Inertial Navigation System - what do I need?

On Dec 27, 7:52 pm, Marc Ramsey <m...@ranlogREMOVE.com> wrote:
> t...@fullnet.com wrote:
> > Depending on what you're going to try to use it for, it might not be
> > NEARLY as difficult or expensive as you've been led to believe.
>
> > Maybe the Analog Devices ADIS16355 "High-Precision Tri-Axis Inertial
> > Sensor" would work for your application:
>
> >http://www.analog.com/en/prod/0,2877,ADIS16355,00.html
>
> > It's only $30 in quantity and has built-in tri-axis gyroscope with
> > +/-75 to +/-300 deg/sec dynamic range (14 bits), and built-in tri-axis
> > accelerometer (+/-10g, 14 bits), and 350 Hz bandwidth.
>
> Actually, it is $359 in quantity, and not quite available yet, but other
> than that you got it right 8^)
>
> Marc

and since you have to order 1000 for that price, that is quite an
order.  can i put it on my visa card?

alan nishioka

On Dec 27, 10:52=A0pm, Marc Ramsey <m...@ranlogREMOVE.com> wrote:
> t...@fullnet.com wrote:
> > Depending on what you're going to try to use it for, it might not be
> > NEARLY as difficult or expensive as you've been led to believe.
>
> > Maybe the Analog Devices ADIS16355 "High-Precision Tri-Axis Inertial
> > Sensor" would work for your application:
>
> >http://www.analog.com/en/prod/0,2877,ADIS16355,00.html
>
> > It's only $30 in quantity and has built-in tri-axis gyroscope with
> > +/-75 to +/-300 deg/sec dynamic range (14 bits), and built-in tri-axis
> > accelerometer (+/-10g, 14 bits), and 350 Hz bandwidth.
>
> Actually, it is $359 in quantity, and not quite available yet, but other
> than that you got it right 8^)
>
> Marc

Oops.  You are correct.   I was looking at the wrong table-entry.
Thanks for pointing that out.

It's still pretty cheap, for what it can do.  And if the OP doesn't
need the high-precision version, there is a somewhat-lower-cost model
that is similar.

On Dec 27, 11:20=A0pm, Alan Nishioka <a...@nishioka.com> wrote:
> On Dec 27, 7:52 pm, Marc Ramsey <m...@ranlogREMOVE.com> wrote:
>
>
>
>
>
> > t...@fullnet.com wrote:
> > > Depending on what you're going to try to use it for, it might not be
> > > NEARLY as difficult or expensive as you've been led to believe.
>
> > > Maybe the Analog Devices ADIS16355 "High-Precision Tri-Axis Inertial
> > > Sensor" would work for your application:
>
> > >http://www.analog.com/en/prod/0,2877,ADIS16355,00.html
>
> > > It's only $30 in quantity and has built-in tri-axis gyroscope with
> > > +/-75 to +/-300 deg/sec dynamic range (14 bits), and built-in tri-axis=

> > > accelerometer (+/-10g, 14 bits), and 350 Hz bandwidth.
>
> > Actually, it is $359 in quantity, and not quite available yet, but other=

> > than that you got it right 8^)
>
> > Marc
>
> and since you have to order 1000 for that price, that is quite an
> order. =A0can i put it on my visa card?
>
> alan nishioka- Hide quoted text -
>
> - Show quoted text -

I don't know.  CAN you?   :-)

Maybe we can all get free samples.

I wonder what the qty 1 price might end up at, from a distributor, and
what it might go down to, in a few years.

On Thu, 27 Dec 2007 15:22:06 -0800, linnix wrote:

