735 replies to this topic

[Daniel Wee]

In fact the systems equations aren't that complex. What is needed is to characterize the noise of the system and the covariance values. This can actually be empirically determined. In saying this, I'm also making some assumptions regarding the cross-axis influence and ignoring some other influences as negligible or linear. This allows us to keep the equations complexity manageable.

As to whether this will outperform a simpler system, well that depends a lot on what that other system is. In fact by the time you tune up a PID loop to get it right, you might as well just use a Kalman EKF or better yet an SRUKF. The problem is that many people find the math a bit daunting even though the actual principle of the system is not that difficult to understand. But if math isn't a problem, the filter shouldn't be all that hard to implement. For lower powered controllers, there are a few tricks you can use to reduce the computing workload, although with the SRUKF - there's going to be quite a bit of floating point calculations so a fast MCU would be needed.

The real advantage of using an alternative system, I think, is that it is more readily understood whereas the Kalman filter is initially very non-intuitive. I can't really see how those systems will in fact perform better than Kalman filter, especially when you are thinking of mass producing the units which may not allow for very precise characterization of the sensors.

In the end, the proof is in the pudding. One reason I decided to pursue the EKF route (will try SRUKF later) is because so much has been said about it, and yet so little done. Everyone seems to know what it is but very few have actually put their apparent ideas to practice. The same can actually be said about alternative systems. It seems that almost every other person has a great idea of how to make a working system but I've not really seen any working models to go with those ideas. As such, one of my goals is to put an end to all the speculation and produce an actually working system. This now works although I would like to see faster convergence. Once I get the smaller prototype boards made, I'll be able to know how well it actually works on a plane.

I would like to encourage those out there with ideas to actually put them to the hardware. That's what we really need right now - real world test results.

Daniel

[cyber-flyer]

In fact by the time you tune up a PID loop to get it right, you might as well just use a Kalman EKF or better yet an SRUKF

You need to tune PID loop in any case as Kalman filter will only "read" the system but not control it.

Everyone seems to know what it is but very few have actually put their apparent ideas to practice

May be there is a reason for that, besides the fact that people are lazy I mean complexity of the approach may prevent detection of otherwise apparent problems. But if you have one working - that's very cool!

That's what we really need right now - real world test results

That's would be good, I don't know anybody who's done comparison of different methods, especialy in actual flight. How would you propose to compare different approaches? Calculating attitude errors during flight will require second, benchmark IMU on board.

[Daniel Wee]

One way would simply be to strap the unit to a test rig with known inclinations and test it that way. Another approach would simply be to see how well it works for the desired purpose - be it stabilization or artificial horizon. If it works, it works.

Daniel

[Dan]

Hi my name is Dan sorry for my English , I will like to arrange my navosd I seek the shematic diagram + pin out for Dragonosd with the PIC 30f4012 .
please I would need your assistance
thank you
Dan

[cyber-flyer]

Daniel, the IMU discussion deserves its own thread. Let's start it.

One way would simply be to strap the unit to a test rig with known inclinations and test it that way

That will be just a test of accelerometers. The actual flight will test if blending of gyros and accelerometers is done properly. If one doesn't have a calibrated IMU, the next best thing will be to put a model into a steep banking turn lasting at least 10 seconds, than quickly recover to a horizontal position and compare IMU output with visible horizon. This condition is impossible to reproduce on the ground, unless one have an access to a big centrifuge.

Edited by cyber-flyer, 18 January 2008 - 07:20 AM.

[Daniel Wee]

I'm hoping to be able to do that in a about a week or so. We're getting a small number of prototype boards made for me and a few beta testers. Once I get them, I'll be able to put the thing on a plane and tweak the performance until I'm happy with it. After that I'll incorporate it into the autopilot once I get a better feel of it's in-flight performance.

Daniel

[Dan]

Hi I have look on this forum of people working on the same project , I would like to have some detail, I've all the parts in my possession , I would like to have the schematic diagram and the code sourse for PIC 30f4012 would it be possible or not ? If not , why ? , I will try to cable with the pictures of the forum, but it will be difficult. thank you for your answer .
please svp porfavor
email me va2dd

Dan

Edited by Dan, 22 January 2008 - 03:58 PM.

[WayneMcClure]

Hi All,
Nice work on the OSD>GPS,
I've been trying to fallow the work done but it's tough when there is 37 post's on it,

so if some one dose not mined questions that would be great!

1. is there any way points >> or just auto pilot return to home?
2. is there any way to make it programed for way point?

Thanks

Edited by WayneMcClure, 23 January 2008 - 01:32 PM.

[Daniel Wee]

1. The system actually supports waypoints but right now only one waypoint is used - HOME. Unfortunately for this version (4.6) we've pretty much used up all available memory so under you start removing stuff, you won't be able to fit anything in. The next version will have more than enough memory for waypoints, maps, and so on. In fact it will have UAV capabilities.

2. See #1.

Daniel

[anci3nt]

1. The system actually supports waypoints but right now only one waypoint is used - HOME. Unfortunately for this version (4.6) we've pretty much used up all available memory so under you start removing stuff, you won't be able to fit anything in. The next version will have more than enough memory for waypoints, maps, and so on. In fact it will have UAV capabilities.

2. See #1.

Daniel

Daniel, very excited to hear about waypoints in the pro version! Looks like I'll be buying another board! Question about the next release.. Will there be any throttle/chan3 control as part of the autopilot? Reason I ask is IMO it would be a great capability to have it kill throttle at some programmable low altitude limit.

I wonder if pro version 2 will have auto landing/take off?! At this development rate, version 3 could probably make coffee!

Edited by anci3nt, 09 February 2008 - 04:02 PM.

[JMS]

I wonder if pro version 2 will have auto landing/take off?! At this development rate, version 3 could probably make coffee!

Not only that but will head for the kitchen and also bring you back a scone and todays newspaper but deploying it's landing gear on it's own first

Edited by JMS, 10 February 2008 - 01:26 AM.

[twinturbostang]

Bah! I'm not interested unless it will clean my house too!

[W3FJW-Ron]

Don't have to do anything extra to hold my interest. I've decided in order to keep my sanity and thin wallet intact, to do nothing but keep an eye on the thread and read about it. Extremely interesting to see what you fellows are doing and how you're going about it. Keep it up and success to you all.....

[twinturbostang]

Be sure to keep an eye on the Dragon thread over on RCGroups in the FPV section. There's been more activity over there recently.

[Daniel Wee]

Hi anci3nt,

Sorry for this late reply - I haven't been dropping by here too much lately.

In answer to your question - yes the Pro version will also control the throttle channel as well as some others. It's got enough PWM channels to control pretty much everything - maybe even flaps. And yes, the idea (eventually) is that this thing will do auto-landing or at least assisted landing. We're still a ways off in terms of software development right now. Have to make sure that the hardware works first.

Daniel

[AsiaSRC]

Hi Daniel,
In fact, I ve not think this is 'RnD in Spore' until I saw those housing photos.
Nice n Cool project. Very well presented too.

Albert

" jet flying, speed = live "