thank you for replying : )

the use of kalman filtering is one of our intentions but fisrt,were are facing a strange problem in double integration..

as we take the accelerations (m/s^2) and we integrate in very short time periods ( equals to the clock of the imu (180Hz=5,5ms) ) during a short period of time ( the experiment is just x-axis movement with constant speed of about 0.5 m/s ) , our results vary from values 0.05 to 0.06.this means an average 10 times smaller value for velocity..the type of waveform is smooth as a constant velocity,but the value is small..this is our main obstacle..the integration should give values much bigger as there is accumulated error during the process.

the kalman filtering we are planning to use will make a better estimation as me assume,but i think the problem is somewhere else..

is there anything vital that we should take into consideration about the acceleration values..

some details..the accelerations are given in the navigation frame,the method of integration is calculating the time slot and multiplying with the accel value ( we also can add the small triangle lost in the procedure as (acc(t+1)-acc(t))*dt/2 ,but there seems to be small difference..)..any ideas would be much appreciated..thank you in advance