I am using a Wii Remote from Nintendo as 3D accelerometer. Thanks to the great aka.wiiremote external, it's possible to capture all Wimote signals and one can calibrate the acceleration quite accurately, using a simple transformation that makes the acceleration range between -1.0 and 1.0 (0 corresponds to no acceleration, for example when there is no movement) instead of 0-255.
Then, I am interested in getting the speed (velocity) of the movement.
As acceleration is the derivative of speed, one solution is interpreting the speed as the integral of acceleration. If we call A the acceleration and V the speed, at a given time Tk we have V(Tk) = A(T=0) + A(T=e) + A(T=2e) + ... + A(T=Tk) --- where e repeasents the interval between the measures.
For some reason, this solution doesn't seem to work : for example, when taking the Wimote, moving it a bit and then laying it again on the table, the speed should be zero at the end and it's clearly not the case. I tried different time resolutions (the e factor above), but this doesn't help.
Maybe this method only works if you have a very accurate and high time resolution measure of the acceleration ... Any idea ?