Be VERY CAREFUL with modules like the MTI-1.
Mems gyros are not really good enough to get the specs they publish, and
they all play tricks with the fact that gravity points down in any real use
case
when measured over a period of time long enough. This is not true in a
rocket or spacecraft.
This is why the drone IMU filter code does not really work in a non
hovering rocket.
I think one pretty much has to write their own filter in a rocket... or use
a much more expensive sensor (Fiber) that has gyros that are good enough.
On Wed, Jan 26, 2022 at 6:14 PM Troy Prideaux <troy@xxxxxxxxxxxxxxxxxxxxx>
wrote:
Fair enough. If you changed your mind and needed any recommendations I
would recommend the Xsens MTI-1 series modules. Excellent technical
support and killer modules that would be smaller than your pinky fingernail.
Troy
*From:* arocket-bounce@xxxxxxxxxxxxx [mailto:arocket-bounce@xxxxxxxxxxxxx]
*On Behalf Of *Robert Watzlavick
*Sent:* Thursday, 27 January 2022 12:51 PM
*To:* arocket@xxxxxxxxxxxxx; Troy Prideaux <troy@xxxxxxxxxxxxxxxxxxxxx>
*Subject:* [AR] Re: Successful liquid launch at FAR
I already bought 2 of the ADIS16354 IMUs a while back but they would
require "real" nav filters to be implemented for them to be useful. I flew
one of them and recorded all the data onboard with a flash card so I'm
hoping to use the onboard video to correlate the results from the nav
filter once I implement it. But you're right, there are probably cheaper
and better solutions out there.
-Bob
On 1/24/22 10:59 PM, Troy Prideaux wrote:
The good news is there’s an abundance of reasonable IMU options out there
now (for your acceleration range) without getting into exotics. Many will
do all the orientation work for you ie. will spit out either euler angles
or quaternion or rotation matrix data at some pretty brisk rates with
magnetic referencing for some flavours.
Troy
*From:* arocket-bounce@xxxxxxxxxxxxx [mailto:arocket-bounce@xxxxxxxxxxxxx
<arocket-bounce@xxxxxxxxxxxxx>] *On Behalf Of *Robert Watzlavick
*Sent:* Tuesday, 25 January 2022 3:07 PM
*To:* arocket@xxxxxxxxxxxxx; Alex Bruccoleri <alexrocketry@xxxxxxxxx>
<alexrocketry@xxxxxxxxx>
*Subject:* [AR] Re: Successful liquid launch at FAR
The plan is to add active stability control to the existing rocket (using
movable control surfaces, not gimbaling), get the bugs worked out with
that, then build a larger vehicle. That may take me a while though. I'm a
bit challenged in linear algebra and control theory so I'll have to dust
off the textbooks for this effort.
-Bob
On 1/24/22 1:23 PM, Alex Bruccoleri wrote:
This is incredible! Very well done. Do you have plans to go for higher
altitude?
Cheers, Alex
On Sun, Jan 16, 2022 at 9:57 AM Robert Watzlavick <rocket@xxxxxxxxxxxxxx>
wrote:
I finally launched my 250 lbf LOX/kerosene rocket yesterday at FAR. It got
to 10800 ft with a 10 second burn and winds were calm so there were no
weathercocking issues off the rail. The drogue and main deployed as
intended and we recovered it about 6000 ft down range. I’ll post more
details in a few days but I want to thank everyone on this list that has
helped me over the years. I had a lot of really smart folks help me along
the way and I appreciate it!
-Bob
