I was going through theory of INS and trying to understand attitude estimation, velocity and position and estimation. Theroy can be summarized as follows, 1) Gyro is integrated to estimate the attitude/orientation, with initial orientation as the initial condition. 2) Accelerations measured in body frame are converted to inertial frame using orientation given by gyro, and then acceleration in inertial frame is integrated to get velocity and again integrated to get position. Initial velocity and position are the initial conditions. So, above two steps are quite clear. But now the doubt/problem comes into picture, 1) Any gyro, however accurate it is will have bias and moreover changing bias, which will mess up the estimated attitude for sure. In this scenario, estmation of postion and velocity will definitely be erroneous. 2) Error in position and velocity can be tackled by GPS, but what about attitude? How to restrain drift in estimated attitude within acceptable limits? 3) Lets assume a scenario in which a small UAV is going in tight horizontal circiular motion for extended period of time. In this scenario, accelerometer cannnot be used to correct for drift, as there is constant acceleration in addition to gravity. How to tackle this problem? Whether this problem is solvable at all in case of MEMS IMUs? I understand that fusion softwares are proprietory solutions but I am not asking for any code here. I just want some explanations about how things are done in this respect. Thank you.
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