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  • Don Kelly's Avatar
    Today, 09:35 PM
    Don Kelly replied to a thread uNav AHRS in General Discussion
    Great! Will check it out tomorrow. Looking forward to it!! Don
    179 replies | 6534 view(s)
  • Don Kelly's Avatar
    01-19-2018, 11:20 PM
    Don Kelly replied to a thread uNav AHRS in General Discussion
    Ooops, sorry... missed that...
    179 replies | 6534 view(s)
  • Don Kelly's Avatar
    01-19-2018, 10:11 PM
    Don Kelly replied to a thread uNav AHRS in General Discussion
    Brian, What are your thoughts on trying the approach from the Watson thesis? For his h(x) equation, he does a transformation on the magnetometer measurements that supposedly isolates pitch/roll from yaw. Also, his h(x)...
    179 replies | 6534 view(s)
  • Don Kelly's Avatar
    01-19-2018, 01:43 PM
    Don Kelly replied to a thread uNav AHRS in General Discussion
    Mike, Yes, it is sort of getting into the realm of adaptive filter. But I really refer to it as building in "smarts," verses making it truly adaptive. But the more smarts built in, the more adaptive it becomes. I've...
    179 replies | 6534 view(s)
  • Don Kelly's Avatar
    01-19-2018, 02:41 AM
    Don Kelly replied to a thread uNav AHRS in General Discussion
    Brian, Some rambling on tuning... This is a bit of a different beast, especially with the use of quaternions, but here's some thoughts... I've had a relatively simple approach to tuning KF applications over the...
    179 replies | 6534 view(s)
  • Don Kelly's Avatar
    01-19-2018, 01:55 AM
    Don Kelly replied to a thread uNav AHRS in General Discussion
    Thanks Mike, will check those links out.... Here's something cool... I started up the 7-State, messed around ("flew") with the board for a bit, then went off for dinner for a couple hours. When I came back, heading...
    179 replies | 6534 view(s)
  • Don Kelly's Avatar
    01-18-2018, 11:12 PM
    Don Kelly replied to a thread uNav AHRS in General Discussion
    Tried to follow the Teensy suggestions on connecting the SPI to the Sparkfun MPU9250, but not working. Here's what I've tried (assuming MOSI is SDA, MISO is AD0, SCK is SCL, SS is CS: SparkFun9250 Teensy3.6 VCC ...
    179 replies | 6534 view(s)
  • Don Kelly's Avatar
    01-18-2018, 10:45 PM
    Don Kelly replied to a thread uNav AHRS in General Discussion
    Yes Mike, same thing I'm seeing. Downloading the new release now and getting ready to see if I can switch to SPI bus. Don
    179 replies | 6534 view(s)
  • Don Kelly's Avatar
    01-18-2018, 08:40 PM
    Don Kelly replied to a thread uNav AHRS in General Discussion
    Brian, Got the 7-State up and running. Are you all seeing drift in yaw and heading? I’m on the I2C bus, will try switching over to SPI bus later today or tonight too. Don
    179 replies | 6534 view(s)
  • Don Kelly's Avatar
    01-18-2018, 02:07 PM
    Don Kelly replied to a thread uNav AHRS in General Discussion
    Brian, Both work, I've implemented filters both ways. What needs to be watched out for is if P is reduced too much with each step then P can cause the filter to think it's doing better than it is or to reduce the...
    179 replies | 6534 view(s)
  • Don Kelly's Avatar
    01-18-2018, 03:10 AM
    Don Kelly replied to a thread uNav AHRS in General Discussion
    Mike, That is curious that your pitch values don’t blow up. My only guess is that asin needs to stay within plus or minus 1, and maybe my float values jump out of that range vs your double values. Guess i’ll try...
    179 replies | 6534 view(s)
  • Don Kelly's Avatar
    01-17-2018, 11:33 PM
    Don Kelly replied to a thread uNav AHRS in General Discussion
    I was telling Tim that TelemetryViewer is a bit picky to get installed. Suggest watching the author's video, and reading the youtube comments. I had a heck of a time getting the right version of JRE (32 vs 64 bit I...
    179 replies | 6534 view(s)
  • Don Kelly's Avatar
    01-17-2018, 09:50 PM
    Don Kelly replied to a thread uNav AHRS in General Discussion
    Brian, Got it up and running, looking good thus far. The pitch (theta) in the Quat2Eul will blow up if pitch is raised to 90 degrees. Here's a quick fix I added to the cpp file to prevent this singularity: /*...
