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From: Sven Schoeberichts on 5 Nov 2009 07:39
Hello all,

I have recorded an acceleration signal during walking, and I want to process it in matlab, by differentiation to get the speed, and the distance travelled. So I need the derivative from the acceleration signal.

While looking for the proper function, I only come across functions which allows to get the derivative of a function, instead of an irregular signal.

Is there a function which fits my needs to do this?
Thanks in advance.

Gr. Sven
From: Lothar Schmidt on 5 Nov 2009 08:14
Sven Schoeberichts schrieb:
> Hello all,
>
> I have recorded an acceleration signal during walking, and I want to process it in matlab, by differentiation to get the speed, and the distance travelled. So I need the derivative from the acceleration signal.
>
> While looking for the proper function, I only come across functions which allows to get the derivative of a function, instead of an irregular signal.
>
> Is there a function which fits my needs to do this?
> Thanks in advance.
>
> Gr. Sven

in order to get the velocity from an acceleration signal a method we
could use is to integrate. The same method leads in good approximation
from speed to distance. Differentiation is usually used to transform
vice versa.

perhaps this will help you:
doc diff
doc cumsum
From: dpb on 5 Nov 2009 08:43
Lothar Schmidt wrote:
> Sven Schoeberichts schrieb:
>> Hello all,
>>
>> I have recorded an acceleration signal during walking, and I want to
>> process it in matlab, by differentiation to get the speed, and the
>> distance travelled. So I need the derivative from the acceleration
>> signal.
>>
>> While looking for the proper function, I only come across functions
>> which allows to get the derivative of a function, instead of an
>> irregular signal.
>>
>> Is there a function which fits my needs to do this?
>> Thanks in advance.
>>
>> Gr. Sven
>
> in order to get the velocity from an acceleration signal a method we
> could use is to integrate. The same method leads in good approximation
> from speed to distance. Differentiation is usually used to transform
> vice versa.
>
> perhaps this will help you:
> doc diff
> doc cumsum

and

doc trapz

You'll need a good estimate/measure of sampling period, too, of course.
In general, while it sounds/seems as if it should be trivial,
obtaining good velocity and displacement measurements via acceleration
is tricky. Any DC bias at all can be a major problem as can (as another
poster recently discovered) sampling irregularity.

--
From: Richard Crozier on 5 Nov 2009 09:39

Use the gradient function.

doc gradient
From: dpb on 5 Nov 2009 09:42
Richard Crozier wrote:
> Use the gradient function.
>
> doc gradient

excepting, of course, _differentiating_ acceleration doesn't yield
displacement... :(

--
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