Confusion about gravity direction about navego HOT 7 CLOSED

from navego.

Hi Dear Rodralez:

Thank you for your explanation, actually I'm more confused about the conversion you've mentioned.

Since the commertial IMUs I used claimed using FRD coordinate system as NaveGo does, at least the accleration except gravity should be in the same direction. But if the Z accelerometer data from a commercial IMU is multiplied by -1, the acceleration except gravity will also be inverted, that will conflict with the FRD coordinate system. An upward acceleration sensed by the commercial IMU will be treated as downward acceleration.

So I'm confused how to deal with this situation? Does the inverted g have any other potential effect on other data such as turn rate and Front-Right acceleration?

from navego.

from navego.

Thank you for your reply. Adding (2 * 9.81) to the Z acc data seems to work. But I still have some confusion of how in different sensors the gravity may have opposite direction with vertical acceleration.

Assuming there is a simplest acceleration sensor which has a spring hanging a weighted object. An upwards acceleration of the body will make the weighted object moving downwards, that means the spring may be stretched longer. And which is simple to imagine, the gravity also have the effect to pulling the weighted object downwards. So this may make me think the gravity should be equal to an upwards acceleration, which physically it should. But in NaveGo the gravity has an opposite direction with an upwards acceleration. Because I'm new with IMUs, does actual acceleration meters such as optical fiber acceleration meters or MEMS ones can sense gravity in the opposite direction with an upwards acceleration?

Regards.

from navego.

from navego.

Glad to have your reply.

As you said，modern IMUs may have coordinate mapping functions, but my point is, using such functions to invert the coordinate axis may invert the acceleration and the gravity at the same time. The invert operation may be like -1*(g+acc). But to make my data work with NaveGo, I did the operation like (acc-2g), witch means the gravity is separated with the acceleration. In my second reply I already have this confusion.

Like the last reply of mine said, the gravity should have the same direction with an upwards acceleration, if inverted the direction of z-axis, the upwards acceleration and gravity should receive -1 at the same time , like -1*(g+acc), but NaveGo have (acc-2g) instead, which means this is not a simple axis inversion, I'm wondering is this gravity-only inversion come from the working principle of mordern IMUs of something else?

Regards

from navego.

from navego.