    179 replies | 6534 view(s)
  • Don Kelly's Avatar
    01-17-2018, 08:07 PM
    Don Kelly replied to a thread uNav AHRS in General Discussion
    Downloaded the 4-State, will take a look. Have still been messing around with the 7-State. Thought I had it working really well until I added a body-2-inertial DCM routine to get the accel values in inertial NED. It...
    179 replies | 6534 view(s)
  • Don Kelly's Avatar
    01-16-2018, 05:53 PM
    Don Kelly replied to a thread uNav AHRS in General Discussion
    I started by watching his TelemetryViewer post on youtube. It was a bit frustrating getting it going at first. I remember having an issue with TelemetryViewer if the correct JRE (32 bit vs 64 bit) is not installed. I...
    179 replies | 6534 view(s)
  • Don Kelly's Avatar
    01-16-2018, 04:54 PM
    Don Kelly replied to a thread uNav AHRS in General Discussion
    A quick update on my 7-State work... - the 7-state still running very solidly for me - I can get it to crash if I raise pitch to 90 deg, which is the typical Euler angle singularity issue. So I guess we need some code...
    179 replies | 6534 view(s)
  • Don Kelly's Avatar
    01-16-2018, 02:48 AM
    Don Kelly replied to a thread uNav AHRS in General Discussion
    Tim, Here's Brian's MPU9250 library. He calls this for the 7-State and 15-State sketches. https://github.com/bolderflight/MPU9250 Be aware that this library is titled the same as other MPU9250 libraries, so could...
    179 replies | 6534 view(s)
  • Don Kelly's Avatar
    01-16-2018, 02:15 AM
    Don Kelly replied to a thread uNav AHRS in General Discussion
    forgot to mention... am more than willing to share my code mods at any point as I plod along... just let me know and I'll post a version... Don
    179 replies | 6534 view(s)
  • Don Kelly's Avatar
    01-16-2018, 02:12 AM
    Don Kelly replied to a thread uNav AHRS in General Discussion
    Mike, Sounds interesting, looking forward to seeing how it progresses! I read through the thesis, it's a great write-up. Thx! I'm seeing what seems to be really good results with the 7-State right now, it has been...
    179 replies | 6534 view(s)
  • Don Kelly's Avatar
    01-15-2018, 08:57 PM
    Don Kelly replied to a thread uNav AHRS in General Discussion
    Tim, Yes, if I just grab IMU values without interrupts, I'll just have to make sure that I'm running the void loop slower than I'm sampling the IMU. I've used the MPU6050 on drones at up to 400Hz without issues,...
    179 replies | 6534 view(s)
  • Don Kelly's Avatar
    01-15-2018, 02:14 AM
    Don Kelly replied to a thread uNav AHRS in General Discussion
    Great, glad it’s stable looking! Mine seems locked in. A couple of things i want to try are: - reduce the serial output to a rate of 2-5 hz and begin plotting parms real-time using TelemetryViewer - change the...
    179 replies | 6534 view(s)
  • Don Kelly's Avatar
    01-15-2018, 12:21 AM
    Don Kelly replied to a thread uNav AHRS in General Discussion
    Forgot to mention that I'm also using I2C instead of SPI bus, so I modded the code to be: // an MPU-9250 object on SPI bus 0 with chip select 10 MPU9250 Imu(Wire,0x68); Are you running I2C or SPI? If you're...
    179 replies | 6534 view(s)
  • Don Kelly's Avatar
    01-14-2018, 11:13 PM
    Don Kelly replied to a thread uNav AHRS in General Discussion
    Ha... Noticed the PRJC Forum just inserted two smiley faces in my code snippets above.... jeeeezzzz
    179 replies | 6534 view(s)
  • Don Kelly's Avatar
    01-14-2018, 11:08 PM
    Don Kelly replied to a thread uNav AHRS in General Discussion
    yes, here's the code: // state transition matrix Eigen::Matrix<float,7,7> Fsys = Eigen::Matrix<float,7,7>::Identity(); In the sketch, I'm using these values: Filter.setAccelCovariance(0.025f); // also...
