using, it depends on the angular width of the beam.

Even maxbotix sonar sensors (which are like 20x more expensive than the cheapo chinese ones) have a lot of interference to deal with.
Read more about it here.

http://www.maxbotix.com/articles/067.htm

[iz77]

Cool input. The more I want to start new project. Hehe

[quadflyer]

From what I remember when I used to fly the AR Drone 2.0 it has both baro & sonar. The sonar was only effective up to 10m hight, after that the baro took over. it also used the down looking camera for position hold based on image comparison algorithms.
A very good mixture of sensors & technology to produce a stable quad.
The sonar gave it the weird ability to "climb" staircases.

[Kaen]

From what I remember when I used to fly the AR Drone 2.0 it has both baro & sonar. The sonar was only effective up to 10m hight, after that the baro took over. it also used the down looking camera for position hold based on image comparison algorithms.
A very good mixture of sensors & technology to produce a stable quad.
The sonar gave it the weird ability to "climb" staircases.

wow didn't know that the AR drone 2.0 came with sonar.... even more surprised that they use computer vision for position hold.
The cheapo chinese sonar that I have officially works up to 10m *cough*.... but it's really only "accurate" from 20cm to 200cm 'ish... but at $2.60... well.. can't complain too much hehe. The maxbotix ones should work pretty good up to 7m and even 10m for the $$$ ones.

I've been digging into people's sonar+baro data charts... so I'm pretty confident that you don't really need sonar that much for alt hold... its still useful for object detection stuff though... so not completely useless! Might end up buying one of the top end maxbotix to play with eventually... (when I have time!)

[perdification]

You might be over-rating sonar by a bit much... it's based on reflected sound... which means way more interference from wind/prop wash and vibrations!
Btw sonar will most likely not even work at 10cm off the ground. I think the minimum range for sonar to work is about 20cm+... to be specific you need to check the model of sonar you are using, it depends on the angular width of the beam.

Even maxbotix sonar sensors (which are like 20x more expensive than the cheapo chinese ones) have a lot of interference to deal with.
Read more about it here.
http://www.maxbotix.com/articles/067.htm

Great article Kaen! I believe all sonar sensors, be it cheapo chinese ones or expensive ones all are subject to the same kind of interference when on a multirotor. But still, I think the baro is affected by prop wash, light and wind to a greater extent than sonar is. So much so that it has to be shielded. Sonar modules don't need shielding I suppose, which means that they are relatively more immune than baros to external influences on performance.

And i don't think the minimum range (shadow zone) is 20+cm. It's more like 2cm. Look here. The datasheet for the cheapo sonar sensor that we all love. It ranges up to 4 metres, not bad I'd say... the baro should be good at 4m and above...

An interesting question would be, would running lower KV motors, bigger props but much longer quad arms help the case? Assuming the sensor is mounted dead center on the frame that is, and that's where it should be mounted I suppose. Lower KV motors=less vibration, larger props = less high pitched interfering noises with the sonar, longer arms = moving the interference further away from the sensor.

[perdification]

From what I remember when I used to fly the AR Drone 2.0 it has both baro & sonar. The sonar was only effective up to 10m hight, after that the baro took over. it also used the down looking camera for position hold based on image comparison algorithms.
A very good mixture of sensors & technology to produce a stable quad.
The sonar gave it the weird ability to "climb" staircases.

The AR Drone has optical flow capabilities? I didn't know that! Now that's cool.

Yeah, using sonar to climb stairs would be a really cool idea.

[perdification]

wow didn't know that the AR drone 2.0 came with sonar.... even more surprised that they use computer vision for position hold.
The cheapo chinese sonar that I have officially works up to 10m *cough*.... but it's really only "accurate" from 20cm to 200cm 'ish... but at $2.60... well.. can't complain too much hehe. The maxbotix ones should work pretty good up to 7m and even 10m for the $$$ ones.

I've been digging into people's sonar+baro data charts... so I'm pretty confident that you don't really need sonar that much for alt hold... its still useful for object detection stuff though... so not completely useless! Might end up buying one of the top end maxbotix to play with eventually... (when I have time!)

Yeah, i thought AR Drone was a nooby toy quad... Kinda surprised to know that it has such capabilities.

Do you use the HC-SR04 as well? If so, the datasheet doesn't state 10m hahaha.

Would it be better to use optical flow for object detection and obstacles? I'm not sure about which is better for detecting objects.