> On Dec 26, 10:42 am, Tim Wescott <t...@seemywebsite.com> wrote:
>> On Wed, 26 Dec 2007 03:58:30 -0800, vorange wrote:
>> > 3 questions :
>>
>> > 1)  Is it possible to build a simple but accurate INS using a 3 axis
>> > accelerometer and 3 axis inclinometer?  Or do I need something more
>> > than that?  Is the inclinometer even needed or would just an
>> > accelerometer surfice?
>>
>> No.  An inclinometer is just a type of accelerometer, and
>> accelerometers alone aren't sufficient.
>>
>> > 2) Is a gyroscopic chip required to measure the yaw or can that be
>> > handled by the accelerometer above?  Is it true that accelerometers
>> > cannot measure yaw but can measure pitch and roll only?  Do I need a
>> > 3 axis gyroscope as well in that case?
>>
>> You need three axes of acceleration, and three axes of angular rate.
>>
>> > 3) If I am in a car parked on a hill, how does the INS know I'm not
>> > accelerating forward but rather that the acceleration is just due to
>> > gravity?  This gets back to my question of whether an inclinometer is
>> > needed I'm guessing.
>>
>> Assuming perfect accelerometers, gyros, and geodetic database
>> information, and assuming that the INS is properly initialized, the INS
>> will "know" that the car has rotated and stopped, and will be able to
>> null out the effect of gravity.
>>
>> > Crap I have not even started and its already sounding complicated.
>>
>> Yes it is.  And you've just scratched the surface.
>>
>> > Please, a simple explanation only as I'm already somewhat befuddled.
>>
>> If you can only survive on simplicity you're screwed.  There.  That's
>> simple.
>>
>> Inertial navigation is a complex subject.  Sensors good enough to do
>> the job purely from inertial measurements are exceedingly expensive
>> (i.e. a rather large fraction of $1M), and if you do want to do it
>> purely inertially you need a pretty detailed knowledge of the geodetic
>> properties of the earth.
>>
>> GPS-aided inertial navigation can use much less expensive sensors,
>> because the data from a GPS system tends to fill in the gaps left by
>> the sensors (and visa-versa), but now instead of combining information
>> from six sensors and a big database, you have to combine three bits of
>> data from the GPS with six bits of data from your sensors, and the
>> required Kalman filter is neither linear nor time invariant.
> 
> GPS is accurate but slow.  By the time you finish all the calcuations,
> you are way-off from the original position.  Accelerometers can apply
> quick but inaccurate corrections to GPS.  Combining the two is not so
> difficult in theory, but of course in practice.
> 
It's better to say that GPS is accurate over the long term, but not the 
short, while accelerometers (and gyros) are accurate over the short term 
but not the long.
> 
>> If you really want to do this instead of buying a solution the AIAA
>> (http://www.aiaa.org) has how-to books -- but in order to understand
>> them you need most of a Master's degree in the right sort of signal
>> processing mathematics.  Only you can say if you're up to it, but it's
>> not the sort of thing you'll do in a few evenings with a high-school
>> math background unless you're _really_ an astounding person.
> 
> Two years of undergrad maths should be enough.  It's just spatial
> geometry and linear algebra.  Some high school students do study this
> stuff.  Oh wait, may be not in the U.S.
> 
It's just spatial geometry, linear algebra, multivariate statistics, with 
some real analysis if you want to understand how the math goes together 
instead of just following someones recipe.  Add to that the fact that you 
need to know and understand the characteristics of your sensors and a 
good dose of how GPS works.

You may be able to understand some of the _principals_ if you're an 
ordinary high school student, and even reason out a solution that kinda 
works -- but I doubt that even one high school student in 100, in any 
given country, could begin to understand all of the issues inherent in a 
professional-grade INS solution.

-- 
Tim Wescott
Control systems and communications consulting
http://www.wescottdesign.com

Need to learn how to apply control theory in your embedded system?
"Applied Control Theory for Embedded Systems" by Tim Wescott
Elsevier/Newnes, http://www.wescottdesign.com/actfes/actfes.html

On Dec 28, 12:04=A0am, Tim Wescott <t...@seemywebsite.com> wrote:
> On Thu, 27 Dec 2007 15:22:06 -0800, linnix wrote:
> > On Dec 26, 10:42 am, Tim Wescott <t...@seemywebsite.com> wrote:
> >> On Wed, 26 Dec 2007 03:58:30 -0800, vorange wrote:
> >> > 3 questions :
>
> >> > 1) =A0Is it possible to build a simple but accurate INS using a 3 axi=
s
> >> > accelerometer and 3 axis inclinometer? =A0Or do I need something more=

> >> > than that? =A0Is the inclinometer even needed or would just an
> >> > accelerometer surfice?
>
> >> No. =A0An inclinometer is just a type of accelerometer, and
> >> accelerometers alone aren't sufficient.
>
> >> > 2) Is a gyroscopic chip required to measure the yaw or can that be
> >> > handled by the accelerometer above? =A0Is it true that accelerometers=

> >> > cannot measure yaw but can measure pitch and roll only? =A0Do I need =
a
> >> > 3 axis gyroscope as well in that case?
>
> >> You need three axes of acceleration, and three axes of angular rate.
>
> >> > 3) If I am in a car parked on a hill, how does the INS know I'm not
> >> > accelerating forward but rather that the acceleration is just due to
> >> > gravity? =A0This gets back to my question of whether an inclinometer =
is
> >> > needed I'm guessing.
>
> >> Assuming perfect accelerometers, gyros, and geodetic database
> >> information, and assuming that the INS is properly initialized, the INS=