    179 replies | 6534 view(s)
  • Don Kelly's Avatar
    01-14-2018, 06:08 PM
    Don Kelly replied to a thread uNav INS in General Discussion
    Mike, Sounds cool. I don’t see his thesis out there, looks like link is gone. may I get copy (don.kelly@mac.com)? Also, see my recent post over at the uNavAHRS blog. Changed the initialization of Fsys on the...
    37 replies | 1152 view(s)
  • Don Kelly's Avatar
    01-14-2018, 05:27 PM
    Don Kelly replied to a thread uNav AHRS in General Discussion
    Looking at the 7-State code, I noticed that the comments refer to the Fsys matrix as Phi. For nonlinear systems, I’m more familiar with Phi being the linearized (via Taylor series expansion) of the system dynamics...
    179 replies | 6534 view(s)
  • Don Kelly's Avatar
    01-13-2018, 10:59 PM
    Don Kelly replied to a thread uNav INS in General Discussion
    So iím back to thinking along your line of thought Brian. Thinking iíll go back to the 7-state, but reduce it to 4 states (the for quaternions), and get that going solidly first, then add back on from there.
    37 replies | 1152 view(s)
  • Don Kelly's Avatar
    01-13-2018, 10:41 PM
    Don Kelly replied to a thread uNav INS in General Discussion
    Looking at the 15-state cpp file again, i think you’re correct, the 15 state is directly using the angle elements of the quaternion as states 7,8,9, not the euler angles. So they are only using 3 of the 4 quaternion...
    37 replies | 1152 view(s)
  • Don Kelly's Avatar
    01-13-2018, 10:01 PM
    Don Kelly replied to a thread uNav INS in General Discussion
    As best i can tell, the 15-state uses the quaternion to get the euler angles, but the euler angles themselves are included as states, not the quaternions. So the 15 states are - 3 posn - 3 velocity - 3 angles - 3...
    37 replies | 1152 view(s)
  • Don Kelly's Avatar
    01-13-2018, 07:18 PM
    Don Kelly replied to a thread uNav INS in General Discussion
    Brian, Trying to think how i’d take a step back and build back into the full 15 state. I’m thinking of using the 15-state code as basis, but stepping back and first get 3 states working, then 9, then 15. The 15...
    37 replies | 1152 view(s)
  • Don Kelly's Avatar
    01-13-2018, 07:04 PM
    Don Kelly replied to a thread uNav AHRS in General Discussion
    Thx, sounds like we’re still not getting good magnetometer calibrations.
    179 replies | 6534 view(s)
  • Don Kelly's Avatar
    01-12-2018, 03:55 PM
    Don Kelly replied to a thread uNav AHRS in General Discussion
    When I line up the MPU9250 x-axis to North (using my cell phone compass), the Heading for the 7-State shows 31 degrees. Per the readme file, Heading should read 0.0 degrees with x-axis pointing North. Does your Heading...
    179 replies | 6534 view(s)
  • Don Kelly's Avatar
    01-12-2018, 03:19 AM
    Don Kelly replied to a thread uNav AHRS in General Discussion
    Also, it seems that if I leave the board alone, everything looks pretty solid even after an hour or so. But if I hold the board up and "fly" it around a bit, and set it back down where it was, pitch and roll are back to...
    179 replies | 6534 view(s)
  • Don Kelly's Avatar
    01-12-2018, 01:41 AM
    Don Kelly replied to a thread uNav AHRS in General Discussion
    Great, thx much. I see he has SetSrd = 9, so I'll try DLPF = 20 as well. Think I'll also just print out the serial data at 2 or 5 Hz and view it using TelemetryViewer (http://www.farrellf.com/TelemetryViewer/). It's a...
    179 replies | 6534 view(s)
  • Don Kelly's Avatar
    01-12-2018, 01:30 AM
    Don Kelly replied to a thread uNav AHRS in General Discussion
    Mike, I updated to Brian's latest version, and his mods seemed to have helped a lot. I'll go in and check out what he changed. Don
    179 replies | 6534 view(s)
  • Don Kelly's Avatar
    01-12-2018, 01:07 AM
    Don Kelly replied to a thread uNav AHRS in General Discussion
    Mike, I've decided to fall back to the 7-State and see if I can get that stable before going back to the 15-State. Your 7-State results look really good, stable yaw for 50 min! Any chance of summarizing your...
