Re: Acceleration

"Gareth" <gareth@xxxxxxxxxx> writes:

Hi

I am having trouble ( a lot of trouble ) trying to get meaningful and
timely acceleration data.

In essence, I have a wheel speed sensor that picks up around 40 to 100
pulses per wheel revolution (adjustable). This is captured by a 16bit
Micro/DSP.

All I want to assert, with reasonable accuracy is the wheel
acceleration.
My acceleration data at the moment is all over place.

How can I filter the data in real time so that I can assert wheel
acceleration? eg. DO I need to implement a Kalman filter or is there a
faster way of doing this?

In other words, as a test, I have fitted this setup to a car and
steady
acceleration does not show steady acceleration data - it's all over
the
place. I can see the acceleration component, but is is saturated with
acceleration spikes.

It's tough to help you determine what's wrong with your algorithm when
you haven't described it to us.

How are you measuring time? Are you using a timer on micro? Are the
pulses coming in as interrupts? What's your interrupt latency time?
Do you keep interrupts enabled all the time? Etc., etc.
--
% Randy Yates % "And all that I can do
%% Fuquay-Varina, NC % is say I'm sorry,
%%% 919-577-9882 % that's the way it goes..."
%%%% <yates@xxxxxxxx> % Getting To The Point', *Balance of
Power*, ELO
http://www.digitalsignallabs.com

I am using a dsPIC. This has capture channels that capture a 16bit timer
value every pulse. I then put a number of sequencial capture values in an
array to do post processing. Right now I am using an array length of 40. I
average the first five and last five values as the start and end velocity,
and then divide that by the time it has taken between (by adding the
values). This, I believe, give me acceleration, but it is very 'noisy'.



.

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