hi,,I have IMU consists of (3-accelometre,3-gyro and 3-megnatometre) and I need to find out the pitch angle for a UAV so if I use the X-accelometre as a measurment,so I get 2 components the first one is due to (gravity sense) which is desirable to measure the pitch angle ,and the second one is making my problem (not desirable now) which is due to motion along X-axis so please help me to fix this ..
Thanks in advance

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Hi, this is fundamental issue with IMU's. In short, you need to use gyros + accelerometer for this task and may also use magnetometer. You may want to consult direction cosine matrix documents found here, as this is one of the possible solutions that you eventually need to implement to "fix" your problem. You also may want to find out, what is Kalman filter.
Hello Andrus , thanks for your replay, I made Y-Rategyro as a process and accelometre as measurment to the pitch angle using Kalman filter and its working perfictly on the table,,but I still didnt build my UAV yet,,so if I make a control system on the (autopilot speed) along with accelometre axis in order to make the speed constant,,what will be the accelometre output in this case ??????????????
Hi, as I wrote, you cannot do just with accelerometer, you also need to use input from pitch gyro in your Kalman filter. Also, in real life, your pitch depends also on roll and yaw, so you need to use Direction Cosine Matrix to find out, how your plane is at any given moment.

Btw, in my uav, I use accelerometer data to reset DCM only when plane is not moving. Once the plane takes off, I use airspeed together with altitude change to calculate pitch angle.
Ziad, people will be more likely to help you if you use fewer question marks. It comes across as shouting.

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