    179 replies | 6534 view(s)
  • Don Kelly's Avatar
    01-11-2018, 07:07 PM
    Don Kelly replied to a thread uNav INS in General Discussion
    Brian, Here's another good reference on tightly vs loosely-coupled, more along the lines of how I've heard it defined. Guess the references aren't consistent! INS/GPS Integration Architectures, George Schmidt and...
    37 replies | 1152 view(s)
  • Don Kelly's Avatar
    01-11-2018, 06:16 PM
    Don Kelly replied to a thread uNav INS in General Discussion
    Great, thx. Saw in the code where you check TOW to decide whether to update or not. Neat.
    37 replies | 1152 view(s)
  • Don Kelly's Avatar
    01-11-2018, 06:14 PM
    Don Kelly replied to a thread uNav INS in General Discussion
    Brian, Funny you should mention starting with 4-State and then building to 7-State and then 15-State. I was originally working on a simple 6-State (3 posn, 3 vel) linear KF that I could loosely-couple with the GPS and...
    37 replies | 1152 view(s)
  • Don Kelly's Avatar
    01-11-2018, 05:59 PM
    Don Kelly replied to a thread uNav INS in General Discussion
    Mike, Shame the M8N doesn't have the PPS readily available. It's on Pin 3 of the Neo M8N, but my soldering skills aren't good enough to tap into off the board directly from that tiny connection! I'm guessing the...
    37 replies | 1152 view(s)
  • Don Kelly's Avatar
    01-11-2018, 03:21 PM
    Don Kelly replied to a thread uNav INS in General Discussion
    Started digging into the 15-State EKF code, and have a couple of observations. Exciting to see it run, and the code looks impressive! Would really like to hear from others on what they think about my observations. ...
    37 replies | 1152 view(s)
  • Don Kelly's Avatar
    01-10-2018, 03:14 AM
    Don Kelly replied to a thread uNav INS in General Discussion
    Mike and Brian, Trying to catch up with where you are, due to my travels last week... Got the 15-State running this afternoon with my Teensy3.6, MPU9250, and uBlox m8n receiver. I'm running at 1Hz for now, but will...
    37 replies | 1152 view(s)
  • Don Kelly's Avatar
    01-07-2018, 04:37 PM
    Don Kelly replied to a thread uNav INS in General Discussion
    Brian, Have been on travel, finally back and catching up... I have a couple of quick questions for you. - What's the output rate on your GPS, 5Hz? - Does the EKF require both GPS position and velocity measurements?...
    37 replies | 1152 view(s)
  • Don Kelly's Avatar
    01-03-2018, 11:24 PM
    Don Kelly replied to a thread uNav INS in General Discussion
    Thx Brian, looking forward to checking it out. Out of pocket for a couple of days tho! Don
    37 replies | 1152 view(s)
  • Don Kelly's Avatar
    01-02-2018, 08:45 PM
    Don Kelly replied to a thread uNav AHRS in General Discussion
    Sounds great Brian!
    179 replies | 6534 view(s)
  • Don Kelly's Avatar
    01-02-2018, 06:51 PM
    Don Kelly replied to a thread uNav AHRS in General Discussion
    Mike, Brian, Same here on the yaw drift. My pitch and roll look really stable, although roll seems to always start with a -4 deg offset. Yaw starts drifting very slowly, but accelerates, and after 15 min or so is...
    179 replies | 6534 view(s)
  • Don Kelly's Avatar
    12-31-2017, 10:55 PM
    Don Kelly replied to a thread uBlox Library in General Discussion
    Thx Brian!!
    16 replies | 4502 view(s)
  • Don Kelly's Avatar
    12-31-2017, 10:16 PM
    Don Kelly replied to a thread uBlox Library in General Discussion
    Brian, I'm currently running an Adafruit GPS using the neoGPS library, but am thinking of getting a uBlox so I can try out your library and the UBX parsing and velocity measurement capability. I'm guessing I should get...
    16 replies | 4502 view(s)
  • Don Kelly's Avatar
    12-29-2017, 10:55 PM
    Don Kelly replied to a thread uNav AHRS in General Discussion
    I'm not sure I'm getting a solid calibration with the uNavAHRS calibration sketch. Sorry if this is a dumb question, but is this roughly what you all are doing during calibration? Accel Calibration: 1. Lay...