[Kaen]

Great article Kaen! I believe all sonar sensors, be it cheapo chinese ones or expensive ones all are subject to the same kind of interference when on a multirotor. But still, I think the baro is affected by prop wash, light and wind to a greater extent than sonar is. So much so that it has to be shielded. Sonar modules don't need shielding I suppose, which means that they are relatively more immune than baros to external influences on performance.

And i don't think the minimum range (shadow zone) is 20+cm. It's more like 2cm. Look here. The datasheet for the cheapo sonar sensor that we all love. It ranges up to 4 metres, not bad I'd say... the baro should be good at 4m and above...

An interesting question would be, would running lower KV motors, bigger props but much longer quad arms help the case? Assuming the sensor is mounted dead center on the frame that is, and that's where it should be mounted I suppose. Lower KV motors=less vibration, larger props = less high pitched interfering noises with the sonar, longer arms = moving the interference further away from the sensor.

Yes all those factors will definitely help a ton! It does mean flying a much bigger, heavier and expensive multirotor though.
Thats along the lines of what I like... since lifting a camera is my basic requirement. But most people seem more interested in flying acro style.

I also ordered some 8000mah batteries hehe... wanted to do some tests on payload:endurance ratios... might try to run a few of those in parallel.

Yeah, i thought AR Drone was a nooby toy quad... Kinda surprised to know that it has such capabilities.

Do you use the HC-SR04 as well? If so, the datasheet doesn't state 10m hahaha.

Would it be better to use optical flow for object detection and obstacles? I'm not sure about which is better for detecting objects.

the HC-SR04 is actually a cheapo clone of some other more common sonar... can't rem the name at the moment. :p
Everyone's so busy cloning one another's products I have no idea who designs them anymore...
I remembered seeing a spec sheet stating 10m ranging... never believed it for a minute of course.

MWC/APM currently only allows you to pick the heights where either sonar or baro are active in alt hold. However if you were logging the sonar data and the baro data... and put them together on a chart.. you would notice that 95% of the time they both report the same altitudes. Without data logging, one could assume (like I once did) that sonar is just superior in alt hold at low altitude. The data seems to prove otherwise. The difference is so marginal that it also explains how the naza can do alt holds so well without a sonar...

[perdification]

Yes all those factors will definitely help a ton! It does mean flying a much bigger, heavier and expensive multirotor though.
Thats along the lines of what I like... since lifting a camera is my basic requirement. But most people seem more interested in flying acro style.

I also ordered some 8000mah batteries hehe... wanted to do some tests on payload:endurance ratios... might try to run a few of those in parallel.



the HC-SR04 is actually a cheapo clone of some other more common sonar... can't rem the name at the moment. :p
Everyone's so busy cloning one another's products I have no idea who designs them anymore...
I remembered seeing a spec sheet stating 10m ranging... never believed it for a minute of course.

MWC/APM currently only allows you to pick the heights where either sonar or baro are active in alt hold. However if you were logging the sonar data and the baro data... and put them together on a chart.. you would notice that 95% of the time they both report the same altitudes. Without data logging, one could assume (like I once did) that sonar is just superior in alt hold at low altitude. The data seems to prove otherwise. The difference is so marginal that it also explains how the naza can do alt holds so well without a sonar...

Just wondering, what happens if you put your quad in a alti hold using sonar, and then shout at the sonar sensor? Hahaha sounds stupid but it's something I would do to experiment with. you could probably shout at your quad and have it run away like a wimp.

Nice find though. Thanks for taking the time to do the research... Just wondering, if you have a lousy microprocessor like the ATmel and a lousy baro like the MS5611 used in the Crius AIOP and WiteSpy, as compared to the ARM Proc and whatever high end baros they use, sonar might play an important role for the stability of these cheapo FCs since their baros are crappier than the Naza?

[perdification]

Just wondering, what happens if you put your quad in a alti hold using sonar, and then shout at the sonar sensor? Hahaha sounds stupid but it's something I would do to experiment with. you could probably shout at your quad and have it run away like a wimp.

Nice find though. Thanks for taking the time to do the research... Just wondering, if you have a lousy microprocessor like the ATmel and a lousy baro like the MS5611 used in the Crius AIOP and WiteSpy, as compared to the ARM Proc and whatever high end baros they use, sonar might play an important role for the stability of these cheapo FCs since their baros are crappier than the Naza?

Sorry in the statement "ompared to the ARM Proc and whatever high end baros they use", they refers to the DJI Naza.