| ??? 07/28/09 03:56 Read: times |
#167940 - Understood but the theird method... Responding to: ???'s previous message |
Kai Klaas said:
Farshid, why do you calculate "2" to the power of "g"??
Think of an accleration sensor of a device containing a small reference mass "m" connected to a "spring", where the force acting on the mass (F = m x a) is determined by measuring the elongation of spring (Hook's law). As the reference mass is constant the elongation of spring is a direct measure of acceleration "a", where "a" is the sum of the "parallel" component of gravitational acceleration "g" and additional accelerations like tangential and centripetal acceleration. Everything then is self explaining. Kai Ahh, My bad! By the 'g' above the numbers I meant the unit not the number power 'g'. (I had a teacher which used to write the units above the number and I got used to it). Both of your drawings show that placing two accelerometers in a line, pointing to one direction or to each other, will not cancel the effect of acceleration on the output. Thanks to your explanation and kind help I finally understood this :) When accelerometers are pointing to each other, if summed up it won't work either. Since in all conditions the output will sum up to zero: 
Kai Klaas said:
But if you mount them symmetrically to a rotation axis, then you can compensate for centrifugal accelerations. Put the two roll tilt sensors symmetrically to the roll axis, and the two pitch tilt sensors symmetrically to pitch axis (with there sensitive axes pointing to the rotation axes) and you can compensate for the corresponding centrifugal accelerations. This will also automatically compensate for rotations around the yaw axis.
Kai I don't understand the third way that you suggested as a solution above. - If I want to place them symmetrically then I can solder one on the top layer and one right below that one on the bottom layer. This way I have both of the 'X' axes pointing to one direction, but 'y' axes will be pointing in opposing directions (left and right)! - Its possible to place them on top of each other so 'x' axes point to one direction and 'y' axes to one other direction. But this no longer would be symmetrical. Thank you for your time and priceless help, Farshid |
