I am using a miniature car and I want to estimate the position.
We can not use GPS modules and most of the tracking systems that I saw, are using IMU senson with the GPS module.
In our car we are able to find our exact correct location with image processing but for some parts that dont have enough markings we can not do this.
So we want to use the IMU as backup for our positioning. so as long as the positioning is close is good for us.
And we are only interested in our 2D position since the car is on a flat ground.
I am using a IMU 9DOF sensor and I want to calculate my movement. I have seen some amazing works with IMU for tracking body movements but no code or simple explanation is anywhere about it. So basically
I have the reading from accelerometer, gyro and magnetometer. I also have orientation in quarternions. From the device I am getting also the linear acceleration but even when I am not moving it in any direction the values are not 0 which is really confusing.
Can you please help me how to approach this?
Thanks in advance
Update :
So right now we are getting the perfect heading from the quaternion values.
We also have the delta_time between each heading. So what I believe we need right now is the velocity. either as a vector or as a total value.
Best Answer
Non-zero rates are normal for MEMS accelerometers and gyros. This is persistent error. It is eliminated by somehow making sure that the device is stationary for a couple of seconds (so the output can stabilize), then getting a reading. Henceforth, subtracting this steady-state error from all future measurements. Look up the datasheet of your sensor - there will be maximum values for this and other types of measurement tolerances.
Now, the much more complex subject of fusing the accelerometer, gyro and compass data. This can get hugely complicated, using Kalman filter, like Apolo once did. It can, however, be quite simple as well.
The general idea is that the magnetic sensor has slow response, low accuracy, but the error does not increase. On the other hand, a gyro's output is velocity, which is integrated to get angular position. The error grows very fast - generally you can't do dead reckoning for more than a minute with only a giro. The accelerometer is worse - it outputs acceleration, which gets integrated twice!
So, a simple fusing filter would be some linear combination of the readings of the accelerometer and compass, with the coefficient in front of the gyro descreasing over tyme.
Here is a discussion by much more knowledgeable people than me on the topic.
Note: What you are trying to do is called dead reckoning.