> >> will "know" that the car has rotated and stopped, and will be able to
> >> null out the effect of gravity.
>
> >> > Crap I have not even started and its already sounding complicated.
>
> >> Yes it is. =A0And you've just scratched the surface.
>
> >> > Please, a simple explanation only as I'm already somewhat befuddled.
>
> >> If you can only survive on simplicity you're screwed. =A0There. =A0That=
's
> >> simple.
>
> >> Inertial navigation is a complex subject. =A0Sensors good enough to do
> >> the job purely from inertial measurements are exceedingly expensive
> >> (i.e. a rather large fraction of $1M), and if you do want to do it
> >> purely inertially you need a pretty detailed knowledge of the geodetic
> >> properties of the earth.
>
> >> GPS-aided inertial navigation can use much less expensive sensors,
> >> because the data from a GPS system tends to fill in the gaps left by
> >> the sensors (and visa-versa), but now instead of combining information
> >> from six sensors and a big database, you have to combine three bits of
> >> data from the GPS with six bits of data from your sensors, and the
> >> required Kalman filter is neither linear nor time invariant.
>
> > GPS is accurate but slow. =A0By the time you finish all the calcuations,=

> > you are way-off from the original position. =A0Accelerometers can apply
> > quick but inaccurate corrections to GPS. =A0Combining the two is not so
> > difficult in theory, but of course in practice.
>
> It's better to say that GPS is accurate over the long term, but not the
> short, while accelerometers (and gyros) are accurate over the short term
> but not the long.
>
> >> If you really want to do this instead of buying a solution the AIAA
> >> (http://www.aiaa.org) has how-to books -- but in order to understand
> >> them you need most of a Master's degree in the right sort of signal
> >> processing mathematics. =A0Only you can say if you're up to it, but it'=
s
> >> not the sort of thing you'll do in a few evenings with a high-school
> >> math background unless you're _really_ an astounding person.
>
> > Two years of undergrad maths should be enough. =A0It's just spatial
> > geometry and linear algebra. =A0Some high school students do study this
> > stuff. =A0Oh wait, may be not in the U.S.
>
> It's just spatial geometry, linear algebra, multivariate statistics, with
> some real analysis if you want to understand how the math goes together
> instead of just following someones recipe. =A0Add to that the fact that yo=
u
> need to know and understand the characteristics of your sensors and a
> good dose of how GPS works.
>
> You may be able to understand some of the _principals_ if you're an
> ordinary high school student, and even reason out a solution that kinda
> works -- but I doubt that even one high school student in 100, in any
> given country, could begin to understand all of the issues inherent in a
> professional-grade INS solution.

The principals will be a problem only if the student steps out of line
and neglects his study of the principles.

