# measuring Tilt

So here is my dilema. I wanted to measure tilt of my aerial vehicle so I bought a gyro. After purchasing it discovered that gyro output angular velocity and not an angle. So i though i could just integrate this with respect to time and call it a day. However, this did not work out due to 'drift' in the gyro sensor. Now im reading that accelerometers can be used to measure tilt. However, wont the tilt angle change if the vehicle is accelerating?? Is there any way to measure tilt that wont cause a fortune or a headache????

wont the tilt angle change if the vehicle is accelerating?

Yes it will. I think the problem here is that the force experienced by an object due to acceleration and that experienced by gravity due to tilt are identical. That's why you can't get a sensor that measures one without being affected by the other.

You are probably better working on the gyro.

That's physics .... sorry. :(

Does this help?

Measuring the platform angle

• The Gyro input gives the angular rate but it drifts a lot
• The Accelerometer input gives the acceleration due to gravity and due to the scooter accelerating
• When the scooter is not accelerating, the inverse-sine of the accelerometer input gives us angle o This isn't very precise o It is susceptible to vibration o But it doesn't drift
• How to combine them? o The Gyro input averaged over time should be zero o This lets the software adjust for drift o We assume gyro starts off stationary o We assume initial angle is given by the accelerometer o Track angle changes with the gyro o If the tracked angle is different to the angle from the accelerometer, track towards it slowly o Subtract any acceleration force we apply to the motors from the accelerometer reading o When moving, rely less on the accelerometer reading o sin(x) ~ (for small x) This omits the need for Trigonometry in the software.

http://members.optusnet.com.au/a4x4kiwi/scooter/

I’m digging this one up from the grave. Did the OP ever figure this out?

If someone has the answer on this problem, please let me know.. Is gyro effected by pitch of the car?

For combining gyro and accelerometer, this could be useful (using Kalman filters): http://stackoverflow.com/questions/1586658/combine-gyroscope-and-accelerometer-data

I also have a question about the installation of gyroscoop/accelerometer. Do they have to be aligned with the road, or is this not necessary?

I figured it out using Kalman BUT once I turn my car on. everything goes nuts. Grumpy_Mike here has a tech write-up on decouping but I couldn't get it to work.