Kalman filter

I have a simple question (with a complex answer i suppose):

is it possible to decouple gravity and inertial acceleration, or better
filter out gravity from measures taken ONLY with a triaxial accelerometer
(without using other sensors as gyroscopes ecc); if it is, can a Kalman
filter minimize effect of gravity? 


		
This message was sent using the Comp.DSP web interface on
www.DSPRelated.com

Ask someone who makes inertial navigation systems?

I guess if you cannot measure rotation, you will not be able to solve 
your problem. With 3 degrees of freedom for moving, and 3 more for 
rotation, you will need at least 6 sensors inputs to get your 6 outputs.

Best regards,

Andre


mik wrote:

> I have a simple question (with a complex answer i suppose):
> 
> is it possible to decouple gravity and inertial acceleration, or better
> filter out gravity from measures taken ONLY with a triaxial accelerometer
> (without using other sensors as gyroscopes ecc); if it is, can a Kalman
> filter minimize effect of gravity? 
> 
> 
> 		
> This message was sent using the Comp.DSP web interface on
> www.DSPRelated.com


-- 

Please change no_spam to a.lodwig when replying via email!

mik wrote:
> I have a simple question (with a complex answer i suppose):
> 
> is it possible to decouple gravity and inertial acceleration, ...

Not according to Special Relativity.

> or filter out gravity from measures taken ONLY with a triaxial accelerometer
> (without using other sensors as gyroscopes ecc); if it is, can a Kalman
> filter minimize effect of gravity? 

Kalman, Shmalman. Even Newton requires six axes: three for translation, 
three more for rotation.

Jerry
-- 
Engineering is the art of making what you want from things you can get.
�����������������������������������������������������������������������

mik wrote:
> I have a simple question (with a complex answer i suppose):
> 
> is it possible to decouple gravity and inertial acceleration, or better
> filter out gravity from measures taken ONLY with a triaxial accelerometer
> (without using other sensors as gyroscopes ecc); if it is, can a Kalman
> filter minimize effect of gravity? 

Seems it would be easy to calibrate it out by a measurement 
taken when it is known to be in at rest relative to the 
earth surface where you are.  Thereafter just subtract it.

Or do you have reason to believe gravity's acceleration will 
be signifigantly changing while in operation?  In that case 
it should still be calculable if you know the local 
relationship of gravity's acceleration with position.  This 
doesn't violate GR because you are taking into account more 
than can be known from within a sealed elevator taking into 
account only local measurements.

In short, it should be instantaneously calculable and not 
require an adaptive filter.


Bob
-- 

"Things should be described as simply as possible, but no 
simpler."

                                              A. Einstein

"mik" <pennese@tiscali.it> wrote in message 
news:0radnTmIJsrgT33fRVn-uA@giganews.com...
> is it possible to decouple gravity and inertial acceleration, or better
> filter out gravity from measures taken ONLY with a triaxial accelerometer

With just one, if rotation is unconstrained, not really.  There are many 
ways you could move the accellerometer to produce any given set of readings.

The closest thing you could do would be to devise a statistical model of the 
motion and choose the most likely way of producing your readings.  The 
result would be "plausible", but not accurate.

> (without using other sensors as gyroscopes ecc);

You can do it with two more triaxial accelerometers.  Will that do?

--
Matt

No,

one has to KNOW the field of gravity and subtract these
values from measured values of the three accelerometers.

No alternative. This has nothing to do with rotated coor-
dinates. Ideally, we have an inertially stabilized plat-
form with three accelerometers.
These cannot distinguish between gravity effects and motion
acceleration.

Best regards --Gernot Hoffmann