On Dec 28, 12:04 am, Tim Wescott <t...@seemywebsite.com> wrote:
> On Thu, 27 Dec 2007 15:22:06 -0800, linnix wrote:
> > On Dec 26, 10:42 am, Tim Wescott <t...@seemywebsite.com> wrote:
> >> On Wed, 26 Dec 2007 03:58:30 -0800, vorange wrote:
> >> > 3 questions :
>
> >> > 1)  Is it possible to build a simple but accurate INS using a 3 axis
> >> > accelerometer and 3 axis inclinometer?  Or do I need something more
> >> > than that?  Is the inclinometer even needed or would just an
> >> > accelerometer surfice?
>
> >> No.  An inclinometer is just a type of accelerometer, and
> >> accelerometers alone aren't sufficient.
>
> >> > 2) Is a gyroscopic chip required to measure the yaw or can that be
> >> > handled by the accelerometer above?  Is it true that accelerometers
> >> > cannot measure yaw but can measure pitch and roll only?  Do I need a
> >> > 3 axis gyroscope as well in that case?
>
> >> You need three axes of acceleration, and three axes of angular rate.
>
> >> > 3) If I am in a car parked on a hill, how does the INS know I'm not
> >> > accelerating forward but rather that the acceleration is just due to
> >> > gravity?  This gets back to my question of whether an inclinometer is
> >> > needed I'm guessing.
>
> >> Assuming perfect accelerometers, gyros, and geodetic database
> >> information, and assuming that the INS is properly initialized, the INS
> >> will "know" that the car has rotated and stopped, and will be able to
> >> null out the effect of gravity.
>
> >> > Crap I have not even started and its already sounding complicated.
>
> >> Yes it is.  And you've just scratched the surface.
>
> >> > Please, a simple explanation only as I'm already somewhat befuddled.
>
> >> If you can only survive on simplicity you're screwed.  There.  That's
> >> simple.
>
> >> Inertial navigation is a complex subject.  Sensors good enough to do
> >> the job purely from inertial measurements are exceedingly expensive
> >> (i.e. a rather large fraction of $1M), and if you do want to do it
> >> purely inertially you need a pretty detailed knowledge of the geodetic
> >> properties of the earth.
>
> >> GPS-aided inertial navigation can use much less expensive sensors,
> >> because the data from a GPS system tends to fill in the gaps left by
> >> the sensors (and visa-versa), but now instead of combining information
> >> from six sensors and a big database, you have to combine three bits of
> >> data from the GPS with six bits of data from your sensors, and the
> >> required Kalman filter is neither linear nor time invariant.
>
> > GPS is accurate but slow.  By the time you finish all the calcuations,
> > you are way-off from the original position.  Accelerometers can apply
> > quick but inaccurate corrections to GPS.  Combining the two is not so
> > difficult in theory, but of course in practice.
>
> It's better to say that GPS is accurate over the long term, but not the
> short, while accelerometers (and gyros) are accurate over the short term
> but not the long.
>
> >> If you really want to do this instead of buying a solution the AIAA
> >> (http://www.aiaa.org) has how-to books -- but in order to understand
> >> them you need most of a Master's degree in the right sort of signal
> >> processing mathematics.  Only you can say if you're up to it, but it's
> >> not the sort of thing you'll do in a few evenings with a high-school
> >> math background unless you're _really_ an astounding person.
>
> > Two years of undergrad maths should be enough.  It's just spatial
> > geometry and linear algebra.  Some high school students do study this
> > stuff.  Oh wait, may be not in the U.S.
>
> It's just spatial geometry, linear algebra, multivariate statistics, with
> some real analysis if you want to understand how the math goes together
> instead of just following someones recipe.  Add to that the fact that you
> need to know and understand the characteristics of your sensors and a
> good dose of how GPS works.
>
> You may be able to understand some of the _principals_ if you're an
> ordinary high school student, and even reason out a solution that kinda
> works -- but I doubt that even one high school student in 100, in any
> given country, could begin to understand all of the issues inherent in a
> professional-grade INS solution.

My statement about high school student is just sarcastic, considering
the low interest in science in the U.S. (driven by misguided
government policies).

However, colleges are more competitive, mostly due to foreign students
anyway.

But I maintained that the first two years of undergrad math should be
enough.  GPS is nothing more than translating time delays into spatial
coordinates and Accelerometers are applied Newtonian physics.  I know
of some heavy duty research facility in these areas, but they are not
in the U.S.

Unfortunately, the applications are often in sensitive areas (fast
moving projectiles) and the interesting stuffs are always hidden.  I
am probably saying too much already.

>
> --
> Tim Wescott
> Control systems and communications consultinghttp://www.wescottdesign.com
>
> Need to learn how to apply control theory in your embedded system?
> "Applied Control Theory for Embedded Systems" by Tim Wescott
> Elsevier/Newnes,http://www.wescottdesign.com/actfes/actfes.html

On Dec 27, 6:22=A0pm, linnix <m...@linnix.info-for.us> wrote:

> Two years of undergrad maths should be enough. =A0It's just spatial
> geometry and linear algebra. =A0Some high school students do study this
> stuff. =A0Oh wait, may be not in the U.S.

Mathematics is no longer taught in the United States.

On Dec 26, 1:42=A0pm, Tim Wescott <t...@seemywebsite.com> wrote:

> If you really want to do this instead of buying a solution the AIAA
> (http://www.aiaa.org) has how-to books -- but in order to understand them

Hey, that's a really really good link there, I see a bunch of books
I've added to my wishlist. Thanks!

On Fri, 28 Dec 2007 09:06:23 -0800, larwe wrote:
> On Dec 27, 6:22&nbsp;pm, linnix <m...@linnix.info-for.us> wrote:
> 
>> Two years of undergrad maths should be enough. &nbsp;It's just spatial
>> geometry and linear algebra. &nbsp;Some high school students do study this
>> stuff. &nbsp;Oh wait, may be not in the U.S.
> 
> Mathematics is no longer taught in the United States.

Depends where you look:
http://pbskids.org/cyberchase/basic.html

Cheers!
Rich

On Dec 28, 2:01=A0pm, Rich Grise <r...@example.net> wrote:
> On Fri, 28 Dec 2007 09:06:23 -0800, larwe wrote:

> > Mathematics is no longer taught in the United States.
>
> Depends where you look:http://pbskids.org/cyberchase/basic.html

Eh? The only vaguely mathematical thing I saw on that page is a
talking calculator, which if anything is arithmetic rather than
mathematics.