    179 replies | 6534 view(s)
  • Don Kelly's Avatar
    12-28-2017, 09:50 PM
    Don Kelly replied to a thread uNav AHRS in General Discussion
    Brian, Please keep me updated on your progress with getting the 15 state EKF ported to Teensy. I'm avail to help if you'd like some assistance with beta testing. I'm getting ready to try out the 7 state EKF on my...
    179 replies | 6534 view(s)
  • Don Kelly's Avatar
    12-22-2017, 10:53 PM
    I appreciate the thoughts, thx! This project does have several challenging parts. But I'm thinking it's definitely doable, if I can get the accel measurements from the IMU accurate enough (timing, correct coordinate...
    27 replies | 1253 view(s)
  • Don Kelly's Avatar
    12-22-2017, 08:08 PM
    Yikes, thx...
    27 replies | 1253 view(s)
  • Don Kelly's Avatar
    12-22-2017, 08:00 PM
    Paul, great thoughts, thx. Do you think using the Time library might work? For example, using GPS to sync the RTC (like in the TimeGPS and TimeTeensy3 examples) and then using the RTC to tell me when to grab the IMU...
    27 replies | 1253 view(s)
  • Don Kelly's Avatar
    12-21-2017, 11:22 PM
    Yes, sorry, I should have said: "The pieces I haven't figured out is really step 3... how to read the current GPS without constant polling. Step 1 I think I can do with a signal from PPS using while or something...
    27 replies | 1253 view(s)
  • Don Kelly's Avatar
    12-21-2017, 10:38 PM
    Here are the links for tinygps and tinygpsplus. Both worked fine, i just had to replace softserial with serial3. tinygpsplus: https://github.com/mikalhart/TinyGPSPlus tinygps: https://github.com/mikalhart/TinyGPS ...
    27 replies | 1253 view(s)
  • Don Kelly's Avatar
    12-21-2017, 09:19 PM
    defragster, totally agree. The tinyGPS library seems to do things a bit smarter with his "smartDelay" routine in the sketch examples, but even he still seems to just continuously poll until he gets the data, and then...
    27 replies | 1253 view(s)
  • Don Kelly's Avatar
    12-21-2017, 08:49 PM
    defragster, that is cool, looks like ellapsedMillis could work better than while.
    27 replies | 1253 view(s)
  • Don Kelly's Avatar
    12-21-2017, 08:43 PM
    The link for the Ultimate GPS is https://www.adafruit.com/product/746 The link for the MPU9250 is: https://www.sparkfun.com/products/13762 I'll check out the elapsedMillis with if to see if know what you mean...
    27 replies | 1253 view(s)
  • Don Kelly's Avatar
    12-21-2017, 08:18 PM
    defragster, yes the PPS is 1 sec, but should be super accurate sync to GPS time. The Ultimate will supposedly run up to 10Hz, but I'll start at 1Hz until I make sure I get the accel values integrated in correctly...
    27 replies | 1253 view(s)
  • Don Kelly's Avatar
    12-21-2017, 08:15 PM
    That's a good idea, Paul. I might be able to do it that way. The challenge, I'm thinking, is how do I get very accurate time-stamping for my IMU accel measurements? The accel values will be feeding the Kalman at a...
    27 replies | 1253 view(s)
  • Don Kelly's Avatar
    12-21-2017, 07:53 PM
    Good point... I'm using a Teensy 3.6, MPU9250, and the Adafruit Ultimate GPS. I've got the example sketches for the Ultimate GPS (adafruit and tinygps libraries) running just fine, but both seem to require continuous...
    27 replies | 1253 view(s)
  • Don Kelly's Avatar
    12-21-2017, 07:37 PM
    I'm getting it to parse just fine. My question is if there is a way to not continually have to poll the GPS to get the GPS data. Can I use the GPS chip's PPS signal as an interrupt to then go and quickly grab the NMEA...
    27 replies | 1253 view(s)
  • Don Kelly's Avatar
    12-21-2017, 07:14 PM
    I have the Ultimate GPS board successfully running on a Teensy3.6 using the tinyGPS (and tinyGPSPlus) library. I'd like to be able to read and parse the lat/long/alt when the PPS signal occurs. Is there a way to do...
    27 replies | 1253 view(s)
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About Don Kelly

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About Don Kelly
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Houston
Interests:
GNC, drones, engineering software, optimal estimation
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engineer

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