- Tue Sep 08, 2009 1:58 pm
#80547
Almost every project with an IMU claims to use gyros and accelerometers to determine attitude and position. I perfectly understand the concept but what I don't get is how you really can use an accelerometer to determine attitude when it's not stationary.
If you put it on a helicopter all it will ever measure is acceleration generated by the rotors. If you are stationary in a hover (disregarding tail rotor) it will be pointed straight up and the accelerometer (3-axis) will measure 1 G straight up. Now the helicopter gets a gust of wind and tilts a few degrees. As the rotor still generates the same force, and still points in the same angle as the accelerometers "up"-axis, the accel will still measure exactly 1 G.
Unless the altitude is compensated for by increasing main rotor thrust (by adding another sensor such as a barrometer), there is no way for the accelerometer to know the craft has tilted.
Am I missing something.
If you put it on a helicopter all it will ever measure is acceleration generated by the rotors. If you are stationary in a hover (disregarding tail rotor) it will be pointed straight up and the accelerometer (3-axis) will measure 1 G straight up. Now the helicopter gets a gust of wind and tilts a few degrees. As the rotor still generates the same force, and still points in the same angle as the accelerometers "up"-axis, the accel will still measure exactly 1 G.
Unless the altitude is compensated for by increasing main rotor thrust (by adding another sensor such as a barrometer), there is no way for the accelerometer to know the craft has tilted.
Am I missing something.