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Caleb Chamberlain commented on Chris Anderson's blog post FAQ: What's the difference between a gyro and an accelerometer? Do I need both?
"Not to resurrect this thread, but I just published a brief explanation of how to combine rate gyro and accelerometer data: http://www.chrobotics.com/library/attitude-estimation"
Nov 22, 2013
Caleb Chamberlain commented on Chris Anderson's blog post FAQ: What's the difference between a gyro and an accelerometer? Do I need both?
"Mario - instead, can you measure the wheel velocity and regulate it so that it is constant on a slope or on a flat surface?  It seems like that would be an easier solution."
Oct 11, 2013
Caleb Chamberlain commented on Matthew Beck's blog post 3d printable quadcopter!! PL1Q Vampire
"Pretty cool!  How much does the printed frame weigh?"
Feb 17, 2012
Caleb Chamberlain posted a discussion
Hey all, I'm finishing up a new quadrotor/octocopter autopilot design.  I just got my second revision board populated and tested. I was excited enough about it that I thought I'd share it... :-D Some of the features of the autopilot are listed…
Jun 22, 2011
Caleb Chamberlain posted a discussion
There has been an ongoing discussion/debate about whether accelerometers are actually useful for attitude estimation on flying rotorcraft (quadrotors, in particular).  The simple, one sentence answer is "yes, they are."  However, the accelerometer…
May 22, 2011
Caleb Chamberlain left a comment for Roy Brewer
"Hey Roy,
I'm happy to answer any question you have.  Email might be the most convenient way to do it: my personal email address is voiceafx [at] gmail.com"
May 19, 2011
Caleb Chamberlain replied to Tom's discussion Extended Kalman Filter design for Attitude Estimation of a Quadrotor (with Acc + Gyro only)
"One more note - if you haven't figured it out yet, your model of the accelerometer outputs will make them impossible to use for state estimation.  If ax and ay are always zero, you can't measure the attitude with the accels and your updates will be…"
Mar 9, 2011
Caleb Chamberlain replied to Tom's discussion Extended Kalman Filter design for Attitude Estimation of a Quadrotor (with Acc + Gyro only)
"Hey Tom,

A chapter in my MS thesis deals with this very topic.  I'm one of Randy Beard's grad students at BYU.  My thesis will be published really soon - I defended it last week and will be submitting it tomorrow.  I'm not sure if there are any…"
Mar 9, 2011
Caleb Chamberlain replied to Caleb Chamberlain's discussion Open Source Attitude Estimation Code with Euler Angle and Quaternion Support
"As an added note, the UM6 doesn't do anything to compensate for centripetal acceleration right now.  There are a bunch of extra pins routed out through two 2x6 2mm headers on the bottom of the sensor, so GPS and airspeed could easily be brought in. …"
Feb 9, 2011
Caleb Chamberlain posted a discussion
Hey everyone.  I recently finished a new AHRS (see the picture below).  The firmware is open-source, and I thought it might be interesting to you guys.  The firmware supports EKF-based Euler Angle and Quaternion estimation, depending on what you…
Feb 9, 2011
Caleb Chamberlain commented on David Ankers's blog post A public thank you to Caleb from CH Robotics
"My personal opinion is that you can make it work by tuning your filter properly - for example, I've set up covariances in an EKF so that it took the accels on the order of ten seconds to make an appreciable (3 to 4 degree) change in angle estimates.…"
Apr 27, 2010
Caleb Chamberlain commented on David Ankers's blog post A public thank you to Caleb from CH Robotics
"That's really interesting. And the bad angle estimates persisted even if you decreased your process covariances and increased your accel covariance?"
Mar 17, 2010
Caleb Chamberlain commented on David Ankers's blog post A public thank you to Caleb from CH Robotics
"@Ryan

Ah, you are the voice of experience, then. :-) What were you trying to use the closed AHRS for? Were you wrapping angle hold control loops around the state estimate outputs? If so, how were you able to decouple the control and state…"
Mar 17, 2010
Caleb Chamberlain commented on David Ankers's blog post A public thank you to Caleb from CH Robotics
"@David

Thanks for the shout out!

@Ryan

An orientation sensor without something to subtract out centripetal acceleration isn't necessarily useless. I'd say it has a lot to do with, say, how long you expect to remain in a coordinated turn compared…"
Mar 16, 2010
Caleb Chamberlain replied to RazorConcepts's discussion Razor 9dof AHRS Code questions
"These would be good questions to ask Sparkfun. :-)

I'd think that even if they do come out with new revisions, they won't make your version obsolete provided that you can still use it...

And RAM wasters aren't that big a deal if you aren't trying…"
Feb 19, 2010
Caleb Chamberlain posted a discussion
Hey everyone.  I'm just finishing up a new AHRS design (see picture below).  The sensors it uses are almost exactly equivalent to the Razor from Sparkfun, but I added a nice 3.3V regulator and a STM32 processor running at 72 Mhz.  The faster…
Feb 19, 2010